 Purpose: The primary hypothesis of this study is that the combination of interval exercise training IET as well as motivational accelerometry MA delivered both as a 5-12 week intervention that will improve cardiorespiratory fitness in patients preparing to undergo allogeneic hematopoietic cell transplantation alloHCT. MA is not an established term, but in respect to this study, MA refers to the use of wearable accelerometry paired with regular intervals of physical activity coaching from members of the study staff during the IET training. The study will also look at several secondary endpoints including the association of the intervention with changes in cyclin-dependent kinase inhibitor 2A, multiple tumor suppressor 1 p16INK4a, and the association of the intervention with changes in symptoms and quality of life before and after transplant. 