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.

Association Between Preseason Training and Performance in Elite Australian Football.

PURPOSE: To examine the association between preseason training variables and subsequent in-season performance in an elite Australian football team. METHODS: Data from 41 elite male Australian footballers (mean [SD] age = 23.4 [3.1] y, height =188.4 [7.1] cm, and mass = 86.7 [7.9] kg) were collected from 1 Australian Football League (AFL) club. Preseason training data (external load, internal load, fitness testing, and session participation) were collected across the 17-wk preseason phase (6 and 11 wk post-Christmas). Champion Data© Player Rank (CDPR), coaches' ratings, and round 1 selection were used as in-season performance measures. CDPR and coaches' ratings were examined over the entire season, first half of the season, and the first 4 games. Both Pearson and partial (controlling for AFL age) correlations were calculated to assess if any associations existed between preseason training variables and in-season performance measures. A median split was also employed to differentiate between higher- and lower-performing players for each performance measure. RESULTS: Preseason training activities appeared to have almost no association with performance measured across the entire season and the first half of the season. However, many preseason training variables were significantly linked with performance measured across the first 4 games. Preseason training variables that were measured post-Christmas were the most strongly associated with in-season performance measures. Specifically, total on-field session rating of perceived exertion post-Christmas, a measurement of internal load, displayed the greatest association with performance. CONCLUSION: Late preseason training (especially on-field match-specific training) is associated with better performance in the early season.

Association Between Pre-season Training and Performance in Elite Australian Football.

PURPOSE: To examine the association between pre-season training variables and subsequent in-season performance in an elite Australian football team. METHODS: Data from forty-one elite male Australian footballers (mean±SD: age=23.4±3.1y; height=188.4±7.1cm; mass=86.7±7.9kg) was collected from one Australian Football League (AFL) club. Pre-season training data (external load, internal load, fitness testing and session participation) were collected across the 17-week pre-season phase (6-weeks pre-Christmas, 11-weeks post-Christmas). Champion Data© Player Rank (CDPR), coaches' ratings (CR) and round one selection were used as in-season performance measures. CDPR and CR were examined over the entire season, first half of the season and the first four games. Both Pearson and partial (controlling for AFL age) correlations were calculated to assess if any associations existed between pre-season training variables and in-season performance measures. A median-split was also employed to differentiate between higher and lower performing players for each performance measure. RESULTS: Pre-season training activities appeared to have almost no association with performance measured across the entire season and the first half of the season. However, many pre-season training variables were significantly linked with performance measured across the first four games. Pre-season training variables that were measured post-Christmas were the most strongly associated with in-season performance measures. Specifically, Total on-field session rating of perceived exertion (sRPE) post-Xmas, a measurement of internal load, displayed the greatest association with performance. CONCLUSIONS: Late pre-season training (especially on-field match specific training) is associated with better performance in the early season.

Different methods of training load quantification and their relationship to injury and illness in elite Australian football.

OBJECTIVES: To compare different methods of training load (TL) quantification and their relationship to injury and illness in elite Australian footballers. DESIGN: Prospective cohort study. METHODS: Forty-five elite Australian footballers (mean±standard deviation: age=23.4±3.8 years) from one elite club participated in this 15 week pre-season study. TL was quantified every session for each individual using four different methods involving rating of perceived exertion (RPE). Two of these methods enabled the quantification of TL for all exercise modalities whilst two were applicable only to outdoor field activities. One- and two-weekly cumulative TL was investigated against injury and illness data using a logistic regression model where the low TL group was considered as the reference group. RESULTS: A general trend existed across all TL methods which suggested lower odds of injury and illness in high TL groups. The one-week RPE (all) and one-week RPExDuration (all) methods detected reduced odds of injury in high TL groups compared to low TL groups (p<0.05, OR=0.199-0.202). Similarly, the one-week RPE (field) method identified lower illness odds in the high TL groups (p<0.05, OR=0.083-0.182). CONCLUSIONS: Higher TL appeared to provide a protective effect against both injury and illness. The inclusion of duration in the quantification of TL via RPE did not improve the ability of RPE to predict change in odds of injury or illness.

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.

Influence of physical fitness, age, experience, and weekly training load on match performance in elite Australian football.

Season long competition schedules in football create unique challenges for coaches in balancing the requirements of recovery, developing and maintaining physical fitness, and adjusting the training load before each match. The aim of this study was to investigate the influence of player characteristics (physical fitness, age, and playing experience) and weekly in-season training load on elite match performance across an Australian football season. Twenty-five players (age: 24.1 ± 3.0 years; height: 188.3 ± 7.3 cm; weight: 90.4 ± 8.3 kg) from one elite team participated in this study. Before the season, player's age, experience, height, and weight along with measures of aerobic (6-minute run) and anaerobic (6 × 40 m repeated sprints) physical fitness were recorded. Individual player training load during the season was measured using global positioning system technology for the main training session of the week. Player match performance was calculated weekly from 33 individual playing statistics. Multilevel modeling was used to investigate the relationship between weekly training load and match performance and to explore the influence of player characteristics on this relationship. Playing experience (p < 0.01) and aerobic fitness (p < 0.05) displayed positive relationships with performance, whereas player age (p < 0.01) showed a negative relationship. Most players coped well with weekly variations in training load; however, the relationship was moderated by the results of the preseason repeated sprint test (p < 0.05). The adverse effect on playing performance in selected players after a more intense training session suggests that recovery from the session may be delayed in players who exhibit a better anaerobic fitness profile.

Can a clinical test of hamstring strength identify football players at risk of hamstring strain?

PURPOSE: To demonstrate the potential for a simple clinical test of hamstring muscle strength to identify susceptibility to muscle strain injury. METHODS: A single-case design was used; specifically, an elite-level male Australian Rules football player performed bilateral isometric maximum voluntary contractions of the hamstring muscles on a weekly basis for a period of 5 weeks preceding a right hamstring muscle strain injury. RESULTS: Minimal asymmetry (no greater than ±1.2% difference) was evident in the hamstring isometric maximum voluntary contractions during the first 4 weeks, but 5 days prior to injury, the right hamstring isometric maximum voluntary contraction was reduced by 10.9% compared to the left. CONCLUSION: Measuring asymmetry in isometric maximum voluntary contractions of the hamstring muscles may be a useful clinical test to identify susceptibility to muscle strain injury.