Development of the Protocol to Deliver Graded Stimulation Intensity on Lower Limbs Using Belt-shaped Electrode Skeletal Muscle Stimulation

OBJECTIVES: Current advancements in neuromuscular electrical stimulation (NMES) include belt-shaped electrode skeletal muscle electrical stimulation (B-SES), which was developed to induce whole leg muscle contraction in a single session. Delivering the optimal amount of stimulation is critical in NMES; therefore, we set out to establish a method to determine the B-SES stimulation intensity needed to induce muscle contraction sufficient for clinical purposes. METHODS: We used the Auto Tens Pro system (Homer Ion Laboratory), which is a B-SES device. Stimulation at 20 Hz was delivered for 5 s, followed by 2 s rest. Twenty-four patients who were hospitalized for musculoskeletal diseases were enrolled at two hospitals. Patients were randomly assigned to one of three groups of subjectively graded stimulation intensities: moderate, strong, or very strong. To achieve each target intensity, we developed a structured verbal instruction protocol that aimed to help therapists deliver the target level of stimulation. As a physiological assessment of muscle contraction, serum lactate levels were measured before and after a single 20-min B-SES session. RESULTS: The electric current intensity required to achieve a target subjective muscle contraction gradually increase according to the subjective contraction level. The increase in serum lactate level was significantly larger in the very strong group than in the moderate group. CONCLUSIONS: B-SES stimulators have the potential to induce efficient muscle strengthening in patients with musculoskeletal diseases. The structured verbal protocol developed here could help therapists achieve the appropriate stimulation intensity for each patient.