This pilot study will examine the safety, feasibility, and effect on quality of life of moderate physical activity on adolescent and young adult patients who are admitted to the hospital periodically for routine chemotherapy. Patients will be asked to participate in daily physical exercise during hospital admissions over a three-month period. Exercise sessions will be monitored and guided by M.D. Anderson physical therapists, a personal trainer, and Dr. Michael Rytting, pediatric oncologist. The personal trainer will meet with each participant for reinforcement and to provide an opportunity for exercise between hospitalizations. If results are positive, the study will be extended to a larger cohort of patients.