Characterising the Cytokine and Circulating Immune Cell Response After a Single Bout of Eccentric Stepping Exercise in Healthy Untrained Males

Abstract

Abstract Purpose The mechanisms that underpin exercise-induced muscle damage and recovery are believed to be mediated, in part, by immune cells recruited to the site of injury. The aim of this study was to characterise the effects of muscle damage from bench-stepping on circulating cytokine and immune cell populations post-exercise and during recovery. Methods Ten untrained, healthy male volunteers completed 30 min of bench-stepping exercise to induce muscle damage to the eccentrically exercised leg. Muscle function, muscle pain and soreness were measured before, immediately after and 24, 48 and 72 h after exercise. Plasma creatine kinase, cartilage oligomeric matrix protein, cytokines and circulating immune cell phenotyping were also measured at these timepoints. Results Significant decreases occurred in eccentric, isometric and concentric (P = 0.018, 0.047 and 0.003, respectively) muscle function in eccentrically, but not concentrically, exercised quadriceps post-exercise. Plasma monocyte chemoattractant protein (MCP)-1 concentrations significantly increased immediately after exercise (69.0 ± 5.8 to 89.5 ± 10.0 pg/mL), then declined to below pre-exercise concentrations (58.8 ± 6.3 pg/mL) 72 h after exercise. These changes corresponded with the significant decrease of circulating CD45+ CD16− CD14+ monocytes (5.8% ± 1.5% to 1.9% ± 0.5%; Pre-exercise vs. 48 h) and increase of CD45+ CD3+ CD56− T-cells (60.5% ± 2.2% to 66.1% ± 2.1%; Pre-exercise vs. 72 h) during recovery. Conclusion Bench-stepping induced muscle damage to the quadriceps, which mediated systemic changes in MCP-1, monocytes and T-cells immediately post-exercise and during recovery. Further research is needed to clarify how modulations in immune subpopulations facilitate muscle recovery and adaptation following muscle damage.