Yohimbine Ingestion As A Potential Confounder To Exercise Intensity Monitoring: Possible Considerations For Safety And Usage

BACKGROUND: Yohimbine (YHM) is a sympathomimetic stimulant from the bark of the Yohimbe tree native to Africa. Our lab has shown that YHM ingestion improves exercise performance through increased heart rate (HR), skeletal muscle blood flow, and enhanced circulation of epinephrine/norepinephrine. Independent of performance, physiological changes induced by YHM may alter responses to exercise and result in unanticipated effects. However, all studies to date have reported exclusively on performance metrics leaving possible safety and intensity monitoring considerations unclear. PURPOSE: The purpose of this study was to report possible adverse effects from acute YHM supplementation and highlight the potential impact on exercise intensity monitoring and testing. METHODS: A combination of published secondary data and unpublished primary from sprint and endurance exercise studies investigating performance enhancing effects of YHM were used. From secondary data, the percentage of participants averaging vigorous intensity HR (≥75% HRmax) and RPE (≥7 out of 10) were derived and compared between PL and YHM treatments. From primary data, self-reported feelings of being lightheaded, nauseous, and lactate levels (mmol/L) were compared. Percentages were compared between treatments using a McNemar Test (χ2) while all other data were analyzed using a paired samples t-test. RESULTS: More participants averaged vigorous intensity HR levels with YHM for sprint (PL = 70%; YHM = 100%; p = 0.009) and endurance (PL = 68%; YHM = 100%; p = 0.015) exercise. Average vigorous intensity RPE levels for sprint (PL = 45%; YHM = 55%; p = 0.109) and endurance (PL = 44% vs YHM = 56% p = 0.074) exercise were unaltered by treatment. Post-exercise blood lactate levels were significantly lower with YHM compared to PL (p = 0.010). Post-exercise feelings of nausea and light headedness were more frequent with YHM ingestion versus PL (p < 0.05). CONCLUSION: Data from our lab has indicated that acute YHM ingestion provides ergogenic benefit. However, current analysis suggests that YHM differentially alters metrics of exercise intensity and induces potential unwanted side-effects post-exercise which could confound athlete and intensity monitoring during exercise.