• The Role of Dopamine on Central Neuromuscular Activation during Passive Hyperthermia

      Scholey, Aiden; Applied Health Sciences Program
      Acute methylphenidate (MPH) (dopamine reuptake inhibitor) ingestion improves cycling time trial performance and power output in hot conditions (30 C), while also allowing for tolerance of higher core temperatures. However, the mechanisms for why this occurs have not been isolated. One potential explanation for this ergogenic benefit is that MPH intake was enhancing neuromuscular activation. Thus, this research project examined the influence of MPH on neuromuscular activation during hyperthermia. Participants ingested either placebo (PLA; 20mg) or MPH (Ritalin; 20mg) 1 hour prior to a passive heating protocol. 6 participants were passively heated until volitional cessation, or after 3 hours of heating had passed. Neuromuscular responses, as indicated by maximal voluntary contraction (MVC) force, and voluntary activation (VA) percentage were assessed prior to drug ingestion, 1 hour after MPH wash-in, throughout the heating protocol and at cessation of heating. A primary non-significant finding of this research project was that participants reached higher rectal temperatures (Tre) by ~0.3 C in trials where they ingested MPH (p = 0.065). This effect occurred in absence of any differences in thermal comfort or sensation ratings or heating durations. However, while MPH improves thermal tolerance, it was not able to attenuate the decreases in MVC force and VA that occurred during passive heating. Therefore, the aforementioned ergogenic benefits that MPH has in hot conditions are not occurring as a result of enhanced neuromuscular activation.