Matthew J. Johnson, George J. Davies, Bryan L. Riemann. Georgia Southern University, Savannah, GA

BACKGROUND: Although studies have examined the acute effects of resistance training (RT) on various performance indicators, such as countermovement jumps (CMJ), fewer have quantified the effects several hours after a resistance training session (RTS). Currently, there is a void of research examining whether propulsion contribution changes differ between the dominant (DL) and nondominant limb (NDL). PURPOSE: To determine if a morning RTS affects afternoon vertical ground reaction force (VGRF) bilateral symmetry during the propulsion phase of CMJ in collegiate women athletes. METHODS: Fifteen National Collegiate Athletic Association Division I women’s soccer and volleyball athletes (18-24 years, 73.6±8.4 kg, 1.74±.19 m) who participated in offseason RT completed 5 CMJ during two afternoon sessions (48hr apart), one which was 4-6hrs after a morning RTS and one on a rest day (RD). The RTS consisted of 6 sets (2 sets per exercise) of 10 repetitions at 80% 1RM for back squat, front squat, and forward lunge. Session order was randomized between participants. CMJ trials were completed with arms akimbo and with 1 minute rest between trials. Dual force plates recorded VGRF separately for the two limbs. Jump height (JH), ground off and ground contact limb differences were computed from the VGRF. Additionally, VGRF impulse for each limb was computed for the eccentric-acceleration, eccentric-deceleration, and concentric phases, as well as peak concentric force. RESULTS: JH was slightly less, but not significantly different (P=.472, d=.19), for the RTS (.208±.038m) compared to RD (.215±.051m). There were no significant (P≥.137) ground off/ground contact limb differences. There were no significant session or limb differences (P>.05) for impulse during the eccentric-acceleration and eccentric-deceleration phases. Concentric phase impulse was less, but statistically significant (P=.048, d=.24), for the RTS (.218±.030 BW•s) compared to the RD (.226±.034 BW•s). DL (.228±.033 BW•s) concentric phase impulse was significantly greater (P=.015, d=.30) than the NDL (.217±.029 BW•s). Peak concentric force had no significant results (P≥.249). CONCLUSIONS: These results suggest a morning RTS has minimal impact on afternoon CMJ performance and no influence on VGRF limb symmetry. As the DL contributed slightly more to CMJ performance, future research should consider the source (i.e., strength differences) of the asymmetry.

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