ALT53NATIYE STRENGTH TESTING METHODS

FOR EMPLOIEE SCREENING

by

CHRISTOPHER C. PLCTT, B,S.

A THESIS

IN

INDUSTRIAL ENGINEERING

Submitted to the Gradaate Faculty of Texas Tech Qniversity in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

IN

INDUSTRIAL ENGINEERING

Approved

December, 1983

7::'

CONTENTS

CHAPTER

I . INTRODUCTION 1

I I . LITERATDBE REVIEW 6-

Current Employee S c r e e n i n g And Job Matching Methods 6

Strength Testing 9 Isonetric Strength 10 Isotonic Strength 12 Isokinetic Strength 15

Other Measures 17 Anthropometric Measures 18 Physiological Measures 18

III. THE STUDY 21

S u b j e c t s 21 V a r i a b l e s 22 Procedures and Equipment 25

P r e l i m i n a r y A c t i v i t i e s 25 P s y c h o p h y s i c a l L i f t i n g C a p a c i t y 26 Anthropometr ic Measures 29 P h y s i o l o g i c a l Measures 31 I s o m e t r i c S t r e n g t h 32 I s o t o n i c S t r e n g t h Measures 33 I s o k i n e t i c S t r e n g t h Measures 37

IV. ANALYSIS AND RESULTS 47

V. CONCLUSIONS AND RECOMMENDATIONS 5U

BIBLIOGRAPHY 58

l i l

APPENDIX

A. CONSENT FORM AND PERSONAL MEDICAL HISTORY QUESTION AIRE ^^

B. ANTHROPOMETRIC DATA

ISOTONIC STRENGTH TESTS

CORRELATIONS

IV

67

C. MISCELLANEOUS VARIABLES " '

D. ISOMETRIC STRENGTH TESTS '^^

85

ISOKINETIC STRENGTH DATA 108

111

LIST OF TABLES

1. Height Weight S t r a t i f i e d Sample Plan 23

2 . Comparison of Mini-Gym Speeds for Floor to Shoulder 45

3 . Comparison of Mini-Gym Speeds for Knuckle t o Shoulder 46

4 . Models For Floor To Shoulder L i f t 51

5 . Model For Knuckle To Shoulder L i f t 52

LIST OP FIGURES

1. L i m i t s For A F l o o r To Knuci-cle L i f t J

2 . S t r e n g t h T e s t s On The Mini-Gym 16

3 . 3.0JC And Lower ing Machine 27

4 . E x e r s e n t r y Hear t R a t e Moni tor - 29

5 . U n i v e r s a l Machine J^

6 . N a u t i l u s Machine 3 5

7 . M o d i f i e d Cytex Machine 36

8. S t a r t i n g p o s i t i o n f o r f l o o r t o s h o u l d e r and f l o o r t o

k n u c k l e l i f t s ^0

9 . S t a r t i n g p o s i t i o n f o r k n u c k l e t o s h o u l d e r l i f t 4 1

10 . M o d i f i e d Mini-Gyni 4 3

1 1 . S u b j e c t P o s t u r e f o r Arm S t r e n g t h Measureinent 76

1 2 . S u b j e c t P o s t u r e f o r S t a n d i n g Back S t r e n g t h

Measure l e n t 7 3

1 3 . S u b j e c t P o s t u r e f o r S h o u l d e r S t r e n g t n r ieasurement dO

14. S u b j e c t P o s t u r e f o r S t a t i c L^2q S t r e n g t h :ieasurc;.-n^nt o 2

1 5 . S u b j e c t I n i t i a l P o s t u r e f o r Dynamic Endurance o7

16. S u b j e c t S e ^ ^ u e n t i a l P o s t u r e f o r Dynamic Endurance 8b

17. U n i v e r s a l Overhead L i f t S t a r t i n g P o s i t i o n 90

1 8 . U n i v e r s a l Overhead L i f t Ending P o s i t i o n ^ 1

19 . U n i v e r s a l Ley L i f t S t a r t i n g P o s i t i o n 9J

2 0 . U n i v e r s a l l ey L i f t Ending P o s i t i o n 94

2 1 . U n i v e r s a l Sguat l i f t S t a r t i n g P o s i t i o n 96

V I

22. Universal Sguat Lift Ending Position 9"

23. Universal Curl Starting Position

24. Universal Curl Ending Position

25. Nautilus Arm Lift Starting Position

26. Nautilus Arm Lift Ending Position

27. Nautilus Leg Lift Starting Position

99

100

101

102

104

28. Nautilus Leg Lift Ending Position '^05

Vll

CHAPTER I

INTRODUCTION

In the l a s t twenty years manual mater ia l s handl ing

(MMH) a c t i v i t i e s have been the subjec t of a great d e a l of

research and i n v e s t i g a t i o n . This i s not surprising when one

considers the e f f e c t s of MMH a c t i v i t i e s on the health and

sa fe ty of workers as well as the re lated cos t s to industry

in compensation and l o s t product iv i ty . In recent l i t e r a t u r e

reviews by Aghazadeh (1982) and in the NIOSH technica l re ­

port Work Pract ices Guide For Manua^ Lif t ing (1981), i t has

been shown that in jur ies and the ir assoc iated cos t s in occu­

pat ions where MMH a c t i v i t i e s occur have been increasing dra­

mat ica l ly . This i s part icular ly true of back i n j u r i e s , which

account for a large proportion of the i n j u r i e s and an even

larger proportion of the resu l t ing c o s t s . This i s rather

s i g n i f i c a n t when one considers that i t i s l i k e l y that about

50% of the U.S. population wi l l suffer from low back pain

during the ir working l i f e (Rowe 1969) and that , as estimated

by Nordby (1981), the medical c o s t s alone are between 18,000

and 22,000 dol lars per case. I t has been the intent of most

of the research in t h i s f ie ld to reduce both the r i sk of

injury to the worker as well as the expense to industry.

In response to t h i s problem the NIOSH Work Pract ices

I S i ^ Z2£ Manua 1 Lif t ing (1981) was developed and in i t c r i ­

t e r i a and recommendations for the control of MMH a c ^ v i t i e s

were given. The c r i t e r i a were given in the form of an act ion

l imi t and a maximum permissible l i m i t . These l i m i t s were

based on the c h a r a c t e r i s t i c s of the l i f t i n g task to be per­

formed and the l ik l ihood that any person in the i n d u s t r i a l

population would be injured. Figure 1 shows the various

l i f t i n g condit ions for low l e v e l l i f t s . Lift ing condi t ions

which f a l l below the action l imi t are considered to repre­

sent nominal risk while those that f a l l above the maximum

permissible l i m i t are considered unacceptable for a l l except

very strong workers. The area between these l i m i t s requires

administrat ive contro l s .

As reviewed in the NIOSH Work Pract ices Guide For Manu­

al Li f i ina (1981), Aghazadeh (1982), and Snook et a l (1977) ,

there are four primary ways in which the control of i n j u r i e s

in MMH a c t i v i t i e s have been approached. The f i r s t , and by

far the most e f f e c t i v e of these methods, i s the use of good

ergonoraic design and engineering controls in the workplace

so as to e l iminate any a c t i v t i e s or condit ions which would

place the worker at r i sk . However, the ergonomic design

approach i s not always pract ica l or economically f e a s i b l e .

Medical screening of the employees has a l so been considered

(la) 200

150-o UJ u.

100-

5 0 -

O-L

iL Body Interfe \ ^ Limrt

fence

Hazardous L if ting

Conditions

Functional Reach

Maximum Permissable

L im i t

Action L im i t

10 20 30 HORIZONTAL LOCATION OF LOAD

(cm)

( in)

Figure 1: L imi t s For A Floor To Knuckle L i f t (from the MIOSH Work P r a c t i c e s Guide For Manual L i f i i n ^ / 198if

and is strongly recommended for the detection of any serious

problems that already exist. Medical screening is not recom­

mended as a single control measure because it has not been

found to be a good indicator of the future risk of injury.

Training of the employees has been recommended as well, but

has limited application as a single control measure due to

the fact that many injuries are a result of chronic stress

or a single extreme overexertion, both of which may not oc­

cur until long after the training is over. The final method

that has been used for the control of MMH injuries is the

development of mathematical models which are used to predict

success or failure in matching the requirements of the job

to the capabilities and limitations of the potential employ­

ee. As noted by Garg and Ayoub (1980) this seems to be the

area with the most promise and as cited in the NIOSH techni­

cal report Preemployment Strength Testing (1977), predictive

modeling was the area most strongly recommended for future

research at three national and international conferences.

Many such models have been developed but there is room for

improvement. Most of these models can be somewhat cumbersome

to use and can require specialized measuring equipment,

particularly for the assesment ot worker capabilities.

It is the purpose of this paper to investigate

alternative methods for the assesment of worker capabilities

which may be incorporated into the models for job and

employee matching. A battery of simulated lifting tasks and

strength measures have been developed and a series of pre­

dictive tests based on them have been determined* The tasks

and measures are both static and dynamic in nature and in­

corporate various types of test equipment. The tests have

been evaluated in terms of safety, reliability, economy,

ease of administration and job relatedness.

CHAPTER II

LITEHATURS REVIEW

Current Employee Screening And Job Matching Methods

There are currently three validated methods using large

subject populations for the matching of employees with jobs.

They are: the method recommended in the NIOSH Work gractic-

ss Guide For Manual Lifting (19 81) which was originally de­

veloped for NIOSH»s Preemployment Strength Testing Manual

(1977); the method developed by Ayoub et al (1978); and the

method developed by Smith and Ayoub (1983) for the Air

Force. While each of these methods have different procedures

the basic concept of matching the employees to the jobs

based on employee capabilities and job requirements is the

same. Both the study by Ayoub et al (1978) and the NIOSH

Work Practices Guide For Manual Lifting (1981), as well as

follow up studies on both of them, have found that employees

were much more likely to be injured if they were placed on

jobs in which the requirements exceeded their capai^ilities.

The approach taken in the NIOSH Preemployment Strength

Testing Manual (1977) involved a three phase longitudinal

investigation. The jobs were first analyzed for

biomechanical stress and a lift strength ratio (LSE) was

determined. The LSR was defined as the load lifted on the

job divided by the predicted strength in the same position

as the job activity. The predicted strength was the strength

of a 97.5 percentile male based on strength testing results

obtained from an industrial population. The employee's stat­

ic strength for the job position, as well as static strength

measures in standard positions for torso, arm and leg

strength were then taken. The medical records and job per­

formance of the employees were then monitored for the dura­

tion of the study. The results indicated that jobs with high

LSR*s had higher incidences of injury. More specifically,

heavier loads, higher frequencies of lifting maximum loads

and the remoteness of the load from the center of gravity of

the person, all contributed to increased incidences of inju­

ry. It was also found that job position strengths could be

reasonably predicted with the use of models that included

arm strength, torso strength, gender, age, weight and stat­

ure if different models were used for very different types

of lifts.

The second method proposed for controlling MMH inju­

ries, developed by Ayoub et al (1978) was called the Job

Severity Index (JSI). The JSI is a function of the ratio of

job demands to worker capacity. Worker capacity is

determined by incorporating various physical measures

8

including sex, weight, age, shoulder height, abdominal

depth, dynamic endurance and static arm and back strengths

into models which predict psychophysical maximum acceptable

weights of lift for various lifting conditions.

In Ayoub's study as well as a follow up study by Liles

and Mahajan (1982), the JSI was found to be highly correlat­

ed with injury incidence. It was further found that for JSI

values greater than 1.5 there was a much greater frequency

and severity of injuries than for values less than 1.5. A

JSI value of 2.25 was tenatively considered an upper limit

or the level at which all but very large and strong individ­

uals would be subjected to a high risk of injury. However,

the data on the 2.25 JSI limit is still somewhat inconclu­

sive. Regardless of the validity of the upper limit, the

JSI is still strongly supported as a control measure for MMH

activities due to its high predictablity and the large sam­

ple sizes used in its development.

The final employee screening/job matching method to be

discussed is the one described by Smith and Ayoub (1983) for

the Air Force. In this study a large variety of tasks con­

ducted by Air Force personnel were analyzed and the forces

necessary to perform each task were determined. The tasks

were then divided into various groups and a battery of

psychophysical tasks was developed to simulate these groups

of activities. A battery of candidate strength tests were

developed utilizing an incremental weight machine which was

already being used for screening by the Air Force. A large

number of personnel were then tested to determine their max­

imum acceptable efforts on both the simulated tasks and the

candidate strength tests. Models based on the candidate

strength tests were then developed to predict the maximum

efforts on the simulated tasks. Significant results were

found for models which included a six foot maximum lift, a

seventy pound elbow hold and a knuckle height lift. This

screening method is currently under consideration by the Air

Force.

Strength Testing

As can be seen in the employee/job matching programs

described earlier, strength testing is a very common method

of employee screening. This is primarily due to the fact

that most other measures, as noted earlier, are not very

good predictors of injuries or, as in the case of anthropo­

metric measurements, are not indicative of the individual's

ability to lift (NIOSH Work Practices guide For Manual

Lifting ,1981). Strength measures have been found to enter

into most models for predicting an individual's ability to

lift. It is the purpose of this investigation to examine and

10

compare the existing strength measures as well as some new

alternatives so that even better models of employee/job

matching can be developed.

The strength measures to be investigated in this study

fall into three basic descriptive catagories. These are iso­

metric, isotonic and isokinetic. Each of these catagories

will be explained in the subseguent sections. Along with

these explanations the various tests that have been investi­

gated will be discussed.

Isometric Strength

An isometric muscular contraction is one in which a

voluntary exertion produces no movement of the joints being

acted upon by the muscles or group of muscles being activat­

ed. Maximal voluntary isometric efforts have been very popu­

lar measures for use in estimating an individual's ability

to lift. The reason for this as suggested by Caldwell et al

(197U) and Chaffin (1975) is that these measures are relia­

ble and easy to make as well as having standardized proce­

dures developed for them. As reviewed in the NIOSH aork

EtiSliS^S. Guide For Manual Lifting (1981) , isometric

strength measures can be found in almost all of the models

for predicting lifting capacity. Those measures which have

been found significant include back, arm and shoulder

11

strength. In a recent study by Agahzadeh (1982) leg strength

and stooped back strength were also found to enter into the

predictive models. Stooped back strength was not recommended

as a suitable strength test because of the great stress it

places on the lower back.

Abdominal strength tested isometrically has also been

investigated as a possible predictor of lifting aoility. In

an early report by Rowe (1963) it was found that patients

suffering from low back pain exhibited abdominal weakness

and, in a later study by Rowe (1971) that abdominal weakness

was highly correlated with the incidence of low back pain.

In a more recent study by Nordgren et al (1980) it was found

that individuals who experienced low back pain during mili­

tary service, and whose military jobs were more strenous

than their civilian jobs, had lower average trunk flexion

and extension strengths. It has been hypothesized that the

abdominal muscles may act to increase abdominal pressure

during lifting which could give the lower back more support.

Thus if the abdominal muscles are weak this support may not

be given and lower back pain or injury may occur. A theoret­

ical model for abdominal strength was presented by Jones

(1971). Investigations to determine whether or not

abdominal strength was a factor in lifting were undertaken

by Carlsoo (198C) and by Legg (1981). The results of these

12

studies indicated that abdominal strength, as they measured

it, did not effect the interabdominal pressure or the abili­

ty to lift. It was pointed out by Carlsoo (1980) was that

the tests that were conducted measured the isometric

strength of the rectus abdominous but that during lifting it

was the oblique muscles that contracted in unison with the

back extensors and that the rectus abdominous showed almost

no EMG activity. This indicated that it may be more appro­

priate to test the oblique muscles.

Isotonic Strength

Isotonic strength can be defined as a dynamic muscular

contraction in which the tension developed in the muscle is

constant throughout the range of motion. Most activities

which are commonly thought of as isotonic are in reality not

isotonic. Such activities are those which involve typical

weight lifting exercises such as the overhead press, bench

press and arm curl. These activities have the individual

work against a constant weight. As the position of the

joints and the lengths of the muscles change during the per­

formance of the activity the tension in the muscles involved

changes as well, making the activity non-isotonic. For ease

of reference these non-isotonic activities will be included

under the heading isotonic.

13

A system has been developed which allows for an

approximate isotonic strength test. It is sold under the

brand name Nautilus and is marketed to gymnasiums and health

spas. It incorporates a series of cams which account for the

changes in joint angle and muscle length. The problem with

Nautilus equipment is that the cams are specific to given

joint configurations and do not account for variations in

body segment sizes among individuals.

Based on the current literature, little investigation

into the use of isotonic strength activities for the pre­

diction of lifting ability has been reported. It can be

speculated that this may be due to the heavy and cumbersome

weights involved in these activities which make them hard to

administer, or that there is no standardized procedure for

conducting strength tests other than those developed and

conventionally used in physical education and athletic

training. These problems may be easily overcome in today's

world, however, because of the great proliferation of health

clubs and gymnasiums around the country which allow for easy

access and use of this equipment. This becomes an even more

feasible alternative when one considers the use of machines

such as the Universal or the Nautilus which allow for quick

and easy adjustment of the weights and apparatus which can

greatly simplify the administration of the test.

14

There were two notable exceptions to the lack of use of

isotonic strength measures in the literature. The first was

the screening method developed by Smith and Ayoub (1983) for

the Air Force. As described earlier, this study incorporated

a weight machine which was used to develop predictive models

for simulated Air Force tasks. The success of this investi­

gation gave additional support to the use of these activi­

ties as predictive tasks for lifting models. The second was

a study conducted by Kroemer (1982) for NIOSH in which a de­

vice similar to the one used by Smith and Ayoub (1983) was

developed to predict lifting capacity. Based on his results

Kroemer concluded that the dynamic test appeared to be more

appropriate for employee screening than static strength

tests.

The only other actvities found in the liturature which

fall into the isotonic strength test catagory are static and

dynamic endurance. These are described by Ayoub et al

(1978) and involve the arm holding or repetitive lifting of

a submaximal load to exhaustion. While activities such as

these measure the endurance of only a small muscle group,

dynamic endurance has been shown to be significant in some

of the models, especially where arm lifting is involved

(NIOSH Work Practices Guide For Manual Lifting 1981).

15

Isokinetic Strength

Isokinetic strength is another form of dynamic strength

testing in which the motion involved in the activity is at a

constant velocity throughout the range of motion. Recent

studies by Pytel and Kamon (198 1) and Kamon et al (1982) in­

corporated the use of a commercially available device called

a Mini-Gym which was modified so that velocity and muscular

force could be monitored. The Mini-Gym was selected be­

cause of its portability, ease of administration, its limit­

ed demand on the subject and its ability to maintain a rela-

tivley constant velocity. In the first investigation by

Pytel and Kamon (1981) the variables of sex, dynamic lift

strength, dynamic back extension strength and dynamic elbow

flexion strength (see figure 2) at velocities of .73 m/s and

.97 m/s, were used to develop models for predicting maximum

dynamic lift. Maximum dynamic lift was determined as the

weight that an individual felt he or she could safely lift

to a height of 113 cm one time. Pytel and Kamon predicted

that a maximum acceptable weight of lift for 6 lifts/min was

about 22% of this one time maximum dynamic lift. This as­

sumption would allow comparison of their data to that of

most other data in the MMH literature which is based on the

maximum acceptable weight of lift.

16

DYNAMIC LIFT STRENGTH

DYNAMIC BACK EXTENSION DYNAMIC ELBOW FLE) STRENGTH STRENGTH

Figure 2: Strength Tests On The Mini-Gym

The r e s u l t s of the Pyte l and Kamon (t981) i n v e s t i g a t i o n

i n d i c a t e d that a t e s t i n g v e l o c i t y of . 7 3 m/s was super ior

for p r e d i c t i o n and that i t was a l s o c l o s e to the average

l i f t v e l o c i t y of a l i f t performed at 6 l i f t s / m i n . In the

models developed for predict ing maximum dynamic l i f t i t was

found that the model containing only sex and dynamic l i f t

s t r e n g t h predicted as wel l as the model conta in ing a l l of

the v a r i a b l e s .

The subsequent i n v e s t i g a t i o n by Kamon e t a l (1982) was

a f i e l d study based on the r e s u l t s of the f i r s t

i n v e s t i g a t i o n . The same three dynamic s trength t e s t s were

17

used at a velocity of .73 m/s. Static strength measurements

for back extension, elbow flexion and an isometric lift were

used as well. The results of this study did show that the

dynamic lifting method was superior to the static measures

for predicting maximum dynamic lift, but the overall results

were not as good as in the first study.

In another study by Aghazadeh (1982) a much more so­

phisticated device called an isokinetic dynomometer, made by

Cybex, was modified to measure isokinetic lifting ability. A

battery of isometric measures were made as well- Both iso­

metric and isokinetic strength measures were used to predict

maximum acceptable weights of lift for boxes and bags at

various heights and frequencies of lift. The results showed

that both isokinetic and isometric models predicted well but

it was determined that the isokinetic models were superior.

2iliS£ Measures

There are many other measures of an indiviual that

could be used as screening criteria that have not been con­

sidered so far. In this section measures which have appeared

in past models for predicting lifting capacities as well as

measures which are commonly taken in investigations of this

sort will be discussed. Some new measures which may be

useful will also be considered in this section.

18

Anthropometric Measures

As discussed in the NIOSH Work Practices Guide For Man-

ii§i Lifting t anthropometric measures alone are not good

predictors of lifting ability. Those that have appeared in

models include: sex, age» weight, stature, chest circumfer­

ence^ forearm circumference^ shoulder height, abdominal

depth, percent body fat and the reciprocal ponderal index

(RPI) which is defined as the body height divided by the

cul)e root of the body weight. By far the most common of

these are sex and weight with sex appearing in almost every

investigation in which it was a variable. The main reason

for taking anthropometric measures in these or any investi­

gation involving human physical performance is to describe

the population being studied.

Physiological Measures

Physiological measures for the control of MMH activi­

ties is an area which has received a great deal of attention

and research. The primary recommendations in the NIOSH Work

Practices Guide For Manual Lifting (198 1) for repetitive

work based on physiological critera are:

1. For occasional lifting (for one hour or less)

metabolic energy expenditure rates should not exceed

9 kcal/min for physically fit males or 6.5 kcal/min

for physically fit females.

19

2, For continous lifting (8 hour) energy expenditures

should not exceed 33X of aerobic capacity or 5.0

kcal/min and 3.5 kcal/min for males and females re­

spectively. These guidline limits do not reflect the

increased metabolic rates which would be associated

with overweight or unconditioned workers.

Physiological guidelines are very useful and important

parameters to be considered when controlling MMH activities.

However, it is surprising to find the limited use of physio­

logical measures in the development of psychophysical mod­

els. The only investigations found in the literature which

incorporated physiological measures were those by McDaniel

(1972) and Dryden (1973). In both of these investigations

the Harvard Step Test was used. According to the authors the

step test was chosen because of its simplicity, reliability,

and because it was a submaximal test and therefore presented

limited risk to the subjects. The Harvard Step Test scores

did enter into the predictive models indicating that futher

investigation into the use of physiological measures for

prediction of lifting ability may be useful. A possible al­

ternative to the Harvard Step Test is the Kasch Pulse

Recovery Test recommended by the YMCA (Myers et al, 1973) as

a test of physical fitness. This test is based on an

investigation by Kasch (1966) and, like the Harvard Step

20

Test, is a function of the recovery heart rate after a

standardized stepping activity. The advantages of the Kasch

Pulse Recovery Test are that it is based on more current

data and is scsewhat easier and less time consuming to ad­

minister.

Another physiological measure which could easily be

used is the physical work capacity as predicted by the nomo­

gram developed by Astrand (196 1). By measuring the steady

state heart rate of an individual at a known submaximal

workload the physical work capacity can be predictied using

the nomogram.

CHAPTER III

THE STUDY

Subjects

Fifteen male subjects were recruited from the student

population of the Texas Tech campus. The recruiting was ac-•

complished through the use of an advertisement in the campus

paper which briefly explained the nature of the investiga­

tion and the wage paid, which was $U.00 per hour. Females

were not used due to the limitations on the size of the

study. Studies by Drury (1975), Konz (1979), and Yates and

Kamon (1980) have found that females lifting capacity is

about 60% of that of males so the results of this investiga­

tion may be approximated for females.

An attempt was made to try to select subjects which

represent the U.S. population based on the height and weight

criteria shown in Table 1 . This is the same table used by

Aghazadeh (1982). The values in this table were determined

by using the stratifying method described by Ayoub and Hal-

comb (1976), and by using the data from a national health

examination survey (National Aeronautics and Space

Administration, 1978). This method divides the ranges of

height and weight into five equal proportions: (1) 1st to

21

22

20th percentile; (2) 20th to 40th percentile; (3) 40th to

60th percentile; (U) 60th to 80th percentile; and (5) 80th

to 99th percentile. By using a correlation coefficient of

.50 for height and weight the 25 numbers in the cells are

obtained. These numbers correspond to the number of

subjects for each height/weight percentile when the total

number of subjects equals 100. This same concept was used

when selecting the subjects for this investigation and the

results for this investigation are given as the numbers in

parentheses in Table 1.

Before the recruiting of any subjects began a proposal

was submitted to the Subject Use Committee of Texas Tech

University for approval. This proposal contained a

description of the study, the objectives, the risks

involved, a subject consent form, and procedures for

handling unexpected injuries. A copy of the subject consent

form is presented in Appendix A.

Variables

The dependent variable was the weight lifted as deter­

mined by the psychophysical method. The independent vari­

ables were task and operator related. The task related vari­

ables were container type and size, freguency of lift, and

23

TABLE 1

Height Weight S t r a t i f i e d Sample Plan

2 3 4 , 7

192 .5

W 175 .8 E 1 I b G s H . T

161 .5

144 .8

1 0 2 . 5

r

1 , r

V -

• 1

0 1

2

r i

1 2

t y

1 —. T

6 ] 11)

10 ,

1 1

2

4

1 4 1 (1)

1 4 1 (3)

1 6

r— -

2

4 1 (1)

1 8 1 (1)

1 4 1 (1)

1 2

- T —

8

1

6 i (1) i

4 (1) 1

4 (1)

4 (2)

2

r — - T

10 1

1 6 J (2) J

1 1 1 1

1 2 1

1 2 ]

1 0 1

6 2 . 7 6 6 . 7 68 .2 6 9 . 6 7 1 . 2 7 5 . 2

HEIGHT ( i n s . )

24

range of lift. The operator variables were the anthropome­

tric measures, isometric strength measures, isotonic

strength measures, isokinetic strength measures, predicted

physical work capacity and the step test score.

For the task related variables, the frequency of lift

and container type and size were constants while the range

of lift had two levels. The frequency was six lifts per

minute and the container was a 15X11.5X9 inch box. The rang­

es of lift were from the floor to shoulder height and from

knuckle to shoulder height. The values for all of the vari­

ables selected were comparable to those used in previous in­

vestigations.

With regard to operator variables, the anthropometric

measures used were age, weight, height, shoulder height,

knuckle height, abdominal depth, chest circumference, for­

earm circumference, reciprocal ponderal index and percent

body fat. The isometric strength measures were back exten­

sion, and shoulder, arm, and leg strengths. Isokinetic

strength measures were floor to shoulder, knuckle to shoul­

der and floor to knuckle lifts using the Cybex. Floor to

shoulder and knuckle to shoulder lifts were used for the

Mini Gym. These variables were chosen based on the fact that

they had appeared in previous predictive models. The

isotonic measures including, the overhead press, arm curl.

25

squat lift, and leg lift, on the Universal machine as well

as the arm curl and leg lift on the Nautilus machine were

chosen based on their similarity to the activities which ap­

peared in the models described by Smith and Ayoub (1983) and

on their similarity to the activities of the isometric and

isokinetic strength measures. Dynamic endurance, also an

isotonic measure, has appeared in previous models and was

included for that reason. The step test used was the Kasch

Recovery Test (Myers et al, 1973) instead of the Harvard

Step Test due tc the Kasch's greater ease of use and the re­

cency of the data on which it was based. The physical work

capacity as predicted by Astrand's (1961) nomogram was also

used.

Procedures and Eguipment

Preliminary Activities

Upon responding to the advertisement the subject was

given a brief description of the study and of what was re­

quired of him. He was also questioned about his current

state of health, any chronic health problems he may have,

and about any past musculoskeletal injuries he may have had,

particularly to the lower back. If no health problems

existed and the subject was agreeable, an appointment was

set up for the subject to come in for further information

26

and evaluation. At this appointment the study was more

thoroughly explained and the equipment was demonstrated. The

subject filled cut a "Personal fledical History Questionaire"

(Appendix A) and his height and weight were measured so that

he could be placed into the height/weight stratification

scheme. Next, an appointment was made for the subject to re­

ceive a physical examination by a physician. After the phys­

ical an appointment for the subject^s first session was

made.

The subject reported to the first experimental session

wearing light gym clothing and athletic shoes. The experi­

mental procedure was explained again in detail, and the sub­

ject signed the "Consent Form" (Appendix A). The session

then began.

Psychophysical Lifting Capacity

The method and equipment for determining psychophysical

lifting capacity used in this study were essentially the

same as those used by Ayoub et al (1978). A 15X11.5X9 inch

box with handles was used for lifting from the floor to

shoulder height and from knuckle height to shoulder height

at a frequency of six lifts per minute. An adjustable

lowering device was used to return the box to its initial

starting position. The lowering machine is shown in figure 3

27

Figure 3: Box And Lowering Machine

28

Irregularly shaped weights and an unknown initial load,

generally around 20 pounds, were used so that the subject

was not aware of the exact amount of weight being lifted. A

metronome signaled the subject to lift at the given freguen­

cy and he lifted for about 25 minutes, adding and taking

away weights until he found a load that he felt he could

lift under the given conditions for an eight hour day. The

subject was carefully instructed to lift as much as he could

based on his estimate of his working endurance capability

without becoming overheated, unusually fatigued, weakened or

out of breath. At the end of the lifting period the subject

was instructed to stop and the box was weighed. This value

was recorded as the maximum acceptable veight of lift.

During the last 15 to 20 minutes of the lifting the

subject's heart rate was monitered using a battery operated

heart rate moniter with a digital read out. The heart rate

monitor was an Exersentry model made by Respironics (figure

4). Four readings were taken at about 3 to 5 minute inter­

vals and the average of these was used as a steady state

working heart rate. According to the recommendations in the

NIOSH Work Practices Guide For 'Manual Lifting (1981), 33

percent of the aerobic capacity should be assumed for an 8

hour work duration. Since heart rate and aerobic capacity

are linearly related this same limit can be applied based on

heart rate. By adding 33 percent of the heart rate ran^e

29

Figure 4: Exersentry Heart Rate Monitor

30

(maximum heart rate - resting heart rate) to the resting

heart rate, an estimate of the steady state working heart

rate can be obtained. By comparing this to the actual steady

state working heart rate any individuals who were working

much too hard or not nearly hard enough could be identified

and their data for that session not included in the

analysis. This was necessary in only a few of the cases and

in all cases at least one acceptable psychophysical weight

of lift was found.

Anthropometric Measures

The following anthropometric measures were taken and

recorded on the data collection form. They are the same as

those used by Ayoub et al (1978).

- Weight - Height - Acromial Height - Standing Iliac Crest Height - Knuckle Height - Knee Height - Forearm Grip Distance - Chest Width - Chest Depth - Abdominal Depth - Chest Circumference - Abdominal Circumference - Forearm Circumference - Biceps Circumference - Thigh Circumference - Calf Circumference

31

The equipment used was an anthropometric kit manufac­

tured by GPM and marketed by Pfister Import-Export, Inc.

(Carlstadt, N.J. 07072). The raw and summary data for the

anthropometric measures are given in Appendix B.

Physiological Measures

The procedures and eguipment for the measurement of

physical work capacity were essentially the same as those

used by Ayoub et al (1978). The subjects were asked not to

eat, smoke or drink carbonated beverages for at least 2

hours before the experiment. The Exersentry was used for

the recording of heart rate. A head set and mouthpeice with

a one way valve which was connected to a Beckman Metabolic

Measurement Cart for the recording of oxygen consumption was

then fitted to the subject. After the equipment was in place

and working, the subject was seated on a Fitron Cycle-Ergom-

eter made by Cybex. The seat and handle bar height of the

ergometer were then adjusted so that the subject could pedal

comfortably.

The test was conducted by having the subject pedal for

four minute intervals at loads of 400, 600, and 800 kpm/min.

The oxygen consumption and heart rate were recorded at the

end of each of these intervals and the physical work

capacity was extrapolated for the predicted maximal heart

32

rate of 220 - his age. The oxygen consumption in 1/min was

converted to ml/kg*min. The heart rate for the 600 kpm/min

workload was used for the prediction of PWC with the Astrand

(1961) nomogram.

The protocol for the Kasch Pulse Recovery Test was the

same as that used by the YMCA (Myers et al, 1973). The sub­

ject began the test by stepping up and down onto a 12 inch

bench at a rate of 24 cycles/min. A cycle was completed by

stepping up onto the box leading with one foot, and then

stepping down off of the box leading with the same foot.

The pace was maintained with the use of a metronome and the

activity continued for a period of 3 minutes. At the end of

three minutes the subject sat down and after 5 seconds his

heart rate was taken for 60 seconds. This heart rate value

was recorded and was used in the formulation of the mathe­

matical models.

The raw and summary data for the physiological measures

as well as percent body fat and reciprocal ponderal index

are given in Appendix B.

Isometric Strength

The equipment and methods for the measurement of iso­

metric strength were the same as those in the investigation

by Ayoub et al (1978). The isometric strength measures taken

33

were for back extension, and shoulder, arm and leg strength.

The procedures and specific pieces of equipment for each

isometric strength test is given in Appendix C. The load

cell used in the isometric strength testing protocal (Model

CA1000-IB-L10) had a capacity of 1000 pounds. The load cell

and it's digital readout unit (Model HSC-11) were manufac­

tured by Ametek Control Division (Feastville, Pa.). It was

calibrated regularly to maintain accuracy. Each subject was

allowed to become familiar with the test equipment and pro­

cedures before the data collection began. The testing was

done by having the subject slowly exert force to his maximum

without jerking and maintaining the peak value for a minimum

of four seconds. This was repeated until three trials were

found to fall within 10 percent of each other. A minimum of

two minutes rest was given between successive trials. The

raw and summary data for these measures is given at the end

of Appendix D.

Isotonic Strength Measures

The equipment used for the isotonic strength tests were

a Universal machine shown in figure 5 and a Nautilus machine

shown in figure 6 . The activities performed on the

Universal were an overhead press, an arm curl, a squat lift,

and a leg extension. It was originally desired to have the

34

P i v:;j r:2 c , -r^ •

l e

35

Figure 6: Nau t i lus Machine

36

subjects perform the same activities on the Nautilus machine

as they did on the Universal machine. However, the Nautilus

equipment available would only allow the arm curl and leg

extension strength tests. Procedures for performing each of

these activities are given in Appendix E. It should be noted

that a different piece of eguipment was used to perform the

squat lift. This is shown in Appendix E along with the sguat

lift. The raw and summary data for the isotonic strength

tests are given at the end of Appendix E.

An incremental lift to maximum was used to determine

the subject's strength for these activities. In this proce­

dure the subject began by lifting a submaximal amount of

weight which was unknown to him. When possible a cloth was

used to cover the weights so that the subject could not see

how much he was lifting. If the weight was lifted success­

fully an additional amount of weight was added and the sub­

ject lifted again. If the subject was successful at lifting

this weight a weight increment equal to the first addition

of weight was added. This procedure continued until the sub­

ject was not able to lift the weight. The weight that he

last successfully lifted was recorded as his maximum. The

initial submaxinal weight and the weight increments for a

particular activity were chosen based on 50 percent of the

static strength measure of a similar activity, and the

37

limitations of the machines, respectively. The only

exception to this was the squat lift in which 30 percent of

the isometric leg strength was used for determining the ini­

tial weight. These values allowed the subject to reacn his

maximum within a short period of time and without becoming

unduely fatigued. A minimum of 5 minutes rest was given be­

tween any two activities to allow for recovery.

Dynamic endurance was also included under isotonic

strength. The equipment and procedures for this were taken

from Ayoub et al (1978) and are .given at the end of Appendix

E.

Isokinetic Strength Measures

The isokinetic strength measures fall into two catago­

ries based on the type of equipment used. The first was a

modified Cybex Isokinetic System (Cybex Division of Lumex

Inc.; Bayshore, N.Y. 11706) shown in fiqure 7 . This was the

same device described by Aghazadeh (1982). The major modifi­

cation of the Cybex was that a large wheel with an attached

cable and handle had been added so that the normal circular

motion of the device had been converted to linear motion.

This set up allowed for torgue readings on the Cybex

throughout the entire lifting range of motion. The speed was

set on the Cybex such that the resulting linear speed of the

38

PijuE-^ 7: : i o l i f i ' 3 l Cyhex ; i acn ine

39

lift was 30 inches/sec. The use of this speed was supported

by both Aghazadeh (1982) and Pytel and Kamon (1981). Stops

were placed on the cable so that the ranges of motion for

the lift were from floor to shoulder, knuckle to shoulder

and floor to knuckle.

For the floor to shoulder and knuckle to shoulder lifts

the subject started in a sguat position with his arms be­

tween his knees and his forehead barely touching the cable

(figure 8). For uniformity and safety reasons this starting

position was strictly adhered to for all subjects. To per­

form the lift the subject was instructed to lift the handle

as quickly as he could without a jerk or sudden motion and

to exert maximal force throughout the range of motion. The

subject was given a few practice lifts until he was comfor­

table with the exercise. He then performed the test three

times with two minute rests between each performance. The

torques produced during these lifts were recorded on a strip

chart and the peak values taken as the measure of isokinetic

strength. The starting position for the knuckle to shoulder

lift had the subject standing erect with his feet shoulder

width apart and gripping the handle with arms fully extended

[figure 9) .

The second method used for i s o k i n e t i c s t rength t e s t i n g

was t h a t used by P y t e l and Kamon (1981) and by Kamon e t a l

40

:i Tur=» 3 Startir.g positijn lor floor to shouliar ani floor to Xnuc'clG liftG

41

r I 4r 4

f

<ieilSt*

i . ; u r 9 9; S t a r t i na g i ^ o s i t i o n r j r h n a c x l c t o : i h o u l i o r l i f t

42

(1982). In this method a Mini-Gym (Model 101) with modifica­

tions was used (figure 10). The modifications were: (1) a

3X3 foot platform enclosing the Mini-Gym was used so that

the handle was approximatly 2 inches above the subjects an­

kle; and (2) a load cell was placed in line just below the

handle to measure the force exerted. The instructions and

activity of the subject were essentially the same as with

the Cybex except that a straight bar and underhand grip were

used with the Mini-Gym instead of the side grip used with

the Cybex. The peak values registered on the load cell were

recorded as the isokinetic strength for the Mini-Gym. As in

the Cybex procedures, three measures were taken with two

minutes' rest between each measure and the average of these

values used as the score on the test.

Although the equipment and procedures for the use of

the Mini-Gym were essentially the same as those used by Py­

tel and Kamon (1981) there were two major differences. The

first was in the setting of the speed of the Mini-Gym. In

the Pytel and Kamon (1981) study a device for constantly

monitoring the speed of the Mini-Gym was used. Due to the

cost of installing such a device and the fact that Pytel and

Kamon (1981) found the Mini-Gym to be able to maintain a

constant velocity, this device was not used in this study.

Instead, a known distance was marked off on the feeding line

43

^

Figure 10: Modified Mini-Gym

44

of the Mini-Gym and a stop watch was used to time its travel

while the Mini-Gym was being used. This allowed for the com­

putation of the velocity of the movement. When tested this

method was found to be a fairly reliable.

The second difference in procedures was in the selec­

tion of velocities for which the Mini-Gym was set. It was

originally intended that the testing be done at 30 in/sec

which was the optimal speed found by Pytel and Kamon (1981)

and the same speed used by Kamon et al (1982) and Aghazadeh

(1982). In this investigation, however, the speed of 30 in/

sec could not be attained. When it was attempted to adjust

the Mini-Gym to go that slowly the clutch mechanism which

controls the speed would seize up after about 30 to 40 inch-

as of travel which was insufficient for testing. As a result

the slowest attainable speed was 38 in/sec. This happened to

be the second speed used by Pytel and Kamon (1981) in their

study. Two other speeds, 41.6 in/sec and 45.5 in/sec, were

used as well. Pytel and Kamon (1981) found that for the

floor to shoulder lift there was no significant difference

between the scores, and that for the knuckle to shoulder

lift there was no difference between the scores for 38

in/sec and 41.6 in/sec, but 45.5 in/sec was different from

the other two. The statistical results for the ANOVA

procedure and Duncan Multiple Range test are given in Table

45

2 and Table 3 , r e s p e c t i v e l y . Speeds of 38 i n / s e c f o r the

f l o o r t o s h o u l d e r l i f t and the knuckle t o s h o u l d e r l i f t , and

4 5 . 5 i n / s e c f o r t h e knuckle to s h o u l d e r l i f t were used for

t h e model d e v e l o p m e n t . The raw s c o r e s and summary data f o r

t h e Cybex and Mini-Gym are g i v e n i n Appendix F.

TABLE 2

Comparison of Mini-Gym Speeds f o r F l o o r to Shoulder

DUNCAN GROUPING

A A A A \

MEAN

1 6 5 . 0 0

1 5 1 . 0 0

1 5 0 . 13

AL?HA = 0 . 0 5 DF = 42 :3SE=932.089 MEANS TTTH THE SAME LETTER ARE MOT SIGNIFICANTLY DIFFERENT.

N SPEED ( i n / s )

15

15

15

J

4 5 . 5

38

4 1 . 6

46

TABLE 3

Comparison of Mini-Gym Speeds for Knuckle to Shoulder

DUNCAN GROUPING MEAN N SPEED (in/s)

A A A

64.367

62.600

54.333

15

15

15

45.5

41.6

38

ALPHA^O.05 DF=42 MSE^I17.968 MEANS WITH THE SAME LETTER ARE NOT SIGNIFICANTLY DIFFERENT.

I .J

CHAPTER IV

ANALYSIS AND RESULTS

The design of the experiment had the data collection

running in a 2 1/2 day cycle with four subjects being run in

each cycle. The exercises were grouped based on the type of

equipment used so that all of those done on the Cybex were

done together, all of those on the Universal were done to­

gether and so on throughout the rest of the exercises. Ade­

quate rest was given between each of the activities so that

the subjects would not become fatigued. The exercises within

each activity were administered in random order so as to

eliminate any systematic errors due to order.

The SAS statistical package was used for the data anal­

ysis which began by first summarizing the data giving the

means, standard deviations, maximums, minimums and coeffi­

cients of variation for all of the varaiables. These are

given at the ends of the respective appendicies.

Due to the large number of independant variabiles and

the limited sasple size it was necessary to eliminate as

lUany of the non-contributing variables as possible and to

break the variables down into groups for the model

development. The grouping was done based on the different

types of equipnent used for the strengtn testing so that

47

48

five different models were developed for predicting

acceptable weights of lift for both floor to shoulder and

knuckle to shoulder lifts.

The coefficients of variation for the data were then

examined and based on this data set. The following criteria

were used for variable selection:

c.V. < .1 eliminate

.1 < c.V. < .15 consider

c.V. > .15 accept

These criteria were based on the assumption that variables

with larger coefficients of variation will generate models

which are more general and not specific to this data set.

As a result of this procedure the following variables were

found to be acceptable; all of the strength measures, dynam­

ic endurance, the step test, percent body fat and PWC as

predicted by the Astrand Nomogram. The variables which fell

into the considered catagory were; weight, chest depth, ao-

dominal depth and abdominal circumference. All other vari­

ables were rejected.

The next step in the analysis was to determine the

correlations between the selected variables and select only

one variable from a group of highly correlated variables so

as to eliminate as much colinearity between the variables

49

chosen for the modeling as p o s s i b l e . Al l of the s t r e n g t h

v a r i a b l e s were found t o be h igh ly corre la ted so tha t only

one was s e l e c t e d for each of the groupings . A l l of the v a r i ­

a b l e s which f e l l i n t o the cons idered catagory based on the

c o e f f i c i e n t of v a r i a t i o n were a l s o found to be highly c o r r e ­

l a t e d , so t h a t only weight was s e l e c t e d for c o n s i d e r a t i o n i n

the modeling. The remainder of the v a r i a o l e s were not found

to be highly c o r r e l a t e d .

As a r e s u l t of the previous a n a l y s i s the f o l l o w i n g

v a r i a b l e s were s e l e c t e d for modeling:

1. Cybex f l oor to shoulder l i f t .

2 . Mini-Gym f l o o r to shoulder l i f t

at 3 8 i n / s e c .

3. I sometr i c shoulder s t r e n g t h .

4 . Universa l overhead l i f t .

5. N a u t i l u s arm s t r e n g t h .

6. Dynamic endurance.

7. Predicted PWC.

8. Step t e s t .

9 . Percent body f a t -

10. Weight.

50

As mentioned b e f o r e , models based on each of the

d i f f e r e n t s t rength measures were developed. I t was a l s o f e l t

t h a t while they were not h igh ly c o r r e l a t e d , predic ted PWC

and the s t e p t e s t , as wel l as percent body f a t and we ight ,

were e s s e n t i a l l y measuring the same parameters, and t h e r e ­

fore were not inc luded in the same models.

The RSQUAEZ and GLM (General Linear Models) procedures

in the SAS package were then used for the actual model de­

velopment. Through t h i s a n a l y s i s , models for each of the

groups were developed and are g iven in t a b l e 4 for p r e d i c t ­

ing maximum a c c e p t a b l e weight of l i f t from f l o o r to shoulder

he ight and in tab le 5 for maximum acceptaiale weight of l i f t

for knuckle t o shoulder he ight . As can be seen in the t a b l e s

a l l of the models c o n t a i n three v a r i a b l e s with the s t e p t e s t

and percent body f a t being common to a l l of them. Dynamic

andurance could a l s o have been included in these models but

i t was excluded because i t did not s i g n i f i c a n t l y c o n t r i b u t e

to the models.

As can be seen i n the t a b l e s the r-square v a l u e s for

t h e s e models are f a i r l y low. These values could be i n c r e a s e d

cy the a d d i t i o n of lore v a r i a b l e s but t h i s would a l s o aiake

them much aore s p e c i f i c to t h i s data s e t . The l i m i t e d sample

s i z e a l s o r e s t r i c t e d the t o t a l number of v a r i a b l e s . The

Tiodels do g ive an i n d i c a t i o n of the r e l a t i v e p r e d i c t i o n

51

TABLE 4

Models For Floor To Shoulder Lift

Model

6 . 2 8 2 + . 1 0 5 CFS > . 1 6 5 STP - . 3 4 1 BDFT

4 . 6 2 2 ^ . 1 5 7 MG8 *- . 1 4 8 STP - . 1 5 4 BDFT

R - s g u a r e MSE

. 6 3 7 4 3 - 1 2

533 55 .07

9 . 8 6 5 + . 1 4 C UO • . 1 7 6 STP - . 1 0 6 BDFT . 22b^ 6 7 . 9 5

2 . 0 6 0 * . 2 6 3 NA ^ . 2 2 4 STP - . 0 3 6 BDFT 216 6 9 . 0 9

2 4 . 7 5 0 + . 0 6 4 IMS * . 1 3 6 STP - . 1 4 2 BDFT . 1 1 8 7 7 . 7 0

KEY

V a r i a b l e

CFS

MG3

UO

NA

IMS

STP

BDFT

Name

Cybex F l o o r t o S h o u l d e r l i f t .

Mini-Gym f l o o r t o s h o u l d e r l i f t a t 3d i n / s e c .

U n i v e r s a l O v e r h e a d l i f t

N a u t i l u s Arm l i f t

I s o m e t r i c S h o u l d e r s t r e n g t h

S t e p t e s t

Percent Body Fat

Units

ft.lbs

lbs

l b s

l b s

l b s

Heart Bea t s

Percen t

52

TABLE 5

Model F o r K n u c k l e To S h o u l d e r L i f t

Model R - s q u a r e MSE

7 . 6 9 2 • . 1 5 4 CFS + . 1 8 2 STP - . 8 8 2 BDFT . 6 7 3 7 3 . 5 6

1 0 . 6 1 9 > . 1 6 6 MG8 * . 2 4 9 STP - . 3 8 0 BDFT . 5 3 3 7 9 . 2 5

1 8 . 9 3 4 f . 1 5 6 IMS > . 2 4 3 STP - . 6 9 0 BDFT . 4 9 3 3 5 . 9 2

- 1 . 4 8 4 • . 3 5 5 NA > . 3 5 6 STP - . 6 8 7 BDFT . 4 9 2 3 6 . 1 2

1 1 . 3 0 0 * - 1 7 6 UO + . 2 8 8 STP - . 7 9 7 BDFT . 4 8 5 8 7 . 3 3

KEY

V a r i a b l e Name U n i t s

CFS Cybex F l o o r t o S h o u l d e r f t . l b s l i f t .

MG8 Mini-Gym floor to shoulder lbs

l i f t at 38 in/sec.

UO Universal Overhead l i f t lbs

NA N a u t i l u s Arm l i f t l b s

IMS I s o m e t r i c S h o u l d e r s t r e n g t h l b s

STP S t e p t e s t H e a r t B e a t s

BDFT P e r c e n t Body F a t P e r c e n t

I

53

a b i l i t y between the v a r i o u s s t r e n g t h measures so t n a t they

can be compared to one a n o t h e r .

An e x a m i n a t i o n of the models r e v e a l s n e g a t i v e c o e f f i ­

c i e n t s f o r p e r c e n t body f a t in a l l of t h e models . I n a s tudy

c o n d u c t e d by Knipfer (1974) , a p r o c e d u r e c a l l e d Ridge Re­

g r e s s i o n was used t o e l i m i n a t e the n e g a t i v e c o e f f i c i e n t s i n

h i s l i f t i n g models . What t h i s p rocedu re does i s t o i n c l u d e

a s c a l i n g f a c t o r i n t o the model so a s to account f o r any

c o l i n e a r i t y between t h e v a r i a b l e s which laay be c a u s i n g a

c o e f f i c i e n t t o he n e g a t i v e . Th i s p rocedure was a p p l i e d t o

t h e c u r r e n t niodels bu t c o l i n e a r i t y was not found to oe a

f a c t o r in the s i g n s of t he c o e f f i c i e n t s .

CHAPTER V

CONCLUSIONS AND RECOMMENDATIONS

This investigation resulted in the development of mod­

els for predicting maximum acceptable weights of lift for

floor to shoulder and knuckle to shoulder heignt lifts. Five

models were developed for each type of lift based on five

different pieces of strength testing apparatus- While none

of these models produced results comparable to those found

in past studies they are felt to be good general models and

do give a basis for comparison of the predictive ability of

each of the different types of strength measures.

The modified Cybex Isokinetic Dynomometer produced the

best results with r-squares of .552 and .573 for the floor

to shoulder and knuckle to shoulder lifts, respectively.

This is in agreement with Aghazadeh (1982). There are some

drawbacks to the Cybex, however, primarily in its much high­

er cost with respect to the other pieces of equipment as

well as its lack of portability. Another problem with the

Cybex is that when performing the activities in this inves­

tigation, particularly the floor to shoulder lift, the

forces produced approach the machine's capacity and the

Z'jcer. output aay become unreliable at these loads. This was

the case for three of the subjects in this investigation lor

which the data could not be used.

54

55

The Mini-Gym gave the next bes t r e s u l t s with an

r - s q u a r e of .375 for the f loor to shoulder l i f t and an r -

sguare of .533 for the knuckle to shoulder l i f t . These r e ­

s u l t s seem to be f a i r l y c o n s i s t e n t with those of P y t e l and

Kamon (1981) and Kamon e t a l (1982) who a l so used the Mini-

Gym as a p r e d i c t i v e t o o l for l i f t i n g c a p a c i t y . Though i t

does not p r e d i c t q u i t e as well as the Cybex i t s p o r t a b i l i t y

and lower cos t do tend to make i t more d e s i r a b l e as a

s c r een ing measure. Some a d d i t i o n a l f indings on the Mini-Gym

were: 1) The speeds used in t h i s study made l i t t l e to no

d i f f e r e n c e in the s t r e n g t h measures; and 2) The lower speed

used in the Pytel and Kamon (1981) and Kamon et a l (1982)

s t u d i e s was not a t t a i n a b l e in t h i s i n v e s t i g a t i o n . This may

i n d i c a t e some problems in the r e l i a b i l i t y of the d e v i c e .

The remaining nodels based on the Universal machine.

N a u t i l u s machine and i somet r ic s t r eng th eguipment were in

g e n e r a l f a i r l y comparable to each other but not as good a s

the Cybex and nini-Gym. I somet r i c s t r eng th t e s t s nave p r o ­

duced b e t t e r models in the past in numerous o ther i n v e s t i g a ­

t i o n s and i t i s not e n t i r e l y c l e a r as to why they f a i l e d to

do so in t h i s c a s e . The Universal and Naut i lus machines were

t e s t e d for the f i r s t time in t h i s i n v e s t i g a t i o n and while

they did not do as well as might have been expected they

s t i l l produced marginal ly a c c e p t a b l e r e s u l t s . Par t of the

56

problem may have been that they could only be incremented

ten or twenty pounds at a time and that this may not be dis­

crete enough for modeling purposes. Further investigation is

needed to determine their suitability for modeling purposes.

All of the Nautilus and Universal measures are guick, easy,

safe and relativily inexpensive so that they should not be

completely discounted without further investigation.

The step test was found to enter into all of the models

and did only slightly better than the PWC as predicted by

the Astrand Ncaogram. This was an interesting finding,

since, with the exception of McDaniel (1972) and Dryden

(1973), most of the previous models for predicting psycho­

physical lifting capacity had not included a physiological

measure. It is speculated that physiological variables may

play a more important role when higher frequencies are used.

Based on the results of this study and the above dis­

cussion the following recommendations are made:

1. A larger sample size is needed and more parameters in

the task related variables should be investigated

(i.e., frequency of lift, height of lift, etc.)

2. In agreement with earlier studies the Cybex and

Mini-Gym produced the best results for prediction of

lifting ability. Due to these findings and the fact

that these activities closely simulate the actual

57

l i f t i n g a c t i v i t y in both motion and speed, further

i n v e s t i g a t i o n in to the ir use for t h i s purpose i s

s trongly recommended.

3 . A method for standardizing the Mini-Gym speed for re­

l i a b i l i t y between machines i s needed.

4. Strength measures on both the Universal and Nautilus

machines should be examined more c l o s e l y with regard

to both method and r e l i a b i l i t y of measurements. Modi­

f i c a t i o n s to the equipment which would allow for a

better simulation of the l i f t i n g a c t i v i t y for both

motion and speed should be explored.

5. The appl i ca t ions of simple phys io logical measures

such as the step t e s t and predicted PWC should be

given more careful consideration in future modeling

e f f o r t s .

BIBLIOGRAPHY

Accident F a c t s 1978 and 1981 e d i t i o n s . Chicago, I l l i n o i s : Nat iona l Safe ty Counc i l .

Aghazadeh, F. "Simulated Dynamic L i f t i n g Models For Manual L i f t i n g . " PhD. D i s s e r t a t i o n , Texas Tech U n i v e r s i t y ,

• 1982.

Ayoub, M. M.; Bethea, N. J . ; Deivanayagam, S . ; Asfour, S. S. ; Bakken, G. H.; L i l e s , D. H. ; J l i t a l , A. and Sher i f , M, Determinat ion and Modeling of L i f t ing Capacity . F ina l Report, DHEW (NIOSH) Grant i?os. IR010fl00545-01SOH and 5R010H-00545-02, 1978.

Ayoub, fl. M. and Halcomb, C. G. Improved Seat Console Design. F i n a l Report, Department of"*the Navy, Contract No. N61756-75-M-2986, October, 1976.

Ayoub, H. M.; L i l e s , D.; Asfour, S. S. ; Bakken^ G. M. ; Mi ta l , A. and S e l a n , J. L. "Ef fec t s of Task Variables on L i f t i n g Capac i ty ." F ina l Report , HEW (NIOSH) Grant No. 5R010H00798-C4, August, 1982.

C a l d w e l l , L. S. ; Chaf f in , D. B. ; Dukes-Dobos, F. N. ; Kroemer, K. B. E . ; Laubach, I . L . ; Snook, S. H. and Wasserman, D. F. "A Proposed Standard Procedure For S t a t i c Muscle Strength T e s t i n g . " American I n d u s t r i a l Hygiene A s s o c i a t i o n Journal , 3 5 , 1974, pp. 2 01-205.

C a r l s o o , S. "A Back L i f t Tes t ." Applied Ergonomics, 1 1 ( 2 ) , 1980, pp . 6 6 - 7 2 .

C h a f f i n , D. B. "Ergonomics Guide for the Assesment of Human S t a t i c S trength ." American I n d u s t r i a l Hygiene A s s o c i a t i o n Journal 3 6, 1975, pp. 505-510 .

Drury, C. G. and P f i e l , R. E. "A Task Based Model of Manual L i f t i n g Performance." I n t e r n a t i o n a l Journal Of Production Research 13(2)7 ^975, pp. 137-148.

Dryden, R- D. "A P r e d i c t i v e Model for the Maximum P e r m i s s i b l e i e i g h t of L i f t from Knuckle to Shoulder H e i g h t . " PhD. D i s s e r t a t i o n , Texas Tech U n i v e r s i t y , 1973.

58

59

Garg, A. and Ayoub, M. M. "What Criteria Exist for Determining How Much Load Can Be Ufted Safely." Human Factors 22(4), 1980, pp. 475-486.

Jones, D. F. "Back Strains: The State Of The Art." Journal ^ Safety Research 3(1), 1971, pp. 28-34.

Kamon, E.; Kiser, D. and Pytel, J. L. "Dynamic And Static Lifting Capacity And Muscular Strength Of Steel Mill Workers." Aaerican Industrial Hygiene Journal 43(11), 1982, pp. 853-857.

Kasch, F. H. ; Phillips, ». H.; Ross, W. D.; Carter, J. E. L. and Boyer, J. L. "A Comparison of Maximal Oxygen Uptake by Treadmill and Step-Test Procedures." Journal Of A£2lied Physiology 21(4), 1966, pp. 1387-13887"

Knipfer, E. E. "Predictive Models for the Maximum Acceptable Weight of Lift." PhD. Dissertation, Texas Tech University, 1974.

Konz, S. Work Cesign. Columbus, Ohio: Grid Publishing Inc., 1979.

Kroemer, K. H. F. Development of "LIFTEST." A dynamic Technique to Asses the Capability to Lift Material7 Final Report, NIOSH contract 210-79-0041, 1982.

Legg, S. J. "The Effects of Abdominal Muscle Fatigue and Training on the Intra-Abdominal Pressure Developed During Lifting." Ergonomics 24(3), 1981, pp. 191-195.

McDaniel, J. W. "Prediction of Acceptable Lifting Capability." PhD. Dissertation, Texas Tech University, 1972.

Meyers, C. fi. ; Golding, L. A. and Sinning, W. E. The Yj s Way To Physical Fitness. Hodale Press, 1973.

National Aeronatics and Space Administration. Anthropometric Source Book Volume II: A Handbook of Anthropometric Data. NASA Reference Publication T024, Scientific and Technical Information Office, 1978.

Norby, E. J. "Epidemiology and Diagnosis in Low Back Injury." Occupational Health And Safety January, 1981.

60

Nordgren, B.; Scheie, fi- and Linroth, K. "Evaluation and Prediction of Back Pain During Military Field Service." Scandinavian Journal Of Rehabilitation Medicine 12(1), 1980, pp. 1-8.

Preemployment Strength Testing DHHS (NIOSH) Publication No. 77-163, May, 1977."

Pytel, J. L. and Kamon, E. "Dynamic Strength Test As A Predictor For Maximal And Acceptable Lifting." Ergonomics 24(9), 1981, pp. 663-672.

Rowe, M. L. "Preliminary Statistical Study Of Low Back Pain." Journal Of Occupational Medicine 5, 1963, pp. 336-341.

Rowe, M. L. "Low Back Pain In Industry: A Position Paper." Journal Of Occupational Medicine 11, 1969, pp. 161-164.

Rowe, M. L. "Low Back Pain: Updated Position." Journal Of Occupational Medicine 13, 1971, pp. 476-478.

Smith, J. L. and Ayoub, M. M. "Interim Modification of the X-Factor Test." Final Report, Contract No. F33625-78-D-C629-0037, Institute for Biotechnology, Texas Tech University, June, 1982.

Snook, S. H. ; Campanelli, B- A. and Hart, J. W. "A Study of Three Preventive Approaches to Low Back Injury." Journal Of Occupational Medicine 20(7), 1978, pp. 478-481.

Work Practices Guide For Manual Lifting. DHHS (NIOSH) Publication Ko. 81-122, March 1981.

Yates, J. W. and Kamon, E. "Static Strength and Maximum Isometric Voluntary Contraction of Back, Arm and Shoulder Muscles." Ergonomics 23(1), 1980, pp. 37-47.

APPENDIX A

CONSENT FORM AND PERSONAL MEDICAL HISTORY QUESTIONAIRE

61

62

PERSONAL CONSENT FORM

E i § ^ £ r e a d c a r e f u l l y

I t i s t h e p u r p o s e of t h i s i n v e s t i g a t i o n t o d e v e l o p m a t h e m a t ­

i c a l mode l s f o r p r e d i c t i n g an i n d i v i d u a l s a b i l i t y t o l i f t

b a s e d on v a r i o u s s t r e n g t h m e a s u r e s . T h i s w i l l a l l o w f o r t h e

s c r e e n i n g of e m p l o y e e s i n i n d u s t r y so t h a t t h e y c a n oe

p l a c e d in j o b s t h a t w i l l no t p u t them a t r i s k of i n j u r y due

t o l i f t i n g .

I h e r e b y g i v e c o n s e n t f o r my p a r t i c i p a t i o n i n t h e p r o j e c t

e n t i t l e d "ALTERNATIVE STRENGTH TESTING METHODS FOR EMPLOYEE

SCREENING". I u n d e r s t a n d t h a t t h e p e r s o n r e s p o n s i b l e f o r

t h i s p r o j e c t i s Dr. J . L. S m i t h , t e l e p h o n e number (806)

7 4 2 - 3 4 1 0 .

D r . J . L. Smi th o r h i s r e p r e s e n t a t i v e h a s a g r e e d t o answer

any i n q u i r i e s I nay have c o n c e r n i n g t h e p r o c e d u r e s . I have

a l s o been i n f o r m e d t h a t I may c o n t a c t t h e Texas Tech Uj i iye£-

2i . t . l I n s t i t u t i o n a l Review 3oard f o ^ t h e P r o t e c t i o n of Human

Su h-j ec^s by w r i t i n g them in c a r e of t h e O f f i c e of R e s e a r c h

S e r v i c e s , T e x a s Tech U n i v e r s i t y , Lubbock , Texas 79409 , o r by

c a l l i n g (806) 7 ^ 2 - 3 8 8 4 .

63

Dr. Smith or his authorized representative has explained tne

procedures to be followed and identified those which are ex­

perimental and described the attendant discomforts and risks

as follows:

1. Briefly the procedures are:

a) Pass a physical examination (at no personal ex­

pense) .

b) Measurement of various body diaensions including

percent body fat.

c) Deteruination of physical work capacity using sub-

maximal tests.

d) Measurement of maximum voluntary strength by per­

forming activities of increasing demand until I

reach but do not exceed my maximum on a Dattery of

static and dynamic strength tests. The strength

tests will be performed on standard equipment like

the Universal, Nautilus and Cybex machines.

2. The risks have been explained to jie as follows: mus-

cle spraines or straines, pulled tendons. nack pain

2£ sprain, hernia, stroke, myocardial iilfarctigji, or

herniated disc.

64

I f t h i s r e s e a r c h p r o j e c t c a u s e s any p h y s i c a l i n j u r y t o p a r ­

t i c i p a n t s in t h i s p r o j e c t , t r e a t m e n t i s not n e c e s s a r i l y

a v a i l a b l e a t Texas Tech U n i v e r s i t y or t he S tuden t Hea l th

C e n t e r , nor i s t h e r e n e c e s s a r i l y any i n s u r a n c e c a r r i e d by

t h e U n i v e r s i t y or i t s p e r s o n n e l a p p l i c a b l e t o cover any such

i n j u r y . F i n a n c i a l compensat ion f o r any such i n j u r y must be

p r o v i d e d t h r o u g h t h e p a r t i c i p a n t ' s own i n s u r a n c e p o l i c y .

F u t h e r i n f o r m a t i o n about t h e s e m a t t e r s may be o b t a i n e d from

Dr. J . Knox J o n e s , J r . , Vice P r e s i d e n t for Research and

G r a d u a t e S t u d i e s , (806) 742-2152, Room 118, A d m i n i s t r a t i o n

B u i l d i n g , Texas Tech U n i v e r s i t y , Lubbock, Tx 79409.

I u n d e r s t a n d t h a t I w i l l not d e r i v e any t h e r a p u t i c t r e a t m e n t

from p a r t i c i p a t i o n in t h i s s t u d y . I u n d e r s t a n d t h a t I may

d i s c o n t i n u e any p a r t i c i p a t i o n in the s t u d y a t any t ime I

choose w i t h o u t p r e j u d i c e .

I u n d e r s t a n d t h a t a l l da ta w i l l be kept c o n f i d e n t i a l and my

name w i l l not be used in any r e p o r t s , w r i t t e n o r u n w r i t t e n .

S i g n a t u r e of Sub jec t . . . D a t e

S i g n a t u r e of P r i n c i p a l I n v e s t i g a t o r or h i s a u t h o r i z e d

r e p r e s e n t a t ive

S i g n a t u r e of Witness t o Oral P r e s e n t a t i o n

65

Personal Medical History Questionnaire

NAME:

DATE:

ADDRESS

?H:

Name and phone # of individual to be contacted in case of

emergency:

Name and phone of physician, and physician's hospital:

AGE: WEIGHT: HEIGHT:

Are you susceptible to:

Shortness of breath ?

Dizziness ?

Chronic headaches ?

Fatigue ?

Are you c u r r e n t l y t a k i n g any type of aiedicine ?

If so e x p l a i n .

iiave you had, or do you now have a hernia ?

C o r r e c t i v e da te

66

Have you had, or do you now have a problem with your olood

pressure ?

Have you ever had extreme shoulder or arm pain ?

If so, explain

Have you had any type of surgery or serious illness within

the past six months ?

If so, explain

Have you ever had back pain, particularly lower back pain ?

Do you know of any reason why physical stress would cause

you injury ?

APPENDIX B

ANTHROPOMETRIC DATA

68 8

KEY

AGE - Age in years KT - Weight (lbs) HT - Height (cm) ACHT - Acromial Height (cm) ICHT - Iliac Crest Height (cm) KHT - Knuckle Height (cm) KEHT - Knee Height (cm) FGD - Forearm Grip Distance (cm) CHW - Chest Width (cm) CHD - Chest Depth (cm) ABD - Abdominal Depth (cm) CHC - Chest Circumference (cm) ABC - Aodominal Circumference (cm) FAC - Forearm Circumference (cm) EC - Buttocks Circumference (cm) IC - Thigh Circumference (cm) CC - Calf Circumference (cm)

Anthropometric Data

69

ID AGE WT HT ACHT ICHT KHT

A 3 C D E F G H I J K L M N 0

28 25 22 22 24 20 21 21 23 19 24 22 23 19 22

164 161 177 178 150 174 158 165 153 145 149 177 228 156 189

169 .5 1 7 8 . 0 1 7 5 . 0 1 8 3 . 0 1 7 2 . 1 182 .2 1 7 4 . 5 173 .9 1 6 2 . 4 169. 4 172 .2 1 8 6 . 8 180 . 1 1 7 0 . 6 1 8 0 . 6

1 3 8 . 5 1 4 7 . 2 1 4 3 . 3 1 5 2 . 4 1 4 3 . 5 1 5 1 . 5 1 4 6 . 6 144 . 1 1 3 5 . 5 1 3 8 . 7 14U. 0 1 5 4 . 9 1 4 7 . 9 1 3 9 . 2 1 4 9 . 9

9 8 . 3 1 0 6 . 4 1 0 6 . 1 1 0 8 . 9 1 0 4 . 4 112 . 1 1 0 7 , 5 1 0 4 . 0 9 5 . 5

1 0 2 . 7 1 0 6 . 6 1 1 8 . 6 1 0 8 . 0 1 0 5 . 0 1 1 1 . 3

7 0 . 4 7 9 . 5 7 9 . 3 8 1 . 5 7 6 . 2 82 - 1 7 9 . 4 7 8 . 8 7 4 . 5 7 1 . 1 7 8 . 1 8 2 . 8 7 8 . 4 7 8 . 9 8 0 . 5

ID KEHT FGD CH' CHD ABD CHC

A 3 C D

F G H I J K L M N 0

4 6 . 6 5 1 . 0 4 8 . 4 5 2 . 5 5 0 . 7 5 2 . 0 5 0 . 9 4 8 . 4 4 3 . 6 4 8 . 3 5 0 . 5 5 4 . 2 4 9 . 7 4 5 . 7 5 0 . C

3 4 . 5 3 6 . 4 3 6 . 2 3 6 . 6 3 5 . 5 3 7 . 5 3 4 . 5 3 4 . 4 3 0 . 4 3 6 . 2 3 3 . 7 3 8 . 4 3 6 . 2 3 2 . 3 3 5 . 9

3 1 . 1 3 1 . 1 3 3 . 2 3 2 . 2 2 9 . 4 2 9 . 5 3 0 . 3 3 4 . 2 3 2 . 0 2 8 . 5 2 9 . 4 3 1 - 3 3 5 . 3 3 0 . 1 3 2 - 1

2 2 . 2 2 0 . 4 1 9 . 3 2 1 . 1 1 9 , 7 2 2 . 4 1 9 . 8 19 .2 1 8 , 2 1 9 . 8 1 7 . 7 2 1 . 9 2 6 . 8 1 8 . 6 2 2 . 1

1 8 . 5 1 7 . 3 1 9 . 8 1 8 . 8 1 9 . 8 1 8 . 0 1 6 . 4 15. 1 19 .7 18 . 0 1 7 . 6 1 8 . 0 2 6 - 0 1 7 . 3 2 0 . 2

9 7 . 0 9 5 . 9 9 9 . 7

1 0 1 . 7 8 9 . 5 9 3 . 6 9 1 . 8

100 .0 9 1 . 2 8 9 , 0 :J0.8 9*^.4

1 1 2 . 3 9 0 . 7 9 6 . 0

70

ID ABC FAC BC TC CC

A 3 C' D E F G H I J K T -^4

M N 0

8 7 . 0 7 6 . 4 8 9 . 8 6 5 . 2 8 6 . 2 8 3 . 7 7 5 . 6 7 5 . 9 8 6 . 6 7 3 . 9 8 2 . 0 8 4 . 5

1 0 8 . 6 8 1 . 2 2 2 . 1

2 7 . 7 2 9 . 7 2 9 , 1 2 9 . 2 2 7 . 7 2 8 . 9 3 0 . 6 3 1 . 0 2 7 . 8 ' 3 0 . 1 2 9 . 3 2 9 . 5 3 0 . 8 2 8 . 7 2 0 . 2

3 2 . 3 3 2 - 5 3 3 . 4 3 1 . 6 2 9 . 7 3 2 . 0 3 6 . 8 3 6 . 9 3 0 . 7 3 0 . 4 3 2 . 8 3 1 . 7 36 . 8 3 3 . 0 9 6 . 0

5 8 . 0 5 5 . 8 5 9 . 0 5 8 . 3 5 2 . 8 5 8 . 4 5 5 .6 5 8 . 4 5 6 . 8 5 4 , 3 5 2 . 1 5 7 . 3 6 1 . 8 5 7 . 9 9 2 . 0

3 9 . 7 3 6 . 5 3 8 . 6 3 9 . 6 3 5 . 7 4 0 . 8 3 5 . 7 3 9 . 4 3 7 . 2 3 7 . 8 3 3 . 5 3 7 . 7 3 7 . 9 3 8 . 0 3 2 . 2

Summary Of A n t h r o p o m e t r i c Data

VARIABLE N MEAN STD MIN MAX C. V.

AGE :7T HT ACHT ICHT KHT KEHT FGD CHW CHD ABD CHC ABC FAC 3C TC CC

15 15 15 15 15 15 15 1 5 15 15 15 1 5 15 15 15 1 5 15

2 2 . 3 3 1 6 8 . 2 6 1 7 5 . 3 5 1 4 5 . 1 4 1 0 6 . 3 9

7 8 . 1 0 4 9 . 5 0 3 5 . 2 3 3 1 . 3 1 2 0 . 6 4 1 8 . 7 0 9 5 . 5 7 8 4 . 5 7 2 9 . 4 8 3 3 . 2 1 5 7 . 0 8 3 7 . 7 2

2. 35 2 0 . 8 6

6 . 4 1 5 , 6 5 5. 46 3 , 6 5 2 . 74 1 . 98 1 . 90 2 . 2 5 2. 44 6 . 10 8. 56 1 .29 2 . 57 2 . 5 9 1 . 35

1 9 . 0 0 1 4 5 . 0 0 1 6 2 . 4 0 1 3 5 . 5 0

9 5 . 5 0 7 0 . 4 0 43- 60 3 0 , 4 0 2 8 . 5 0 1 7 . 7 0 15 . 10 3 9 . 0 0 7 3 . 9 0 2 7 , 7 0 2 9 . 7 0 5 2 . 10 3 3 . 5 0

2 8 . 0 0 2 2 8 . 0 0 1 8 6 . 8 0 1 5 4 . 9 0 1 1 3 . 6 0 8 2 . 8 0 5 4 . 2 0 3 8 . 4 0 3 5 .30 2 6 . 8 0 2 6 . 0 0

1 1 2 . 3 0 108.D0 3 2 . 2 0 3 7 . 6 0 6 1 . 8 0 4 0 . 8 0

. 1 0 5

. 1 2 4

. 0 3 7

. 0 3 9

. 0 5 1

. 0 4 7

. 0 5 6

. 0 5 6 . 0 6 1 , 109 . 1 3 1 . 0 6 4 .•101 . 0 4 4 . 0 7 8 . 0 4 5 . 0 4 9

APPENDIX C

MISCELLANEOUS VARIABLES

71

72

KEY

pl-r^* Phys ica l work Capacity (1/min) P^CH - Phys ica l Work Capacity per

kilogram body weight (l /min/kg) l^l^ ' J ^ ^ ^ i ^ ^ ! ^ Physica l work Capacty (1/min) S.P - s t e p Test Score (hear t beats) £vPI - Rec iproca l Ponderal Index BDFT - Percent Body Pat (percent)

Miscel laneous Data

73

ID PWC PWCW PPWC STP RPI BDFT

A B C D E F G !i I J K L M N 0

2 . 7 5 3 . 43 3 . 2 3 3 . 7 1 2 . 4 5 2 . 7 8 2 . 9 3 3 . 5 0 2 . 5 5 3 . 4 2 2 . 9 8 4 . 30 3. 20 2 . 9 6 3 . 10

3 6 . 9 4 7 . 0 4 0 . 2 4 6 . 0

. 3 6 . 0 3 5 . 2 4 0 . 9 4 6 . 7 3 6 . 8 5 2 . 0 4 4 . 2 5 3 . 7 2 9 , 2 4 1 . 8 3 6 . 2

2 . 1 0 3 . 9 0 3 . 3 0 3 . 9 0 2 , 2 5 2 . 2 8 3 , 6 5 3 . 2 8 2 , 3 0 4 , 6 0 2 . 8 5 3 . 5 8 3 . 0 0 2 . 7 0 3 . 3 0

142 82 99 87 86 89 74 85 94 59 87 87 87 78 79

1 2 . 1 9 1 2 . 8 8 1 2 . 2 7 1 2 . 8 1 1 2 . 7 5 1 2 . 8 5 1 2 . 7 1 12 -48 1 1 . 9 5 1 2 . 6 9 1 2 . 7 9 13 . 10 1 1 . 6 1 12. 48 1 2 . 3 9

2 5 . 9 6 - 3

2 2 . 0 1 0 . 6 2 8 . 0 1 6 . 8 1 2 . 3 1 4 . 3 3 2 . 1

9 . 5 1 1 . 5

8 . 7 2 2 . 4 1 6 . 6 2 3 . 3

SUMMARY OF M I S C E L A N E O U S V A R I A B L E S

VARIABLE

PWC PWCW PPWC S T ? R P I BDFT

N MEAN S T D MIN MAX " V

15 15 15 15 15 15

3 . 1 5 4 1 . 5 2

3 .13 8 7 . 6 6 1 2 . 5 3 1 7 . 3 5

0 . 4 7 6 . 7 5 0 . 7 2

17. 6 1 0 .39 7. 84

2 - 4 5 29. 20

2 . 10 5 9 - 0 0 1 1 . 6 1

6 . 3 0

4 . 3 0 5 3 . 7 0

4 . 6 0 142-00

13. 10 32 . 10

. 1 5 1

. 1 63 ,233 . 2 0 1 . 0 3 2 , 4 5 2

APPENDIX C

ISOMETRIC STRENGTH TESTS

74

75

S t a t i c Arm S t r e n g h t Measurement (Figure 11) :

The measurement r e g u i r e s t h a t the long handle be a d ­

j u s t e d such t h a t t h e fo rea rms a r e f l exed 90 d e g r e e s , i . e . ,

p e r p e n d i c u l a r t o t h e s u b j e c t ' s t o r s o , and the arms a r e v e r ­

t i c a l , i . e . , p a r a l l e l and a d j a c e n t t o t h e t o r s o . The s u b ­

j e c t s t a n d s e r e c t , with l e g s and back s t r a i g h t and wi th t he

f e e t f l a t . A load c e l l and a c h a i n c o n n e c t the h a n d l e t o

t h e p l a t f o r m on which t h e s u b j e c t i s s t a n d i n g . The e x e r t e d

f o r c e i s t o be upward, v e r t i c a l and g e n e r a t e d by only t h e

arm m u s c l e s . The s u b j e c t i s i n s t r u c t e d t o avoid any s h o u l ­

der movement.

76

•icjiire n : S u b i ^ c t P o s t u r e f o r Am S t r e r . J t n ^. e a s u r e men

77

S t a t i c Standing Back St rength lleasurement (Figure 12):

The s u b j e c t s t a n d s e r e c t and r e s t s the a n t e r i o r su faces

of the p e l v i s and the abdominal muscles aga ins t a padded

b race . The brace i s adjus ted to a height oUch tha t the sub­

j e c t can comfortably apply a h o r i z o n t a l pe lv ic /abdomina l

p r e s s u r e . A padded board i s placed on the s u b j e c t ' s back a t

the l e v e l of the p o s t e r i o r sur face of the c r e s t of the sp ine

on the s c a p u l a e . The load c e l l i s hooked to a s t r a p which

i s connected to the padded board. A l ink chain connec ts the

load c e l l t o a v e r t i c a l b race . The chain and load c e l l a re

to be kept pe rpend i cu l a r to the t o r s o .

The measurement r e g u i r e s the sub jec t to exer t a h o r i ­

z o n t a l rearward force aga in s t the padded board, by extending

the t o r s o . The knees a re fu l ly extended, the upper ex t r emi ­

t i e s a r e p a r a l l e l to the l a t e r a l su r faces of the t o r s o and

the f e e t a r e kept f l a t .

73

i j a r S u b j e c t P o s t u r e f j r Standincr 3icX Stren^^th

79

S t a t i c Shoulder S t rength Measurement (Figure 13):

The s u b j e c t s t a n d s e r e c t and suppo r t s , with both arms,

a bar with two s t r a p s . The s t r a p s a r e pos i t ioned over the

d i s t a l end of the humerus by i n s e r t i n g the arms o u t s i d e - i n .

The arms a r e flexed to a pos ture such t h a t the arms a r e per ­

pend icu la r to the s u b j e c t ' s t o r s o , i . e . , a t the shoulder

l e v e l , and the forearms are v e r t i c a l , i . e . , p a r a l l e l to the

t o r s o . The s u b j e c t ' s fee t a r e to remain f l a t , the l egs

s t r a i g h t , and the back e r e c t . A load c e l l and a v e r t i c a l

l i nk chain connect the bar to the platfornj on which the sub­

j e c t i s s t a n d i n g . The exer ted force i s to be upward, v e r t i ­

ca l and genera ted by only the shoulder muscles .

3 0

" i >T a r G 13: S u b j e c t ? O o t u r e :i e a s u r e " ^ en t

Shoui . ] 2r o t r e n ] t a

81

Static Leg Strength Measurement (Figure 14):

The height of the bar is based on the subject having a

120 degree angle at the knee as determined by use of a tem­

plate shown at the bottom of Figure 7. The horizontal bar

is gripped with the palm of the the hands (finger grasping

is not permitted) such that the dorsal surfaces of the hands

are facing outward (visible to the experimenter). The sub­

ject exerts an upward, vertical force on the bar, by extend­

ing the knees, \*hile keeping the scapulae, the buttocks and

the heels against a common vertical plane, such as a wall.

The feet are to be kept flat.

82

Figura 14: Subject Posture for S t a t i c Leg S t rength Measurement

83

KEY

IMA - Isometric Arm Strength (lbs) IMS - Isometric Shoulder Strength (lbs) 1MB - Isonetric Back Strength (lbs) IML - Isometric Leg Strength (lbs)

84

Isometric Strength Data

ID IMA IMS 1MB IML

A B C D E F G H I J K L M N 0

56 89 77 100 55 67 116 105 64 82 67 94 95 57 113

89 117 82 163 54 83 147 149 38 119 72 115 104 72 120

149 201 150 243 89 109 158 188 180 188 128 169 164 54 208

284 328 260 444 134 286 390 408 248 309 279 231 461 159 375

Summary Of I s o m e t r i c S t r e n g t h Measures

VARIABLES N MEAN STD MIN MAX C.V.

IMA 15 8 2 . 4 6 2 0 . 9 7 5 5 . 0 0 116 .00 . 2 5 4 IMS 15 1 0 4 , 9 3 3 1 . 6 9 5 4 . 0 0 163 ,00 . 3 0 2 1MB 15 1 5 8 . 5 3 4 8 . 5 7 5 4 , 0 0 243 .00 . 3 0 6 IML 15 3 0 6 . 4 0 9 6 . 2 4 134 .00 4 6 1 . 0 0 . 3 1 4

APPENDIX E

ISOTONIC STRENGTH TESTS

85

86

Dynamic Endurance Measurement (Figures 15 and 16):

The subjec t s tands erec t , against a wal l , while hold­

ing , with both hands, bar/weights at the waist l e v e l (Figure

15) . Heels , buttocks and scapulae maintain contact with the

wa l l . The t o t a l bar weight i s 25% of the s u b j e c t ' s average

s t a t i c arm s trength .

Prior to the measurement the subject i s instructed to

maintain the es tabl i shed task pace of 50 movements per min­

ute for as long as poss ib le . The pace i s es tabl i shed by the

percussion of an e l e c t r o n i c metronome.

The subject assumes the measurement posture and i s

handed the weights. The subject rhythmically l i f t s and low­

e r s , by elbow f l ex ion and extens ion , the weights from a hor­

i z o n t a l plane (establ ished by 90 degree f lex ion of the elbow

from the anatomical posit ion) to the chest and vice versa

(Figure 16) . The only movement permitted i s that of the e l ­

bow j o i n t . The task duration time i s recorded as the dynam­

i c endurance t i n e .

37

-^ijure 15: Subject Initial Postur? for Dyna:ii r. lurance

38

r i ' i ' j r ? TS: S u b j e c t S e ' i u e n t i a l P o s t u r e f o r Dvnu.nic Er . iu ra r . ce

89

Oniverasal Overhead Lift (Figures 17 and 18) :

The subject sits on the stool and positions himself so

that he is sitting erect with his back straight and with the

grips of the machine just in front of his shoulders. He

sits looking straight ahead, with his hands on the grips,

palms forward (see Figure 17). He then fully extends his

arms over his head, lifting the weights (see Figure 18).

90

riguro 17: Universal Overhead Lift Starting Pooition

9 1

'^^ > w ^ v .v*!-:^:

"^i^jure 18: ' J n i v e r s a l Overhea^^. L i f t Zndinq P o s i t i o n

92

Universal Leg Lift (Figures 19 and 20):

The subject sits fully back into the seat and the seat

position is adjusted so that he is as close as he can get to

the foot pedals and still able to fully extend his legs

without becoming restricted by the machine. He begins the

exercise by sitting fully back in the seat with his feet on

the pedals and his hands holding onto the bars at his side

(see Figure 19). He then fully extends his legs to lift the

weight (see Figure 20) .

93

igur '^ 19: ' I n i v e r s a l 1-ej L i f t S t a r t i n q P o s i t i o n

j a

F i j u r e PO: ^JnivRunal \o j L i f t Zn.Uacj P o s i t i o n

95

Universal Sguat Lift (Figures 21 and 22):

The subject leans back into the apparatus and the

shoulder pads are adjusted so that the hands can hold the

handgrips with the arms comfortably extended. The feet are

placed onto the platform and the subject is ready to begin

(see Figure 21). It is important to instruct the subject to

push up with his legs and not lift with his arms, which is

the natural tendency. Several practice trials should be

given. Once the subject is used to the apparatus and is in

position to begin, he lifts the weights by fully extending

his legs and pushing the lifting sled up (see Figure 22).

96

i g u r ^ 2 1 : ' J n i v e r s a l 3 ' juat L i f t o t a r t i n ; P o s i t i o n

97

i . ' u r e 22: ^ ^ n i v e r s a i 3 ;ud t L i f t En- i in j P o s i t i o n

98

Universal Curl and Nautilus arm Lift (Figures 23, 24,

25 and 26) :

The subject takes hold of the bar with an underhand

grip and then stands erect holding the bar with his arms

fully extended (see Figures 23 and 25). He then flexes his

forearms bringing the bar toward his chin and lifting the

weight {see Figures 24 and 26). It should be noted that due

to the mechanical limitations of the Nautilus machine the

arms cannot be fully flexed (see Figure 26) .

99

IjuTt.^ 2.1: ' J n i v e r s a l Cur l ;3t3r"-ing ? 0 3 i t i j n

i:o

^ i g u r e 2'i : ' J n i v e r s a l C u r l Cn l i n j P o s i t

101 1 1

^^v-vf^r/r-

1JII r e -) Q> • J d u t i l u s Ar^ L i f t S t a r t i n g P o s i t i o n

102

F i g u r e 26: N a u t i l u s Ar-n L i f t ^ n . l i n ; P o s i t i o n

103

Nauti lus Leg Lif t (Figures 27 and 28):

The s t r a p is placed comfortably around the s u b j e c t ' s

waist so tha t i t i s r e s t ing on the hips and i s then secured

by the f i r s t chain l ink to the Nautilus machine. The sub-

jact then s t eps onto the second step of the apparatus and

f lexes his knees so tha t the weights are not Jaeing l i f t e d .

He holds on to the r a i l s of the machine for balance (see

Figure 27)• He then stands s t r a i g h t up fully extending h is

legs (see Figure 28) . I t i s important to make sure tha t he

s tands s t r a i g h t up and does not lean back which is the natu­

r a l tendency.

104

i j u r e 27: ' U u t i l u s Le j L i f t S t a r t i n g o s 111 o n

105

1 J'l rc> M a u t i l u s Lej L i f t I-ndin^ P o s i t i o n