Author(s): KLEIN, J., FRÖHLICH, B., OEPPERT, T., SCHAPSCHRÖER, M., ABEL, T., Institution: GERMAN SPORT UNIVERSITY COLOGNE, Country: GERMANY, Abstract-ID: 2492

INTRODUCTION:
Maximum sprinting speed (MSS) is constrained by the ability to generate sufficient mass-specific vertical forces within short ground contact times(tc), leading to an inverse relationship between tc and sprinting speed [1]. ‘Assisted’ sprinting has been proposed as a promising method to increase MSS, with traditional methods relying on horizontal towing forces. Conversely, body-mass support systems (BMSS) offer a unique ‘vertical assistance’ approach,that reduce vertical force demands during stance [2]. While BMSS has been explored in low-speed running, its effects on maximal and supramaximal sprinting remain poorly understood. Therefore, this study examined the impact of a novel BMSS on spatiotemporal parameters during high-speed treadmill sprinting.
METHODS:
Seven male (100m PR: 10.84 ± 0.56s) and 11 female (100m PR: 12.49 ± 0.70 s) trained sprinters participated. The study consisted of two testing sessions separated by 72 hours. During the first visit, athletes performed three maximal 70 m sprints on an indoor athletic track. MSS, defined as the highest velocity over two consecutive steps, was measured via a laser device. During the second visit, athletes completed two treadmill sprints for each of the three conditions in the following order: a) unassisted at 100% MSS (FREE), b) assisted at 100% MSS (ASSIST) c) assisted at 105% MSS (ASSIST-SUPRA). A motorized treadmill was accelerated within 5 s to the individually selected velocity and this velocity was maintained for a period of 3 s (peak velocity phase) before decelerating. Vertical assistance, corresponding to a 10% reduction in body mass during upright standing, was applied using a custom-built BMSS (LEVER UP, Lever Movement, Boulder, USA). Spatiotemporal parameters - including step length (SL), step frequency (SF), tc, and flight time (ta) - were measured via photoelectric cells during the peak velocity phase. A one-way RM ANOVA was conducted to assess differences between the three conditions, followed by Bonferroni-corrected post-hoc tests.
RESULTS:
Multivariate analysis revealed statistically significant differences across conditions for all spatiotemporal parameters (p < 0.001) with large effect sizes (part. eta2 = [0.14, 0.89]). In ASSIST-SUPRA, participants exhibited significantly greater SL (p < 0.01) and SF (p < 0.001), alongside reduced tc (p < 0.001) while ta remained unchanged compared to FREE and ASSIST. No significant differences in SL and SF were observed between FREE and ASSIST. However, ASSIST altered step time distribution, reducing tc (p < 0.001) and increasing ta (p < 0.01).
CONCLUSION:
Unlike horizontal towing devices, which primarily increase velocity by lengthening SL through extended ta [3], this study observed a combination of supramaximal speed and reduced tc. These findings highlight the potential advantages of BMSS as a training tool to possibly enhance MSS, warranting further investigation in applied sprint training.

(1) Clark et al., 2022
(2) Kratky et al., 2016
(3) Gleadhill et al., 2024