Reference intervals for serum creatine kinase in athletes

Abstract

Background: The serum concentration of creatine kinase (CK) is used widely as an index of skeletal muscle fibre damage in sport and exercise. Since athletes have higher CK values than non-athletes, comparing the values of athletes to the normal values established in non-athletes is pointless. The purpose of this study was to introduce reference intervals for CK in athletes. Method: CK was assayed in serum samples from 483 male athletes and 245 female athletes, aged 7-44. Samples had been obtained throughout the training and competition period. For comparison, CK was also assayed in a smaller number of non-athletes. Reference intervals (2.5th to 97.5th percentile) were calculated by the non-parametric method. Results: The reference intervals were 82-1083 U/L (37˚C) in male and 47-513 U/L in female athletes. The upper reference limits were twice the limits reported for moderately active non-athletes in the literature or calculated in the non-athletes in this study. The upper limits were up to six times higher than the limits reported for inactive individuals in the literature. When reference intervals were calculated specifically in male football (soccer) players and swimmers, a threefold difference in the upper reference limit was found (1492 vs 523 U/ L, respectively), probably resulting from the different training and competition demands of the two sports. Conclusion: Sport training and competition have profound effects on the reference intervals for serum CK. Introducing sport-specific reference intervals may help to avoid misinterpretation of high values and to optimise training.

Post-Match Changes in Muscle Damage Markers among U-21 Soccer Players

“…It is possible that due to the high frequency of matches and inadequate recovery soccer players can have consistently elevated CK, which was confi rmed in one study (Heisterberg et al, 2013 ). Our data show much higher values compared to the upper reference value (270 UI/L), for the general population (Mougios, 2007). Furthermore, the high variability of the measure of CK activity must also be taken into account (Halson, 2014), which was the case in this study.…”

Individual analysis of creatine kinase concentration in Brazilian elite soccer players

“…The CK concentration of 14 soccer players remained below the threshold value for the increased risk of injury suggested by Mougios 13 (1492 U/L) and Lazarim et al 10 (975 U/L). It should be noted that the CK concentration of three soccer players was above 975 U/L and the highest being above 1492 U/L, but no clinical problems were reported.…”

“…While some studies reported no changes in CK concentration 9,12 others showed CK concentration decreases during a competition 10 . In addition, the absolute values of CK concentration have been used in some of the previous studies which evaluated CK concentration of soccer players 1,9,10,13,14 .…”

“…In sports, the use of fixed reference values for CK concentration has been proposed for monitoring training load, these fixed reference values indicate a threefold for injury risk augmented 13,15 . The reference value of physiological parameters are important for interpretation of data 16 .…”

Avaliação da demanda fisiológica aguda no futebol

“…These values correspond to the normal daily physical demand of soccer players throughout a season, but they are considered high for nonathletes, as studied by Mougios 29 .…”