Kylie Nixon, Mckenzie Parker, Megan Barnes, Lauren Boag, Camryn Cowan, Julianne Hill, Shelby Parker, Shelby Tidwell, Lenox Jones, Mary Raymond, Hope Sternenberg, Taylor Yount, Rebecca R. Rogers, Tyler D. Williams, Christopher G. Ballmann, FACSM. Samford University, Birmingham, AL.

BACKGROUND: Supramaximal exercise can induce conspicuous alterations in both physiological and psychophysiological responses to exercise, many of which may have implications for adaptive or maladaptive consequences. Yohimbine Hydrochloride (YHM) is an alpha-2-adrenergic receptor antagonist popular in many commercially available supplements which increases sympathetic stimulation. Given that supramaximal exercise already imposes considerable demands on the exerciser, ingestion of YHM may further exacerbate responses although this is currently unknown. PURPOSE: The purpose of this study was to elucidate the effects of acute YHM ingestion on heart rate (HR), rate of perceived exertion (RPE), and blood lactate [La-] during repeated supramaximal exercise. METHODS: Physically active females (18-25 years) participated in two separate repeated supramaximal sprint trials each with a different single-dose treatment: Placebo (PL; gluten free corn starch) or Yohimbine Hydrochloride (YHM; 2.5 mg). For each trial, participants consumed their respective treatment 20 minutes prior to exercise. Following a warm-up, participants completed 3 × 15 second Wingate anaerobic tests (WAnT) separated by 2 minutes of active recovery. Blood [La-] was measured pre- and post-exercise. HR and RPE were measured following each WAnT. Signs of vasovagal syncope were also documented. RESULTS: Mean HR (p= 0.187) and RPE (p= 0.454) were not significantly different between treatments. However, post-exercise [La-] (p= 0.0124) was significantly higher with PL treatment versus YHM. Reports of nausea were more frequent with YHM treatment that PL. CONCLUSIONS: Current findings suggest that YHM does not alter HR or RPE during supramaximal exercise. However, [La-] was significantly lower with YHM than PL indicating possible increases in [La-] clearance. Feelings of nausea were more frequent with YHM which suggests that despite possible benefits of [La-] clearance, unwanted side effects may limit practical application of usage.

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