Greater Association of Relative Thresholds Than Absolute Thresholds With Noncontact Lower-Body Injury in Professional Australian Rules Footballers: Implications for Sprint Monitoring

O'Connor, F., Thornton, H.R., Ritchie, D., Anderson, J., Bull, L., Rigby, A., Leonard, Z., Stern, S., Bartlett, J.D.

To examine the relationship between sprint workloads using relative vs absolute thresholds and lower-body soft-tissue and bone-stress injury incidence in professional Australian Rules Football (AF).

Fifty-three professional AF athletes’ noncontact soft-tissue and bone-stress lower-body injuries (N = 62) were recorded, and sprint workloads were quantified over approximately 18 months using GPS. Sprint volume (m) and exposures (n) were determined using 2 methods: absolute (>24.9 km·h⁻¹) and relative (>75%, >80%, >85%, >90%, >95% of maximal velocity). Relationships between threshold methods and injury incidence were assessed using logistic generalized additive models. Incidence-rate ratios (IRR) and model performances’ area under the curve (AUC) were reported.

Mean ± SD maximal velocity for the group was 31.5 ± 1.4, range 28.6–34.9 km·h⁻¹. In comparing relative and absolute thresholds, 75% maximal velocity equated to ~1.5 km·h⁻¹ below the absolute speed threshold, while 80% and 85% maximal velocity were 0.1 km·h⁻¹ and 1.7 km·h⁻¹ above the absolute speed threshold, respectively. Model AUC ranged from 0.48 to 0.61. Very low and very high cumulative sprint loads >80% across a 4-week period, when measured relatively, resulted in higher IRR (2.54–3.29), than absolute thresholds (1.18–1.58).

Monitoring sprinting volume relative to an athlete’s maximal velocity should be incorporated into athlete-monitoring systems. Specifically, quantifying the distance covered at >80% maximal velocity will ensure greater accuracy in determining sprint workloads and associated injury risk.

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