Effects of Acute Dietary Nitrate Supplementation on Selected Isokinetic Performance Variables in Physically Active...

Dietary nitrate may enhance skeletal muscle performance by increasing nitric oxide bioavailability. Although its benefits for endurance exercise are well documented, less is known about its effects on isokinetic strength and power performance. This study examined the effects of acute nitrate ingestion on isokinetic performance, neuromuscular activity, and metabolic responses in physically active men.

Thirteen physically active young men (25.0 ± 5.2 years) participated in a randomized, double-blind, placebo-controlled crossover study. During separate experimental sessions, participants consumed either nitrate-rich beetroot juice containing 800 mg of nitrate or a low-nitrate placebo. Following a 2 h absorption period, they performed isokinetic knee extension-flexion tests at angular velocities of 60°/s, 180°/s, and 240°/s. Surface electromyography was recorded from the vastus medialis oblique and vastus lateralis oblique muscles, and blood lactate concentrations were measured before and after exercise.

Nitrate supplementation significantly improved peak torque, relative peak power, and selected torque angle variables at 60°/s and 180°/s compared with placebo (p < 0.05). In contrast, no significant differences were observed during the 240°/s fatigue protocol (p > 0.05). No significant differences were observed in electromyographic parameters or post-exercise blood lactate concentration. Similarly, post-exercise blood lactate concentrations were comparable between treatments (p > 0.05).

Acute dietary nitrate supplementation may improve selected isokinetic performance variables during low- and moderate-velocity contractions, whereas no significant effects were observed during the 240°/s fatigue protocol. No changes were detected in electromyographic parameters or post-exercise blood lactate concentration. The physiological mechanisms underlying these findings remain to be established.