Effect of Red Spinach Extract Supplementation on Cycle Time Trial Performance in Recreationally Active Individuals


Exercise Science and Sport Management

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Red spinach extract (RSE) offers a rich source of dietary nitrates and evidence suggests that it may positively impact exercise performance. PURPOSE: The purpose of this investigation was to examine the effects of short-term red RSE supplementation on cycling time trial performance. METHODS: Seventeen recreationally active men (n=9, 22.2±3.8 y) and women (n=8, 22.8±3.5 y) underwent two testing sessions administered in a randomized, counterbalanced, double-blind fashion. Participants were assigned to supplement daily with 1 gram of RSE or placebo (PL) for seven days prior to each testing session. During each testing session, an additional serving was provided 1 hour prior to completing a 4-km cycling time trial test. Performance variables (time-to-completion, average power, relative power, cadence, and average speed) and subjective measures (perceived exertion and muscle fatigue) were assessed during each testing session. Heart rate, systolic blood pressure, and diastolic blood pressure (DBP) were also assessed around exercise. RESULTS: Compared to PL, RSE supplementation significantly improved (p<0.05, ηp2≥0.24) 4-km completion time (404.6 ± 24.6 vs. 410.6 ± 31.3 s), relative power (2.53 ± 0.44 vs. 2.46 ± 0.40 W.kg-1), and average speed (35.7 ± 2.2 vs. 35.3 ± 2.5 km.hr-1). Additionally, a trial × time interaction was observed for DBP (F=4.5, p=0.020, ηp2=0.22) where DBP was lower following the RSE trial compared to the PL trial (66.1 ± 6.1 vs. 70.1 ± 5.0 mmHg). No other differences were observed between trials. CONCLUSION: In conclusion, RSE supplementation significantly reduced time-to-completion and increased measures of power and speed during a 4-km cycling time trial. RSE also appeared to lower DBP following the cycling time trial, without altering participants' perceived exertion or subjective measures of muscle fatigue.

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Medicine & Science in Sports & Exercise

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