Individual and Family-based Approaches to Increase Physical Activity in Adolescents With IDD
Phase: NA
Conditions: Adolescent Behavior, Intellectual Disability, Down Syndrome, Physical Activity
Sponsor: University of Kansas

 
Individual and Family-Based Approaches to Increase Physical Activity in Adolescents with Intellectual 
and Developmental Disabilities 
 
NCT Title: Promotion of Physical Activity in Adolescents with Intellectual and Developmental 
Disabilities 
 
NCT03684512 
 
Protocol and Analysis Plan 
 
Last updated 11/17/20 
 
 
 
 
 
 
 

 
Specific Aims  
Adolescents with intellectual and developmental disabilities (IDD) are less physically active and have lower 
cardiovascular fitness compared with their typically developing peers. Similar to their typically developing 
peers, low moderate-to-vigorous physical activity (MVPA) and low cardiovascular fitness are associated with 
increased chronic disease risk and decreased quality of life in this group. Adolescents with IDD also face 
additional barriers to participation in MVPA including dependence on parents for transportation to exercise 
facilities, lack of appropriate exercise facilities, lack of professionals with expertise regarding their specific 
needs, and lack of peer support. The limited number of trials that have evaluated strategies to increase MVPA 
in adolescents with IDD were generally short-term (8-24 wks.), non-randomized, and were conducted in small 
samples (n=≤ 30), at a gym, community center or other type of facility, and were generally unsuccessful in 
increasing MVPA. Data from our group, and others, suggest that the time and expense required for parents to 
transport their adolescents to a facility represents a major barrier to participation in PA. This suggests that 
alternative strategies for delivery of PA interventions for adolescents with IDD, which eliminate the 
transportation barrier, need to be developed and evaluated. Results from our single arm, short-term (12 wks.) 
pilot trial (n= 29) suggest the feasibility of delivering an intervention to increase MVPA in adolescents with IDD 
via video conferencing. In our pilot, health coaches delivered three 30-min. real-time MVPA sessions/wk. via 
video conferencing on an iPad (Zoom software), to groups of 5-6 adolescents with IDD in their homes. 
Participants were asked to complete additional MVPA between scheduled group sessions. Participants 
attended 77% of possible sessions, with an average heart rate of ~124 beats/min. This approach promoted 
interactions between both the group leader and participants (24/session), and between individual participants 
(12/session), and a 25% increase from baseline in objectively assessed daily PA (Garmin Vivofit). However, 
the effectiveness of the group video approach, or the effect of including parental education/support to increase 
and maintain MVPA over a longer time-frame (12-18 mos.) in adolescents with IDD is unknown. Parental 
involvement may be important in increasing MVPA in adolescents with IDD, who by the nature of their 
condition are more dependent on parents that typically developing adolescents. Thus, as requested by PAR-
14-315, we propose to compare the effect of two strategies to increase MVPA in adolescents with IDD; a single 
level intervention delivered to the adolescent only, and a multi-level intervention delivered to both the 
adolescent and a parent. We propose an 18 mo. trial (6 mos. active, 6 mos. maintenance, 6 mos. no-contact 
follow-up) using intent-to-treat principles to compare changes in objectively assessed MVPA in 114 
adolescents with IDD randomized to a single level intervention delivered to the adolescent only (AO) or a multi-
level intervention delivered to both the adolescent and a parent (A+P). Adolescents in both intervention arms 
will be asked to attend three 40-min., home-based, group MVPA sessions/wk. (0-6 mos.) and one 40-min. 
sessions/wk. during mos. 7-12. A trained health coach will conduct group exercise sessions using video 
conferencing software (ZoomTM Video Conferencing Inc., San Jose, CA). Adolescents will be asked to 
complete a weekly activity homework assignment to reach a target of 300 min. of MVPA/wk.  Parents of 
adolescents in the AO group will receive a reminder phone call if the adolescent misses more than two 
consecutive scheduled MVPA sessions. Parents of adolescents in the A+P group will be asked to participate in 
the group video MVPA sessions, attend educational/support sessions  with their adolescent and the health 
coach regarding the role of MVPA in health and function and support their adolescent in completing their 
activity homework assignments. Education/support sessions will include strategies for increasing MVPA in both 
the adolescent and parent (0-6 mos. 2 session/mo.; 7-12 mos. 1 session/mo.).   
Primary aim: To compare changes in MVPA (min./d) between the AO and A+P groups across 6 mos. We 
expect a significantly greater increases in MVPA in adolescents in the A+P vs. the AO group. 
Secondary aims: To compare changes between the AO and A+P groups on the following variables across 18 
mos.:1) MVPA (min/d) and sedentary time (adolescents and parents).  Adolescents only: 2) cardiovascular 
fitness, 3) muscular strength, 4) motor ability, 5) quality of life. We will also compare the percentage of 
adolescents achieving an average of 60 min/d of MVPA (US recommendation) across 18 mos.  We expect 
more favorable changes for all secondary outcomes in adolescents in the A+P vs. the AO group.    
Exploratory aims. To examine the influence of the following process variables/participant characteristics to 
identify salient factors impacting change in MVPA across 18 mos.:  attendance at group video (AO-adolescent; 
A+P-adolescent/parent) and education/support sessions (A+P only), self-monitoring of PA (AO-adolescent; 
A+P-adolescent/parent), parental use of Facebook page (A+P only), peer interactions/support during group PA 
sessions, adolescent self-efficacy, social support and barriers for PA, parental MVPA, parental beliefs and 
attitudes toward PA, and parental time constraints, adolescent age, sex and IDD diagnosis.    

 
Rationale 
Approximately 1-3% of the US population is diagnosed with an intellectual or developmental disability 
(IDD) defined as a disability originating before the age of 10, characterized by significant limitations in both 
intellectual functioning (IQ < 75) and limitations in 2 or more adaptive behaviors 1.  Both typically developing 
adolescents and adolescents with IDD have low levels of moderate-to-vigorous physical activity (MVPA) 2, 3  
However, compared to their typically developing peers, adolescents with IDD have even lower daily MVPA 3. 
Phillips and Holland reported no adolescents with IDD achieved the recommended 60 min. of daily MVPA 4. In 
a previous trial by our group, MVPA, assessed by accelerometer of adolescents with IDD (n=20), was only 23 
min./d 5. Low MVPA is associated with reduced cardiovascular fitness 6, 7, reduced muscular strength and 
endurance 8, 9, and high prevalence of overweight and obesity in adolescents with IDD 10, 11.  
Several trials have evaluated the impact of exercise training on cardiovascular fitness and chronic 
disease risk factors in individuals with IDD 12-14. However, few interventions have been designed specifically to 
evaluate strategies to improve PA in adolescents with IDD. A 2019 review identified only five PA trials in 
adolescents with IDD, most of which were unsuccessful 15. Thus, there is a need to develop and evaluate 
effective intervention to increase PA in adolescents with IDD. 
Interventions targeting interpersonal factors, e.g., parental or caregiver education/support, can shape 
the PA behavior of adolescents through direct modeling, providing support and positive reinforcement, 
enforcing household rules that encourage or discourage PA, and creating a home environment supportive of 
PA 16, 17. In typically developing children/adolescents, interventions to increase PA by targeting parenting 
practices have been minimally effective 18, 19. However, adolescents with IDD are more dependent on their 
parents than typically developing adolescents. Thus, interventions that include a parent component may be 
effective for increasing PA in this group. Several cross-sectional studies have shown an association between 
greater parental support and higher parent/caregiver proxy reported PA in adolescents with IDD 20-22. Curtin et 
al. 23 randomized overweight adolescents with Down syndrome (DS) to a 6-mo. intervention designed to 
improve nutrition and MVPA with (n=11) or without parental training/support (n= 10). On average MVPA 
(accelerometer) increased 18 min./d (p=0.01) with parental training/support and decreased 7 min./d (p=0.30) 
without parental training/support. However, Hinckson et al. 24 reported no change in PA assessed by parent 
self-report in a 10-wk. school-based, single-arm trial in 22 adolescents with IDD that included a family 
educational component.  
The limited information available and the potential health benefits of increased MVPA highlight the need 
to evaluate the effectiveness of multi-component interventions targeting both intra (adolescent) and 
interpersonal levels (parents and peers) to promote increased MVPA in adolescents with IDD.  
 
Research Plan and Design 
Overview of study design (Table 1) 
One hundred fourteen adolescents with mild to moderate IDD and one of their parents will be randomized to an 
18-mo. trial with 6 mos. active intervention period, a 6 mos. maintenance period,  and a 6 mos. no-contact 
follow-up to compare changes in objectively assessed MVPA (ActiGraph LLC, Pensacola, FL) in adolescents 
with IDD randomized to a single level intervention delivered to the adolescent only (AO), or a multi-level 
intervention delivered to both the adolescent and a parent (A+P). Adolescents in both intervention groups will 
be asked to attend three 40-min., home-based, group MVPA sessions/wk. (5-7 adolescents, 0-6 mos.) and one 
40-min. education/support session/wk. during mos. 7-12. Group sessions will be conducted by a trained health 
coach using video conferencing software (ZoomTM Video Conferencing Inc., San Jose, CA). Adolescents will 
be asked to complete a weekly activity homework assignment that in conjunction with the remote sessions will 
help them achieve a target of 300 min. of MVPA/wk. Parents of adolescents in the AO group will receive a 
reminder phone call if the adolescent misses more than 3 consecutive scheduled sessions. Parents of 
adolescents in the A+P group will be asked to participate in the group video MVPA sessions and homework 
activity, and to attend education/support sessions with their adolescent and health coach. These sessions will 
inform parents regarding the role of MVPA in health and function and provide strategies for increasing MVPA in 
both their adolescent and themselves.  
 
Table 1. Design Overview for the Active 18-Month Weight Management Intervention 
 
Interventions Groups 
 
Adolescent Only (AO) 
Adolescent + Parent (A+P) 

 
MVPA recommendation 
60 min/d 
60 min/d 
MVPA group sessions via video 
conferencing 
Yes 
Yes 
Session Participants Adolescent Only 
Adolescent + Parent 
Session frequency  
 
0-6 mos. 3 d/wk. 
3 d/wk. 
7-12 mos. 1 d/wk. 
1 d/wk. 
13-18 mos. 0 d/wk. 
0 d/wk. 
Session intensity ≥ 4 METs 
≥ 4 METs 
Session duration 40 min 
40 min 
Session content Stretch/aerobic activity/RE 
Stretch/aerobic activity/RE 
Provide access to PA resources 
Yes 
Yes 
MVPA Self-monitoring 
Fitbit 
Fitbit 
Parent contacts 
 
 
Participants NA 
Parent + Adolescent 
Purpose NA 
Education/support/feedback 
Format NA 
FaceTimeTM 
Session Frequency  
 
0-6 mos. NA 
1 d/mo. 
7-12 mos. NA 
1 d/mo. 
13-18 mos. NA 
0 d/mo. 
Duration NA 
30 min 
Parent Facebook group 
NA 
Yes 
Note: MVPA= Moderate-to-Vigorous Physical Activity, RE= resistance exercise 
 
Participant eligibility.  
Primary care physician (PCP) clearance will be required for both adolescents and the participating parent. To 
enhance generalizability, adolescents with congenital heart disease, or other chronic diseases, will be allowed 
to participate with PCP clearance. Inclusion/Exclusion criteria are presented in Table 2. 
 
Table 2: Participant Eligibility Criteria for an 18-month Physical Activity Intervention in Adolescents with 
Intellectual and Developmental Disabilities 
 
Inclusion  
 
Residential Status:  
Living at home with a parent or guardian who is willing to participate in the 
intervention, with no plans to change this living situation and/or to leave the study 
area in the next 18 mos. 
Age:  
10-21 years 
Diagnosis: 
Mild to moderate IDD as verified by their PCP 
Ambulatory:  
Must be able to participate in physical activity.  
Health status:  
Must provide physician clearance to participate.  
Communication: 
Sufficient functional ability to understand directions, communicate preferences, 
wants, and needs through spoken language 
Internet: 
Internet access in the home  
Exclusion 
 
Parent health concerns: 
If the parent who will participate in the intervention with the participant has a serious 
medical risk, such as cancer, recent cardiac event, i.e., heart attack, stroke, 
angioplasty, or cannot participate in physical activity. 

 
Pregnancy: 
Pregnancy during the previous 6 mos., currently lactating or planned pregnancy in 
the following 24 mos. Participants who become pregnant will be removed from the 
study and referred to appropriate agencies for consultation. 
 
Recruitment Procedures/Randomization. Organizations and community agencies serving individuals with 
IDD will be mailed/emailed an information brochure that describes the project. Additionally, we will use email 
list serves and media advertising (print, radio, internet) to target families living in the recruitment area. Potential 
participants will be asked to contact a member of the study team to obtain details about the program and 
complete the initial eligibility screening. Remote video chat sessions (Zoom) will be scheduled with interested 
participants and their parent to describe the project in detail, answer questions, verify eligibility, and to obtain 
parent consent and adolescent assent. Study staff will set up a virtual Zoom meeting that allows for remote 
video chat. Prior to the consent meeting families will be emailed a link for a KUMC REDCap survey they will 
contain the consent and assent documents. Additionally, Study staff will “share screen” the consent document 
and walk through each section, noting questions that arise, and answer these questions fully. Participants and 
adolescents will sign the consent/assent documents on the REDCap survey. Study staff will then print and 
provide the participant with a full-signed consent form for their records at the baseline testing meeting.  
Adolescents age 18 and over, who are their own legal guardian, will sign their own consent. Project staff will 
fax/email a form to the potential participant’s PCP, which describes the eligibility criteria, study requirements, 
and request for clearance for participation. Parents of adolescents found to be ineligible will be provided with 
written materials describing available resources for assisting their adolescent with increasing PA. Cohorts of 
~10-20 adolescent/parent dyads will be recruited and computer randomized. Adolescents will be stratified by 
sex and the presence or absence of DS, and sequentially randomized by the study statistician with equal 
allocation to the AO or A+P arms.  
 
Intervention Components 
The intervention components for the AO and A+P arms are identical with the exception of the parental 
involvement component.   
 
MVPA recommendations 
Current US guidelines recommend a minimum of 60 min. of MVPA each day for children/adolescents with or 
without disabilities 25. However, as described the limited available data suggest that few adolescents with IDD 
currently meet this recommendation 4, 26. Therefore, the recommended daily MVPA, which will be identical for 
both groups, will progress from ~15 min./d during wk. 1, and gradually increase 10 min./d every 2 wks. during 
the active intervention to ~ 60 min./d at wk. 11, and remain at 60 min./d through mo. 18.  
 
PA Self-Monitoring. 
Participants in both arms will be asked to wear a Fitbit Charge 3TM (35.5 mm x 28 mm) activity tracker on their 
non-dominant wrist over the duration of the 18-mo. trial. Real-time data from the Fitbit is automatically 
transferred, via the web, to cloud storage maintained by Small Steps Labs LLC (Fitabase, San Diego, CA). 
Immediate participant feedback via a graphic display of daily steps, minutes of sedentary time, time spent in 
light, moderate and vigorous PA, and heart rate relative to pre-set goals will be available on the iPad. This 
data, accessible to health coaches, will be used only to provide motivation and feedback during intervention 
sessions. Outcome data for MVPA and sedentary time will be assessed by accelerometer. Participants will be 
reminded to wear and charge the Fitbit during group exercise sessions, and will receive automatic reminder 
messages via the iPad using the iCal app.  
 
Introduction to Materials 
After each participant’s baseline testing appointment (described in detail below), a member of the study team 
will outline study requirements and distribute all equipment, iPads, Fitbits, resistance bands, etc. The health 
coach will describe and demonstrate the ZoomTM software and the Fitbit, and will allow time for practice and 
questions. 
 
Zoom Orientation 

 
Each cohort of adolescents and parents in both intervention arms will be asked to attend an orientation session 
(~30 min.) led by their health coach. These sessions will be conducted on a Zoom conference call one week 
before the start of the intervention. This meeting is designed to establish rapport between the health coach and 
participants, and between participants themselves, prior to initiating the group video conference exercise 
sessions. Additionally, basic stretching exercises, the use of the resistance bands, and simple dance 
movements will be demonstrated and practiced.  
 
Remote Group Physical Activity Sessions 
Schedule. Group exercise sessions will be scheduled between 4 and 8 p.m., on 3 days/wk. from baseline to 6 
mos. and 1 day/wk. during mos. 7-12. Participants in each cohort will be offered the choice between 2 session 
times each day. This meeting frequency and time were selected based on the preferences of parents of 
adolescents with IDD that participated in our pilot trial27. Prompts reminding participants in both intervention 
groups of upcoming sessions will be sent via the iPad.  
 
Delivery. Group exercise sessions will be delivered using an iPad tablet computer provided to all participants. 
The iPad will be pre-loaded with video-conferencing software (ZoomTM) which allows participation by multiple 
users. Participants will be provided with an iPad/HDMI adaptor, which allows video conference sessions to be 
displayed on a larger TV screen, if desired. Tutorials describing trouble shooting for common technical 
problems, e.g., internet connectivity etc., will be loaded on the iPad. Participants with technical issues during 
the intervention can also contact research staff by phone or email. Access to non-study related materials, e.g., 
web browsing, app store etc., will be blocked on all iPads until completion of the maintenance intervention (12 
mos.). The iPads for both groups will also be pre-loaded with the Fitbit, Zoom, Dropbox, and Rooster Money 
applications.  
 
Content. Each session will include a warm-up (~5 min.), moderate-to-vigorous intensity aerobic and resistance 
exercise (~30 min.), and cool-down/stretching (~5 min.). The resistance exercise component may be especially 
relevant for adolescents with DS who have reduced muscle strength compared with adolescents with other 
forms of IDD, as well as their typically developing peers 9. All exercise sessions will be conducted by a health 
coach experienced in working with adolescents with IDD. The aerobic/resistance exercises, accompanied by 
music, will include walking/jogging in place, dancing, imitating animal movements, vertical/horizontal jumps, 
squats, and Thera-Band exercises for major muscle groups. Activities will be modified for participants having 
difficulty with specific movements. The intensity of the initial sessions will be light-to-moderate, with intensity 
increasing to moderate-to-vigorous at ~ 6 weeks. During each session, health coaches will encourage 
interactions between participants in support of their peer’s efforts to increase MVPA, and provide participant 
feedback relative to their level of weekly MVPA as assessed by the Fitbit. As the intervention progresses, 
adolescent participants will be asked to volunteer to create and lead the group in a brief (3-5 min.) exercise 
bout. Adolescents will also be encouraged to interact with each other by performing activities such as tossing 
an imaginary ball to other participants, or challenging other participants to complete a skill such as 10 hops on 
one leg etc. All group sessions will be video recorded, and will be available on a Dropbox folder on the iPad for 
use by participants and/or parents across the 18-mo. trial.  
 
Homework assignments 
Adolescents who participate in all 3 weekly exercise sessions will have the potential to accumulate ~90 min. of 
MVPA/wk. (~13 min./d). Thus, MVPA outside these sessions will be required to meet weekly 
recommendations. Health coaches will provide weekly challenges in the form of meeting a goal for increased 
steps, trying a new activity, or creating and performing their own exercise routine etc. Scheduled group 
sessions will be reduced to 1/wk. during mos. 7-12, thus the volume of MVPA to be completed outside the 
group session, i.e., “homework” will increase to meet the recommended daily MVPA. Participants will be 
provided Dropbox access to previous exercise sessions they can complete on their own to meet weekly MVPA 
goals, if desired. Information regarding increasing PA, available from the National Center on Health, Physical 
Activity and Disability (NCHPAD) and the Special Olympic athletes home training guide, and similar material 
appropriate for parents, will also be loaded on the iPads of both intervention arms.  
 
Parental Involvement 

 
AO Arm. One parent/guardian will be asked to attend the orientation session, monitor MVPA across the 
intervention, and complete survey instruments at baseline, 6, 12, and 18 mos. (See assessments). By design, 
parental involvement in the AO group will be limited to reminder contacts (phone/text/email) from the health 
coach if their adolescent misses 2 consecutive exercise sessions. Contact attempts will be limited to 3 for each 
occurrence.  
 
A+P Arm. One parent/guardian will be asked to attend the orientation session, monitor MVPA across the 
intervention, and complete survey instruments at baseline, 6, 12, and 18 mos. In additional that parent will be 
asked to participate in the group video exercise sessions, and attend 30-min. education/support sessions with 
their adolescent (1 session/mo., 0-12 mos.) delivered remotely on the iPad using FaceTimeTM. These sessions, 
led by the health coach, will be designed to educate and support parents in assisting their adolescent with 
meeting their 300 min./wk. goal for MVPA, and to assist parents with meeting their own weekly MVPA goal 
(150 min./wk.) 25. Each session will include a review of PA self-monitoring data, goal setting, strategies to 
increase and support MVPA, and discussion of a topic relevant to MVPA. Topics will include the importance of 
MVPA for health and function, how to include MVPA in the daily schedule, how to reduce barriers to PA, 
appropriate types of activity, creating a safe environment for PA, alternative activities for inclement weather, 
importance of hydration, etc. Session outlines and materials will be preloaded on the iPad where they can be 
accessed by adolescents/parents at any time. We will also create a private Facebook page for parents of 
adolescents in the A+P arm. Health coaches will post weekly helpful tips for adolescents/parents relative to 
increasing their MVPA, and provide information on community events and resources relative to PA (e.g., 
walk/running events, recreation center activities, etc.). Parents will also be encouraged to exchange 
information regarding opportunities for PA in their area, form support or activity groups, and post questions for 
the health coach to be answered during education/support sessions, etc.  
 
Participant Incentives 
Participants will be able to earn stars which can later be exchanged for money. Participants will be able to earn 
up to 2 stars each week, one for completing self-monitoring of PA on 5 of 7 days of that week, and one for 
attending 2 of the 3 scheduled exercise sessions during mos. 0-6 or the one session scheduled session during 
mos. 7-12. The allowance iPad app, Rooster Money (Rooster Money LLC, London, England), will be used to 
distribute stars to participants. Participants will get a notification on their iPad every time they receive a star as 
well as a note for what goal they achieved to get the star, and how many stars they currently have. Participants 
will receive $10 each time they obtain 10 stars. Additionally, adolescents and parents will both receive $50 for 
completion of each of the 4 outcome assessments. As an additional incentive, participants will be allowed to 
keep the iPad and the Fitbit on completion of the active intervention (12 mos.). 
 
Outcome Assessments 
With the exception of our primary outcome, MVPA, all outcomes will be assessed at either our Lawrence, or 
Kansas City, KS laboratories, based on participant preference at 0, 6, 12 and 18 mos. These assessments will 
be completed by trained staff blinded to intervention conditions. Staff will receive refresher training and 
complete reliability assessments for all physical measures 2-3 times/yr. 
 
MVPA  
MVPA and sedentary time (secondary outcome) in both adolescents and parents will be assessed at baseline 
(mo. 0), 3, 6, 9, 12, 15, and 18 mos. using an ActiGraph model wGT3x-BT tri-axial accelerometer. The 
ActiGraph provides valid and reliable assessments of PA in typically developing adolescents 28, 29 and in 
adolescents with IDD 30, 31. Participants will be asked to wear the ActiGraph on a belt over the non-dominant 
hip at the anterior axillary line during waking hours for 7 consecutive days, with the exception of bathing, 
swimming, and contact sports. Research staff will distribute and demonstrate proper placement of the 
ActiGraphs at laboratory visits scheduled at baseline 6, 12, and 18 mos. ActiGraphs will be distributed by mail 
for the 3, 9, and 15 mo. assessments. Daily reminders to comply with the ActiGraph protocol will be sent to 
participants’ iPads each morning during the 7-day monitoring period. ActiGraphs will be initialized and 
downloaded using ActiLife Software version 6.13.3 or higher (ActiGraph Corp, Pensacola, FL) and set to 
collect in the raw data mode from all 3 axes at 60 Hz. For the participants younger than 18 years of age, we 
will use the age-specific cut-points for children/adolescents proposed by Freedson et al. 28, 32. Data will be 

 
aggregated over 60-sec epochs to mirror the collection interval on which the Freedson age-specific cut-points 
were developed 28, 32. For parents and adolescents over 18 years old, accelerometer data will be processed 
using the protocol for adults used in the 2003-2004 and 2005-2006 cycles of NHANES 2, 33.  
 
Cardiovascular Fitness 
Cardiovascular fitness will be assessed using a modified Balke treadmill test 34. The treadmill will initially be set 
at 2.6 m.p.h., 0% grade. The speed will remain constant and grade will increase 1% each min. until the 
participant reaches 75% age predicted maximal heart rate (HRmax). HRmax for participants without DS will be 
predicted using the equation for typically developing children and adolescents (208–0.7*(age in years)) 35. 
HRmax for participants with DS will be predicted as 210–0.56*(age in years)–15.5*(DS), where DS=2, as 
suggested by Fernhall et al. 36 to account for the lower HRmax associated with DS 6, 37. Submaximal treadmill 
protocols have been previously validated in individuals with IDD 38, 39. 
 
Muscular Strength 
Lower body muscle strength will be assessed using a standard 5-repetition maximum protocol 40 on a Cybex 
plate-loaded leg press calculated with the Brzycki, et al. 1-repetition maximum prediction equation 41. 
Participants will begin with a brief warm-up (~5 min.) on the treadmill followed by instruction on proper leg 
press form. After one light warm-up set (~10 repetitions) to ensure proper form, weight will be selected with the 
goal of achieving 5-repetiton maximum. Weight will continue to be increased until the goal is reached, with 60 
sec. rest between each attempt. Predicted 1-repetition maximum assessments have been used successfully in 
adolescents with IDD 42. We will use grip strength as an indicator of upper body strength. Grip strength will be 
measured using a hand dynamometer (Model: Jamar Plus Electronic, Patterson Medical, Warrenville, IL). 
Participants will be asked to stand straight with their elbows flexed at 90° and instructed to clench the handle 
as strong as possible. We will collect 3 measures from both their dominant and non-dominant hand, and 
scores from each hand will be averaged. Grip strength has been successfully used in individuals with IDD 43, 44. 
 
Motor ability 
Motor ability will be assessed by the Gross Motor Quotient and Percentile obtained from Test of Gross Motor 
Development-second edition (TGM-2) 45. The TGM-2 requires ~20 min. to administer and has been used in the 
NHANES National Youth Fitness Survey 46, and in individuals with IDD 47, 48. During the COVID 19 lockdown 
motor ability will be assessed remotely.  
 
Quality of life  
Quality of life will be assessed with the Personal Well-Being Index-Intellectual Disability 49, 50. Cronbach alpha 
of 0.76, and 1- to 2-wk. test-retest reliability of 0.58 have been reported in individuals  with IDD 49.  
 
Self-Efficacy and Social Support 
Self-efficacy and social support will be assessed using the Self-Efficacy for Activity for Persons with Intellectual 
Disabilities Scale, and the Social Support for Activity for Persons with Intellectual Disabilities Family Scale 51. 
Chronbach’s alpha in individuals with IDD was 0.73 for both scales. Barriers for PA will be assessed using the 
12-item Barriers to and Support for PA questionnaire 52. 
 
Parent’s Beliefs/Attitudes Towards PA 
Parent’s beliefs/attitudes toward PA will be assessed with an adapted version of the Healthy Buddies Parent 
Nutrition and Physical Activity Survey, which has been previously used with parents of adolescents with IDD 53.  
 
Parent Time Constraints 
Parent time constraints will be assessed with the Leisure Time Satisfaction Scale 54 and parent stress scales.   
 
Descriptive Outcomes 
To characterize our study sample, we will measure weight, height, and waist circumference in adolescents and 
parents at baseline, 6, 12, and 18 mos. Weight will be measured in light clothing on a calibrated scale (Model 
#PS6600, Belfour, Saukville, WI) to the nearest 0.1 kg. Standing height will be measured with a portable 
stadiometer (Model: #IP0955, Invicta Plastics Limited, Leicester, UK). BMI will be calculated as weight 

 
(kg)/height (m2). BMI percentile for adolescents will be obtained using the CDC calculator 
(http://apps.nccd.cdc.gov). Waist circumference will be assessed using the procedures described by Lohman 
et al.55. During the COVID-19 lockdown height, weight, and waist circumference will not be collected.  
 
Process variables  
Intervention fidelity. Study staff will review recordings from all scheduled exercise sessions and 
parent/participant meetings (A+P group). The content delivered will be compared with a checklist of scheduled 
activities/topics. Feedback will be provided to all health coaches, and those covering <80% of scheduled 
activities/topics will receive additional training and will be dismissed if the problem recurs.  
 
Session attendance for both group exercise and adolescent/parent education/support sessions will be obtained 
from records maintained by the health coach, and expressed as the percent of possible sessions from 0-6 
mos. and 7-12 mos.  
 
Self-monitoring of PA will be assessed as the percentage(total days worn/ total days enrolled in the 
intervention) of days with Fitbit data over a minimum of 8 hrs. between 6 am and midnight (0-6, 7-12, 13-18 
mos.).   
 
Parental use of the Facebook page (A+P group) will be tracked as the frequency of posting, i.e., posts/d (initial 
and replies) averaged over 3 time periods: (0-6, 7-12, 13-18 mos.). 
 
Peer interactions/support. Staff will review video recordings of a random sample (33%) of group exercise 
sessions to identify and classify both peer-to-peer and health coach to adolescent interactions.  Interactions 
will be quantified and coded as verbal/non-verbal (waving, pointing, shaking head in agreement/disagreement), 
and as positive, neutral or negative, and relative to support, using a checklist.  
 
Exit Interview 
We will conduct structured interviews by phone with a 20% random sample of participants and parents from 
both intervention arms to gather information that might be useful for improving the intervention and/or 
implementing the intervention in settings serving adolescents with IDD. Topics will include preference for the 
AO or A+P interventions, reasons for missing scheduled sessions for both the parent and participant, 
intervention length, difficulties with compliance, suggestions for improvements and overall satisfaction with the 
intervention, parent’s enjoyment of the exercise and educational sessions, health coaches, PA 
recommendations etc. 
 
Analysis plan and statistical power 
Power. This trial is powered to detect a between arm difference (AO vs. A+P) in the change of MVPA (0-6 
mos.) of 10 min./d. This represents an additional 70 min. of MVPA/wk. An increase in MVPA of this magnitude 
is associated with improved adiposity and cardiovascular fitness in typically developing adolescents 56, 57, and 
potentially in adolescents with IDD, a group with low baseline levels of MVPA 58, 59. Statistical power to detect a 
significant effect on MVPA across 6 mos., the primary aim in the proposed 2-arm randomized design, depends 
on the following parameters: the number of participants in each arm (J), the number of measurements (n = 21; 
7 days at 0, 3, and 6 mos.), correlations among repeated measures (r), and effect size (f). Assuming a 
conservatively large standard deviation for change in MVPA in both arms (35 min./d), corresponds to a small to 
moderate effect size (f = 0.14). The correlation between repeated measures of MVPA (3 mo. interval) in our 
pilot trial was r = 0.22. To be conservative, we assumed a higher correlation (r = 0.25) for this sample size 
calculation. Based on these assumptions, power analysis using G*Power 3.1.9.2 shows a sample of 114 
adolescents (J = 57/arm) would provide 81% power to test overall between arm differences across time, i.e., 
group effect. This sample size would also provide ≥80% power to detect a group difference in change, i.e., 
time-by-group interaction, as small as f = 0.09. Missing data will be fully recovered via multiple imputation as 
discussed subsequently, which will remove or minimize (if present) confounding effects of missingness on our 
statistical power. The secondary aims were not powered to detect between group differences.  
 

 
Baseline equivalence. We will compare baseline characteristics, e.g., age, sex, race/ethnicity, BMI, IDD 
diagnosis, etc., between the AO and A+P arms using independent-samples t-test for continuous variables and 
chi-square/Fisher test for categorical variables, to assess the degree to which randomization resulted in 
equivalent groups. Variables that demonstrate a significant nonequivalence will be controlled for in our analytic 
models to improve the accuracy in estimates of the intervention effect. Prior to modeling, missing data for each 
outcome will be imputed as described subsequently.   
 
Primary aim analysis. Our primary aim, to compare changes in MVPA (min./d) between the AO and A+P arms 
from 0 to 6 mos., will be evaluated using general mixed modeling for repeated measures.  Specifically, the 
model will examine linear/nonlinear change over time (21 measurements = 7 days at each of 0, 3, and 6 mos.); 
i.e., time effect, overall group difference across time, i.e., group effect, and group difference in change, i.e., 
time-by-group interaction, controlling for day of the week (weekday/weekend) and baseline characteristics 
imbalanced between the groups. For example, a significant interaction will indicate that adolescents in the A+P 
arm achieve more minutes of MVPA compared to adolescent in the AO arm, and this difference becomes 
greater across time. A proper error covariance structure will be determined based on relative model fit, e.g., 
Akaike information criteria, adjusted Bayesian information criteria.  
 
Secondary Aim analysis. Our secondary aim, to compare changes between the AO and A+P arms on the 
following variables across 18 mos.: 1) MVPA (min./d) and sedentary time (adolescents and parents), 2) 
cardiovascular fitness, 3) muscular strength, 4) motor ability, and 5) quality of life, will be evaluated using a 
similar general mixed modeling approach. The models will examine linear/nonlinear change over time (7 days 
at each of 0, 3, 6, 9, 12, 15, and 18 mos. for MVPA and sedentary time; 0, 6, 12, and 18 mos. for all other 
outcomes), overall group difference across time, and group difference in change. We will also longitudinally 
compare the percentage of adolescents achieving the 60 min./d MVPA (US recommendation) using 
generalized mixed modeling for repeated binary measures (yes/no in each observed day). In a secondary 
analysis, we will fit a general mixed model that includes cardiovascular fitness, muscular strength, motor ability, 
and quality of life as time-varying covariates, and assess their association with MVPA aggregated across 
months controlling for group. 
 
Exploratory aims. If there are no between arm differences in the longitudinal change in MVPA across 18 mos., 
general mixed models will be fitted for the two arms combined to examine the association for the process 
variables/participant characteristics with MVPA. These variables include: attendance at group video (AO-
adolescent; A+P-adolescent/parent) and education/support sessions (A+P only), self-monitoring of PA (AO-
adolescent; A+P-adolescent/parent), parental use of Facebook page (A+P only), peer interactions/support 
during group PA sessions, adolescent self-efficacy, social support and barriers for PA, parental MVPA, beliefs 
and attitudes toward PA and parental time constraints, age, sex, and IDD diagnosis. However, if there is a 
significant group difference in MVPA, we will determine whether the previously listed process 
variables/participant characteristics explain/attenuate the intervention effect, i.e., moderation, by testing a 2-
way interaction with the group effect and/or a 3-way interaction with the group-by-time interaction term. Some 
covariates will be measured only at baseline (age, sex, IDD diagnosis), some will be summarized across the 
trial (attendance at group video and education/support sessions, self-monitoring of PA, parental use of 
Facebook page, peer interactions/support during group PA sessions), while others will be assessed at specific 
time points (BMI, adolescent self-efficacy, social support and barriers for PA, parental MVPA, beliefs and 
attitudes toward PA and parental time constraints). Thus, we will carefully design our models to assure the 
appropriateness of the analysis. All analyses will be conducted using R and SAS 9.4 or higher. 
 
Missing data. Missing due to either attrition, e.g., participant dropout or nonresponse, will be handled by 
multiple imputation, in which an expectation-maximization (EM) algorithm supplies prior estimates of missing 
values for a subsequent Monte Carlo Markov Chain (MCMC) procedure 60. A sufficient number of imputed 
datasets will be created to ensure accurate recovery of missing data; and analysis results from each imputed 
dataset will be combined to make valid statistical inferences. All measured variables will be incorporated into 
the imputation process as auxiliary variables, thereby satisfying the missing at random (MAR) assumption 61.  
 
 
 

 
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