Effects of auto-selected intensity in neuromuscular electrical stimulation and resistance training on muscle responses and functional capacity of elderly people

Aim: Resistance training (RT) and neuromuscular electrical stimulation (NMES) are often used to combat sarcopenia and functional decline in elderly people. However, intensity is a barrier to adherence and regularity in training programs for this population. This study aimed to evaluate and compare the effects of RT and NMES, performed at autoselected intensity, on adaptive responses of the neuromuscular system and functional capacity in healthy elderly people. Methods: After health screening, the total sample (n = 18) was randomized into three groups: control group CO (age = 71.7 (1.9) yrs.; n = 6), NMES group (age = 68.8 (5.3) yrs.; n = 6) or RT group (age = 72.3 (6.1) yrs.; n = 6).The training groups performed a tenweek training period, while the CO group were advised to maintain their habitual lifestyle. Auto-selected load was determined as training intensity: The RT group used the maximal load to perform a range of 8–12 repetitions; the NMSE group trained at the pain threshold. Biopsies in the quadriceps muscles, strength and functional capacity were performed at the pre and post-training moments. Dependent variables included: (MVIC), predicted (1-RM), concentric isokinetic peak power and concentric power resistance of the quadriceps muscles and handgrip test to evaluate strength responses; the Five Times Sit-to-Stand test and the Timed Up and Go test performances, to evaluate the functional capacity; single fibre characteristics and satellite cell responses were used to evaluate muscle fibre responses. Results:RT positively affected 1-RM and MVIC performances. Both training protocols positively affected handgrip and functional capacity test performances. The CO group did not demonstrate improvements in strength performance, but did demonstrate decrements in functional capacity tests. Molecular and cellular responses did not present alterations after the training period. Conclusions: This study revealed that both RT and NMES protocols, using auto-selected loads, are valid strategies for promoting significant improvements in functional capacity in elderly people, even with modest improvements in strength capacity and an absence of alterations in myofibre responses.