 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 IETMA 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. 