The Cumulative Impacts of Fatigue during Overload Training Can Be Tracked Using Field-Based Monitoring of Running Stride Interval Correlations.

Integrating running gait coordination assessment into athlete monitoring systems could provide unique insight into training tolerance and fatigue-related gait alterations. This study investigated the impact of an overload training intervention and recovery on running gait coordination assessed by field-based self-testing. Fifteen trained distance runners were recruited to perform 1-week of light training (baseline), 2 weeks of heavy training (high intensity, duration, and frequency) designed to overload participants, and a 10-day light taper to allow recovery and adaptation. Field-based running assessments using ankle accelerometry and online short recovery and stress scale (SRSS) surveys were completed daily. Running performance was assessed after each training phase using a maximal effort multi-stage running test-to-exhaustion (RTE). Gait coordination was assessed using detrended fluctuation analysis (DFA) of a stride interval time series. Two participants withdrew during baseline training due to changed personal circumstances. Four participants withdrew during heavy training due to injury. The remaining nine participants completed heavy training and were included in the final analysis. Heavy training reduced DFA values (standardised mean difference (SMD) = -1.44 ± 0.90; = 0.004), recovery (SMD = -1.83 ± 0.82; less than 0.001), performance (SMD = -0.36 ± 0.32; = 0.03), and increased stress (SMD = 1.78 ± 0.94; = 0.001) compared to baseline. DFA values ( = 0.73), recovery ( = 0.77), and stress ( = 0.73) returned to baseline levels after tapering while performance trended towards improvement from baseline (SMD = 0.28 ± 0.37; = 0.13). Reduced DFA values were associated with reduced performance (r = 0.55) and recovery (r = 0.55) and increased stress (r = 0.62). Field-based testing of running gait coordination is a promising method of monitoring training tolerance in running athletes during overload training.