Today about 80% childhood cancer patients become long-time survivors. In spite of the high cure rates the diagnosis cancer is associated with a variety of disease and treatment-related psychological and physical impairments mostly present into adulthood. So the attention has to focus on the improvement of these problems such as motor limitation, dysfunction of the cardiovascular system, reduced muscle strength, overweight, osteoporosis and diminished quality of life (Qol). Although exercisel intervention studies in this field are generally scarce, the results of these studies are promising. Up to now studies during the acute phase of treatment are missing almost completely. The aim of this feasibility study is to evaluate the potential benefits of a modular exercise intervention program for childhood cancer patients startunf in parallel with treatment and longlasting for one year. Across two years cancer patients of the Children's Hospital of the University Clinic of Heidelberg aged 5-21 years, free of any contraindications for physical activity will be recruited. All participants are asked to complete a physical assessment battery (strength, endurance and balance capacity, posture control, functional mobility, range of motion) and additionally two questionnaires concerning Qol and motivation, at baseline and every three months following one year

Inclusion Criteria:

• pediatric cancer diagnosis (primary leukemia, brain tumors and bone tumors
• date of diagnosis not longer than 8 weeks ago

Exclusion Criteria:

• severe cardiac impairment
• bone metastasis inducing skeletal fragility
• other orthopedic diseases or any other circumstance that would impede ability to give informed consent or adherence to study requirements.