The investigator team for the current protocol has recently completed a single-arm pilot protocol (LCCC 1311) of a 6-week home-based unsupervised IET program (goal of three IET sessions per week, 65%-95% Max Heart Rate \[MHR\]) in patients planning to undergo alloHCT. In our study, participants preparing to undergo alloHCT experienced an average 3.8ml/kg\*min improvement in peak volume of oxygen consumed (VO2peak) from pre to post-intervention. Patients in LCCC 1311 wore FitBit accelerometers throughout the study period.

The primary purpose of the current randomized controlled trial is to determine, in patients preparing to undergo alloHCT, whether an intervention comprised of interval exercise training and motivational accelerometry (IET/MA) will improve cardiorespiratory fitness more than the control group who receives usual care and an accelerometer without motivational physical activity coaching. The study will also look at several secondary endpoints including the association of the intervention with changes in p16INK4a, and the association of the intervention with changes in symptoms and quality of life before and after transplant.

This randomized controlled trial will include 60 patients preparing to undergo alloHCT (30 in the intervention group, 30 in the control group). We plan to analyze the effect of IET/MA on VO2peak. Subjects will be recruited after their transplant teams have determined that they will undergo alloHCT within the subsequent 5-12 weeks. Following recruitment, patients will undergo baseline fitness assessments consisting of cardiorespiratory exercise testing using indirect calorimetry on a cycle ergometry (for the assessment of VO2peak), 6 minute walk distance testing, and baseline physical activity, symptom and quality of life questionnaires. Participants randomized to the IET/MA group will then receive an individualized IET/MA prescription for a duration of at least 5 weeks, up until the time of admission for alloHCT or 12 weeks from the initiation of IET/MA, whichever occurs first. The mode of exercise can be walking, jogging, running, cycling, elliptical, stair climbing, or a combination of these, and will be performed unsupervised at home. For the first week, participants will be asked to engage in 30 minutes of aerobic exercise at any intensity for 3-4 days. For weeks two and beyond, participants will undergo 3-4 sessions of IET, consisting of a 5 minute warm-up and five 2-minute intervals, with the goal of reaching 80% MHR, separated by 3 minutes of recovery/light activity in between each interval. Each exercise session is a total of 30 minutes. Fitness assessments will be completed at the end of the intervention period, at the time of admission for alloHCT. Based on the improvement in VO2peak seen in the pre-alloHCT patient population in LCCC 1311, the current study is powered to detect a 3.8ml/kg\*min VO2peak improvement in the intervention group relative to the control group.

All participants in both groups will be provided with a FitBit Surge accelerometer. Participants in the intervention group will also receive weekly motivation from a study team member to achieve a 10% week over week improvement in average steps/day. Participants in the control group will not receive this physical activity coaching. Participants will continue to wear the accelerometers after the intervention and until 1 year following alloHCT. Participants in both groups will have blood drawn for p16INK4a levels before and after the IET intervention. Participants in both groups will also complete symptom and quality of life questionnaires before the intervention and periodically throughout the year following alloHCT (please see study plan and time and events tables).