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Exercising with reserve: Evidence that the CNS regulates prolonged exercise performance.
  1. Jeroen Swart (jeroen.swart{at}uct.ac.za)
  1. UCT/MRC Research Unit for Exercise Science and Sports Medicine, South Africa
    1. Robert Patrick Lamberts (robert.lamberts{at}uct.ac.za)
    1. UCT/MRC Research Unit for Exercise Science and Sports Medicine, South Africa
      1. Michael Ian Lambert (mike.lambert{at}uct.ac.za)
      1. UCT/MRC Research Unit for Exercise Science and Sports Medicine, South Africa
        1. Alan St Clair Gibson (a.stclairgibson{at}unn.ac.uk)
        1. School of Psychology and Sports Sciences, Sports Sciences, United Kingdom
          1. Estelle Vicki Lambert (vicki.lambert{at}uct.ac.za)
          1. School of Psychology and Sports Sciences, Sports Sciences, United Kingdom
            1. Justin Skowno (jskowno{at}worldonline.co.za)
            1. Department of Anaesthesia, University of Cape Town, South Africa
              1. Timothy David Noakes (timothy.noakes{at}uct.ac.za)
              1. Department of Anaesthesia, University of Cape Town, South Africa

                Abstract

                Objective: The purpose of this study was to measure the effects of an amphetamine (methylphenidate) on exercise performance at a fixed rating of perceived exertion of 16.

                Methods: Eight elite cyclists ingested 10mg Methylphenidate in a randomized, placebo-controlled cross-over trial.

                Results: Compared to placebo, subjects 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, subjects receiving methylphenidate had significantly higher power outputs, oxygen consumptions, heart rates, ventilatory volumes and blood lactate concentrations although EMG activity remained unchanged. Thus the ingestion of a centrally-acting stimulant allowed subjects to exercise for longer at higher cardio-respiratory and metabolic stress indicating the presence of a muscular reserve in the natural state.

                Conclusions: This suggests that 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 CNS to insure that whole body homeostasis is protected and an emergency reserve is always present.

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