Abstract

Aim. Although muscle electrical stimulation (ES) is widely used for training and rehabilitative purposes, its acute demand on cardiorespiratory system is still poorly investigated. Aims of the present study were to assess the acute cardiorespiratory adjustments to maximal ES of biceps brachii and quadriceps femoris muscles. Methods. Thirteen healthy well-trained male subjects (age 27±3 years (m±SD); weight 74±6 kg, height 178±8 cm) volunteered the study. Dominant biceps brachii and quadriceps femoris muscles were electrically stimulated up to the maximal tolerable intensity in 2 different experimental sessions. Oxygen uptake (VO2), respiratory exchange ratio, pulmonary ventilation (PV), heart rate (HR), systolic (SAP) and diastolic arterial pressures (DAP) were monitored: 1) in resting conditions (10 min before ES beginning) and 2) during ES session (last 5 min of training contraction phase). Results. All metabolic parameters increased significantly during the ES of both muscles (p< 0.001), with no differences between quadriceps and biceps stimulation. Both SAP and DAP significantly increased during quadriceps and biceps stimulation(p<0-001), and SAP increment was significantly higher during ES of the quadriceps than during biceps stimulation (p<0.005). No correlation between physiological parameters and current intensity occurred, but a positive correlation between tight muscular area and SAP increnebt was found.
Conclusion. Although ES was applied monolaterally, at maximal tolerable intensity muscular stimulation significantly activates cardiovascular and respiratory systems. Rising of arterial pressure during stimulation could depend either on the vascular section area of stimulated muscle or on a higher catecholamines release, but it seems not to be influenced by the stimulation current amplitude. Therefore, cardiovascular and pressure adjustments during ES training protocol seems to be considered, especially in subjects with borderline/high arterial pressure or at risk for cardiovascular diseases.