External oblique activation is augmented with a water-filled resistance training implement compared to a static load
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Abstract
This study investigated the effects of a water-filled resistance training device (WTD) compared to a static training load on core muscle activation in the rectus abdominis (RA) and external obliques (EO) during a rotational core exercise. Twelve college-aged male participants with moderate resistance training experience performed 4 sets of 12 repetitions on each side of the Russian twist exercise using both the WTD and a static-weight control in a randomized crossover design on two separate days. Surface electromyography (sEMG) was used to measure muscle activation in both conditions. Results indicated that the WTD condition elicited greater mean and peak muscle activation in both muscle groups compared to the control. EO activation was 85% higher in mean (p = .002, d = 0.95) and 77% greater in peak (p = .002, d = 1.59) values, while no significant difference in RA activation was identified between groups. These findings suggest that the WTD enhances activation of the external obliques relative to a static load, supporting its potential use in instability-based training for moderately trained males.
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