The Effect of Beetroot Juice Supplementation Dose on Neuromuscular Performance During Resistance Exercise

High Nitrate Dose, Low Nitrate Dose, Moderate Nitrate Dose, Nitrate-depleted Dose

Dietary nitrate supplementation, administered in the form of nitrate-rich beetroot juice, has been shown to improve exercise performance and may have more pronounced effects on exercise that requires high-power and high-velocity muscle contraction such as weightlifting and body-mass resisted exercise (i.e, resistance exercise). However, limited data are available that have examined the potential performance enhancing effect of beetroot juice in resistance exercise. Moreover, there is no information on the dose of nitrate required for performance enhancing effects during resistance exercise which limits its widespread use to enhance performance. Therefore, the investigators will assess if supplementing the diet with nitrate-rich beetroot juice impacts resistance exercise performance (e.g., power, velocity), when compared to supplementing the diet with nitrate-depleted beetroot juice (i.e. placebo). The investigators will also investigate the dose-response effect of beetroot juice on resistance exercise performance by providing a low, moderate, and high nitrate dose of concentrated beetroot juice. The results of this study will improve understanding of whether beetroot juice influences resistance exercise performance and will provide insight on whether different doses of beetroot juice influence the efficacy of nitrate supplementation on resistance exercise performance. Together, these data will guide supplementation strategies for enhancing resistance exercise performance.

Supplementation with inorganic nitrate, which is most commonly administered in the form of concentrated nitrate-rich beetroot juice shots, has emerged as an ergogenic nutritional strategy. Beetroot juice ingestion has been reported to enhance endurance and high-intensity intermittent exercise performance in running and cycling. These improvements are attributed to augmented muscle contractility, force production and blood flow distribution, specifically in muscle groups comprised predominantly of type II muscle fibers. Together, such changes provide a strong physiological rationale supporting the potential for dietary nitrate to enhance high-power and high-velocity muscle contractions since type II muscle fibers are heavily activated during these tasks. However, the influence of dietary nitrate on resistance exercise performance is substantially underdeveloped with most previous studies having assessed the effect of nitrate supplementation on running and cycling endurance and high-intensity intermittent exercise. Moreover, there is no information on the dose of nitrate required to evoke ergogenic effects during resistance exercise, which greatly hinders the potential implementation of beetroot juice as a research-informed performance enhancing supplement for resistance exercise. Thus, the proposed project will investigate if acute dietary nitrate ingestion, provided as nitrate-rich beetroot juice, elicits improvements in various neuromuscular performance parameters (e.g., power, velocity) during resistance exercise performance when compared to supplementing the diet with a nitrate-depleted beetroot juice placebo. The investigators will also investigate the dose-response effect of beetroot juice on resistance exercise performance by providing low (70 ml i.e., \ 6.5 mmol or \ 400 mg of nitrate), moderate (140 ml i.e., \ 13 mmol or \ 800 mg of nitrate) and a high nitrate dose (280 ml i.e., \ 26 mmol or \ 1600 mg of nitrate) of concentrated beetroot juice. This project will provide insight to practitioners (coaches/athletes) aiming to enhance performance in settings where muscular power and speed are key determinants for success, as well as to scientists exploring the efficacy of beetroot juice as a form of dietary nitrate supplementation to improve muscle contractile function.

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