Training loads and injury risk in Australian football—differing acute: chronic workload ratios influence match injury risk

Abstract

Aims (1) To investigate whether a daily acute:chronic workload ratio informs injury risk in Australian football players; (2) to identify which combination of workload variable, acute and chronic time window best explains injury likelihood. Methods Workload and injury data were collected from 53 athletes over 2 seasons in a professional Australian football club. Acute:chronic workload ratios were calculated daily for each athlete, and modelled against non-contact injury likelihood using a quadratic relationship. 6 workload variables, 8 acute time windows (2-9 days) and 7 chronic time windows (14-35 days) were considered (336 combinations). Each parameter combination was compared for injury likelihood fit (using R 2 ).Results The ratio of moderate speed running workload (18-24 km/h) in the previous 3 days (acute time window) compared with the previous 21 days (chronic time window) best explained the injury likelihood in matches (R 2 =0.79) and in the immediate 2 or 5 days following matches (R 2 =0.76-0.82). The 3:21 acute: chronic workload ratio discriminated between high-risk and low-risk athletes (relative risk=1.98-2.43). Using the previous 6 days to calculate the acute workload time window yielded similar results. The choice of acute time window significantly influenced model performance and appeared to reflect the competition and training schedule. Conclusions Daily workload ratios can inform injury risk in Australian football. Clinicians and conditioning coaches should consider the sport-specific schedule of competition and training when choosing acute and chronic time windows. For Australian football, the ratio of moderate speed running in a 3-day or 6-day acute time window and a 21-day chronic time window best explained injury risk.

<p>The Relationship Between Acute: Chronic Workload Ratios and Injury Risk in Sports: A Systematic Review</p>

“…[9][10][11]17,18,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Other timeframes included a 3-day acute load and a 21 daychronic load, 19 or varying timeframes. [37][38][39][40] One study examined various timeframes for calculating ACWR, 37 utilizing 2-9 days for acute loads, and chronic loads varying from 14 to 35 days, while the other study ranged from 1 to 2 weeks for acute loads, and 3-8 weeks for chronic loads, but only utilized the 1:4 week ratio for relationship to injury. 38 Five studies utilized exponentially weighted moving averages (EWMA) for their calculation of ACWR 17,27,29,36,39 and four articles studied a combination of ACWR and chronic workload.…”

“…38 Colby et al 30 reported, compared to ACWR range of 0.99 to 1.08, ranges of <0.88 (IRR=1.17), 1.08-1.21 (IRR=1.37), and >1.21 (IRR=1.53) resulted in higher incidence of injury, while 0.88-0.99 (IRR=0.60) resulted in a lower incidence when using TD. This same study found that when compared to an above average chronic TD load (81694m over 4 weeks) and moderate 27,30,34,[36][37][38][39] Total [9,10,17,20,21,[23][24][25][26][28][29][30][31][32][33][35][36][37][38]40] ACWR [11,[17][18][19][20][21][22][23][25][26][27][28][29][30][31][32][33][34][35][36]…”

“…While multiple studies utilized distance at various speeds as a variable, their definitions of these speeds varied. 19,22,25,27,30,34,[36][37][38] For example, one study states high speed running (HSR) ranges from 18.01 to 24.00 km/h, 27 while another study stated HSR is anything greater than 14.40 km/h. 19 In the study by Murray et al, 27 an ACWR of 2.00 with HSR (18.01-24.00 km/h) increased injury risk relative to an ACWR ranging from 1.00 to 1.49 (RR=4.66).…”

“…Combining recent leg injuries in the comparison led to a higher HR for both EWMA ACWR (HR=5.70) and ACWR (HR=4.60). Carey et al 37 examined both HSR (>24 km/h) and MSR (18-24 km/h). This study compared various daily ACWR (acute period ranging from 2 to 9 days; chronic 14, 18, 21, 24, 28, 32, and 35 days), and examined the relative injury risk of ratios outside the range of 0.80-1.20.…”

Applying the acute:chronic workload ratio in elite football: worth the effort?

“…While the use of session-RPE as an alternative input of load may be relevant, some substantial limitations remain, such as the lack of sensitivity of RPE to subtle differences in high running speeds. The optimal duration of both the chronic (2 vs 3 vs 4 weeks, based on off-season and preseason durations) and acute (3 vs 7 days, based on matches occurrence) periods of load need probably to be discussed to better fit the specific training/completive patterns of elite football 9. Injury prevention cannot be limited to the monitoring of a single (A/C) number; understanding players' individual needs and profiles, and using common sense when programming workloads are probably as important to keep players fit and healthy.…”