The relationship between changes in interstitial creatine kinase and game-related impacts in rugby union.
OBJECTIVE
The primary purpose of this study was to investigate the relationship between the pre-game to post-game changes in creatine kinase concentration (Delta[CK]) and impact-related game statistics in elite rugby union players.


METHODS
Twenty-three elite male rugby union players each provided interstitial fluid samples obtained via electrosonophoresis (ESoP) 210 min before and within a maximum time of 30 min after up to five rugby union games. Specific game statistics that were deemed to be important in determining the relationship between impact and [CK] were obtained from AnalyRugby software for each individual player. Regression equations to predict Delta[CK] from game statistics were created using a backwards random-effects maximum likelihood regression.


RESULTS
The Delta[CK] (mean (SD)) from pre-game to post-game was 926.8 (204.2) IU. Game time and time defending were significantly correlated to Delta[CK] in both the forwards and backs. The predicted Delta[CK] (mean (95% confidence limit)) was 1439.8 (204.9) IU for the forwards and 545.3 (78.0) IU for the backs and was significantly correlated with the actual Delta[CK] (r = 0.69 and r = 0.74).


CONCLUSIONS
CK increased from pre-game to post-game in a position-specific manner. A large proportion of the Delta[CK] can be explained by physical impact and thus can be predicted using a prescribed number of game statistics. As the Delta[CK] is an indicator of muscle damage, the prediction of Delta[CK] provides a theoretical basis for recovery strategies and adjustment of subsequent training sessions after rugby union games.
Smart
D J
DJ
School of Sport and Exercise Science, Waikato Institute of Technology, Private Bag 3036, Hamilton, New Zealand. daniel.smart@wintec.ac.nz
Gill
N D
ND
Beaven
C M
CM
Cook
C J
CJ
Blazevich
A J
AJ
D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism*; D004586:Electrophoresis; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D010806:Physical Education and Training / Q000379:methods; D012044:Regression Analysis
D015415:Biomarkers; D003402:Creatine Kinase