In flue nces on Phys ical Act ivit y of 

Ch ildr en, Adol esce nts, and Adu lts

Ja mes F. S alli s

SAN DIE GO STA TE UNI VERS ITY

ORIGINALLY PUBLISHED AS SERIES 1, NUMBER 7, OF THE PCPFS RESEARCH DIGEST.

HI GHLI GHT

“U n d er st a n d in g t h e m a n y fa ct or s t h a t in flu e n ce p h ysic a l

a c t ivi t y m a y h e lp im p rov e t h e ef fect iven ess of p h ysic a l a c t ivi t y

in t erv en t i on p r ogra m s. Re sea r ch su gges t s t h a t t h e ef fect iven ess

of p r ogra m s sh ou ld be m a xim i zed wh en p a rt ic ip a n t s’

co n fid en ce a b ou t t h eir a b ilit y t o co n t in u e p h ysic a l a c t ivi t ies is 

n u rt u r ed , t h ey en joy t h e a c t ivi t ies t h ey h a ve ch osen , re ceiv e

en cou r a gem en t a n d a s sist a n ce fr om ot h er p e op le in t h eir li ves, 

a n d re sid e in a su p p or t ive en viro n m en t t h a t p r ovid es

co n ven ien t , a t t ra c t ive , a n d sa fe p l a ces fo r p h ysic a l a c t ivi t y.” 

The U.S. Department of Health and Human Services has adopted a policy of increasing

regular physical activity of children, adolescents and adults, because of the numerous health

benefits that have been documented through research (Bouchard et al., 1994). The physical

activity guidelines are published in Healthy People 2000 (USDHHS, 1990). The Surgeon

General’s Report, Physical Activity and Health (USDHHS, 1996) concludes that most

Americans are not physically active enough to optimize their health, and a sizable percent of

adults are extremely sedentary.

Before launching large-scale programs to stimulate more physical activity, it is widely

accepted that a better understanding of the various influences on physical activity habits is

needed. If the most important influences can be identified, then they could be targeted for

change in educational or other intervention programs. In this paper, some of the theory and

research on “determinants” of physical activity are summarized, and both the commonalities

and differences between youth and adults are described. An attempt is made to apply these

findings to the improvement of physical activity intervention programs.
EX PLAI NING HUM AN B EHAV IOR

Human behavior is complex enough to frustrate all attempts to explain it, but the attempts

continue because of the importance of the task. Efforts to explain individual differences in

physical activity are further complicated by variations in frequency, intensity, duration, and

type. The objectives in Healthy People 2000 (USDHHS, 1990) call for decreases in sedentary

behaviors and increases in light-to-moderate, vigorous, strength-building, and flexibilitypromoting activities. The influences may differ for each of these categories of physical

activity. Most of the research work to date has focused on vigorous exercise in leisure time,

but some studies are beginning to examine the influences on moderate-intensity activities, like

walking (Hovell et al., 1992), that are now emphasized in public health recommendations

because of their health benefits (Pate et al., 1995). There are many studies of special

populations, such as cardiac patients, but the pres-ent paper focuses on physical activity in the

general population.

Theoretical models are the starting point for research on human behavior, because

theories simplify the complex phenomena under study by suggesting which factors should be

studied. Psychological models that emphasize the role of knowledge, beliefs, attitudes,

motivations, and emotions have been dominant and have inspired studies that have shown

many psychological factors influence physical activity patterns of adults and youth. These

models include the theory of planned behavior (Godin & Shephard, 1990) and the intrinsic

motivation model (Whitehead, 1993).

Other models take into consideration that beliefs and perceptions are not the only

influences on physical activity. The behavior of others and factors in the external

environment can also play a role in influencing physical activity. Social cognitive theory

(Bandura, 1986) emphasizes multiple influences from within the person, the social

environment, and the physical environment.

Over 300 studies of the influences on physical activity have produced a scientific

literature rich with information, but the picture is not yet entirely clear. The following sections

summarize some of the major findings, and readers desiring more detailed information can

consult recent reviews (Dishman & Sallis, 1994; Sallis & Owen, 1998; USDHHS, 1996).

BI OLOG ICAL AND PSY CHOL OGIC AL I NFLU ENCE S

Biologic factors are strongly associated with level of physical activity, even though it is not

clear these factors actually “cause” physical activity to vary. Age is a potent predictor, and

the level of physical activity is known to decrease throughout the entire age span, beginning

at least with entry into school. During the school years, the activity level declines about 50%

(Sallis, 1993), and the decline continues until the typical elderly person is almost entirely

sedentary (USDHHS, 1996). Females are less physically active than males at virtually all ages

(Pate et al., 1994; USDHHS, 1996), but many people feel this difference is due to

socialization rather than biology.

A biological reason why adults drop out of vigorous exercise programs is musculoskeletal

injuries. In one study, injuries were the most common reason for dropping out (Sallis et al.,

1990), and the history of injuries is a good predictor of future injuries. Though most people

believe the obese are less active than the normal weight, it is difficult to find evidence to

support this notion in either adults or youth. However, recent studies indicate that a substantial

portion of physical activity may be explained by genetic factors (Pérusse et al., 1989).
The personal characteristics of being well educated and affluent are consistently

associated with higher levels of leisure time physical activity. African Americans and Latinos

are usually found to be less active than Anglos, even in childhood (McKenzie et al., 1992).

However, these ethnic differences are largely due to socioeconomic factors (Shea et al.,

1991). It is surprising that health behaviors such as cigarette smoking, dietary habits, and

alcohol consumption are not consistently related to physical activity habits, but it appears that

people selectively choose their health behaviors. Recent physical activity predicts future

activity in leisure time, but activity levels in childhood are not reliable predictors of exercise

habits in adulthood. One explanation is that children may be taught activities, like team sports,

that are difficult to carry over to adulthood.

A wide variety of psychological factors appear to influence participation in physical

activity among adults. Much of our current understanding can be summarized by stating that

beliefs and perceptions that are not personal in nature, such as knowledge about exercise,

personality traits, and general attitudes, are weakly related to behavior. Personal beliefs about

one’s own physical activity are usually found to be significant influences on physical activity.

One of the strongest predictors of future activity is perceptions of personal efficacy, or

confidence regarding one’s ability to be active on a regular basis. Simple ratings are useful in

predicting activity levels among adolescents (Reynolds et al., 1990) and adults of all ages

(Garcia & King, 1991; McAuley, 1992; Sallis, Hovell, Hofstetter, et al., 1992). Program

leaders could use such ratings to estimate which participants are likely to continue activity and

which are at risk of dropping out.

There is a growing literature that supports the common belief that people must enjoy

physical activity if they are to continue. Enjoyment appears to influence the activity levels of

both children (Stucky-Ropp & DiLorenzo, 1993) and adults (Garcia & King, 1991). One of

the main influences on enjoyment is the amount of exertion required by the activity. Children

(Epstein et al., 1991) and adults (Garcia & King, 1991) prefer activities with lower levels of

exertion, and dropout rates are higher from vigorous activity than from moderate-intensity

activity (Dishman & Sallis, 1994). One of the reasons behind the recent emphasis on

encouraging people to engage in moderate activities (USDHHS, 1990) is that more people are

expected to adhere.

Every sedentary person seems to have a reason for not being active, and knowing what

those reasons are can provide clues about how to design an intervention. It is well known that

the most common reason is “lack of time.” In addition, the number and strength of

perceived barriers to activity are consistently related to physical activity in both adults (Sallis,

Hovell, Hofstetter, et al., 1992) and adolescents (Tappe et at., 1989).

Psychological influences on children’s physical activity have not been widely researched,

in part because of the difficulties of assessing psychological states in children, and in part

because parents and teachers select and control many of children’s physical activities. Most

children enjoy “playing,” but our research group has encountered many children in

elementary schools who complain, in the same way adults do, they do not have the time for

physical activity.
SO CIAL AND PHY SICA L EN VIRO NMEN T IN FLUE NCES 

Significant others can make it more or less likely that a person is active on a regular basis.

Social influences on physical activity are strong for people of all ages, but the nature of the

support varies with developmental level. Social support for adults can come from friends,

coworkers, or family members, and the main types of support are encouragement,

participating m physical activities, and providing assistance, such as child care (Dishman &

Sallis, 1994). For adolescents, the influence of peers is paramount. If a given adolescent

identifies with a peer group that values and participates in physical activity, the group creates

a supportive environment for its members. If the main peer group devalues physical activity,

this is an effective deterrent.

The younger the child, the more influential parents are. Studies of children aged 9 to 13

years have shown there are several ways that parents can support children’s physical activity.

Serving as active role models and providing encouragement may have limited influence, but

two studies show that parents can have the most impact by directly helping children be active.

Parents who participate in activities with their children (Stucky-Ropp & DiLorenzo, 1993),

organize activities (Anderssen & Wold, 1992), or transport children to places where they can

be active are the most effective supporters (Sallis, Alcaraz, et al., 1992). For preschool

children, prompts and encouragement to be active can be helpful (Sallis et al., 1993).

It seems self-evident that physical environmental factors such as climate and weather can

have a major effect on physical activities, but few of many possible environmental factors

have been documented in research. It is probable that changes in the environment have made

it necessary to focus attention on increasing physical activity. Automobiles, television,

computers, labor-saving devices, and sedentary jobs have created an environment that makes

possible a profoundly sedentary lifestyle for large numbers of people, maybe for the first

time in history. Thus, it is critical to be aware of the effect of our artificial environments on

physical activity levels (Sallis & Owen, 1998).

A supportive environment for adults might consist of a safe and attractive space for

outdoor activities, exercise equipment or supplies in or near the home, and convenient access

to exercise facilities and programs. One study showed that adults were more likely to be active

if they had a number of exercise facilities within a short distance from their homes (Sallis et

al., 1990). For adolescents, it may be especially important to have organized activities in

convenient locations, such as afterschool intramural teams.

A supportive environment is essential for younger children. Because it is difficult for

children to be active indoors, time spent outdoors is highly correlated with physical activity

levels (Klesges et al., 1990; Sallis et al., 1993). Many parents are concerned about the safety

of the their neighborhoods and prohibit children from going outside to play. Unfortunately,

the more parental rules that limit children’s play, the less physically active young children are

(Sallis et al., 1993). The more places the child can play that are within walking distance from

home, the more active the child is (Sallis et al., 1993). Balancing safety concerns with the

need to let children play outdoors is a serious challenge.

Television is a ubiquitous part of the environment of children, adolescents, and adults that

encourages sedentary behavior. However, there is little indication that children or adults who

watch the most television are the least active. There is reason to limit the hours per week

children watch television, because of associations between amount of television viewing and

obesity (Robinson et al., 1993).
AP PLYI NG T HE R ESEA RCH TO T HE I MPRO VEME NT O F

PR OGRA MS

The research on influences on physical activity provides information that may be useful in

more effectively promoting physical activity in individuals or groups of adults and youth.

Figure 4.1 is a checklist that can be used to assess some of the key influences. Steps can then

be taken to modify these influences so that physical activity is facilitated.

The biological and demographic influences are not easily changeable, but they provide

some index of risk. A person or group with a low score on this section may need additional

assistance in developing regular physical activity habits.

The higher the scores on the Psychological, Social, and Physical Environment sections,

the more likely the person or group is to be physically active. Ideally, there are some checks

in all of the sections. If there are few checks in a section, consider how to make changes in

some of the influences listed. This checklist provides a rough assessment of existing resources

and strengths as well as an indication of areas that need improvement. The reader is

challenged to use this assessment to guide appropriate changes in personal or other physical

activity programs.

FI GURE 4 .1 

As sess in g in flu e n ces on p h y sic al ac tiv i ty .

Ch eck thos e th at a pply . Ea ch c heck rep rese nts an i nflu ence tha t su ppor ts p hysi cal acti vity .

Bi olog ical and Dem ogra phic Inf luen ces

Ag e. O ne c heck if less tha n 50 ; tw o ch ecks if less tha n 18 yea rs.

Ma le s ex.

No (or min or) hist ory of a ctiv ity- rela ted inju ries .

Ge neti cs. Both par ents led act ive life styl es.

Gr adua ted coll ege (for chi ldre n, o ne p aren t gr adua ted coll ege) .

Wh ite- coll ar o ccup atio n (f or c hild ren, par ents hav e wh ite- coll ar o ccup atio n).

Ps ycho logi cal Infl uenc es

Se lf-e ffic acy. Hig h le vel of c onfi denc e in abi lity to do r egul ar p hysi cal acti vity .

En joy phys ical act ivit y.

Be lief tha t ti me f or p hysi cal acti vity can be foun d.

Pe rcei ve f ew b arri ers to d oing reg ular phy sica l ac tivi ty.

St rong int enti ons to b e ph ysic ally act ive. 

Be lief tha t pe rson al b enef its of p hysi cal acti vity out weig h th e co sts. 

So cial Inf luen ces

Fr iend s or fam ily are acti ve r ole mode ls.

Fr iend s or fam ily enco urag e ph ysic al a ctiv ity. 

Fr iend s or fam ily part icip ate in p hysi cal acti vity wit h yo u.

Fr iend s or fam ily dire ctly hel p yo u be phy sica lly acti ve.

Ph ysic al E nvir onme nt

We athe r or cli mate is favo rabl e fo r pr efer red acti viti es.

Fe el s afe bein g ac tive out door s ne ar h ome. 

At trac tive out door spa ce i s co nven ient .

Ex erci se f acil itie s or pro gram s ar e co nven ient and aff orda ble. 
Ex erci se e quip ment or supp lies in home .

S UM MA RY 

Many health benefits of physical activity are documented, but large numbers of Americans

are not engaging in the recommended levels of physical activity. Understanding the many

factors that influence physical activity may help improve the effectiveness of physical activity

intervention programs. Research suggests that the effectiveness of programs should be

maximized when participants’ confidence about their ability to continue physical activities is

nurtured, they enjoy the activities they have chosen, receive encouragement and assistance

from other people in their lives, and reside in a supportive environment that provides

convenient, attractive and safe places for physical activity.

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