Comentarios a la última Declaración de Helsinki, emitida en octubre de 2013 Pau Ferrer Salvans Institut Borja de Bioètica Secretario del CEIC del Hospital de San Juan de Dios de Barcelona Como es sabido la Declaración de Helsinki (DH) (1) es un documento de referencia, que desde el año 1964, en que fue publicada por primera vez, sirve de guía ética a los médicos que quieren
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Pii: s0749-3797(98)00083-xIntegrating Theoretical Approaches
to Promote Physical Activity
Leonard H. Epstein
Research on the promotion of physical activity has been based on a variety of conceptualmodels. These models generally target one level of analysis, such as the individual,community, or the environment, and differ in their relative contact with basic or appliedscience. There have been limited attempts to develop approaches that target multiple levelsof analysis and can stimulate basic and applied research.
Theoretical integration in a multidiscliplinary field such as promotion of physical activityshould take into account that social, behavioral, and biomedical colleagues may usedifferent explanatory models, and use different approaches to the development ofscientific knowledge. This essay argues for the development of integration of theory acrossmultiple domains that can incorporate methods and findings of basic and appliedscientists, and that uses language and methods common to social, behavioral, andbiomedical scientists.
Behavioral choice theory is presented as an example of one theoretical approach thatbridges different approaches to physical activity intervention, and that can stimulate bothbasic and applied research on physical activity. Behavioral research on choice was discussedin relationship to basic research, human laboratory research, and community and clinicalresearch.
Implications of behavioral choice theory for community and environmental change wasdiscussed. The essay ends with ideas for future directions in integration of theory forphysical activity research.
Medical Subject Headings (MeSH): physical fitness; health promotion; leisure activities
(recreation); models, theoretical; behavior (Am J Prev Med 1998;15(4):257–265) 1998
American Journal of Preventive Medicine
mental laws that influence behavior, while applied research uses knowledge gained in basic work. Anotherdistinction among scientific approaches is the concep- Withinactivityasamajorpublichealthprob- tualization of methods of inquiry as “bottom up” or “top down.” Bottom up approaches attempt to under- suggested to modify physical activity. The stand a phenomenon by examining the building blocks Surgeon General’s report on physical activity provides of the phenomenon. Basic scientists are often inter- an excellent overview of a variety of conceptual ap- ested in understanding how the component parts work, proaches to increasing physical activity.1 This report and then attempting to relate the component to the presents eight different models of behavior change that integrated organism. The top down approach argues are focused at three levels of analysis: individual, inter- that you have to study the integrated organism in the context in which the organism normally behaves. Pro- There are distinctions other than level of analysis ponents of the top down approach believe that studying that can be drawn between approaches to research on the component parts separately will not inform you the promotion of physical activity. One distinction is how they work together in the complex organism.
the extent to which research is basic or applied. Basic Differentiation of theoretical approaches to a prob- research is designed to develop knowledge on funda- lem broadens the scope of intellectual inquiry byincluding a variety of assumptions, investigative para- From the Department of Psychology, University at Buffalo, Buffalo, digms, and methods of inquiry. It takes time and a body of research to understand the strengths and limitations Address Correspondence to: Dr. L.H. Epstein, Department of of different theoretical perspectives. As a field matures, Psychology, University at Buffalo, Park Hall, Box 604110, Buffalo,New York 14260-4110.
a more parsimonious theory or conceptual approach is 1998 American Journal of Preventive Medicine needed that can address issues across levels of analysis, level of analysis, and conceptualize problems using providing a common language and set of concepts that tools of basic and applied sciences.
are relevant to the field. The research questions thatare asked become refined, and answers often shift from Behavioral Economics or Behavioral Choice Theory complex interactions in multivariate models to morebasic mechanisms that operate for selected groups of Behavioral economics, or behavioral choice theory,5,6 is a theoretical approach that attempts to understand There is another challenge for researchers interested decision making and how time and responses are in the promotion of physical activity. This area of allocated given the options available. The theory is research usually involves multidisciplinary collabora- based in part on basic research on learning,7 cognitive tions. For example, a team might include specialists in psychology and decision making,8,9 and economics.10 behavior change, health care, and exercise physiology, As will be illustrated in the next section, this theoretical interested in increasing activity, the effect of exercise approach has been used to guide basic and applied on a disease process, and quantification of the changes research across individual, community, and environ- in fitness that mediate the changes in health outcome, mental levels of analysis. Behavioral choice theory may respectively. These investigators address different as- also be useful in bridging the gap between social and pects of the problem using theories and methods behavioral science and biomedical researchers. New comprehensive theories have combined biological con- Members of a multidisciplinary team can benefit trol theory2 and learning theory4 with many common from theoretical approaches that are relevant to bio- constructs in behavioral choice theory and biological medical as well as social and behavioral scientists.
control theory. In addition, behavioral choice theory However, there are several factors that may impede a includes a strong tradition of theory building anddeductive research, as well an equally strong tradition common theoretical approach in multidisciplinary re- of inductive, or empirical, approaches to knowledge search. First, the working models and approaches to acquisition.5 A similarity in approaches to knowledge theory that biomedical researchers often use are very acquisition in the social and behavioral and biomedical different from those used by social and behavioral sciences may make it easier to develop integrated science researchers. Biomedical researchers often use a model of physiological regulation based on homoeo-static control and positive and negative feedback.2 Thismodel is generally not used in most social and behav- ioral science theories, with exceptions.3,4 Second, most There are several general principles that can be derived biomedical researchers use a combination of empiri- from research on basic behavioral choice theory. These cally derived (inductive) and deductive theoretical principles can be applied to sedentary individuals, who, models to approach a problem. Many social science given the opportunity between sedentary and physically approaches are strongly tied to deductive models of active alternatives, will reliably choose the sedentary inquiry, and research that is not theory-based, or does alternative. First, choice of an alternative depends on not conform to the use of deductive models, is consid- the behavioral cost.11 Thus, even very powerful phar- ered inferior and less likely to yield new scientific macological reinforcers, such as addictive drugs, are knowledge. This bias disregards the fact that theory subject to the demands of cost. This general principle building can include both inductive (empirical) and provides an empirical basis for policy decisions that deductive (model testing) approaches. Both ap- attempt to reduce demand by increasing the cost of a proaches contribute to knowledge, and major advances substance.12,13 The choice of being sedentary is very in a field are often based on new approaches and a responsive to cost,14–16 and reducing the accessibility of paradigm shift, rather than knowledge derived from sedentary behaviors or increasing the cost of being deductive theory testing. It is likely that a combination sedentary are both methods for reducing sedentary of inductive and deductive approaches is best.
The goal of this essay is to present a brief overview of A second general principle is that the choice and behavioral choice theory, and show how this theory can reinforcing value of a commodity depends in part on incorporate methods and findings relevant to basic and the available alternatives. Providing a reinforcing alter- applied investigators, using bottom up and top down native can shift choice, without changing cost or avail- approaches, across multiple levels of analysis. The goal ability of the usual choice. For example, Higgins and is not to present this as the best approach to research colleagues17 have demonstrated that cocaine self-ad- on promoting physical activity, but rather to illustrate ministration (10 mg unit dose) in cocaine users can be how investigators interested in modifying physical ac- reduced by providing alternative monetary reinforcers tivity can utilize theories that address more than one (up to $20.00). While subjects may generally choose to American Journal of Preventive Medicine, Volume 15, Number 4 be sedentary, choice may shift if the sedentary behavior immediately available. This phenomenon has been is not valued as highly as the active alternative.
labeled impulsive behavior, and individual differences The reinforcing value of the alternative is not static, in the shift from more valuable to less valuable alterna- but may change over time or be modified by other tive is an index of impulsivity. Subjects who switch behaviors. Experience with the alternative can influ- quickly as the more valuable reinforcer is delayed are ence the extent to which an alternative can substitute more impulsive. This is very relevant to physical activity for the usual choice. For example, Carrol and col- since some of the benefits of being active are delayed, leagues studied the relative reinforcing value of cocaine while benefits of sedentary alternatives may be imme- versus water sweetened with glucose and saccharin.18 diately experienced. This self-control paradigm is cen- For animals who were dependent on cocaine, animals tral to understanding choice and decision making21 chose cocaine almost exclusively. However, for animals and has provided interesting individual differences in who first had experience with sweetened water, they the reinforcing value of food in humans.22 were less likely to become dependent on cocaine, Behavioral choice theory is based in part on under- suggesting that access to an alternative reinforcer re- standing factors that influence the reinforcing value of duced the development of drug dependence. A similar an alternative, and thus behavioral choice theory makes effect of experience with the nondrug reinforcer has contact with biological mechanisms involved in rein- been observed on the development of cocaine self- forcement. There is considerable interest in neuro- administration in primates.19 The observation that ex- sciences in identifying the biological mechanisms of perience with an alternative nondrug reinforcer can reinforcement, and progress has been made in identi- influence the development of dependence is important fying the biological basis of psychostimulant drugs and as we consider how to increase activity. Early exposure food.23,24 One of the major new theories on psychobi- to an active lifestyle may protect some from the rein- ological mechanisms for drug reinforcement include both the dopaminergic and opioid systems. Robinson A third general principle is that choice is important and Berridge23 argue that the opioid system is involved to motivate people to obtain a reinforcer. For example, in liking, or the affective quality of a stimulus, and the Wolffgramm20 and colleagues compared rats provided opioid system contributes to the motivational drive to access to a choice of alcohol or water, to rats forced to obtain the stimulus, which is regulated primarily by the consume alcohol by providing that as the only fluid dopaminergic system. These two systems can be acti- option, versus a control group that had access only to vated independently. Long-term drug reinforcement, water. After eight months of access to alcohol, the rats and perhaps mechanisms for many nonpharmacologi- were tested for dependence, and then abstained from cal reinforcers, depend on activation of the dopaminer- alcohol for three months. Rats were then reintroduced gic system, and people may be motivated to use drugs to alcohol to test the extent to which alcohol became a even in situations where they report not liking the drug.
reinforcer. Only rats who were given the choice to Behaviors such as physical activity may not be moti- consume alcohol during development of dependence vated exclusively by positive reinforcement. Many stud- chose to drink it. Being forced to consume alcohol did ies have used a negative reinforcement model for not establish alcohol as a reinforcer. Similarly, rats had exercise, focusing on stress reduction and negative choice or forced access to opiates for 30 weeks, were affect reduction as motivations to be physically active.25 tested for dependence, and then were abstinent for 19 Robinson and Berridge23 acknowledge that negative weeks. Only animals that initially chose the opiate reinforcement can make a contribution to motivated self-administered it later. Thus, in order for these behaviors such as drug use, but they argue that in many powerful drugs to become reinforcers, consumption situations, and for many people, the positively reinforc- had to be voluntary, rather than forced. If people ing effects of the drug predominate. This may be a perceive that they are forced to initiate activity pro- relevant distinction for physical activity, since the posi- grams as part of treatment, but do not perceive that tively reinforcing effects of activity have not received as they chose to be active, they may not be motivated to much attention as the stress-reducing effects of physical make being physically active part of their lifestyle.
A fourth general principle is that choice depends in Behavioral genetics may yield important insights into part on the delay between choosing and receiving the factors that influence physical activity as a reinforcer.
alternatives. In many choice situations, the outcomes Significant progress has been made in the genetics of are delayed from the responses. When human subjects the dopaminergic system for drug susceptibility and are provided a choice of two reinforcers immediately food.26 There has been considerable interest in the available, subjects reliably choose the more valuable genetics of fitness, and genetic responses to training,27 reinforcer. But as the more valuable reinforcer is but to my knowledge there are no data that would link delayed, subjects may switch from the more valuable genetics to individual differences in reinforcing or delayed reinforcer to the less valuable reinforcer that is physical activity more then lower valued sedentary The observation that children are more physically Although physical activity is part of a healthy lifestyle, active when the alternative is a lower preference seden- approximately 40% of the population remains com- tary behavior suggests that reducing access to high- pletely sedentary and the majority of the United States preference sedentary behaviors may increase activity.
population is not active enough to derive health bene- We found in a series of laboratory studies that reinforc- fits from their physical activity.1,28 The majority of ing obese children for decreasing high-preference sed- leisure time, and increasingly more work time, is spent entary activities such as television watching and video being sedentary. Inactivity is a significant public health game playing was associated with increases in physical activity that are similar to the changes that occur when Some people find exercise to be very reinforcing, physical activity is reinforced.15,16 These studies also and engage in physical activity on nearly a daily basis.
suggest that sedentary activities do not readily substi- Others find sedentary activities more reinforcing. One tute for each other. If sedentary activities were com- important variable that may influence physical activity pletely substitutable, children would replace all prior is obesity. Epstein et al.14 found that when obese and time spent in high-preference sedentary activities with nonobese children were given the choice between time engaged in low-preference sedentary activities.
sedentary and active alternatives, they chose to spend Liking of activity is often considered to be an impor- the majority of their time being sedentary. However, tant influence on activity, but liking represents a differ- when the cost of being sedentary was increased, a direct ent construct than reinforcing value, with a different relationship was observed between the degree of obe- psychobiological basis.23 To test the influence of liking sity and substitutability of physically active for sedentary of different physical activities on choice, Epstein et al.14 behaviors. Very obese children did not switch to phys- gave children the choice of a highly liked sedentary ical activities despite large disparities in the work re- activity and either a highly liked physical activity or a quired to obtain access to sedentary versus physical least liked physical activity. When the sedentary and physical activity options were equally available in both The cost of being physically active is related to the tasks, children chose to be sedentary. Children de- accessibility of physical activity, and it is not surprising creased their choice of being sedentary with increasing that accessibility is correlated with activity levels.29 In a cost for sedentary activity, but the point of switching to laboratory test of the influence of accessibility on physical activity was the same regardless of whether the choice of sedentary and physically active alternatives,30 physical activity option was highly liked or least liked.
we randomized sedentary male college students to If sedentary behaviors are more reinforcing for some groups that varied the proximity of sedentary and people than being active, perhaps sedentary behaviors physical activities, with near defined as immediately can be used to reinforce these people for being more accessible in the same room and far as a 5-minute walk.
active. Saelens and Epstein32 studied whether making When sedentary alternatives were near, subjects chose sedentary activities such as video game playing and to be sedentary, but when sedentary activities were far watching movies on a videocassette recorder contin- and physical activities were near, subjects spent the gent on riding the cycle ergometer would increase entire session being physically active. The requirement physical activity. In a control group, being active or of making people walk for 5 minutes to get access to sedentary was freely available. Children in the contin- sedentary activities was enough to shift their choice to gent group dramatically increased their physical activity physical activity. This makes a strong case for reducing to get access to television activities even though other proximity to sedentary behaviors to prompt the choice sedentary activities were freely available, whereas those in the control group remained sedentary. There may be How powerful are different sedentary behaviors in considerable potential for motivating activity by arrang-ing access to sedentary activities that are normally freely competing with being active? Saelens and Epstein31 provided children the choice between physical activityand high- or low-preference sedentary activities, withpreference defined by the amount of time the child spent in that activity during a baseline session. Children choose to be more physically active when given thechoice between low-preference sedentary activity and One of the first studies to highlight the choice among physical activity than when the choice was between active alternatives was by Brownell and colleagues33 high-preference sedentary activity and physical activity.
who observed over 45,000 choices of people taking the Highly valued sedentary activities may compete with stairs or an escalator in a shopping mall, train station, American Journal of Preventive Medicine, Volume 15, Number 4 and bus terminal. After collecting baseline data, a tions that involve decision making as intervening vari- colorful sign depicting a heart using the stairs was ables in activity level. For example, the stages-of-change placed at the choice point between the escalator and model uses the construct of decisional balance theory stairs. The use of the stairs doubled, and remained to understand why people choose to be active or not.41 doubled over 15 days. The use of stairs decreased when This approach is based on rational choice theory, in the sign was removed. These results show that small which people weigh the pluses and minuses of their prompts to be active may alter choice of physical decisions, and respond on the basis of a hypothetical activity. The influence of a sign to modify stair versus balance sheet. Contemporary decision and choice the- ories have recognized limitations of rational choice Wolffgramm and Heyne20 found that in basic animal theories, and have attempted to include additional research, choice of a behavior is important for motiva- variables in the decision-making process.6,42,43 Behav- tion to repeat that behavior. In naturalistic settings, ioral choice theory may represent an approach that perception of choice may be as important as actual extends beyond rational choice theory to improve the control of choice. Thompson and Wankel35 studied prediction of choice. An example of the influence of females who had enrolled at a health club and were psychological variables on choice is research on impul- randomized to one of two groups. Subjects were asked sive behavior and self-control that provides subjects their activity preferences, and then randomized to with a choice between alternatives that are provided at groups who were provided a standardized exercise different points after the choice, such as a pencil now, program set up by the staff, or subjects were told their or five dollars in two weeks. This choice depends not program was based on individual preferences. At the only on the rational choice of which is more valuable, end of the six weeks, adherence was significantly but also individual differences in waiting for the larger, greater for subjects who perceived that they had choice over their exercise program, versus those who did nothave choice.
The generalizability of laboratory studies that reduce access to sedentary behaviors14 was tested for obese children participating in family-based weight controlprograms. Children and their families were random- Behavioral choice theory has been extended to com- ized to groups in which they were reinforced for being munity interventions and used to influence policy more active, reinforced for being less sedentary, or decisions for important community problems such as reinforced for the combination of the two.36 All chil- drug use,12,13 energy conservation,44 and obesity.45 One dren were provided the same dietary changes. At one extension of behavioral choice theory is to increase the year, the best changes in obesity were seen for children cost of drugs, thereby reducing their use. Increasing reinforced for reducing sedentary behaviors. Each the tax on drugs can reduce demand, but the influence group showed similar changes in fitness. The improve- will be greater in situations in which the reinforcing ment in weight control was probably due in part to shift value is less, as in new users, or situations in which there in allocation of time from sedentary to physically active are other powerful alternative reinforcers.12 Likewise, alternatives, and to a decrease in eating opportunities taxing can influence food consumption. Brownell has as time in sedentary behaviors was decreased.
argued that the increase in obesity is due to a toxic There are additional studies that suggest that in- environment that fosters increased intake of food and creased choice and control are related to better adher- decreases activity. Taxing snack foods significantly re- ence to activity programs. King and colleagues random- duced snack food intake in California,46 which is easy to ized sedentary elderly adults to structured aerobic understand given the vast options available to consum- exercise conditions at exercise sites versus home-based ers of acceptable food alternatives. Obviously, increased exercise where subjects had more flexibility regarding cost of engaging in a behavior will be less effective if when and where to exercise. Long-term results showed better maintenance for the home-based, rather than There are potential monetary incentives that could site-based exercise programs.37 Perri and colleagues be used to influence physical activity at the community similarly showed that home-based exercise programs level. Incentives could include reduced insurance pre- were superior to site-based programs for the treatment miums for regular exercisers, or tax rebates for busi- of obesity.38 More flexible, lifestyle activity programs nesses that arrange environments that promote activity, are also associated with better weight loss up to two or direct reinforcement for regular exercise, with the years after initiation of treatment in obese children.39,40 amount of exercise related to the amount of rebate at a Behavioral choice theory provides a rich theoretical health club. It might be interesting to consider taxing framework for understanding how people make people for car use, with the money being used to choices, and therefore may be able to improve predic- increase access to active modes of transportation to work. Pay-per-view television, more costly movies, and people who lived within two miles of work, and had safe increasing the cost of video games might influence the level of sedentary behavior, though it is difficult to Finally, as community, environmental, and policy imagine the circumstances that would give rise to these approaches to physical activity are considered, it is important to keep in mind the importance of choice It is not necessary to use monetary incentives to and the perception of control in developing options for promote physical activity. Behavioral choice theory being active. There is a delicate balance between ag- suggests that environmental changes that both increase gressively promoting, encouraging, and reinforcing the proximity and convenience of physical activity and physical activity and the need to boost self-regulation decrease access to sedentary activities can increase and control. At a policy level, it is often assumed that physical activity. Unfortunately, environments have be- restriction of things that are bad for you is the best come saturated with labor-saving and convenient sed- approach, and the more restriction, the better the entary activities that decrease the need to be physically approach will work. However, restriction is a powerful active. It is possible that such sedentary environments method for increasing the reinforcing value of the have increased the value of sedentary activities or behavior that is being restricted. Reduction can also decreased the value of physical activity, both of which take place by reinforcing people for reducing their would contribute to higher rates of sedentary activity.
behavior, rather than restricting access to the behavior.
Interventions that increase access to opportunities for For example, we were able to increase activity and being active, such as creating bicycle lanes, providing decrease liking of being sedentary more by reinforcing more opportunities for children to be active, and sedentary children for being less sedentary than by ensuring that indoor walking is available for inclement removing the television, VCR, and computer games weather, may have some impact on activity. Likewise, reducing access to sedentary behaviors may have animpact on activity, as people have to make choices about new ways to allocate time. It is logical thatinterventions that both increase access to active oppor- The purpose of this paper was to encourage investiga- tunities as well as decreasing access to sedentary behav- tors to integrate theoretical perspectives that address iors are most likely to have long-term success.
multiple levels of inquiry. This includes paradigms There are many things that are possible in contem- within the social and behavioral sciences that may porary workplaces that could increase activity by mod- target different levels of influence, as well as paradigms ifying lifestyles. A great example of a choice situation in that can bridge basic and applied interests, as well as many workplaces is the choice to take the elevator or top-down or bottom-up approaches to knowledge ac- the stairs. This choice may be influenced not only by the motivation to be more active, but by accessibility to This paper dealt with one approach, behavioral elevator or stairs. It is more common to have easy access choice theory, that can serve as an example of a theory to an elevator that is well lighted and freshly painted, that can organize and stimulate research across multi- while the stairs are hidden, locked, or dirty. It would be ple levels. This discussion will focus on two issues, interesting to assess stair use in situations in which the future directions in theory integration for physical stairs are easily accessible and brightly lit, with music activity, and future directions for behavioral choice activated by the footsteps, while the elevator is hard to theory in physical activity research.
find and dimly lit. Choice of stair use over escalator orelevator is a good target for environmental studies, as Future Directions in Theory Integration for
research has shown it may be relatively easy to Physical Activity
The incorporation of increased activity into lifestyles Physical activity research has benefitted from social and is one of the most interesting new approaches to behavioral science research, whereas physical activity promoting physical activity. One very important com- research in biomedicine has often contributed to fun- ponent of lifestyle exercise is using transportation as a damental new knowledge. Attempts to assess whether form of exercise. Walking or bicycling to work would social and behavioral science research in physical activ- provide the opportunity for many people to get all the ity can develop fundamental new knowledge or theory exercise they needed in a day, without the need to find additional time to be active. Businesses would need to Theories can be developed in part from new princi- provide opportunities for employees to have lockers ples or advances in fields other than social and behav- and a place to shower to take advantage of using ioral science. There are numerous examples of this in transportation as a form of physical activity. It would be regard to basic theory construction. For example, be- interesting to evaluate this by studying a sample of havioral choice theory has borrowed considerably from American Journal of Preventive Medicine, Volume 15, Number 4 economic theory,6 behavioral momentum theory has haviors is needed. People may be inactive because they borrowed from physics,47 and new approaches to nutri- find sedentary behaviors reinforcing and/or because tional assessment have borrowed from developments in they do not like to be physically active. Individual differences may assist investigators in matching inter- The use and development of theoretical approaches ventions with the characteristics of the sedentary sub- that are accessible to both biomedical and social and jects. If there are individual differences, are they influ- behavioral scientists are needed. When possible, inte- enced by genetic factors? Will developing a better grative approaches that utilize common theoretical understanding of genetics and reinforcement provide constructs should be encouraged. An excellent exam- clues to why people differ in their motivation to be ple of this is the use of negative feedback theory in active? Are these individual differences influenced by learning? Can environments be arranged that maxi- Differences in use of inductive and deductive theo- mize the development of a motivation to be active? rizing across social and behavioral sciences and bio- Ideas about choice of being active, rather than forced medical sciences should be better appreciated, and activity; the use of activity as a reinforcer, rather than an both approaches to knowledge acquisition integrated instrumental response; pairing physical activity with in future theoretical development for physical activity.
pleasant associations; and the arrangement of environ- More rigorous evaluation of what constitutes theory ments that foster physical activity and suppress being and theoretical models is needed, rather than elevating sedentary may provide theoretical constructs that can ideas and conceptual approaches to physical activity as theories. It should be possible to confirm, or discon- Can deprivation of physical activity be used to make firm, theories applied to physical activity research, such activity more reinforcing? As deprivation increases the that some theories are tested and discarded. It is reinforcing value of food, can deprivation increase the generally the case that lists grow, rather than shrink, reinforcing value of being active? According to disequi- with more research. No one wants to offend particular librium theory of reinforcement,50 reducing physical groups of investigators, and few theories are discon- activity below baseline levels would result in an increase in the reinforcing value of activity. It would be interest- It is common in the social and behavioral sciences to ing to determine if these brief shifts in reinforcing make distinctions regarding controlling variables or value could be used to produce more permanent shifts mechanisms in terms of opposing classes of indepen- in the level, and reinforcing value of activity.
dent variables, such as mind versus body, psychological Behavioral economic analyses of physical activity versus physiological, or environmental versus genetic, bring into focus the significant impact that environ- when the distinction is more an issue of level of analysis ments have on our choices. More research is needed than difference. A better appreciation of the integra- that focuses on the influence of environmental context tion of these positions in physical activity research is to increase access to activity, increase the reinforcing or punishing influence of the environment on physicalactivity, and establish the influence of the environmenton reducing access to sedentary activities.
Future Directions for Behavioral Choice Theory
Is the low level of physical activity in part due to Considerable progress has been made in understand- environmental constraints on activity, or prompts to be ing the substitutability of sedentary and active behav- inactive, and might more progress be obtained by iors, as well as substitutability within classes of sedentary focusing on environmental and policy issues than on behaviors. People will shift from being sedentary to being active if the cost of being sedentary increases,14 Research is needed on behaviors that compete with and people will not choose sedentary behaviors if access being active. How reinforcing is it for some people to to them is reduced.30 The types or variety14,49 of be sedentary, and can we develop physically active physical activities used as alternatives to being sedentary substitutes to being sedentary? If this is not possible for have not influenced physical activity when the alterna- some people, how much constraint is required on the tive is highly liked and preferred sedentary behaviors.
sedentary alternatives to shift choice from being seden- However, the types of sedentary behaviors provided as alternatives to the physical activities may be very rele- Research on the reinforcing value of physical activity vant. Reducing access to highly preferred sedentary is needed that focuses on distinctions among physical behaviors shifts activity, while reducing access to less activities made by exercise physiologists that influence preferred sedentary behaviors has little effect on fitness. For example, is exercise intensity related to the motivation to be physically active? Are there important Additional research on individual differences in the motivational differences among types of activities, such reinforcing value of physical activity or sedentary be- as aerobic, stretching, or resistance activities? Are there entry activities that may stimulate other activities, or is Kagel JH, eds. Advances in behavioral economics, volume the motivation to be active specific to each physical 13. Hursh SR. Behavioral economics of drug self-administra- It should not be assumed that the choice of being tion and drug abuse policy. J Exp Anal Behav 1991;56: physically active is stable over time. It may shift as a 14. Epstein LH, Smith JA, Vara LS, Rodefer JS. Behavioral function of the alternatives available, competing de- economic analysis of activity choice in obese children.
mands on the person, and shifts in the reinforcing value of activity if a person habituates to the positive 15. Epstein LH, Saelens BE, O’Brien JG. Effects of reinforc- sensory experiences associated with being active, or ing increases in active behavior versus decreases in sed- satiates to a particular activity. Interventions may have entary behavior for obese children. Int J Behav Med to be adjusted, or modified over time as shifts in the relative reinforcing value of the available choices 16. Epstein LH, Saelens BE, Myers MD, Vito D. The effects of decreasing sedentary behaviors on activity choice inobese children. Health Psychol 1997;16:107–13.
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