epidemiology of physical activity: 101 july 17, 2007 steven h. kelder, phd, mph professor, division...

Epidemiology of Physical Activity: 101July 17, 2007

Steven H. Kelder, PhD, MPHProfessor, Division of Epidemiology

Co-Director, Michael & Susan Dell Center for Advancement of Healthy Living

The Dilemma

Most Americans are not physically active enough to achieve substantial health benefit

Related disease outcomes are very costly

With adults, traditional PA promotion efforts have had limited effect

Sustaining higher activity levels will require a comprehensive approach

The World According to Steve Start young – school based programs work. Children can

be found at school. Young parents, preschool. Physical activity quickly declines as students enter

middle school and high school (especially girls). Promote calcium consumption and weight bearing

physical activities to women and girls. Reinforce school lessons at home and in the community. Promote use of community parks and recreation. Create social events; eating and PA are social behaviors. Where: worksites, point of purchase, church, school Stay in it for the long haul.

What Do We Mean by Food and Physical Activity Environments? (from macro to micro)

Physical and economic environments: food product (including packaging, portion size), price, promotion, placement – access, availability, affordability, convenience, parks and recreation

Information environments: media, marketing, public education (including point of purchase information, food labels)

Social environments: social and cultural norms/practices, role models; health provider and other social support for health behavior change

Behavioral settings: schools, homes, neighborhoods, communities, youth-serving organizations, child care centers, grocery and convenience stores, restaurants/fast food outlets, vending machines, worksites, worksites

Mass media saturated with unhealthy messages and advertising

Proliferation of easily available low nutrient, calorie dense foods

Increasing frequency of restaurant eating and larger portion sizes (Super Size Me!)

The (possible) causes

Increasing amount of time spent indoors with mass media and games

Increased car travel and less person-powered transport

Increased concerns over child safety - stranger danger and traffic

Fewer walkable destinations - shops, grocery, post office


More families with two working parents “Go inside and lock the door until we get home”

Parents working longer hours - too tired and too busy to play

Personal injury litigation and reduced opportunities for physical activity

Poor fundamental movement skills - as children participate less, they fail to develop these fundamental skills so want to participate less


Schools increasingly reluctant to devote time to health education

Poor fundamental movement skills - as children participate less, they fail to develop these fundamental skills so want to participate less


Increased Life Expectancy

Source: Centers for Disease Control and Prevention (CDC).

77 years

47 years

0

20

40

60

80

1900 2000

Increased years due to

medical care advances:

5

Increased years due to

public health measures:

25

Causes of Death in United States – 2002

Actual Causes of Death2

Tobacco

Poor diet/lack of exercise3

Alcohol

Infectious agents

Pollutants/toxins

Firearms

Sexual behavior

Motor vehicles

Illicit drug use

Leading Causes of Death1

Percentage (of all deaths)

Heart Disease

Cancer

Chronic lower respiratory disease

Unintentional Injuries

Pneumonia/influenza

Diabetes

Alzheimer’s disease

Kidney Disease

Stroke

Percentage (of all deaths)0 5 10 15 20 25 30 35 0 5 10 15 20

Sources: 1 National Vital Statistics Reports, Vol. 53, No. 15, February 28, 2005.2 Adapted from McGinnis Foege, updated by Mokdad et. al., 2000.3 JAMA, April 20, 2005—Vol 293, No. 15, pg 1861.

Physical Activity and Fitness Benefits

Builds and maintains healthy bones and muscles, controls weight, builds lean muscle, reduces fat, reduces blood pressure, and improves blood glucose control

Decreases the risk of obesity and chronic diseases (CHD, high blood pressure, diabetes, colon cancer, and osteoporosis)

Reduces feelings of depression and anxiety and promotes psychological well-being

Related to functional independence of older adults and quality of life of people of all ages

Physical Activity Improves Lives A physically active Texas population would expect to see:

30 % fewer cases of heart disease, stroke, colon cancer, and osteoporosis

18 % fewer cases of type 2 diabetes and hypertension 16 % fewer injuries from falls in the elderly 12 % fewer cases of depression and anxiety 5 % fewer cases of breast cancer PA helps the elderly maintain their independence

longer. PA results in more productive employees by

decreasing illness and absenteeism.

Sedentary Behavior is a Natural Response to our Environment

Our culture increasingly values cars, television, computers, and convenience, making physical activity less a natural part of our lives.

Newer communities are often designed without sidewalks or streetlights, decreasing walkability.

Communities are designed with housing far from schools, shopping, or other activities, making walking or biking for transportation infeasible.

Increasing traffic congestion and aggressive driving hampers the walkability of neighborhoods.

More and more employees have sedentary jobs decreasing the amount of activity incurred during daily routines.

Children are taking fewer physical education classes in school.

Activity can be Easy

Achieving the recommended amount of physical activity is as simple as taking three ten-minute walks per day.

Health benefits occur even with very modest increases in activity, even if the recommendation is not met.

The largest benefits occur to those who were previously completely sedentary.

Any incremental physical activity is beneficial to health. Vigorous exercise is very beneficial to health, but a brisk

walk is beneficial as well. Little changes, such as parking farther away from the

store or opting for the stairs instead of the elevator, go a long way toward promoting health and preventing disease.

Dietary Guidelines for Americans

Aim for Fitness Aim for a healthy weight Be physically active each day

Build a Healthy Base Let the Pyramid guide your food choices Choose a variety of grains daily, especially whole grains Choose a variety of fruits and vegetables daily Keep food safe to eat

Dietary Guidelines for Americans

Choose Sensibly Choose a diet that is low in saturated fat and

cholesterol and moderate in total fat Choose beverages and foods to moderate your

intake of sugars Choose and prepare foods with less salt If you drink alcoholic beverages, do so in

moderation

Vegetables and Fruits

5 or more servings of vegetables and fruits each day

Research suggests this one dietary change could prevent as many as 20% of all cancers

Vegetables and fruits provide vitamins, minerals, and phytochemicals

Variety is important to get the widest array – dark green, deep orange, citrus

Other Plant-based Foods

7 or more servings of other plant-based foods such as whole grains and legumes

Whole grains are higher in fiber, vitamins, minerals, and phytochemicals than refined grains

The New American Plate

2/3 or more of the plate should be covered by plant-based foods – vegetables, fruits, whole grains, and beans – 1 or more vegetables or fruits and not just grain products

1/3 or less of the plate should be covered by meat, fish, poultry, or low-fat dairy

Physical Activity Engage in regular physical activity and reduce

sedentary activities to promote health, psychological well-being, and a healthy body weight.

Achieve physical fitness by including cardiovascular conditioning, stretching, and resistance exercises.

Children and adolescents – At least 60 minutes on most, preferably all, days of the week.

New for 2005 Specificity of recommendations

– At least 30 minutes to reduce risk of chronic disease– Up to 60 minutes of moderate to vigorous physical

activity may be needed to prevent gradual weight gain that occurs over time

– 60 to 90 minutes of moderate-intensity physical activity to sustain weight loss

Recommendations for specific populations– Those who need to lose weight, overweight children,

pregnant women, breastfeeding women, overweight adults and overweight children with chronic diseases and/or on medication

Change May Occur Slowly

U.S. Obesity and Diabetes Trends in

U.S. Obesity and Diabetes Trends in

Source: Mokdad AH, Serdula MK, Dietz WH, et al.

JAMA, October 27, 1999; 282(16):1519-1522

Source: Mokdad AH, Serdula MK, Dietz WH, et al.

JAMA, October 27, 1999; 282(16):1519-1522

The data shown in these maps were collected through CDC’s Behavioral Risk Factor Surveillance System (BRFSS).

Obesity Trends* Among U.S. AdultsBRFSS, 1985

No Data <10% 10%–14%

(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” person)


No Data <10% 10%–14%



No Data <10% 10%–14% 15%–19%



No Data <10% 10%–14% 15%–19% ≥20



No Data <10% 10%–14% 15%–19% 20%–24% ≥25%


Source: Mokdad et al., Diabetes Care 2000;23:1278-83.

Diabetes Trends* Among Adults in the U.S.,(Includes Gestational Diabetes)

BRFSS 1990

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%


BRFSS 1995

Source: Mokdad et al., Diabetes Care 2000;23:1278-83.

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%


BRFSS 2000

Source: Mokdad et al., J Am Med Assoc 2001;286:10.

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%


BRFSS 2001

Source: Mokdad et al., J Am Med Assoc 2001;286:10.

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

Prevalence of Obesity* in Adults by Gender and Race

0

20

40

60

Males Females Overall

% o

bese

White African Am Mex Am Total

NHANES 2003-2004

Source: Ogden et al., JAMA, 2006

*BMI > 30

Most Recent NHANES Results

66.3% of American adults are overweight (BMI ≥ 25)

4.8% of American adults are extremely obese (BMI ≥ 40)– 10.5% of Non-Hispanic Black

JAMA, 2006:295:1549-1555

Costs of Obesity $75 billion: Annual U.S. medical expenditures

attributed to obesity in 2003 Amount obese people spent on health care costs

compared to normal weight people: 37% more For Youth (6-17 years) between 1979 and 1999:

Hospital discharges for diabetes were nearly 2x Sleep apnea increased 5x Obesity-associated costs were $35 million during 1979-

81 and increased to $127 million during 1997-1999 Annual costs associated with overweight and obesity in

Texas in 2001: $10.5 billion dollars Projected costs for 2040 in Texas: $39 billion in Texas

Sources: Surgeon General’s Report on Obesity, 2001; Finkelstein et al., 2004; Thorpe et al., 2004; Wang & Dietz, 1999-2002

02468

1012141618202224

Total W H A Total W H A

BMI > 40 BMI 35-39 BMI 30-34

W = White, H = Hispanic, A = African American

Figure 1. Prevalence of BMI > 30 within BMI category; 11th grade

Female Male

2001 Grade 5 SAT 9 and Physical Fitness

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6

No. Fitness Standards Achieved

SA

T 9

Pe

rce

nti

le

Reading Math

CA Dept. of Education, 2002


0

10

20

30

40

50

60

70

1 2 3 4 5 6


SA

T 9

Per

cent

ile

Reading Math



0

10

20

30

40

50

60

70

80

1 2 3 4 5 6


SA

T 9

Pe

rce

nti

le

Reading Math


Defining Physical Activity

Physical Activity = any bodily movement produced by skeletal muscles that results in an energy expenditure. It can be categorized in various ways, including type, intensity, and purpose. In terms of disease prevention, the activity usually considered is aerobic in nature, with large muscle groups contracting in a continuous manner

Defining Physical IN-Activity

Physical IN-Activity = a level of activity less than that needed to maintain good health.

– Inactive as per CDC: less than 10 minutes per week of moderate or vigorous physical activity

– Sallis and Owen, 1999: People are considered sedentary when they report no physical

New Description! = Screen Time

Defining Physical FitnessPhysical Fitness = The ability to carry

our daily tasks with vigor and alertness, without undue fatigue, and with ample energy to enjoy leisure-time pursuits and to meet unforeseen emergencies.

A measure of a person’s ability to perform physical activities that require endurance, strength, flexibility

Defining Exercise

Exercise = physical activity that is planned or structured

Repetitive movement to improve/ maintain: Repetitive movement to improve/ maintain:

–Aerobic capacityAerobic capacity–Muscular strengthMuscular strength–Muscular enduranceMuscular endurance–FlexibilityFlexibility–Body compositionBody composition

Quantifying PA measures

Need PA intensity measure Need frequency Need duration Body weight may be needed

Outcome Measures

5 Health Related Components of PA

Caloric Expenditure (CE) Activity Intensity (AI) Weight Bearing (WB) Flexibility (FL) Musculoskeletal (MS)

Physical activity intensity is frequently quantified in terms of metabolic equivalents, or METS

1 MET is rest (as in, 1 times your resting metabolic rate)

1 MET = 1 kcal/kg/hr

All activities are some multiple of this resting MET level

Defining Recommended Activity Recommended Activity =

minimum amount of physical activity required for health benefits

Either regular moderate or vigorous activities equivalent to burn 150 calories/day (1,000 calories/wk)

Physical ActivityTypes/Examples

Vigorous Activities Brisk walking or climbing

uphill High Impact Aerobics Step aerobics Swim laps Bicycling (hills) Jogging

Moderate Activities Walking 3-4.5 mph

(level surface) Low Impact Aerobics Swimming Bicycling (level ground) Mowing grass

Note: Intensity of activity is often determined in metabolic equivalents (METS). METS estimate the metabolic cost of activity;1 MET=resting metabolic rate.

Measurement Survey: diary, recall, quantitative history, global

self-report.

Direct observation, job classification

Heart rate monitor, motion sensors, pedometer, gait assessment, accelerometers.

Direct calorimetry (heat), indirect calorimetry (oxygen), cycle, treadmill, doubly labeled water (H and O).

Doubly Labeled Water Drink water with 2H and 18O isotopes

(natural isotopes) Urine or saliva samples collected pre-

drink, and every few days up to ~14 days Assumption: 2H disappears in H2O and

18O disappears in H2O and CO2 removal Differential loss is equivalent to EE

Doubly Labeled Water 3

Disadvantages– Isotope is very expensive (~$500 per

subject)– Expensive equipment needed for analysis

– Assumes that CO2 ~ O2

– Only Total EE is measured

– Components of PA?

Activity Monitors Assessing PA What are accelerometers? They measure accelerations of the human body They record activity patterns over a period of time Benefits: small, non-invasive, large storage capacity,

used widely in field settings Different types:

– Actigraph (or CSA) - most widely used – Caltrac - estimates energy expenditure– Tritrac - measures PA in 3 directions

(Welk, 2002)

The Actigraph Records levels of PA Worn on waist, wrist or

ankle Records frequency, time

and intensity of PA Can detail percentage

time spent at different activity levels

Monitors continuously

Paediatric monitoring Used in the Liverpool Sporting Playgrounds Project Quantified intensity, duration and frequency of

activity in playtime (10 year-old girl's data shown)

0

200

400

600

800

1000

1200

1400

1600

1800

Tim e

Co

un

ts (

5 s

ec

ep

oc

hs

)

Playtime activity

163

480

790

Moderate PA: 46% (6½ mins)

High PA: 11% (1¾ mins)

Very high PA: 5.6% (1 min)

Heart Rate Monitors HRM measure cardiorespiratory response to

physical activity Transmitter and belt worn around the upper body Data commonly displayed on a wrist receiver Downloaded via interface for analysis

Heart Rate Monitors

Advantages Relationship with

energy expenditure Valid & reliable in lab &

field Describes tempo Easy & quick for data

collection & analyses

Limitations Cost (large samples) Data attrition Discomfort over long

periods Age, sex, training

status affect HR No information on

physical activity context

Direct observation instruments

Measure behavioural aspects of physical activity Provides information on specific activities

occurring in a variety of settings over time Quantitative & qualitative information Useful with younger children Trained observers Pen and paper instruments

Direct observation instruments

Advantages Detailed quantitative

& qualitative data Describes tempo Low financial cost Computer software

allows real time recording & analysis of data

Limitations Time-intensive training Time & labour intensive

data collection Limited sample sizes Observer presence

(reactivity) Limited validation against

physiological criteria

System for Observing Children's Activity during Playtime (SOCAP) Recording Form

Time Area Activity Activities Behaviour Other

Level

0-2 1 3B St T A T to LA

4G W W & T Linked arms

2-4 2 2B V Tick

2B W-V Chasing PF

• Benefits: combines PA with behaviours and identifies contextual influences on PA

• Limitations: new measure which is currently undergoing reliability & validity studies

Physical Activity Questionnaires

• International Physical Activity Questionnaire (IPAQ)

• Physical Activity Questionnaire for Adolescents (PAQ-A)

• Leisure Time Exercise Questionnaire (LTEQ)

Advantages

• Inexpensive, allows large sample size.

• Can be administered quickly and easily.

Limitations

• Reliability and validity problems associated with recall of activity, especially in children.

• Lack objectivity.

Measures = Frequency, Intensity, Time (and Energy Expenditure).

Pedometers Ped- Walk

Meters-measure

Fixed to waistband

Small-light-unobtrusive

Display:-

Steps

Distance

Kcals

• Target:-

• Adult:- 10,000 steps/day

• Children:- 127 steps per

minute.

60 mins=8000 steps/day

Expediency vs Accuracy

Heart rate monitoring

Accelerometry Actiheart GPS systems Direct Observation Doubley labelled

water

QuestionnairesLongShort

Pedometers

Cost

Physical Activity SurveillancePhysical Activity Surveillance Routine surveillance

• Youth Risk Behavior Survey• Behavior Risk Factor Surveillance System• National Health and Nutrition Examination

Survey• National Health Interview Survey• National Personal Transportation Survey• Pediatric Nutrition Surveillance System

Cross-sectional or population studies

Guide to Community Preventive Services (www.thecommunityguide.org/pa)

Community-wide campaigns. Large-scale, highly visible, multicomponent campaigns with messages promoted to large audiences through diverse media, including television, radio, newspapers, movie theaters, billboards, and mailings.

Individually targeted programs. Programs tailored to a person’s readiness for change or specific interests; these programs help people incorporate physical activity into their daily routines by teaching them behavioral skills such as setting goals, building social support, rewarding themselves for small achievements, solving problems, and avoiding relapse.

School-based physical education (PE). School curricula and policies that require students to engage in sufficient moderate to vigorous activity while in school PE class. Schools can accomplish this by increasing the amount of time students spend in PE class or by increasing their activity level during PE class.

Guide to Community Preventive Services (www.thecommunityguide.org/pa)

Interventions that provide social support for physical activity in community settings. Interventions designed to promote physical activity by helping people create, strengthen, and maintain social networks that support their efforts to exercise more; examples include exercise buddy programs and the establishment of exercise contracts or walking groups.

Interventions to provide people greater access to places for physical activity. Examples include building walking or biking trails and making exercise facilities available in community centers or workplaces.

U.S. and Texas adults who meet physical activity guidelines- 2003

05

101520253035404550

Moderate P.A. Vigorous P.A.

U.S. Total

Texas

Source: CDC BRFSS

Physical activity among U.S. adults by gender- 2003

0

10

20

30

40

50

60

Mod PA Inactive

Females

Males

Source: CDC BRFSS

Physical activity among U.S. adults by race/ethnicity- 2003

0

10

20

30

40

50

60

Mod PA

Inactive

Source: CDC BRFSS

Physical activity among U.S. adults by age- 2003

0

10

20

30

40

50

60

18-24 25-34 35-44 45-65 65+

Mod PA

Inactive

Source: CDC BRFSS

Percentage of U.S. adults who meet physical activity recommendations by

education level: 2003

0

10

20

30

40

50

60

<HS HS or GED Some College College Grad

Source: CDC BRFSS

Physical activity among U.S. adults by poverty level- 1999-2001

0

5

10

15

20

25

30

35

Belowpoverty

level

>=1 but<2

>=2 but<4

>=4 Xspoverty

Mod PA 5 or moredaysVig PA 3 or moredays

Source: NHIS

No leisure-time physical activity among U.S. adults by poverty level 1999-2001

0

10

20

30

40

50

60

70

80

BelowPoverty

Level

>=1 <2Xs

Poverty

>=2 but<4 Xs

>=4 Xspoverty

No Mod PA

No Vig PA

Source: NHIS

Physical Activity & U.S. AdultsPrevalence More than 50% of adult Americans do not get enough PA to provide health benefits 26% are not active at all in their leisure time (BRFSS, 2003;)/ 38.6% according to

National Health Interview Survey 1999-2001.

Gender Men (64.2%) more likely than women (59%) to engage in some leisure-time physical

activity; Men more likely than women to engage in light moderate and/or vigorous physical

activity than women five times per week. (NHIS, CDC 2004).

Ethnicity White adults (63.5%) and Asian adults (61.9%) were more likely than African

American adults to engage in some leisure-time physical activity (NHIS, CDC 2004). White adults (49%) more likely to meet moderate PA guidelines compared to African

American (36%) and Hispanics (37%). (BRFSS, 2003) Whites (12%) reported lower inactivity compared to African Americans (24%) and

Hispanics (26%) (BRFSS, 2003)

Source: CDC

Physical Activity & U.S. AdultsAge Engagement in physical activity declines steadily with age.

Education Physical activity increases with educational level. Adults with a graduate degree (81%) were about twice as likely as adults with less

than a high school diploma (41%) to engage in at least some leisure-time physical activity (NHIS, 2004).

Adults with highest educational attainment were almost twice as likely as adults with the least education to engage in light-moderate or vigorous activities five or more times per week (NHIS, 2004).

Women with a bachelor’s degree & graduate-level degree were four times as likely as women with less than a high school diploma to engage in strengthening exercise. (NHIS, 2004)

Poverty Adults with incomes four times the poverty level or more (29.1%) were more likely

than adults with incomes below the poverty level (20.5%) to engage in light-moderate physical activity at least five times per week and more than two times as likely to engage in vigorous physical activity (17.9% and 7.0%, respectively).

Source: CDC

Physical Activity & U.S. AdultsGeographic Region Adults living in the West were more likely to engage in any regular physical

activity (35%) and adults living in the south (28.4%) were least likely to engage in any regular physical activity.

Adults living in a Metropolitan Statistical Area were more likely than adults living outside an MSA and adults living in the central city of an MSA to engage in at least some leisure-time physical activity (64%, 59%, and 59%, respectively).

Marital Status Married women (61.0%) were more likely than women in any other marital status

group to engage in at least some leisure-time physical activity. (NHIS- CDC, 2004)

Widowed adults (23.6%) were less likely than never married (33.0%), married (31.1%) and divorced or separated adults (29.1%) to engage in regular physical activity.

Adults who had never been married (27.5%) were more likely than adults in any other marital status group to engage in strengthening activities. (NHIS – CDC-NCHS, 2004)

Trends 1991-2003 Leisure-time physical activity appears to have increased slightly from 1991

(71.3%) to 2003 (75.6%)

Source: CDC-NCHS: National Health Interview Survey, 1999-2001

U.S. Youth Participation in Sufficient Vigorous (V) and Moderate (M) Physical Activity Levels

by Gender (Grades 9-12)

0

10

20

30

40

50

60

70

80

Vigorous Moderate

Female

Male

Source: CDC YRBS 2003

U.S. Youth Participation in Sufficient Vigorous and Moderate Physical Activity Levels by

Ethnicity (Grades 9-12): 2003

0

10

20

30

40

50

60

70

White African Am. Hispanic

Vigorous

Moderate


U.S. Youth Participation in Sufficient Vigorous (V) Physical Activity Levels by Grade and Sex

30

40

50

60

70

80

9 10 11 12

Grade

Male: V Female: V


U.S. Youth Physical Activity Levels by Age and Sex: Vigorous (V) and Moderate (M)

0

20

40

60

80

12 13 14 15 16 17 18 19 20 21

Age

Male: V Female: V Male: M Female: M

Source: CDC YRBS

Trends in Prevalence of Physical Activity among U.S. Youth: 1991-2003

0

20

40

60

80

1991 1993 1995 1997 1999 2001 2003

Vigorous Moderate Strength Ex Attended PE

Source: CDC YRBS

*

*

*Significant changes over time

Reported Physical Activities from Mid to Late Adolescence - Boys

Physical Activity

% Participants- 1990

% Participants-1993

Basketball 66 59

Football 66 42

Bicycling 58 3

Baseball 55 29

Street hockey 42 30

Weight lifting 31 40

Aaron et al., 2002, Arch Pediatr Adolesc Med

Reported Physical Activities from Mid to Late Adolescence - Girls

Physical Activity

% Participants- 1990

% Participants-1993

Bicycling 52 2

Softball 36 22

Basketball 34 18

Running 29 28

Aerobics 20 23

Bowling 19 10

Aaron et al., 2002, Arch Pediatr Adolesc Med

Prevalence of Obesity by Daily Hours of TV Watching

U.S. children aged 8 – 16, 1988-94

Crespo et al., Arch Ped Adol Med. 2001;155:360-365.

Physical Activity & YouthPrevalence of Physical Activity & Inactivity More than a third of young people in grades 9-12 do not engage in

sufficient vigorous physical activity. About 14% of young people report no recent physical activity. Only 19 percent of high school students are physically active for 20

minutes or more, five days a week, during physical education classes. 38% of youth watch ≥3 hours of TV on a school day

Gender Physical activity is higher among male adolescents, and inactivity is more

common among females than males (14% vs. 7%).

Ethnicity Physical activity levels differ by race/ethnicity, with white adolescents

appearing to engage in more physical activity than African American and Hispanic adolescents

Source: CDC

Physical Activity & YouthAge Participation in all types of physical activity declines strikingly as

grade in school and age increases.

Trends: 1991 - 2003 Slight drop in vigorous physical activity, with around a third who

do not get enough vigorous activity (66% in ‘91 to 63% in 2003). Slight increase in participation in strengthening exercises that

was statistically significant, from 48% in 1991 to 52% in 2003. Daily participation in high school physical education classes

dropped from 42% in 1991 to around 28% in 2003.

Source: CDC

epidemiology of physical activity: 101 july 17, 2007 steven h. kelder, phd, mph professor, division...

Documents

possible causes slide

physical activity environments

comprehensive approach

physical activities

fewer cases of heart

disease control

social environments

fewer injuries