trunk posture affects upper extremity function of adults 1

Perceptualand Motor Skzlls, 2007, 104,371-380. O Perceptual and Motor Skills 2007

TRUNK POSTURE AFFECTS UPPER EXTREMITY FUNCTION OF ADULTS '

GLEN GILLEN, CHANIE BOIANGIU, MICHELLE NEUMAN,

RACHEL REINSTEIN, YONA SCHAAP

Programs in Occupational Therapy, Columbza University

Summary.-This study examined the effects of various seated trunk postures on upper extremity function. 59 adults were tested using the Jebsen Taylor Hand Func- tion Test while in three different trunk postures. Significant mean differences between the neutral versus the flexed and laterally flexed trunk postures were noted during selected tasks. Specifically, dominant hand performance during the tasks of feeding and lifting heavy cans was significantly slower while the trunk was flexed and laterally flexed than when performed in the neutral trunk position. Performance of the nondominant hand during the tasks of picking up small objects, page turning, as well as the total score was slower while thc trunk was flexed compared to performance in the neutral trunk position. These findings support the assumption that neutral trunk posture improves upper extremity performance during daily activities although the effect is not consistent across tasks. Findings are discussed along with limitations and recommen- dations for research.

Rehabilitation practitioners often assume that trunk control and alignment affects functioning of the extremities as well as the performance of functional activities. This assumption is based predominantly on anecdotal evidence. For more than 40 years the neurorehabilitation literature has discussed this relationship, and several authors have proposed clinical relationships between the trunk and the limbs (Rood, 1956; Bobath, 1970, 1990; Eg- gers, 1983; Fisher, 1987; Boehme, 1988; Gillen, 2004a, 2004b). Despite this apparent clinical focus, insufficient empirical research has been published to support these assumptions.

Anatomical Considerations: Arm and Trunk Connection Many different groups of muscles and bony landmarks contribute to

the intricate biomechanical and kinesiological interactions between the trunk and the upper extremities. To begin to understand these intricate connec- tions it is imperative to explore the relationship between the axial and appen- dicular skeleton. In his classic paper, Basmajian (1963) termed this relationship the "arm-trunk mechanism." In terms of the axial skeleton, the vertebral column and pelvis are primary foundations for stability of the trunk,

'Address corres ondence to Glen Gillen, EdD, OTR, FAOTA, Columbia Universit Programs in ~ c c u p a t i o n a f ~ h e r a p y , 710 West 168th Street-8th Floor, New York, New ~ o r i 10032 or e-mail ([email protected]). The authors acknowledge the contributions of Saritte Grosser, Ariella Neuman, Michelle Pruzansky, and Edward Roman.

G. GILLEN, ET AL.

supporting the abdomen and connecting the vertebral column to the lower extremities. For every pelvic motion there is a repositioning of the spinal column (Gillen, 2004a; Green & Roberts, 2005). Also, the ribcage of the axial skeleton provides support for the upper limbs (Kapandji, 1974; Moore & Dalley, 2005).

The clavicle and the scapula are also important landmarks on the proxi- mal skeleton. The scapula includes the glenoid fossa, a "cradle" for the head of the humerus (Gillen, 2004b). To maintain the anatomical connection between the scapula and the humerus, the glenoid fossa rests in the upward, forward, and outward positions (Moore & Dalley, 2005). The scapula glides along the surface of the thoracic cavity allowing complete range of arm movement. The clavicle serves as the only bony connection between the trunk and upper extremity. It is the bony support of the arm and serves as a strut. Because the clavicle is the bony "bridge" between the trunk and the upper extremity and the muscles that stabilize and mobilize the upper extremity originate at the trunk, it may follow that any change in the alignment of the trunk or the stability of the trunk will have a biomechanical effect on the upper extremity.

Trunk fllzgnment~

The body assumes various postures in preparation for engagement in various activities (Green & Roberts, 2005). Sitting is the most common position assumed during daily motor activities; therefore, it appears to be important to evaluate seated stability and other components of sitting posture to assess accurately a person's ability to function (Lanzetta, Cattaneo, Pellegat- ta, & Cardini, 2004).

The curvatures of the spine are an important element of sitting alignment. Typically, the cervical and lumbar curvatures are concave posteriorly, while the thoracic and sacral curvatures are concave anteriorly (Moore & Dalley, 2005). In the typical erect sitting position, the spine is properly aligned and maintains these curvatures. Curvatures of the spine allow symmetrical weight bearing through the pelvis while seated. Symmetrical weight bearing is characterized by equal weight bearing on both ischial tuberosities, a neutral spine, symmetry of the shoulders, neutral position of the head and neck, knees in line with the hips, and the feet bearing weight equally under- neath the knees. This neutral posture is maintained by cocontraction of the anterior and posterior muscles (Gillen, 2004a).

Deviations from this neutral alignment will have an influence on sitting posture. When the trunk is in flexion while seated, the pelvis is tilted posteriorly, there is a decrease in the lumbar curve and an accentuation of the thoracic curve (Kapandji, 1974; Gillen, 2004a). When the trunk is in lateral flexion, the upper trunk bends laterally towards the hip. The pelvis is shift-

TRUNK POSTURE AND FUNCTION 373

ed laterally resulting in a lateral weight shift. The spine assumes an s curve open to the shortened side (Green & Roberts, 2005).

Motor Control This interaction between the trunk and the upper extremities is also

evident during functional activities. The trunk maintains stability (active with subtle movements) during activities in which the upper extremities must move within the arm span, e.g., during feeding and grooming, while it more significantly shifts weight to support movements beyond the arm span such as reaching into a medicine cabinet while seated in a wheelchair (Gillen, 2004b). Tyler and Hasan (1995) provide classifications useful in understand- ing these movements. They differentiate between focal and nonfocal movements. Focal movements are the movements of the arm and the muscles directly involved in producing the movement. Nonfocal movements, on the other hand, are the mavements and muscle activity that support the focal movement. According to these premises the trunk musculature performs nonfocal movements in anticipation of the focal movements of the arm. Before a focal arm movement is performed, postural muscles are activated to allow focal movements of the arm to occur more smoothly and to prevent destabi- lization of the postural system. These anticipatory postural reactions have been well documented in the literature (Belenki, Gurfinkel, & Palitsev, 1967; Bouisset & Zattara, 1981; Cordo & Nashner, 1982; Massion, 1992). This documented relationship between the arm and trunk is impaired in those living with diseases of the central nervous system (Poizner, Feldman, Levin, Berkinblit, Hening, Patel, & Adamovich, 2000; Reft & Hasan, 2002; Ustino- va, Goussev, Balasubramaniam, & Levin, 2004).

Relatknship Between Trunk and Functional Activitie~ There is some support in the literature regarding the effect of trunk

control on functional performance. Examinations of stroke survivors (Bohan- non, 1992, 1995) documented a statistically significant correlation between sitting balance and trunk strength. Hsieh, Sheu, Hsueh, and Wang (2002) concluded that trunk control could predict performance of basic and instru- mental activities of daily living by those living with stroke. Similarly, Fran- chignoni, Tesio, Rtcupero, and Martino (1997) concluded that trunk control is highly correlated with functional performance in stroke survivors and pre- dicts functional outcomes.

Based on these paragraphs on anatomical, motor control, and functional relationships between the trunk and the upper extremity, there is no published research on effects of trunk alignment on upper extremity function. Further investigation into this relationship is warranted so the purpose of this study was to examine the influence of three trunk postures (neutral, flexion, and lateral flexion) on upper extremity function as measured by the

G. GILLEN, ET AL.

Jebsen Taylor Hand Function Test. It was hypothesized that the three different postures would yield significantly different timed scores on the test, and specifically that, when in a neutral seated posture, upper extremity performance would be most efficient as evidenced by significantly faster scores on the outcome measure.

Participants A sample of convenience was recruited through person to person con-

tact at a large private urban university. All subjects were healthy adults with no self-reported spine or upper extremity injuries.

Measurement The Jebsen Taylor Hand Function Test is a timed test used to measure

hand and arm function. The test has seven subtests including writing, page turning, picking up small familiar objects, stacking checkers, simulated eat- ing, lifting empty cans, and lifting heavy cans. The test is administered using both the nondominant and dominant hands.

The Jebsen Taylor Hand Function Test was developed to assess upper extremity and hand function, a cornerstone of evaluation of a person's functional abilities. It evaluates function or dysfunction via the timed performance of simulated activities of daily living (Jebsen, Taylor, Trieschmann, Trotter, & Howard, 1969). Prior research indicates the test is both valid and reliable. The test-retest reliability coefficients range from .60 to .99. Each subtest of the Jebsen Taylor hand Function Test has been shown to be reliable in test-retest situations. Also, the effects of practice were not significant (Jebsen, et al., 1969). Stern (1991) confirmed the test-retest reliability to be adequate, with a range of .67 to .99.

Procedure Before administering the Jebsen Taylor Hand Function Test, interrater

reliability was established between the test administrators. Prior to being tested, each participant provided informed consent and completed a demo- graphic questionnaire.

The test was administered in a quiet room free of distraction. Each subject sat on a backless bench 18 in. high, and at a desk 30 in. high with the feet flat on the floor. The subtests required strict measurement during administration, so measurements were taken on the testing surface prior to testing and marked with masking tape to ensure accurate and standardized testing.

The subjects performed the test three times consecutively, each time in a different posture: neutral, lateral flexion, and flexion. In the neutral position, the participants were asked to "sit up tall" and sat upright with a

TRUNK POSTURE AND FUNCTION 3 75

neutral pelvic tilt, with a straight back and shoulders aligned over the hips. In lateral flexion, the participant sat with a maximum but comfortable lateral pelvic tilt towards the dominant side with trunk correction so that the head was held in midline. In flexion, the participant assumed a kyphotic spinal posture with a posterior pelvic tilt and rounded shoulders. In all of these positions, the participant's feet were flat on the floor. The order of the postures was randomized to control for fatigue and to reduce the practice effect. To assess order of the administration of these postures the test administrator fanned out three index cards with different postures written on them. The cards were held face down while the participant randomly selected an index card. The order of selected cards set the order of sitting postures in which each performed the test. The cards were reshuffled between test ad- ministrations.

Each posture was visually demonstrated by the test administrator and reinforced with a light physical cue prior to test administration. At least two testers were present during the test administration. One administered, timed the test with a digital stopwatch, and recorded the results, while the other ensured that the participants maintained the correct posture through verbal cueing.

The seven subtests were always administered in the same order, using both the dominant and nondominant hands. Each of the seven subtests were timed and then recorded. The subject started when the tester said "Go". Upon the subject's completion of each subtest, the tester stopped the timer and then recorded the results.

Data Analysis The intraclass coefficient was calculated to estimate interrater reliability.

An analysis of variance for repeated measures to detect within-subject changes was performed to examine mean differences among the three postures. The significant F ratios were subjected to a post hoc multiple-comparison test with a Bonferroni adjustment of p,05 to evaluate differences between the specific postures. The results were considered to be significant if at the adjusted .05 level of confidence.

RESULTS Prior to initiating testing, an intraclass correlation coefficient of .96 was

established between the test administrators. A total of 59 subjects were tested, 53 (89.9%) women and 6 (10.1%) men whose ages ranged from 21 to 62 years, with a mean age of 27.0 yr. (SD=7.8). Fifty-five (93.2%) subjects were right-hand dominant and four (6.8%) subjects were left-hand dominant based on self-reports of the hand used to write. None of the subjects reported having upper extremity or spinal impairments which interfered with daily functioning.

376 C. CILLEN, ET AL.

Overall the neutral trunk posture was consistently the most efficient posture to perform the examined tasks as evidenced by faster times for all subtest and total times calculated in seconds (see Table 1). Significant findings were evident on five of the subcomponents of this study. Dominant hand performance during feeding in the three different trunk postures was significantly different (F , ,,, = 8.24, p < .001). Feeding with the dominant hand was significantly slower while flexed in a posture ( p < .001) or when laterally flexed ( p < .001). Dominant hand performance during lifting heavy cans in the three different trunk postures was also significantly different (F, ,,,= 5.56, p < ,005). Specifically, lifting cans with the dominant hand was significantly slower while flexed ( p < .01) and laterally flexed ( p < .005) than while neutral.

TABLE 1

Task Neutral Trunk Flexed Trunk -. Laterally Flexed Trunk M SD M SD M SD

. -

Dominant I Iand Writing 10.3 3.8 11.1 3.4 11.8 3.1 Page turning 3.7 1.1 4 .0 1.4 3.9 1.2 Lifting small objects 6.3 1.2 6.5 1.3 6.6 1.1 Feeding 7.0 1.5 7.9 2.6t 7.8 2.4t Stacking checkers 3.7 1.2 3.7 1.0 3.9 1.0 Lifting light cans 3.0 .5 3.2 .6 3.2 .7 Lifting heavy cans 3.1 .5 3.3 .6t 3.3 .5 -i- Total time 38.2 6.3 39.9 7.0 39.7 6.2

Nondominant Hand Writing 22.8 7.7 23.8 8.2 23.3 9.0 Page turning 3.9 .9 4.2 1.2t 4.3 1.5% Lifting small objects 6.6 1.0 7.1 1.3t 6.8 1.2 Feeding 8.5 2.6 9.3 2.7 9.6 4.4 Stacking checkers 4.1 1 .0 4.4 1.4 4.2 .9 Lifting light cans 3.4 .6 3.4 .7 3.4 .7 Lifting heavy cans 3.4 .6 3.5 .6 3.5 .6 Total time 52.6 10.7 55.8 11.4t 55.0 12.2

- - --

Nolc.-Higher scores indicate poorer performance. "Time longer, p _< .05. tTime longer, p 5 .01.

The performance of the nondominant hand while picking up small objects in the three different trunk postures was significantly different (F, , , , = 4.63, p<.Ol). Picking up small objects with the nondominant hand was significantly slower while flexed ( p < .008) than while neutral. Similarly, performance of the nondominant hand while turning pages in the three different trunk postures was also significantly different (F , , ,, = 4.06, p < .02). Turn-


ing pages with the nondominant hand was significantly slower while flexed (p < ,002) and laterally flexed ( p < .O3) than while neutral. Finally, the total time to complete the tasks with the nondominant hand was significantly different in the three postures (F,,,,,=3.02, p < .05). Specifically, total timed performance of the nondominant hand was significantly slower while flexed (p < .01) than while neutral. See Table 1.

DISCUSSION The results of this study indicate that trunk alignment affects upper ex-

tremity filnction in typical adults, defined as performance on the Jebsen Tay- lor Hand Function Test, although not consistently for all tasks examined. The effect of posture on upper extremity functioning seems to be task-specific in ordinary healthy adults as some subtests were significantly related to deviations from neutral posture while others were not. These results support the hypothesis and the assumption of many rehabilitation practitioners that there is a relationship between trunk posture and upper extremity functioning.

Overall, the present analysis showed that neutral trunk alignment appears to provide the most efficient postural alignment for upper extremity functional performance. Across all of the tasks examined, upper extremity performance while in the flexed and laterally flexed position was slower than while in the neutral trunk position. This was particularly evident for the total performance for the nondominant upper extremity and for the specific subtests of lifting small objects and page turning while in the flexed posture. The dominant upper extremity performed significantly faster in the neutral posture than in both the flexed and laterally flexed posture while lifting heavy cans and during simulated feeding.

The finding that the effect seems to be task-specific is consistent with motor control research. Postural adjustments vary according to the distance reached, the amount of external support, the amount of weight lifted, the di- rection of movement, and whether the action is unilateral or bilateral (Bouis- set & Zattara, 1981, 1987; Eng, Winter, MacKinnon, & Patla, 1992; Dean, Shepherd, & Adams, 1999; Vernazza-Martin, Martin, Cincera, Pedotti, & Massion, 1999; Arce, Katz, & Sugerman, 2004). Measurements used in this study included several tasks, each requiring varying accuracy, skill, and ability to scale movements based on the load placed on the upper extremity.

The tasks most affected by the change in trunk posture were those that required accuracy (lifting small objects, feeding, turning pages) or that loaded the upper extremity (lifting heavy cans). While this study was not designed to specify the basis for the differences, perhaps these tasks place a fair de- mand on anticipatory control mechanisms and place demands on the postural system to support accurate upper extremity movements and the desta- bilization caused by loading the upper extremity.

G. GILLEN, ET AL.

The present study also showed a difference between overall performance of the dominant and nondominant hands. While the total mean performance of the nondominant hand in the neutral posture was significantly faster than in the flexed position, there was no significant difference in the total performance of the dominant hand based on posture. This difference may reflect that the dominant hand moves more quickly and is more accurate than the nondominant hand (Ozcan, Tulum, Pinar, & Baskurt, 2004). Once the different postures were superimposed on this limitation, the performance of the nondominant hand was less efficient. The combination of change in posture and the lack of skilled movement may have amplified the difference in efficiency. As the test administered was designed to simulate everyday tasks (typically performed with the dominant hand), it seems that the dominant hand performance may be less likely to be influenced by changes in task parameters such as a change in trunk posture.

The present study has several limitations. The study utilized a relatively small sample of convenience. Predominantly examined were healthy young adults which restricts generalization of findings. Participants were predominantly women. In addition to documented sex-related strength differences (Ikemoto, Demura, Yamaji, Nakada, Kitabayashi, & Nagasawa, 20061, sex differences can be observed in other aspects of motor tasks such as accuracy (Tottenham, Saucier, Elias, & Gutwin, 2005) which further may have been reflected in the results. Finally, the definition of upper extremity function was limited to performance on a specific timed test of simulated activities of daily living.

While the present study was limited to healthy adults, researchers should as well examine the effect of trunk alignment on function in clinical populations. Such information might help clinicians to make informed choices related to interventions such as positioning and preparatory tech- niques focused on improving postural alignment which may in turn influence function. The present test includes performance of activities performed in the middle range (tabletop) of upper extremity function. Researchers should explore the effect of postural deviations at high as well as low reach. In addition, motion analysis or electromyography could be utilized to docu- ment the changes in recruitment of upper extremity muscles and movement trajectories that may occur secondary to any changes in trunk alignment.

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Accepted Januay, 30 , 2007

trunk posture affects upper extremity function of adults 1

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