AMPHETAMINES PARTIALLY UNLOCK ENDURANCE PERFORMANCE RESERVES

Swart, J., Lamberts, R. P., Lambert, M. I., St Clair-Gibson, A., Lambert, E. V., Skowno, J., & Noakes, T. D. (December 3, 2008). Exercising with reserve: Evidence that the CNS regulates prolonged exercise performance. British Journal of Sports Medicine, [http://www.ncbi.nlm.nih.gov/pubmed/19052141?dopt=Abstract]

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This study measured the effects of an amphetamine (methylphenidate) on exercise performance at a fixed rating of perceived exertion of 16. Elite cyclists (N = 8) ingested 10 mg Methylphenidate in a randomized, placebo-controlled cross-over trial.

Compared to placebo, Ss receiving methylphenidate cycled for ~ 32% longer before power output fell to 70% of the starting value. At the equivalent time at which the placebo trial terminated, methylphenidate Ss had significantly higher power outputs, oxygen consumptions, heart rates, ventilatory volumes, and blood lactate concentrations although EMG activity remained unchanged. The ingestion of a centrally-acting stimulant allowed Ss to exercise for longer at higher cardio-respiratory and metabolic stress levels indicating the presence of a muscular reserve in the natural state.

Implication. Endurance performance is not only "limited" by mechanical failure of the exercising muscles ("peripheral fatigue"). Rather performance during prolonged endurance exercise under normal conditions is highly regulated by the central nervous system to insure that whole body homeostasis is protected and an emergency reserve is always present. An athlete still retains performance potential reserves, even after total volitional fatigue. Those reserves are partially unlocked by the ingestion of amphetamines.

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