Creatine kinase after an official amateur boxing bout: magnitude, variability and response to sports massage, BCAA supplementation or passive recovery

Creatine kinase (CK) is often used to inform recovery decisions in combat sports, yet its behaviour after competition is poorly described. This exploratory, non-randomised field study described the magnitude and variability of CK after an official amateur boxing bout and compared its trajectory after sports massage, acute branched-chain amino acid (BCAA) supplementation or passive recovery. Forty-five male amateur boxers were allocated within weight-class clusters to the three conditions (n = 15 per group). CK was measured before competition, 8 h after the bout (immediately before the intervention), 30 min after the intervention and 24 h after the bout. CK did not rise detectably after the bout, 40% of values fell below the published reference range for male athletes, and most of the variation in CK occurred within rather than between athletes. At 24 h, CK was about 60% lower after BCAA supplementation than after passive recovery (geometric-mean ratio 0.40, 95% CI 0.25–0.64), a difference that was consistent across sensitivity analyses; massage did not differ significantly from either condition. An apparent difference 30 min after supplementation is unlikely to reflect a treatment effect, given the slow clearance of CK. Under the conditions of this study, a single CK value appeared to have limited utility for individual recovery decisions. The 24-h difference should be regarded as preliminary and tested in a registered, randomised, placebo-controlled trial.