The impact of ammonia inhalants on neuromuscular function during fatigued isometric contractions

Abstract

Ammonia inhalants (AIs) are commonly used by athletes to increase arousal and prepare for maximal physical effort; however, evidence supporting their ergogenic effects remains insignificant and/or inconsistent, particularly when exercise is performed under fatigued conditions. The purpose of this study was to determine the effect of ammonia inhalation on neuromuscular function following fatiguing exercise. Fourteen male varsity athletes completed a randomized, counterbalanced crossover design consisting of an AI condition and a control condition separated by one week. During each visit, participants completed a baseline 30-s maximal voluntary isometric contraction (MVIC) of the elbow flexors, followed by a standardized dynamic biceps fatigue protocol and a subsequent 30-s fatigued MVIC. Force and surface electromyography (sEMG) were recorded concurrently. Maximal isometric force, rate of force development to peak force production (RTP), time to maximal force (T2M), biceps sEMG amplitude, rate of force decline (RFDDecline), and mean power frequency (MPF) were assessed. Repeated-measures statistical analyses of variance were used to evaluate differences between treatment conditions and fatigue states. Maximal isometric force significantly decreased following the fatigue protocol (p < .001), with reductions of approximately 20% in both treatment conditions. However, no significant treatment × fatigue state interactions were observed for maximal force, RTP, T2M, biceps sEMG amplitude, or RFDDecline (p > .05). MPF progressively decreased across the 30-s fatigued contraction (p < .001), consistent with the frequency shift phenomenon and the development of myoelectric fatigue; however, neither the treatment effect nor treatment × time interaction was significant (p > .05). Collectively, the results provided evidence that the experimental protocol produced measurable mechanical and myoelectric manifestations of fatigue but did not provide evidence that ammonia inhalation significantly altered the measured indices of neuromuscular function during fatigued sustained isometric contractions in male varsity athletes. These finding suggest that athletes, coaches, and sport practitioners should not rely on AIs to preserve neuromuscular performance during sustained isometric exercise with performed under fatigue. Instead, performance preparation should prioritize evidence-based strategies for managing fatigue and recovery.