Neural Correlates to the Increase in Maximal Force after Dexamethasone Administration.

Purpose: This study investigated the effects of short-term glucocorticoid administration on voluntary activation and intracortical inhibitory and facilitatory circuits. Methods: Seventeen healthy men participated in a pseudo randomized double-blind study to receive either dexamethasone (8 mg[middle dot]d-1, n = 9 subjects) or placebo (n = 8 subjects) for 7 days. The ankle dorsiflexion torque, corresponding electromyography (EMG) of the tibialis anterior, and voluntary activation assessed by the interpolated twitch method using transcranial magnetic stimulation (TMS) were measured during a maximal voluntary contraction (MVC). Short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) were assessed at rest and during submaximal contraction (50% MVC torque) by paired-pulse TMS with the conditioning stimulus set at 0.8x of motor threshold (0.8x MT) and delivered 2 ms (SICI) and 13 ms (ICF) prior to the test stimulus (1.2x MT). Results: The MVC torque (+14%), tibialis anterior EMG (+31%) and voluntary activation (+3%) increased after glucocorticoid treatment (p

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