Feasibility of electrical stimulation eccentric training: A pilot study

Neuromuscular electrical stimulation training has been utilized in conjunction with voluntary actions or as the prime activation of muscles for physical training and rehabilitation. This study explores the feasibility of twelve sessions of high intensity electrical stimulation training using only unilateral eccentric contractions in the quadriceps muscle in young healthy adults. Prior to and following the intervention, participants were tested for maximal isometric and eccentric muscle strength using a dynamometer. Moreover, muscle and fat layer thickness were assessed using ultrasound. While n=11 participants were enrolled, n=4 dropped out after the familiarization sessions (i.e., before pre-test). In n=2 completers of the study, transient articular pain in the knee was experienced, leading to a short-term decrease in intensity of stimulation. The maximal electrically evoked torque increased from 48 % ± 30 [20.4 : 75.4] of MVC during the first training session to 101 % ± 17 [85.3 : 116.4] of MVC during the last training session. Following the twelve sessions isometric strength was reassessed (Pre: 278 ± 116 Nm, Post: 282 ± 116 Nm). The same for muscle thickness (Pre: 44.3mm ± 13.0, Post: 45.9 mm ± 13.5, mean change 1.6 [1;2.1] mm), and fat layer thickness (Pre: 13.4mm ± 5.56, Post: 13.2 mm ± 5.93). In conclusion, it appears that high-intensity electrical stimulation is poorly tolerated in someyoung healthy adults. Among completers of the study, the increases in electrical stimulation intensity was tolerated and high eccentric torques were possible.