Increase in Maximal Cycling Power With Acute Dietary Nitrate Supplementation

Abstract

Muscle-shortening velocity and hence power have been shown to increase in the presence of nitric oxide (NO). NO availability increases after consuming nitrate (NO₃^-). Ingestion of NO₃^-rich beetroot juice (BRJ) has increased muscle power in untrained adults.

Purpose: This study determined whether NO₃^- supplementation could acutely enhance maximal power in trained athletes.

Methods: In this double-blind, crossover study, 13 trained athletes performed maximal inertial-load cycling trials (3-4 s) immediately before (PRE) and after (POST) consuming either NO₃^-rich (NO3) or NO₃^-depleted (PLA) BRJ to assess acute changes (ie, within the same day) in maximal power (P_MAX) and optimal pedaling rate (RPM_opt). Participants also performed maximal isokinetic cycling (30 s) to assess performance differences after supplementation.

Results: 2 x 2 repeated-measures ANOVA indicated a greater increase in P_MAX from PRE to POST NO3 (PRE 1160 ± 301 W to POST 1229 ± 317 W) than with PLA (PRE 1191 ± 298 W to POST 1213 ± 300 W) (P = .009; η_p² = 0.45). A paired t-test verified a greater relative change in P_MAX after NO3 (6.0% ± 2.6%) than with PLA (2.0% ± 3.8%) (P = .014; d = 1.21). RPM_opt remained unchanged from PRE (123 ± 14 rpm) to POST PLA (122 ± 14 rpm) but increased from PRE (120 ± 14 rpm) to POST NO3 (127 ± 13 rpm) (P = .043; η_p² = 0.30). There was no relative change in RPM_opt after PLA (-0.3% ± 4.1%), but there was an increase after NO3 (6.5% ± 11.4%) (P = .049; d = 0.79). No differences were observed between the 30-s isokinetic trials.

Conclusions: Acute NO₃^- supplementation can enhance maximal muscle power in trained athletes. These findings may particularly benefit power-sport athletes who perform brief explosive actions.

Keywords: beetroot juice; ergogenic aid; inertial load; muscle power; nitric oxide.