Biology of Sport · Published 2026-01-01 · DOI 10.5114/biolsport.2026.157992
We examined if creatine kinase (CK) activity differed between congested (CS) and non-congested schedules (NCS) in elite youth national team soccer players. The CK activity of 188 players (16.53 ± 1.78 years) was measured in national team training camps (2489 individual data points). Training load one day before the match (MD-1) was monitored with global positioning system (GPS) devices. CS occurred, when the athlete played at least 60 minutes in the previous 3 days leading into the match (MD). CK MD was significantly higher in CS than in NCS (median: 309 vs 220 U/L, p < 0.05). More recovery days between matches were associated with lower values on the second CK MD . CK values one (CK MD+1 : 678 vs 487 U/L) and two days after the match (CKMD+2: 395 vs 303 U/L) were higher for CS (p < 0.05), however relative CK changes from MD to one (CK MD→MD+1% : 181 vs 135%) or two days after (CK MD→MD+2% : 74 vs 44%) were higher for NCS (p < 0.05). 11 out of 15 MD-1 training load parameters were significantly higher for NCS (p < 0.05). CK MD was sensitive to congested schedule and the number of recovery days between matches. Therefore three recovery days between matches might be inadequate for complete recovery. Higher CK MD , CK MD+1 and CK MD+2 values, but lower CK MD→MD+1% and CK MD→MD+2% changes were found for CS than for NCS. MD-1 training load was lower in CS than in NCS, making it an unlikely cause of the elevated CK MD and CK MD+1 values. Instead, it might be the result of residual fatigue from the last match.
Abstract from DOAJ. Public domain (CC0 1.0).
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