Effects of peripheral and cerebral electrical stimulation on maximal isometric strength of knee extensors: a randomized clinical trial

Abstract

INTRODUCTION: Recent evidence has shown very promising results for the use of noninvasive neuromodulation strategies in improving physical or sports skills. Peripheral electrical stimulation (PES) and transcranial direct current stimulation (tDCS) are non-invasive and non-pharmacological techniques widely used to modulate neuronal excitability of corticomotor areas and to stimulate functional. However, few studies have investigated the effect of these techniques on improving muscle performance. OBJECTIVE: To investigate the effect of sensory peripheral electrical stimulation (PESs) followed by motor peripheral electrical stimulation (PESm) or transcranial direct current stimulation (tDCS) in the maximal isometric force of knee extensors in healthy individuals. METHODS: Twenty healthy university students were randomly assigned to two distinct blocks with 10 participants in each block: Block n°1 real PESs + real PESm or sham PESs + real PESm and block n°2 real PESs + real tDCS or sham PESs + real tDCS in a single session. The maximum voluntary isometric contraction (MVIC) of the knee extensors was evaluated by manual dynamometry before, during and 10 min post-stimulation. RESULTS: MVIC of the knee extensors was significantly increased 10 minutes post-tDCS alone (mean difference = 0.23 N/kg, 95% CI = 0.01 to 0.44 N/kg, p = 0.04). Isolated tDCS also had a higher cumulative proportion of responders followed by PESs + tDCS. CONCLUSIONS: Transcranial direct current stimulation induces a significant increase in MVIC in healthy subjects. However, prior application of peripheral electrical stimulation does not boost the effects of peripheral electrical motor or cerebral stimulation.