(A) Before week 0: A booklet and video will be developed for educating children and adolescents with cancer and their parents on how to improve muscle mass through daily walking.(B) Week 0 (Baseline): After agreeing to participate in the study, participants will answer the pre-test questionnaires. The research assistant will enter their age and body weight in ActiGraph. The patient will be educated on the general use of the ActiGraph through verbal and written information, and will be asked to wear the ActiGraph for 3 days, including one weekend, to measure baseline walking steps during week 0. (C) Weeks 1–5 (Intervention): The patient will be asked to wear the ActiGraph for a whole week to collect baseline step counts. The ActiGraph will then be delivered to the research assistant in order to retrieve walking steps and walking time. A member of the research team, in consultation with the physical therapist, will call the patient and parent for a phone conference and recommend a weekly goal of walking time that is tailored to the patient’s baseline and guided by research, with a 15%–20% increase over baseline up to a 2,000-step increase (M. C. Hooke et al., 2016). The daily increase in step goal will be a fraction of the weekly goal, providing a gradual increase. A middle assessment will be conducted at week 3.(D) Week 6 (Close up intervention): A final assessment will be conducted at week 6. The participant will be reminded that the ActiGraph and post-test questionnaires will be picked up at the end of week 6.