Discrete physiological effects of beetroot juice and potassium nitrate supplementation following 4-wk sprint interval training

Abstract

The physiological and exercise performance adaptations to sprint interval training (SIT) may be modified by dietary nitrate (NO3) supplementation. However, it is possible that different types of NO3 supplementation evoke divergent physiological and performance adaptations to SIT. The purpose of this study was to compare the effects of 4-wk SIT with and without concurrent dietary NO3 supplementation administered as either NO3-rich beetroot juice (BR) or potassium NO3 (KNO3). Thirty recreationally active subjects completed a battery of exercise tests before and after a 4-wk intervention in which they were allocated to one of three groups: 1) SIT undertaken without dietary NO3 supplementation (SIT); 2) SIT accompanied by concurrent BR supplementation (SIT BR); or 3) SIT accompanied by concurrent KNO3 supplementation (SIT KNO3). During severe-intensity exercise, V O2peak and time to task failure were improved to a greater extent with SIT +BR than SIT and SIT KNO3 (P 0.05). There was also a greater reduction in the accumulation of muscle lactate at 3 min of severe-intensity exercise in SIT BR compared with SIT KNO3 (P <0.05). Plasma NO2 concentration fell to a greater extent during severe-intensity exercise in SIT BR compared with SIT and SIT KNO3 (P <0.05). There were no differences between groups in the reduction in the muscle phosphocreatine recovery time constant from pre- to postintervention (P <0.05). These findings indicate that 4-wk SIT with concurrent BR supplementation results in greater exercise capacity adaptations compared with SIT alone and SIT with concurrent KNO3 supplementation. This may be the result of greater NO-mediated signaling in SIT +BR compared with SIT+ KNO3. NEW & NOTEWORTHY We compared the influence of different forms of dietary nitrate supplementation on the physiological and performance adaptations to sprint interval training (SIT). Compared with SIT alone, supplementation with nitrate-rich beetroot juice, but not potassium NO3, enhanced some physiological adaptations to training.