Deceleration, Acceleration, and Impacts Are Strong Contributors to Muscle Damage in Professional Australian Football.

Gastin, PB, Hunkin, SL, Fahrner, B, and Robertson, S. Deceleration, acceleration, and impacts are strong contributors to muscle damage in professional Australian football. J Strength Cond Res 33(12): 3374-3383, 2019-The purpose of this study was to investigate the relationships between serum creatine kinase [CK], an indirect marker of muscle damage, and specific indices of match load in elite Australian football. Twenty-six professional players were assessed during a competitive Australian Football League (AFL) season. [CK] was collected 24-36 hours before match and 34-40 hours after match during 8 in-season rounds. An athlete-tracking technology was used to quantify match load. Generalized estimating equations and random forest models were constructed to determine the extent to which match-load indices and pre-match [CK] explained post-match [CK]. There was a 129 ± 152% increase in [CK] in response to AFL competition. Generalized estimating equations found that number of impacts >3g (p = 0.004) and game time (p = 0.016) were most strongly associated with post-match [CK]. Random forest, with considerably lower errors (130 vs. 316 U·L), found deceleration, acceleration, impacts >3g, and sprint distance to be the strongest predictors. Pre-match [CK] accounted for 11% of post-match [CK], and considerable interindividual and intraindividual variability existed in the data. Creatine kinase, an indicator of muscle damage, was considerably elevated as a result of AFL competition. Parametric and machine-learning analysis techniques found several indices of physical load associated with muscle damage during competition, with impacts >3g and high-intensity running variables as the strongest predictors. [CK] may be used as a global measure of muscle damage in field team sports such as AF, yet with some caution given cost, invasiveness, and inherent variability. Quantifying physical load and the responses to that load can guide athlete management decision-making and is best undertaken within a suite of practical, sport-specific measures, where data are interpreted individually and with an understanding of the limitations.

Creatine kinase and its relationship with match performance in elite Australian Rules football.

OBJECTIVES: The purpose of this study was to examine the relationships of pre-match creatine kinase on match performance measures in elite Australian Rules football. DESIGN: Repeated measures single cohort longitudinal. METHODS: Twenty-nine elite Australian Rules football players were assessed across a competitive season. Creatine kinase was collected 24-36 h pre-match, and investigated against two measures of match performance; performance ranking scores (based on playing statistics) and coach's performance ratings. Multi-level modelling was applied and player characteristics were considered as moderating variables in the analysis. RESULTS: Average player pre-match creatine kinase was 485% greater than baseline values. Six-minute running performance was negatively related with average player pre-match creatine kinase (r=-0.432, p=0.019). Creatine kinase was negatively associated with performance ranking scores (r=-0.149, p=0.035), although increases in playing experience reversed this relationship (p=0.003). Coach's subjective ratings declined with elevations in pre-match creatine kinase (p=0.002). CONCLUSIONS: Increases in creatine kinase from baseline to pre-match indicate residual muscle damage. Small decrements in match performance were explained by increases in pre-match creatine kinase. However, player characteristics related to age and experience appear to be important moderating variables. Elevated pre-match creatine kinase likely represents a state of incomplete recovery from the preceding week, and over time, residual muscle damage. Creatine kinase monitoring may be most appropriately used with young and inexperienced players, and those with lower aerobic running performance to assist in the modulation of training and recovery loads to optimise match preparation and performance.