Effects of Self-selected Maiximal Intensity of Neuromuscular Electrical Stimulation (NMES) on Energy Expenditure, Glycaemia and Hormonal Responses on Healthy Individuals

Participants were asked to perform 3 trials [sitting (SIT), standing (STAND) and sitting with neuromuscular electrical stimulation (NMES) to the lower limbs in randomised counter-balanced study design. Trials were separated by at least 48 h and were completed within 14 days. In all trials, participants were required to remain relaxed and motionless. SIT: participants sat in a chair with back, arms and legs supported. STAND: participants were asked to stand with arms supported and feet spaced approximately 15 cm apart. If needed, adjustment of standing posture was allowed during the standing trial to prevent orthostatic hypotension. NMES: prior to the NMES trial, participants underwent preliminary testing to ensure that stimulation was comfortable. Before the NMES, a small area of the body hair was shaved and skin was cleaned with an alcohol wipe and electrodes were stuck to the surface of the skin. Small electrodes placed (5*5 cm) on the lower limb of both legs (gastrocnemius, rectus femoris, vastus medialis). The two devices (EM 80, Beurer UK Ltd, Golborne, UK) were set up with the frequency of 20 Hz along with stimulation period of 1 second on and 1 second off throughout a 2 h oral glucose tolerance test (OGTT). The instruction for NMES intensity was that the maximal intensity participants were be able to withstand for 2 hours whilst imagining sitting at home watching TV without feeling discomfort. Prior to the OGTT, 5 min was given to identify the suitable intensity of stimulation and within the first 10 min of the OGTT participants were allowed to adjust the intensity once, after which, the intensity remained the same for the rest of OGTT. Participants were asked to sit in a chair with back, arms and legs supported during the stimulation. During trials, participants could watch TV, or read, but typing on a laptop or computer were avoided.