Influence Of Stride Frequency Manipulation On Muscle Activity During Running At Reduced Body Weight

Abstract

Running with body weight support (BWS) (e.g., running on a lower positive pressure treadmill) has been used for physical fitness enhancement. Nevertheless, gait mechanics of running with BWS is not fully understood. PURPOSE: To investigate influence of stride frequency (SF) manipulation on muscle activity during running at different BWS conditions. METHODS: Nineteen subjects (23.8±4.1 years) ran on a lower body positive pressure treadmill at their preferred running speed (PS) for different BWS conditions (i.e., 0%, 50%, and 80% of BWS conditions). The SF conditions consist of running at preferred SF (PSF), PSF+10%, and PSF-10%. Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GA) were measured. In addition, rating of perceived exertion (RPE) and SF were measured. Muscle activity, RPE, and SF were analyzed using a 3 (mode) x 3 (BWS) repeated measures analysis of variance (ANOVA) (α = 0.05). PS was analyzed using a one-way repeated measures ANOVA (α = 0.05). RESULTS: Muscle activity (RF, BF, TA, and GA), RPE, and SF were not influenced by the interaction of BW support and SF (P>0.05). Muscle activity from the RF, TA, and GA were different between BWS conditions (P<0.001). Specifically, muscle activity from the RF, TA, and GA were lower with increasing BWS (e.g., a decrease of 26%~46% between 80%BWS and 0%BWS conditions). Muscle activity from the RF, BF, and TA were different between SF conditions (P<0.05). For example, RF muscle activity during running at PSF was 11%~18% lower than when running at PSF+10%. Additionally, BF muscle activity during running was higher with increasing SF (e.g., a 20% increase in SF resulted in 12%~27% increase in the BF muscle activity). RPE was not different between BWS conditions (P>0.05) and between SF conditions (P>0.05). SF was different between BWS conditions (P<0.001) and between SF conditions (P<0.001). For example, SF was lower with increasing BWS (e.g., a decrease of 15% between 80%BWS and 0%BWS conditions). PS was higher with increasing BWS (9.8±2.1 km/h, 11.0±2.6 km/h, and 11.8±2.8 km/h for 0%, 50%, and 80% of BWS conditions, respectively: P<0.001). CONCLUSION: These observations suggest that a change in SF may influence muscle activity (i.e., RF and TA) during running, regardless of BWS.