Effect of Beetroot Juice Supplementation on Conduit Artery and Microvascular Hemodynamics During Small Muscle Mass Handgrip Exercise

Abstract

Beetroot juice (BR) supplementation has been shown to have positive ergogenic effects on blood flow (Q) as well as mitochondrial and muscle efficiency during large muscle mass aerobic exercise in animals and man.PurposeTo determine if the previously demonstrated effects of BR translate to small muscle mass exercise.MethodsSubjects completed constant power two‐handed handgrip tests at 40% peak power for 10 min under both BR and placebo (PLA) conditions. Mean arterial pressure (MAP) was measured using an automated cuff, Q was measured in the brachial artery via Doppler ultrasound, and muscle oxygenation characteristics were measured in the flexor digitorum superficialis (FDS) using near infrared spectroscopy.ResultsBR decreased resting MAP (76.3 ± 3.4 vs 84.1 ± 5.7 mmHg, p=0.014) but did not significantly lower exercising values. There were no significant differences in Q or vascular conductance between conditions. There were no significant differences between FDS deoxy‐[Hb+Mb] at rest or during the first minute of exercise, but after an initial overshoot PLA deoxy‐[Hb+Mb] decreased to a lower steady‐state value, while BR remained significantly elevated (49.3 ± 0.96 vs 43.8 ± 0.31 μM, p<0.013) until min 8. BR deoxy‐[Hb+Mb] decreased to values similar to PLA for min 8 through 10. FDS total‐[Hb+Mb] was not significantly different at rest or during exercise.ConclusionThese preliminary findings suggest that BR may have no effect on Q during moderate intensity small muscle mass exercise. Contrary to contemporary findings in large muscle mass exercise, BR may lead to an increased deoxy‐[Hb+Mb] in small muscle mass exercise.