Effects Of Lower Limb Light-weight Wearable Resistance On Running Biomechanics

Abstract

Resistance training is important to maintain an athlete´s health and regain strength after injury. Light-weight wearable resistance allows loading in the context of sport specific movements and can lead to specific strength adaptations benefiting the athlete. However, limited knowledge of the associated biomechanical changes with such a training modality exists. PURPOSE: To determine biomechanical changes during running with lower limb light-weight wearable resistance. METHODS: Fourteen healthy participants volunteered for the study (age: 28±4 years; height: 180±8 cm; body mass (BM): 77±6 kg). Participants wore shorts and calf sleeves allowing attachment of light loads and performed 4 x 2 mins 20-m over-ground shuttle running bouts at 3.3 m*s-1, alternating by 3 mins rest. The first running bout was unloaded and the other three bouts under randomised loaded conditions. The loaded conditions consisted of 1 %, 3 % and 5 % additional loading of the BM. Loads were distribution on the legs with 2/3 on the thigh and 1/3 on the shank. Two force plates embedded in the floor at the 10-m mark of the runway recorded peak vertical ground reaction forces (vGRF) and ground contact time (GCT). Recorded kinetic data was filtered using a low-pass Butterworth filter at frequency 120 Hz and normalised to body weight. A repeated measures ANOVA (α ≤ 0.05) was used to determine differences between conditions and Cohens d was calculated with effect sizes defined as small (d = 0.2), medium (d = 0.5) and strong (d = 0.8). RESULTS: Peak vGRF decreased (-0.5 %) with additional loading of 1% BM (d = 0.17, p = 1) and slightly increased (+1.1 %) with 3% BM loading (d = 0.13, p = 0.91) compared to unloaded condition. Higher peak vGRF (+1.4 %) was also found during 5 % BM loading (d = 0.19, p = 1). Ground contact time showed no significant differences (0.13 ≤ d ≥ 0.20, 0.4 ≤ p ≥ 1) between all conditions and only a slightly increased with 5 % BM loading (+1 %). CONCLUSION: Small changes in peak vGRF and GCT during loaded running occurred. Maintaining targeted speed and running economically might result from kinematic adaptations, needing further evaluation. Additionally, examination of acute neuromuscular alterations, hypothesised by increased muscular output before gait pattern changes develop, are necessary for appropriate use of light-weight wearable resistance.