Effects of low intensity electrical stimulation on quadriceps muscle voluntary maximal strength

Background. Evaluate the effect of low intensity electrical stimulation (ES) training on strength. We purposefully used a low ES stimulation intensity to have it well accepted by middle aged and low performing people. Relate strength to metabolic parameters. Methods. Experimental design. Protocol 1: effects of 11 day low intensity ES training on quadriceps muscle maximal voluntary contraction (MVC). Protocol 2: effects of 3 day training at low intensity ES voluntary contraction at 60% of MVC (co-contraction). Variables measured: maximal voluntary strength (F-MAX), strength during ES (F-ES), strength developed during co-contraction (FES-C) oxygen consumption, heart rate. Experimental design included a basal session, a training program and controls of measured variables during and at the end of the training program. Participants: protocol 1: experiments were done on 13 healthy and sedentary subjects (6 males and 7 women, mean age 50.6 years). Protocol 2: experiments done on 6 healthy sedentary men (mean age 31.5 years). Results. Protocol 1: F-MAX increased significantly (p<0.05) to 14 and 19% at day 6 and 11, respectively. During ES, oxygen consumption increased by 20%, but no change in heart rate was observed. Protocol 2: F-MAX significantly increased (about 5%) in subjects who trained with co-contraction; conversely, F-MAX did not significantly increase in a control group matched for age who trained only with voluntary contractions. Conclusions. Low intensity ES in sedentary and poorly performing people increases significantly F-MAX during MVC possibly via facilitatory neurogenic mechanism