Researchers at CHOP are recruiting patients diagnosed with either acute leukemia (myeloid, lymphoid), myelodysplastic syndromes, or aplastic anemia and treated with allogeneic hematopoietic cell transplantation (HCT) within the past 6-48 months.
Research has shown that adolescents and young adults who are treated with HCT are at increased risk for skeletal muscle loss. So, the purpose of this study is to investigate if a combination of exercise training and an exercise supplement can mitigate this effect. Thesupplement is called nicotinamide riboside.

Participants will be randomly assigned to 1 of 4 groups:

• Exercise + Supplement
• Exercise + Placebo
• No Exercise + Supplement
• No Exercise + Placebo

The study will provide all the exercise equipment required to complete the exercise intervention, including remote sessions.