Abstract
Objective: Nitrate-rich (NR) supplements can enhance exercise performance by improving neuromuscular function and the aerobic cost of exercise. However, little is known about the effects of nitrate on dynamic, multijoint resistance exercise.
Methods: Fourteen resistance-trained men (age, 21.1 ± 0.9 years; height, 173.2 ± 2.9 cm: body mass, 77.6 ± 4.3 kg; squat one-repetition maximum [1RM], 127.5 ± 18.8 kg) participated in a randomized, double-blind, crossover experiment. Subjects consumed an NR or nitrate-poor (NP) supplement for 3 days, performed a bout of heavy resistance exercise, completed a washout, and then repeated the procedures with the remaining supplement. Before, during, and after exercise, individual and gross motor unit efficiency was assessed during isometric and dynamic muscle contractions. In addition, we compared physical performance, heart rate, lactate, and oxygen consumption (VO2).
Results: Nitrate-rich supplementation resulted in lower initial muscle firing rates at rest and lower mean and maximum firing rates over the course of fatiguing exercise. Nitrate-poor supplementation was accompanied by increased mean and maximum firing rates by the end of exercise and lower initial firing rates. In addition, NR supplementation resulted in higher mean peak electromyography (EMG) amplitudes. Heart rate, lactate, and physical performance did not differ by treatment, but oxygen consumption increased more frequently when the NP supplement was consumed.
Conclusion: Supplementation with an NR beetroot extract–based supplement provided neuromuscular advantages during metabolically taxing resistance exercise.
ACKNOWLEDGMENTS
We thank the research staff and participants for their contributions and dedication to this research project. We also thank the following research assistants for their help in the project: Lindsey A. Ellis, Hayley J. Root, Paul J. Secola, Christopher E. Giacchino, Lexie L. Dulkis, Alexander R. Bryce, and Kaitlin Carter.
Funding
This project was supported, in part, by a grant from AdvoCare International, Plano, Texas.
Received June 4, 2015; accepted August 6, 2015.