Kaitlyn F. Overstreet, Ryan J. Colquhoun, Sydnie R. Fleming, Katie G. Kennedy, Caitlyn C. White, Keelan I. Stricklin. University of South Alabama, Mobile, AL.

BACKGROUND: Previous research investigating the effects of caffeine on rapid force characteristics have mainly been performed in males, with little to no research in females, especially those on oral contraceptives (OC). Therefore, the purpose of this study was to assess rate of torque development (RTD) of the quadriceps following acute caffeine supplementation in college-aged females on OCs. METHODS: Twenty recreationally active females (Mean ± SD; 20 ± 1 y) volunteered to participate in a randomized, double-blind crossover, placebo-controlled study. Participants completed a familiarization visit and a 1-week caffeine (CAF) washout, followed by two experimental visits in which RTD of the right quadriceps was assessed in 20-minute intervals prior to and following the consumption of either CAF (6 mg/kg/bw) or placebo (PLA). RTD was assessed via maximum voluntary isometric contraction (MVIC), in which subjects were asked to “kick as hard and fast as possible.” Peak RTD (pRTD), as well as RTD during 0-100 ms (RTD0-100) and 100-200 ms (RTD100-200) were calculated from each MVIC offline. RESULTS: Repeated measures ANOVAs indicated that pRTD was greater in CAF when compared to PLA (750.6 ± 328.7 Nm·s-1 vs. 649.5 ± 318.9 Nm·s-1; p=0.010) and collapsed across time. A significant interaction effect and post-hoc analyses indicated that RTD0-100 was significantly greater at CAF20 (552 ± 356.6 Nm·s-1) when compared to CAF100 (400.6 ± 305.7 Nm·s-1; p=0.025) and at PLAPRE (338.0 ± 240.9 Nm·s-1) when compared to PLA20 (231.4 ± 173.3 Nm·s-1; p=0.022). RTD0-100 was also significantly greater in CAF at PRE (555.0 ± 385.7 vs. 338.0 ± 240.9 Nm·s-1; p<0.001), POST20 (552.0 ± 356.6 vs. 231.4 ± 173.3 Nm·s-1; p=0.001), POST60 (523.9 ± 293.5 vs. 261.6 ± 244.5 Nm·s-1; p=0.002), and POST100 (400.6 ± 305.7 vs. 324.8 ± 175.4 Nm·s-1; p<0.001), when compared to PLA. There were no changes in RTD100-200. CONCLUSIONS: The primary finding of the present study was significantly greater early-phase and pRTD in CAF, when compared to PLA. Specifically, RTD0-100 significantly declined from PRE to POST20 in PLA, but not CAF. While there was a significant decrease in RTD0-100 in CAF from POST20 to POST100, RTD0-100 was significantly greater during CAF at POST20, POST60, and POST100. Thus, these data suggest that CAF resulted in a net increase in early-phase RTD when compared to PLA, despite the lack change from PRE in the CAF condition.

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