Transcutaneous neuromuscular electrical stimulation: influence of electrode positioning and stimulus amplitude settings on muscle response.

Gobbo, M.; Gaffurini, P.; Bissolotti, L.; Esposito, F.; Orizio, C.

The aim of the study was to investigate the influence of two different transcutaneous neuromuscular electrical stimulation procedures on evoked muscle torque and local tissue oxygenation. In the first one (MP mode), the cathode was facing the muscle main motor point and stimulus amplitude was set to the level eliciting the maximal myoelectrical activation according to the amplitude of the evoked electromyogram (EMG); in the second one (RC mode), the electrodes were positioned following common reference charts for electrode placement while stimulus amplitude was set according to subject tolerance. Tibialis Anterior (TA) and Vastus Lateralis (VL) muscles of 10 subjects (28.4 ± 8.2 years) were tested in specific dynamometers to measure the evoked isometric torque. The EMG and near-infrared spectroscopy probes were placed on muscle belly to detect the electrical activity and local metabolic modifications of the stimulated muscle, respectively. The stimulation protocol consisted of a gradually increasing frequency ramp from 2 to 50 Hz in 7.5 s. Compared to RC mode, in MP mode the contractile parameters (peak twitch, tetanic torque, area under the torque build-up) and the metabolic solicitation (oxygen consumption and hyperemia due to metabolites accumulation) resulted significantly higher for both TA and VL muscles. MP mode resulted also to be more comfortable for the subjects. Based on the assumption that proper mechanical and metabolic stimuli are necessary to induce muscle strengthening, our results witness the importance of an optimized, i.e., comfortable and effective, stimulation to promote the aforementioned muscle adaptive modifications.

TRANSCUTANEOUS electrical nerve stimulation; HYPERBARIC oxygenation; VASTUS lateralis; NEAR infrared spectroscopy; MUSCLE strength; SKELETAL muscle physiology; PHYSIOLOGICAL adaptation; CLINICAL trials; COMPARATIVE studies; ELECTRIC stimulation; ELECTRODES; ELECTROMYOGRAPHY; RESEARCH methodology; MEDICAL cooperation; MUSCLE contraction; PATIENT positioning; RESEARCH; TORQUE; EVALUATION research; SKELETAL muscle; INNERVATION; EQUIPMENT & supplies

European Journal of Applied Physiology, 2011, Vol 111, Issue 10, p2451

1439-6319

Academic Journal

10.1007/s00421-011-2047-4