Noradrenaline Reuptake Inhibition Impairs Cortical Output and Limits Endurance Time

Purpose: To assess the neural mechanisms that limit endurance time, we compared a fatiguing task performed under the influence of reboxetine (REB), a noradrenaline reuptake inhibitor, and placebo (PLA). Methods: Nine male subjects (age = 24 ± 2 yr) participated in this study. The fatiguing task involved repeated 3-s submaximal isometric contractions of the knee extensors (∼33% maximal voluntary contraction) with a 2-s rest between each contraction and performed until task failure. Before, during, and after exercise, changes in voluntary activation, corticospinal (motor-evoked potential) and spinal excitability (Hoffman reflex), and muscle contractile properties were tested using electrical and transcranial magnetic stimulations. A psychomotor vigilance task assessed reaction time before and after exercise. Results: Compared with PLA, REB reduced the endurance time by 15.6% (P = 0.04). The maximal voluntary contraction torque decreased to a similar extent at task failure in both conditions (P

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