Effect of resistance training on chronic inflammation: A systematic review and meta-analysis

Objectives To determine the pooled effect of resistance training compared with a control, on chronic inflammation in adults through systematic review and meta-analysis (osf.io/xastp). Methods Intervention trials that assessed resistance training versus control, on peripheral, chronic pro-inflammatory markers [C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha] in adults were included, from four databases. Random-effect meta-analyses were conducted to calculate standardized mean differences (SMD) in post-intervention values between groups. Meta-regression explored the influence of age, chronic disease, body mass index, progressive resistance training (PRT), and intervention intensity, volume, duration, and "optimal prescription" on the pooled effect. Results Of 3,186 studies identified, 59 were included. Resistance training reduced CRP (SMD = -0.28; 95% CI = -0.46, -0.10), but not IL-6 (SMD = -0.12; 95% CI = -0.31, 0.07) or TNF-alpha (SMD = -0.07; 95% CI = -0.31, 0.16). Some heterogeneity was explained by interventions of lower intensity (<75% 1RM; 11.47%) or volume between 201 and 300 reps (6.14%). Conclusion Resistance training instigates small but significant reductions in CRP, but not IL-6 or TNF-alpha. Reductions in inflammation caused by resistance training may be influenced by intensity and volume, warranting further investigation. Resistance training should be implemented for chronic disease prevention or reduced progression, given pooled reductions in CRP.