Thigh positioned wearable resistance affects step frequency not step length during 50 m sprint-running

Abstract

This study determined the acute changes in spatio-temporal and impulse variables when wearable resistance (WR) of 2% body mass was attached distally to the thighs during 50 m maximal sprint-running. Fifteen sub-elite male sprinters performed sprints with and without WR over 50 m of in-ground force platforms in a randomised order. A paired t-test was used to determine statistical differences (p < .05), with effect sizes (ES) calculated between conditions over steps: 1–4, 5–14, and 15–23. WR resulted in small increased 10 and 50 m sprint times (1.0%, ES = 0.31, 0.9%, ES = 0.44, respectively, p > .05) compared to the unloaded sprint condition. For spatio-temporal variables, the WR condition resulted in moderate ES changes in step frequency (−2.8%, ES = −0.53, steps 5–14, p > .05), and contact time (2.5%, ES = 0.57, steps 5–14, and 3.2%, ES = 0.51, average of 23 steps, p > .05), while step length was unaffected during all step phases of the sprint (ES = 0.02–0.07, p > .05). Regarding kinetics, during steps 5–14, WR resulted in a moderate decrease (−4.8%, ES = −0.73, p < .05) in net anterior-posterior impulses and a moderate decrease in vertical stiffness (−5.7%, ES = −0.57, p > .05). For athletes seeking to overload step frequency and develop anterior-posterior impulse during mid to late accelerated sprinting, WR enables the application of a sprint-specific form of resistance training to be completed without decreasing step length.

Keywords:

• Specificity
• acceleration
• maximum velocity
• kinematics

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Acknowledgments

The authors would like to thank all the subjects for participating in this research and wish to extend our gratitude to Mai Kameda from the National Institute of Fitness and Sports (NIFS) in Kanoya for her assistance with this research.

Disclosure statement

John Cronin is Head of Research for Lila but is blinded from data collection, statistical analyses and writing of article, and is typically involved in methodological design and final proofing.

Paul Macadam's PhD was funded by Lila from March 2018 to March 2020, which therefore includes his involvement in the study design, data collection, statistical analyses, and writing of this article.

Additional information

Funding

This work was supported by Sportboleh, Sdh Bhd.: [Grant Number n/a].