Author(s): SCHWARZ, Y., WIEDENMANN, T., LEMBERG, P., BÖDDEKER, K., CHRISTMANN, R., SCHWARZ, A., REIN, R., BRAUNSTEIN, B., Institution: KARLSRUHE INSTITUTE OF TECHNOLOGY, Country: GERMANY, Abstract-ID: 2122

INTRODUCTION:
Sprint running performance is the product of the spatiotemporal variables step frequency [SF] and length [SL].[1] While the 100-m dash has been in the spotlight of biomechanical investigations, less research has looked at the 400-m distance. Hence, purpose of this study was to extract spatiotemporal parameters from a large sample of world-class 400-m performances and gain insights on potential determining factors.
METHODS:
Publicly available video footage was obtained from 84 world-class 400m races (Olympics, World & Europ. Champ., Diamond League), including 289 performances of 101 athletes (m=51; f=50) between 2015 to 2020. Footage was only considered valid if athletes were visible without interruption and if markings were visible every 100m. Time and step count were extracted visually and mean velocities, SL and SF calculated for each 100m section of the race. Differences in performance and sex were evaluated via Welch two sample t-test for every section.
RESULTS:
Over the entire 400m distance, mean velocity was 8.85±0.15 m∙s-1 for male and 7.81±0.14 m∙s-1 female sprinters. On average male athletes displayed a SL of 2.31±0.11 m and SF of 3.84±0.17 steps∙s-1, while female athletes had a mean SL of 2.09±0.09 m and SF of 3.75±0.13 m∙s-1. Greater differences between men and women were found in SL (11.8%; p<0.001) than in SF (2.4%; p<0.001) and even if SL was normalized to body height (3.9%, p<0.001). Both sexes showed highest velocity between 100m and 200m (m=9.68±0.26 m∙s-1; f=8.43±0.22 m∙s-1) and a decrease in velocity thereafter (m=-20.7%, f=-22.8%). The velocity decrease in the 2nd half of the race seems to coincide with decreases in SF (m=-11.7%, f=-10.9%) and SL (m=9.2%, f=8.9%). In relation to their mean race velocity, the 1st 100m were slightly faster in women (104.7% vs. 103%, p<0.001), whereas the 2nd (109.3% vs. 107.9%, p<0.001) and 3rd (101.2 vs. 100.3%, p<0.001) 100-m sections were faster in men. No difference was found for the last 100m section (89.0 vs. 89.4%, p=0.23). When the fastest male (n=20) and females (n=21) performances were compared with the slowest (n=19; n=21), the greatest group differences for both sexes were found to be mean SL (m= 5.52%, p<0.001; f= 6.00%, p<0.001) and relative velocity during the final 100m (m=1.96%, p=0.04; f=1.72%, p=0.04).
CONCLUSION:
Previously reported, fast first half and decrease in velocity during the second half of world-class 400-m running, can be confirmed for both sexes by this analyses.[2,3] The velocity decrease coincides with reduction in SL and SF, which are likely caused by decreased force production and muscular acidosis.[4] However, higher mean SL in all sections seems to distinguish superior performance on a world-class level, while SF plays a subordinate role. Additionally, a more even positive pacing strategy might be optimal for 400-m performance.

1) Haugen et al. (2019) Eur J Appl Physiol
2) Pollitt et al. (2017a) World Athletics
3) Pollitt et al. (2017b) World Athletics
4) Nummela et al. (1992) J Sports Sci