Motivation to Exercise (Motiv2Ex)

This investigation will address increased physical activity and will yield empirical evidence to inform developing tools to help individuals make healthy choices regarding physical activity (PA) and maintenance of healthy body weight. Behavioral Choice Theory provides a framework for understanding choices people make and how to shift an individual's choice toward healthier alternatives. The theory holds that choice is based on the relative motivating values of alternatives. One way to shift choice toward a healthier alternative is to increase the relative reinforcing value (RRV), or motivating value, of that alternative. Thus, increasing the RRV of PA behaviors could shift choice towards PA and away from less healthy, sedentary alternatives. Increasing the RRV of PA may allow PA to compete with more reinforcing, sedentary behaviors, resulting in a shift in behavioral choice. This process is termed "incentive sensitization", which was originally proposed to explain drug addiction. Incentive Sensitization theory posits that the RRV of a behavior is increased through repeated exposures, which produce neuroadaptations that increase craving of the behavior - after repeated exposures to a stimulus, a 'sensitization' or hypersensitivity to the incentive motivational effects of the stimulus follows. Another factor that influences motivation for a behavior is the development of tolerance to unpleasant aspects of that behavior. Opponent-Process Theory would account for the acquisition of motives where the initial reinforcer may be negative - the affect experienced after repeated exposures is opposite to that experienced during the first few presentations. For exercise, this would include tolerance to any discomfort, pain, fatigue and displeasure and a greater positive post-exercise affective response: the affect experienced during and after exercise has a greater motivational significance in PA participation than knowledge and beliefs regarding health benefits. Therefore, the investigators propose that repeated exposures to PA will produce tolerance to unpleasant aspects while increasing the post-exercise affect. Sensitizing PA reinforcement and increasing discomfort tolerance may be associated with increasing the duration and intensity of daily activity. There are likely to be individual differences in sensitization of PA reinforcement and development of discomfort tolerance. Single-nucleotide polymorphisms (SNPs) that alter dopamine tone in the central dopaminergic reward system and SNPs associated with altered pain perception may contribute to such individual differences. The investigators anticipate that a moderate PA dose (300 kilocalorie [kcal] expenditure) will produce greater incentive sensitization and tolerance than a low dose (150 kcal) and that SNPs related to central dopamine tone and pain perception may contribute to individual differences in incentive sensitization and changes in physical activity after repeated exposures to physical activity.

Relative Reinforcing Value of high dose exercise (300 kcal expenditure per session) versus sedentary activity will be determined.

Relative Reinforcing Value of low dose exercise (150 kcal expenditure per session) versus sedentary activity will be determined.

Relative Reinforcing Value of no exercise (0 kcal expenditure per session) versus sedentary activity will be determined.

Subjects will participate in 3 physical activity sessions per week expending 300 kcal per session and rate their liking of exercise.

Subjects will participate in 3 physical activity sessions per week expending 150 kcal per session and rate their liking of exercise.

Subjects will participate in 3 sessions per week expending 0 kcal per session and rate their liking of exercise.

Subjects will rate their liking of sedentary activities (reading magazines, playing word games, puzzles) as an alternative to exercise.

RRV of physical activity will be assessed by evaluating the number of responses (mouse button presses) a subject is willing to complete to gain access to physical activity or a sedentary alternative.

Changes in preference for intense physical activity and tolerance for exercise discomfort will be assessed by self-report questionnaire responses to the Preference for and Tolerance of the Intensity of Exercise Questionnaire (PRETIE-Q).

Minutes of physical activity will be assessed by having participants wear an Actigraph accelerometer for 7 days (minimum 10 hours per day) on the right hip.

Changes perceived support for physical activity from friends and family members will be assessed by self-report questionnaire responses to the Social Norms and Support for Exercise Questionnaire.

Changes in perceptions of how much exercise satisfies autonomy, relatedness, and competence needs will be assessed by self-report questionnaire responses to the Psychological Need Satisfaction in Exercise Scale.

Changes in intrinsic, external, interrogated, identified, introjected and amotivation for physical activity

Changes in intrinsic, external, interrogated, identified, introjected and amotivation for physical activity will be assessed by self-report questionnaire responses to the Behavioral Regulation in Exercise, 3rd Edition (BREQ-3).

Changes in perceived effort expended during exercise will be assessed by self-report questionnaire responses to the Rating of Perceived Exertion Scale.

Changes in perceived pain/discomfort during exercise will be assessed by self-report questionnaire responses to the Muscle Pain Questionnaire.

Changes in perceived ability to continue exercise long-term will be assessed by self-report questionnaire responses to the Exercise Self-Efficacy Scale.

Changes in perceived ability to stick to an exercise routine will be assessed by self-report questionnaire responses to the Exercise Confidence Survey.

Changes in perceived affective responses (energy, tiredness, tension, calmness) to exercise will be assessed by self-report questionnaire responses to the Activation Deactivation Adjective Check List (ADCL).

Changes in average daily calorie intake will be assessed by reporting all foods and beverages consumed over a 3-day period.

Inclusion Criteria: BMI within 19-35 kg/m2 Healthy enough to exercise Sedentary (not regularly engaging in exercise more than once per week) Exclusion Criteria: Taking any medications that affect energy expenditure or eating Have gained or lost more than 10 pounds over the past 3 months Use tobacco Pregnant or lactating or plan to become pregnant in the next 6 months Have any medical conditions that prevent the individual from safely joining in physical activity Have high work-related activity such as construction and farm work