The effect of acute running and cycling exercise on T cell apoptosis in humans: A systematic review.

This review analyses the influence of acute running and cycling exercise on T lymphocyte apoptosis. We included randomized controlled trials (RCTs) and non-randomized case-control studies (NRCTs) measuring apoptosis by flow cytometry. Cochrane Library, Scopus, PubMed and Ovid were searched for running and cycling intervention studies. Risk of bias was assessed by Cochrane Collaboration's tools. We included five NRCTs and one RCT with a total of 93 participants. The RCT found a higher percentage of apoptotic T helper cells identified by upregulation of Annexin V, caspase-3 and caspase-9 under hypoxic conditions, and only one NRCT reported a higher percentage of highly differentiated apoptotic T cells immediately after exercise. Three hours after exercise, the same NRCT showed an increase in several T cell subsets such as T helper, cytotoxic T, low differentiated and regulatory T cells. The interventions were very heterogeneous by exercise protocol and external conditions. High risk of bias in NRCTs restricts accuracy of the included studies. Imprecision due to the small sample size limits further evidence. In the future, scientists should include apoptotic measures into their research design, plan RCTs, measure apoptosis at different time points post-exercise and increase sample size.