Hamstring strain injury risk factors in Australian Football change over the course of the season

Background/aim:
To determine which factors were most predictive of hamstring strain injury (HSI) during different stages of the competition in professional Australian Football.

Methods:
Across two competitive seasons, eccentric knee flexor strength and BFlh architecture of 311 Australian Football players (455 player seasons) were assessed at the start and end of pre-season and in the middle of the competitive season. Details of any prospective HSIs were collated by medical staff of participating teams. Multiple logistic regression models were built to identify important risk factors for HSI at the different time points across the season.

Results:
There were sixteen, thirty-three and twenty-one new HSIs reported in preseason, early in-season, and late in-season, respectively across two competitive seasons. Multivariate logistic regression and recursive feature selection revealed that risk factors were different for pre-season, early in-season and late in-season HSIs. A combination of prior HSI, age, height and muscle thickness were most associated with pre-season injuries (median AUC, 0.83). Pennation angle and fascicle length had the strongest association with early in-season injuries (median AUC, 0.86). None of the input variables were associated with late in-season injuries (median AUC, 0.46). Identification of early in-season HSIs and late in-season HSIs was not improved by the magnitude of change of data across pre-season (median AUC, 0.67).

Conclusion:
Risk factors associated with prospective HSIs were different across the season in Australian Rules Football, with non-modifiable factors (prior HSI, age, and height) mostly associated with pre-season injuries. Early in-season HSIs were associated with modifiable factors, notably BFlh architectural measures. The prediction of in-season HSIs was not improved by assessing the magnitude of change in data across pre-season.