Testicular germ cell tumor (TGCT) is the most common malignancy in men between 15 and 40 years. Although TCGT survivors have a good survival prognosis, they suffer from short- and long-term sequelae such as chronic fatigue, psychological disorders, cardiovascular toxicities and second malignancies. The benefits of physical activity (PA) during treatments have been demonstrated in cancer patients to improve quality of life (QoL) and physical fitness and to reduce fatigue. However, few PA programs have been proposed to TGCT patients and their effects on sequelae have not been assessed yet. A growing body of evidence links treatment-related alteration in the gut microbiota to sequelae of cancer survivors, including fatigue and cardiovascular toxicities. Also, PA has been known as a possible modulator of the gut microbiota composition. To date, no study has been conducted to examine how the gut microbiota and its metabolites moderate the effect of PA on fatigue and other late effects in TGCT survivors. The objectives will be to assess the impact of a PA program on fatigue and other sequelae and to investigate how the gut microbiota and its metabolites moderate the associations between PA and sequelae. We will conduct a prospective, multicenter, phase III, randomized controlled trial of a one-year supervised PA program. 236 men with metastatic TGCT and eligible for a first line of chemotherapy will be randomly assigned to either PA intervention or control arm. All patients will benefit from a connected activity tracker and PA recommendations. In the intervention arm, PA will be based on supervised sessions and motivational interviews. The primary endpoint (fatigue) will be assessed at 3 years. The trial will provide novel insights into the impact of PA on fatigue and other sequelae in TGCT survivors with understanding a potential underlying mechanism of gut microbiota. This evidence will support the development of targeted PA guidelines to improve QoL and reduce sequelae in TGCT survivors.