Mobile Health Fitness Program for Adolescent and Young Adult Childhood Cancer Survivors

Feasibility will be evaluated by the number of participants who enroll and complete baseline assessment for the randomized trial. In total, 354 participants were mailed letters; 68 were contacted/screened, of which 56 were eligible and 49 enrolled (88% of those screened eligible, 14% of total potentially eligible pool).

Percentage of participants who compete the 3 month assessment

Fatigue measured using the PedsQL Multidimensional Fatigue Scale. The PedsQL Multidimensional Fatigue Scale yields three subscales: general, sleep/rest, and cognitive fatigue. Scores are transformed on a 0-100 scale, with higher scores indicating better functioning.

The PedsQL Generic Core Scale is a well-validated measure of HRQOL with physical, emotional, social, and cognitive functioning domains. The PedsQL Generic Core yields two summary scores - Physical Summary and Psychosocial Summary. Scores are transformed on a 0-100 scale, with higher scores indicating better functioning.

Cardiorespiratory fitness was measured via submaximal treadmill testing using a modified Bruce protocol. This standardized graded treadmill test adds two warm-up stages, with the first performed at a 1.7 mph and 0% grade and the second at 1.7 mph and 5% grade. Participants performed the graded exercise test until they reached 85% of their age-predicted maximum heart rate, which was measured using a chest-worn Polar heart rate monitor. Estimated VO2 max was calculated for each participant using the multi-stage model and American College of Sports Medicine metabolic equations.

Lower and upper body muscular strength/endurance were measured via 10-repetition maximum (10-RM) tests following National Strength and Conditioning Association guidelines (leg press machine for lower body and barbell bench press for upper body). Weight was increased until participants executed 10 repetitions in good form for both exercises. Estimates of 1-RM leg and bench press were made using a linear prediction equation. Higher scores indicate greater muscular strength/endurance.

Engagement with the app was measured by 1) number of in-app exercises completed; 2) points earned (more active = more points); 3) achievements unlocked; and 4) number of likes and comments posted within the social feed. These are count data. Achievements unlocked has possible range of 0 to 20. Number of in-app exercises completed, points earned, and number of likes and comments posted within the social feed have a possible lower limit of 0 and no upper limit; higher numbers indicate more instances of each. The full range of participant data are: number of in-app exercises completed = 0-44; points earned = 0-1,195; number of achievements unlocked = 1-20; number of likes/comments posted = 0-8.