BACKGROUND: Cancer-cachexia is associated with chronic inflammation, impaired muscle metabolism and body mass loss, all of which are classical targets of physical exercise. OBJECTIVES: This systematic review and meta-analysis aimed to determine the effects of exercise on body and muscle mass in cachectic cancer hosts. DATA SOURCES: PubMed/Medline, Embase, CINAHL, ISI Web of Science, and Cochrane Library were searched until July 2019. STUDY SELECTION: Trials had to be randomized controlled trials or controlled trials including cancer patients or animal models with cachexia-inducing tumors. Only sole exercise interventions over at least 7 days performed in a controlled environment were included. DATA EXTRACTION: Risk of bias was assessed and a random-effects model was used to pool effect sizes by standardized mean differences (SMD). RESULTS: All eligible 20 studies were performed in rodents. Studies prescribed aerobic (n = 15), strength (n = 3) or combined training (n = 2). No statistical differences were observed for body mass and muscle weight of the gastrocnemius, soleus, and tibialis muscles between the exercise and control conditions (SMD -0.05, 95%CI -0.64 to 0.55, p = 0.87). Exercise duration prior to tumor inoculation was a statistical moderator for changes in body mass under tumor presence (p = 0.04). LIMITATIONS: No human trials were identified. A large study heterogeneity was present, probably due to different exercise modalities and outcome reporting. CONCLUSION: Exercise does not seem to affect cancer-cachexia in rodents. However, the linear regression revealed that exercise duration prior to tumor inoculation led to reduced cachexia-severity, possibly strengthening the rationale for the use of exercise in cancer patients at cachexia risk.

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