Acute Effects of Training Loads on Muscle Damage Markers and Performance in Semi-elite and Elite Athletes: A Systematic Review and Meta-analysis

Abstract

Background: The relationship between exercise-induced muscle damage (EIMD) indicators and acute training loads (TL) is yet to be reviewed extensively in semi-elite and elite athlete populations.

Objectives: The objectives of this systematic review and meta-analysis were threefold: (1) to evaluate studies of EIMD following the initial period of the preseason in semi-elite and elite athletes: (2) to examine acute physiological and performance responses across two periods of the season with similar TL; and (3) to examine acute physiological and performance responses to acute changes in TL during the season.

Methods: The CINAHL, PubMed, Scopus, SPORTDiscus and Web of Science databases were systematically searched for studies that investigated: (1) semi-elite or elite athletes in team or individual sports following a periodised training programme; and (2) measured acute responses to training. Studies were excluded if: (1) conducted in animals; (2) non-English language; or (3) a conference abstract, review or case report. The Kmet Quality Scoring of Quantitative Studies tool was used for study appraisal.

Synthesis methods: Data were quantitatively analysed by generating forest plots to report test statistics for statistical significance and inter-trial heterogeneity.

Results: Of the included studies (n = 32), athletes experienced greater creatine kinase (CK) concentrations (Z = 4.99, p < 0.00001, I² = 74%), inflammatory factors and other indirect measures of muscle damage in the initial phase of the preseason period compared to the off-season; there were no changes in CK (Z = 1.43, p = 0.15, I² = 74%) across two time points of similar TL; and there were concurrent increases in CK with increases in TL (Z = 4.26, p < 0.0001, I² = 36%) and vice versa (Z = 4.33, p < 0.0001, I² = 79%).The qualitative analysis identified that the response of inflammatory factors and other indirect measures of muscle damage to changes in load were inconclusive.

Limitations: This review included varying age, sex, sports and competition levels. The group level meta-analysis failed to identify within-athlete or position-specific differences across time.

Conclusion: Blood biomarkers of EIMD may not differ across periods of similar TL, however can be considered a sensitive monitoring tool for assessing responses following acute TL changes in semi-elite and elite athletes.