Incentivizing Behavior: Promoting More Physical Activity in American Indian Youth
Phase: NA
Conditions: Insulin Resistance, Obesity, Sedentary Lifestyle
Sponsor: University of Oklahoma

 
 
 
Protocol Title:   Incentivizing behavior: promoting more physical activity in American Indian youth  
 
ClinicalTrials.gov Identifier: NCT01848353 
 
Version date of this document: January 4, 2016 
 
Principle Investigators:  Kevin R. Short, PhD; Kenneth C. Copeland, MD,  Section of Diabetes/ 
Endocrinology, Department of Pediatrics, University of Oklahoma Health Sciences Center 
 
Funding:  NIH/NIMHD.  Project 2 of P20MD000528, American Indian Diabetes Prevention Center  
 
 
 
 
 
 

 
SPECIFIC AIMS 
Half of adolescents in the United States fail to reach recommended levels of physical activity and nearly a 
third are overweight, elevating cardiometabolic risk early in life and setting the stage for adult disease.  
American Indians have the highest prevalence of type 2 diabetes in the United States, an elevated risk that is 
evident even in childhood.  Thus, effective interventions are needed to reduce the lifetime medical and 
socioeconomic burdens of diabetes and related diseases.  Through our prior clinical and research partnerships 
with American Indians in Oklahoma, we have gained insight into the health concerns of American Indian youth 
and the importance of community and healthcare leaders in developing creative collaborative approaches that 
work towards solutions.  Based on this expertise, we developed the proposed strategy to improve the health of 
sedentary, obese American Indian youth by providing incentives for increased physical activity.   
The high-risk youth who will be enrolled in the proposed study live in a predominantly rural, low 
socioeconomic region of Oklahoma.  They currently have access to several well-equipped fitness centers in 
the region, but these resources are underutilized.  Although it is well-accepted that regular exercise can 
improve individual health and reduce the socioeconomic burden of diabetes, reducing barriers and effectively 
modifying behavior presents a significant challenge.  Prior studies have shown that paying adults for desired 
behaviors and/or health outcomes can be effective, but the use of financial incentives to shape exercise 
behavior in adolescents has not been reported.  We hypothesize that monetary incentives will encourage 
obese, insulin resistant American Indian youth to establish and maintain better exercise habits, ultimately 
resulting in better health.  We propose to provide transportation for participants to the wellness centers and 
individually tailored instruction and oversight by fitness professionals so that the centers are accessible and 
appealing.  The provision of monetary incentives is designed to reinforce the frequency and duration of 
exercise.  Our strategy to accomplish these goals is outlined in the following Specific Aims:   
Aim 1: To determine whether financial incentives will increase the frequency of exercise sessions 
performed by American Indian youth at a community fitness center.  Obese, insulin resistant American Indian 
adolescents will be randomly assigned to one of two groups for a 16-week exercise program: Control 
($4/session, up to 3 sessions/week, provided as compensation for time), or Incentive ($4, $10, and $16 for the 
first, second, and third session each week, respectively).  All participants will be provided transportation to and 
from the fitness center and professional instruction and supervision for aerobic exercise training, but will differ 
only in the amount of money they are eligible to collect for their attendance.  A secondary goal of this Aim is to 
assess the association between exercise frequency and changes in diabetes-related risk factors, including 
insulin sensitivity, body composition, and blood lipids. 
Aim 2: To determine whether financial incentives will increase the duration of exercise performed by 
American Indian youth at a community fitness center.  Participants who complete Aim 1 will be re-randomized 
to one of two groups for a second 16-week period of exercise: Control ($4/session, up to 3 sessions/week), or 
Incentive ($4, $7, or $10 for 20-, 40-, or 60- minute sessions, respectively, up to 3 sessions and $30/week). 
Transportation and professional supervision will remain the same as in Aim 1.  A secondary goal is to assess 
the association between exercise duration and changes in diabetes-related risk factors. 
Aim 3: To determine whether ongoing incentives are required for maintenance of fitness center utilization 
established with financial incentives.  Participants who complete Aim 2 will enter a third 16-week exercise 
period with diminished monetary incentives.  Each person will be re-randomized to one of two incentive 
structures:  a) Ramp-down, with financial incentives diminishing to zero by 8 weeks, or b) Raffle, with monetary 
prizes awarded through a drawing in which chances of winning are dependent on frequency and duration of 
exercise.  We hypothesize that exercise behavior will remain above zero even after financial incentives decline 
and that the Raffle approach will reinforce the best exercise behavior maintenance.  Clinical diabetes risk 
outcomes will be measured as in Aims 1 and 2. 
Aim 4: To measure the impact of physical activity and physical fitness on circulating biomarkers of 
metabolic disease risk.  Normal weight American Indian youth with either low physical activity and fitness or 
high physical activity and fitness will be studied on a single occasion.  Serum/plasma concentrations of lipids, 
amino acids, and related markers of inflammation, and oxidative and vascular stress will be compared among 
the normal weight participants and the overweight/obese youth enrolled in Aims 1-3. 
This study will clarify how specific incentive structures can be used to promote exercise in a population of 
adolescents at exceptionally high risk for diabetes and cardiometabolic disease.  The study will also provide 
needed insight on the volume of exercise needed to elicit changes in clinical outcomes.  These results will be 
used to develop better lifestyle intervention strategies for American Indian youth. 

 
RESEARCH STRATEGY: APPROACH 
Design: Specific Aims 1-3 will follow a single prospective, randomized trial design, with 105 participants 
enrolled and 80-90 entering the exercise program (Fig 1).  The 
individual Aims are distinguished by sequential study phases and 
varying incentive structures (Fig 2 and 3).  Aim 4 is a cross-
sectional comparison between overweight/obese participants 
entering the main trial and two groups of normal weight youth (up 
to 40 participants per group) with either low physical activity and 
fitness or high physical activity and fitness (up to 40 participants 
per group). 
Participants: Male and female American Indian youth 11-21 
years old will be recruited from the Choctaw Health Service Area 
of SE Oklahoma.  For the primary exercise incentives study, the 
eligibility criteria include BMI ≥85th percentile for age- and sex-
specific norms based on growth charts from the Centers for 
Disease Control, maturation level ≥Tanner Stage 2 for breasts 
(girls) or genitalia (boys), family history of T2D, and recent history 
of low physical activity.   Low physical activity, defined as attaining 
<30 minutes of structured moderate-to-vigorous intensity exercise 
on ≤ 3 days/week over the preceding 3 months, will be confirmed 
through questionnaires and objective monitoring as described 
below.  For both normal weight comparison groups in Aim 4, 
eligibility will include BMI greater than 20th and less than 85th 
percentile, maturation level ≥Tanner Stage 2 for breasts (girls) or 
genitalia (boys), and recent history of either a) low physical 
activity (same as the overweight/obese group) or, b) high physical 
activity (>30 minutes of structured moderate-to-vigorous intensity 
exercise on >3 days/week over the preceding 3 months.  T2D 
family history will be recorded but will not be an inclusion criterion 
for the normal weight groups.  Fitness level and physical activity 
will be determined through testing, described below.  Additional 
enrollment and retention eligibility criteria are: lack of diabetes or 
other potentially confounding metabolic disorders, able to safely 
exercise, willingness to complete the testing and participation 
schedule, and not on medications known to impact the stated 
outcomes.  A medical history and physical exam will be performed 
to assure suitability for the study during the initial screening.   
Protocol:  All overweight/obese participants will follow the same 
protocol.  After an initial screening to ensure eligibility, a standard 
set of clinical outcome assessments will be performed at baseline 
(Pre-test), after completing 16-weeks of exercise training in Aim 1 
(Post-test 1), again after completing the second 16-week exercise 
period in Aim 2 (Post-test 2), and once more after completing the 
16-week exercise period in Aim 3 (Post test 3).  Normal weight participants enrolled into Aim 4 will complete 
only the screening and baseline tests; they will not continue with the incentivized exercise program. 
Screening:  During this visit, informed written consent/ assent of participants and their parents will be 
obtained in accordance with IRB guidelines.  A medical history and physical exam will be performed.  Each 
child and a parent/guardian will be interviewed to educate them on their child’s health status, the importance of 
physical activity as a component of a healthy lifestyle, and the potential improvements in clinical outcomes that 
may occur in response to increased exercise behavior.  The interview will also be used to assess potential 
barriers to change.  This may include, but is not limited to several identifiable personal and environmental 
concerns that could interfere with the child’s ability to complete the study, such as family employment 
demands, income and education status, transportation and food availability, social structure, and competing 
 
Fig 1.  Projected protocol flow. 

 
time demands.  A comprehensive, individualized plan will be developed to reduce barriers.  A motivation 
assessment questionnaire with established validity and reliability (62, 73, 91) and adapted for a rural 
community will be used to evaluate preferred types of exercise, social support, and perceptions of barriers to 
exercise by child and family.  Community and environmental barriers to exercise will also be assessed.  The 
Choctaw Nation of Oklahoma offers several social service programs designed to eliminate distress, including 
academic tutoring, mentoring, organized activities, housing assistance, nutrition classes, and counseling.  
Many of these services are located near the Wellness Centers.  The interviewer will be responsible for linking 
the family to these services when appropriate and performing follow-up to address new and existing barriers.  
The goal of this effort is to insure that a decision by the child or family to discontinue the study is due to choice 
and not due to barriers that can be reasonably addressed. 
Baseline pre-training testing: The baseline tests may be combined with the screening visit.  Baseline 
tests will be comprised of measurements of daily physical activity, aerobic fitness, body composition, and 
insulin resistance.  Daily physical activity will be objectively measured with a step-activity monitor worn for 7 
days during waking hours.  Participants will be asked to maintain their normal lifestyle patterns during this time.  
A registered dietitian will provide instruction on a healthy eating plan but specific weight loss goals or dietary 
monitoring will not be part of this study.  Insulin resistance and other clinical outcomes will be assessed using 
fasting blood samples.  Participants will report to the research center in the morning following an overnight fast.  
Body composition and exercise tests will be performed as described below. 
Exercise training: The 16-week Aim 1 exercise training period will begin within two weeks after the Pre-
test.  Training sessions will be performed at one of the Wellness Centers described in Facilities, with potential 
for additional sites depending on needs and the availability of appropriate supervision.  All participants already 
have free membership to the Wellness Centers as a benefit provided to Certificate Degree of Indian Blood 
(CDIB) cardholders.  Free transportation will be arranged through a shuttle service already in place for medical 
visits.  Fitness professionals at each center will provide instruction, supervision, and ongoing guidance to 
assure that exercise sessions are completed safely and effectively.  Participants and their parent/guardian will 
be instructed that the exercise goal throughout the entire 48-week study is to achieve 60 min/day of moderate-
to-vigorous physical activity (MVPA), consistent with current guidelines for children (13, 31, 90).  MVPA is 
defined as continuous exercise that elicits a heart rate ≥ 70% of peak heart rate.  Each participant will be able 
to choose the frequency of visits to the wellness center and the length of time engaged in MVPA, since the 
purpose of the study is to test the effect of incentives on exercise behavior.  Several types of exercise can be 
selected, including walking, running, cycling, stair stepping, aerobic dance or other activities.  Instructors will 
advise a gradual increase in exercise intensity and duration as tolerated over the first 2-3 weeks to allow for 
familiarization and safety.  To promote healthy behavior within the community and foster social support, all 
participants will be invited to exercise with family members or friends if they choose and this will be recorded 
as a covariate.  As in our previous studies, exercise intensity will be monitored by recording heart rate with a 
chest strap transmitter that outputs to a computer for quantification and data storage.  These data will be used 
to document training sessions.  To provide backup in the event of technical failure, training sessions will also 
be recorded in an exercise log by each participant and confirmed by fitness center staff.  Exercise will be 
quantified by frequency (sessions per week), duration (length of sessions), and total volume (Metabolic 
Equivalent of Task-hours, MET-h, a measure of intensity relative to resting x activity time). 
After completing Aim 1 and the associated post-test, all participants who completed an average of ≥ 1 
exercise session per week will be eligible to continue on to Aim 2.  The only difference between Aims 1 and 2 
will be the financial incentive scheme; the overall exercise goals, and provision of transportation and 
professional oversight will remain the same.  Similarly, after completing Aim 2 and the associated post-test, all 
participants who have averaged ≥ 1 exercise session per week in Aim 2 will be eligible to continue on to Aim 3.  
No changes will be made to the exercise goals or availability of transportation and facilities in Aim 3.   
To allow for potential schedule conflicts and missed sessions (e.g., illness, travel) participants will be 
allowed to “catch-up” by performing up to 3 extra sessions within the 3 weeks following a week with less than 3 
sessions.  Thus, if an entire week is missed due to illness, 12 sessions for payment can be completed over the 
next 3 weeks instead of the targeted 9 sessions.  Additionally, participants will not be discouraged from 
performing more than the targeted exercise volume of 3 days per week of 60 minutes per session.  Exercise 
beyond this target that is performed at school, at home or at the Wellness Centers is acceptable, since the goal 
of this program is to foster increased physical activity.  Participants will be instructed to include such extra 

 
physical activity in their exercise log book, though they will not receive payment for days or time beyond the 
structured incentive program.  This information will be used as part of the data analysis plan if applicable. 
Post-training testing:  After each of the 16-week exercise phases in Aims 1, 2, and 3, the clinical outcome 
tests performed at the baseline will be repeated.  Staff that supervise exercise sessions will not be blinded to 
group assignment, but most other staff, including nurses and chemistry lab staff, will not know group 
assignments, so the potential for bias is expected to be low.  The fasting blood sample will be acquired 2 days 
(38-48 hours) after the last exercise session in order to assess exercise adaptations that are distinct from the 
residual effects of the most recent training session.  The exercise fitness and body composition tests will also 
be repeated at the end of each study phase. 
Group assignment:  Within each Aim, participants will be assigned to one of two groups using a randomized 
stratified block design that was selected to reduce the potential for baseline variability among the groups.  
Participants will be assigned to blocks of 2 (duos) matched for age and sex.  A participant who is not yet 
matched on the two factors will determine the age and sex for a newly established duo. The next participant to 
meet those matching criteria will be assigned to that duo.  Each duo will have one participant in each of the 
intervention groups, but the group to which each participant in a block is assigned will be pre-determined by a 
unique random permutation. 
Incentive programs 
Overview and rationale:  Each participant will receive $50 for completing the initial screening visit and 
baseline set of clinical and fitness tests.  Normal weight participants in Aim 4 will stop after completing the 
baseline tests.  Overweight/obese participants who continue into the exercise program will also receive and 
$50 each time they complete the end-of-phase set of clinical and fitness tests (3 Post-tests after each 16-week 
study phase).  These payments are similar to amounts used in our recent and ongoing studies of children that 
have similar procedures and time requirements.  The payment schedules for exercise sessions are detailed in 
each of the separate Aims sections below.  We set the payment levels for Aims 1 and 2 based on our 
experience with exercise studies for adolescents.  Payments were selected to be commensurate with the time 
commitment of participants, as well as the need to create a distinctly higher payment in the incentivized groups 
so as to elicit the targeted high adherence.  The total time for testing and exercise sessions per participant is 
~164 hours over ~50 weeks, not including transportation time to and from the participant’s home or school and 
the wellness and testing sites.  Depending on group assignment, the range of total compensation to 
participants who complete all assigned study visits will be $716-1,292, or ~$4.40-7.90 per hour of involvement.  
We deemed this to be an appropriate compensation/ incentive without inducing undue influence.  Payments for 
screening and baseline test will be arranged at the time of completion using a reloadable debit card provided at 
no charge to the participants.  Thereafter, payments for completed exercise training sessions and Post-
exercise tests will be provided every 2 weeks for as long as the participant remains in the study. 
Aim 1:  This aim will test the hypothesis that the frequency of exercise sessions at the wellness center will 
vary with the amount of money offered for the number of 
sessions per week.  Participants will be assigned to one of 
two groups that only differ in the payments for completing 
their exercise sessions.  For both groups, payment will be 
provided for the number of sessions performed, up to 3 per 
week.  As shown in Fig 2, the Control group can earn up to 
$12 per week at a flat rate of $4 per session, while those in 
the Incentive group can earn up to $30 per week through 
an incentive structure meant to encourage exercise on 3 
days per week.  Qualifying exercise sessions for both 
groups must be ≥ 20 minutes/session of MVPA during the 
first 3 weeks, increasing to ≥ 30 minutes/ session of MVPA 
in weeks 4-16.  To allow for rest breaks, the activity time 
can be accumulated rather than continuous.  The plan for 
recording sessions and making up missed sessions is 
outlined in the Exercise Training section.  By completing all 
of the targeted 48 exercise sessions participants can earn 
a maximum of $192 (Control) or $480 (Incentive) for exercise in this Aim. 
Aim 1 payments, exercise sessions/week: 
 
Session of the week 
 
Group 
Day 1 Day 2 Day 3 Max. 
Control 
$4 
$4 
$4 
$12 
Incentive 
$4 
$10 
$16 
$30 
 
Aim 2 payments, exercise time/session: 
 
Time per session 
 
Group 
20 min 40 min 60 min Max. 
Control 
$4 
$4 
$4 
$12 
Incentive 
$4 
$7 
$10 
$30 
 
Fig 2.  Aims 1 & 2 incentive structures.  
Values are payments per visit and weekly 
maximum.

 
Aim 2:  This aim will test the hypothesis that exercise time per visit will vary with the amount of money 
offered for the length of exercise sessions.  In this aim, as in Aim 1, the Control group will earn $4 per session 
for up to 3 sessions per week.  The Incentive group can earn up to $30/week, with a payment structure based 
on the length of time for each exercise session (Fig 2).  The incentive is meant to encourage at least 60 
minutes of MVPA per exercise session, consistent with the daily activity recommendations for youth.  As in Aim 
1, this study phase is 16 weeks so completion of all 48 targeted exercise sessions will result in payments of 
$192 (Control) or $480 (Incentive). 
Aim 3:  This aim will determine if exercise behavior 
developed during the preceding 32 weeks will continue 
when payments for exercise are diminished.  
Participants will be randomized to either the Ramp-down 
or Raffle group.  Maximum payments for the Ramp-
down group will begin at $20/week, through a payment 
structure that incentivizes exercise time, as in Aim 2, 
with a bonus for completing 3 sessions in a week (Fig 
3).  The weekly payments will be decreased over 8 
weeks, reaching $0 for weeks 9-16.  The Raffle group 
will earn chances to win prize money based on the 
number of fitness center exercise sessions and time 
spent exercising each week.  The number of raffle 
entries earned for each session will vary from 1-16 per 
participant each week (Fig 3).  Random drawings will be 
conducted to determine winners, with the total value of 
the weekly prize pool set to ~$7 per person.  All 
participants will continue to receive the same 
transportation and Wellness Center access as before.  
Total potential payment for exercise in Aim 3 will be 
~$112 per participant, though the actual amount for 
Raffle group members will vary according to chance. 
Clinical outcome tests 
Insulin sensitivity: Fasting insulin sensitivity will be 
assessed by Homeostasis Model of Assessment - 
Insulin Resistance (HOMA-IR), calculated as: [fasting insulin (µIU/ml) x fasting glucose (mg/dl)/405].  
Anthropometry and blood pressure:  Height, body mass, and waist and hip circumference will be 
measured by trained nurses.  As regularly performed by our lab, total body and regional fat and lean tissue will 
be measured using bioelectrical impedance analysis at each of the pre- and post-training visits.  Blood 
pressure will be measured in duplicate after the child has rested quietly for 15 minutes using an appropriately 
sized arm cuff. 
Fitness testing: Bicycle ergometer tests with increasing workloads will be used to measure maximal 
aerobic work output, peak rate of oxygen consumption (VO2peak) and heart rate, and the workload 
corresponding to a heart rate of 170 beats/min (48, 77).  Submaximal stages will be used to establish 
relationships among heart rate and power and used to assess work economy.  Continuous measurements of 
expired gases will be performed with a facemask and metabolic measurement cart and heart rate with Polar 
heart rate monitors.  For normal weight participants, the cut point for fitness level (low versus high) will be a 
VO2peak of 46 ml/kg/min for boys and 37 ml/kg/min for girls.  This threshold was identified as a marker of 
elevated metabolic risk, based on a composite of standard clinical outcomes such as blood pressure, glucose, 
lipids, and waist circumference, in a cohort of more than 2,000 adolescents (age ~15 y), who performed a 
standard bicycle fitness test (4). 
Physical activity assessment:  Free-living daily ambulatory activity will be measured with accelerometers 
worn on the waist (Fitbit Zip, Fitbit Inc.) throughout the day, recording data each minute for 7 days.  Data 
analysis includes total step count and activity patterns based on step rates. We have recently completed 
validation and reliability assessments of these monitors in our laboratory have found very high levels of 
agreement with other waist or ankle-worn accelerometers. 
Aim 3 Ramp-down payments: 
 
Time per session 
3d/wk 
 
Week 20 min 40 min 60 min Bonus Max. 
1 
$2 
$4 
$6 
$2 
$20 
2 
$2 
$4 
$6 
$2 
$20 
3 
$2 
$4 
$5 
$2 
$17 
4 
$2 
$4 
$4 
$2 
$14 
5 
$1 
$2 
$4 
$2 
$14 
6 
$1 
$2 
$3 
$1 
$10 
7 
$1 
$1 
$3 
$1 
$10 
8 
$1 
$1 
$2 
$1 
$7 
  
Aim 3 Raffle chances earned: 
Exercise time 
per session 
Session of the week  
Day 1  Day 2  Day 3 Max. 
20 min 
1 
2 
3 
6 
40 min 
2 
3 
5 
10 
60 min 
4 
5 
7 
16 
 
Fig 3.  Aim 3 incentive schemes. The Ramp-down 
bonus is for completing 3 sessions/week.  Max. = 
total payment or raffle chances per week. 

 
Plasma/serum analysis: In addition to measurements of glucose and insulin performed to measure insulin 
resistance, blood will be collected for measurement of lipids, inflammatory and related disease risk markers.  
All planned assays are established on campus or in our laboratory.  Lipid analyses include total-, HDL- and 
LDL-cholesterol and non-esterified fatty acids (colorimetric assay, Wako Chemicals, Richmond, VA).  Pro-
inflammatory biomarkers associated with obesity and insulin resistance include oxidized LDL (oxLDL) and HDL 
(oxHDL), high-sensitivity C-reactive protein, myeloperoxidase, high-molecular weight adiponectin, visfatin, and 
the soluble vascular-derived molecules, intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell 
adhesion molecule-1 (VCAM-1), measured with ELISAs from Phoenix Pharmaceuticals, R&D Systems and 
Millipore.  Additionally, we will measure the plasma concentration of a panel of amino acids and their 
metabolites (particularly isoleucine, leucine, valine, and adiptic acid), and a panel of fatty acyl CoA’s, that have 
been reported to be increased in children and adults with diabetes, and have been shown to predict the future 
onset of diabetes (2, 3, 8, 16, 39, 57, 64, 74, 75, 83, 101, 104, 105).  Hemoglobin A1c will be measured to 
assess recent history of glycemic regulation and diabetes risk (Choctaw Nation Health Clinic).   Blood 
collection, sample analysis and destruction of unused samples will adhere to NIH, IRB and Choctaw Nation of 
Oklahoma guidelines.  
Data analyses:  Since group assignments will be balanced for age and sex, the groups are expected to be 
similar at baseline.  Additional comparisons will be performed to identify demographic or other variables on 
which the groups might differ (e.g., weight loss) that could affect the primary outcomes.  Subsequent analyses 
will adjust for these potentially confounding variables.  Regression models, which adjust for modifier (or 
confounding) variables identified in initial data exploration, will compare between-group differences in the 
primary outcomes.  Since we anticipate that the number of fitness center visits, which is the primary outcome in 
Aim 1, will follow a Poisson distribution typical of counts, we will explore a multivariable Poisson regression 
model to analyze that aim.  To assess Aim 2, a more conventional regression model will analyze the primary 
outcome, which is the total time that participants engage in exercise.  The effects of exercise training on 
secondary outcomes will be analyzed similarly, using multiple linear regression.  Analysis of Aim 3 will also 
utilize multivariate modeling to determine which factors, including exercise group assignment, best explain the 
change in exercise volume and clinical outcomes over the final phase of the study.  Residuals generated from 
regression models will be inspected for normality and data will be log-transformed or subjected to non-
parametric testing as appropriate.  Aim 4 is a cross-sectional study design so the main effects of physical 
activity (high versus low), fitness (high versus low) and body size (normal weight versus overweight/obese) on 
biomarkers of metabolic disease risk will be initially determined using an analysis of variance approach, with 
Bonferroni tests to make pairwise comparisons between groups.  A multivariate modeling approach, similar to 
that used in Aims 1-3, will be used to identify the best sets of predictor variables for specific biomarkers.   A P 
value <0.05 will be considered statistically significant. 
 
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