Neuromuscular electrical stimulation increases serum brain-derived neurotrophic factor in humans

Brain-derived neurotrophic factor (BDNF) plays several important roles in nervous system function including neuronal growth and plasticity. The purpose of the present study was to clarify whether neuromuscular electrical stimulation (NMES) and voluntary exercise to the same integrated force as by the NMES-induced exercise would enhance serum BDNF. Eleven healthy male subjects completed three interventions (NMES, voluntary exercise, and resting interventions) for 20 min on different days. In the NMES intervention, NMES was applied to the quadriceps femoris muscles. The stimulus intensity of NMES was progressively increased to the highest tolerated intensity during the experiment. In the voluntary exercise intervention, subjects performed an isometric knee-extension task; in this intervention, the target torque was calculated in accordance with the integrated force of knee extension obtained during the NMES intervention. In the resting intervention, subjects relaxed in a sitting posture. We measured serum BDNF, blood lactate, heart rate, oxygen uptake, respiratory ratio, and blood pressure. Serum BDNF was increased in the NMES (p = 0.003) and voluntary exercise interventions (p = 0.004) after each intervention. At the post-timepoint, serum BDNF in the NMES intervention was highest among all interventions (p = 0.038) and significantly higher than in the voluntary exercise (p = 0.036) and resting (p = 0.037) interventions. Our results showed that NMES was more effective for enhancing serum BDNF than voluntary exercise at least when employing the same method and integrated force.