Author(s): OH, Y.K., TUCKER, C.B., HANLEY, B., Institution: LEEDS BECKETT UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1555

INTRODUCTION:
It is important to understand mechanical changes in athletes over the course of a high-intensity bout such as a distance race. Changes in running style were measured during the women's 800m [1] and men’s 1500m finals [2] at the 2017 World Athletics (WA) Championships that highlighted the importance of measuring these changes in race conditions. A laboratory study on mechanical adaptations to reflect middle-distance pacing profiles could reveal useful findings. This study therefore examined the changes in running mechanics of competitive female middle-distance athletes during a simulated 1500m race.
METHODS:
Twenty athletes (WA score 944 ± 117) ran a 1500m season’s best-matched four-stage continuous protocol on an instrumented Gaitway treadmill (1000 Hz). The four stages comprised an opening 200 m at a constant speed of 20 – 23 km/h, a subsequent decrease by 4 km/h for the next 600 m, an increase by 2 km/h for the next 500 m, and a final 200 m at the same speed as the first stage. 2D video data were simultaneously collected for 10 s using two Fastec cameras (200 Hz) placed perpendicular to the centre of the treadmill during the first and last stages. Fingertip blood samples were taken before the start and immediately after completing the protocol to determine blood lactate concentration and differences were analysed using a paired t test. Leg stiffness was normalised to body weight and leg length. We used linear mixed-effect models with first vs last stage as a fixed effect and participant as a random factor to assess effects on discrete kinematics at key gait events, as well as spatiotemporal and global stiffness variables. Significance was set at p < 0.05 and Cohen’s d was used to assess effect size.
RESULTS:
There was an increase in blood lactate (1.6 ± 0.7 to 10.5 ± 3.2 mmol/L, p < 0.001; d = 2.83). Between the first and last stages, there were decreases in flight time (4 ± 6 ms, p = 0.005; d = 0.73), and increases in contact time (5 ± 3 ms, p < 0.001; d = 1.29) and duty factor (0.007 ± 0.006, p < 0.001; d = 1.13). Hip-ankle distance increased at contact (0.01 ± 0.01 m, p < 0.001; d = 0.55) and toe-off (0.02 ± 0.01 m, p < 0.001; d = 1.69), arising from greater hip (7%) and knee extension (12%) in the unloading phase (midstance to toe-off). There were also decreases in leg stiffness (−1.18 ± 0.93, p < 0.001; d = 1.53), as well as increases in forward mechanical work (p = 0.004, d = 0.74) and work ratio (forward/total) (p < 0.001, d = 1.04).
CONCLUSION:
Athletes achieved the same high speed in the first and last stages, reflecting the same performance outcome in running. However, more terrestrial style mechanics were adopted in the fatigued final stage to achieve greater forward mechanical work with decreased leg stiffness. These findings indicate mechanical competencies to sustain forward propulsion under fatigue are key for high-speed running.
REFERENCES:
1. Hanley et al. Front Sports Act Living 2022; 4:834813
2. Hanley et al. Scand J Med Sci Sports 2023; 33:931-942