Training effects on central and peripheral components of force, in old healthy subjects: the role of central command.

Abstract

AimThe aim of this study, was to investigate the role of central command (CC), during resistance training in old healthy men. For this purpose, maximal voluntary contraction (MVC), percentage of neuromuscular activation (%VMA) and rest twitch (RT) were determined before and after 4 weeks of quadriceps electro‐stimulation (ES), or voluntary isometric training (VT).Methods12 old (65–70 years) and 12 young male subjects (20–25 years) were recruited for this study. ES was performed by a commercially available electrical stimulator. ES included 15 minutes of isometric‐evoked contractions (6 s contraction/ 11 s of recovery) in the quadriceps, 3 times a week for a total of 12 training sessions. VT was performed after a washout period of 8 weeks, matching the force‐output recorded during the ES.ResultsMVC was minimally increased (+4%) after ES in old subjects, while young subjects showed a larger amelioration (+28%). After ES, %VMA was not changed (+3%) but RT was increased (+16%) in old individuals, while in the young subjects the changes were greater, +17% and +78%, respectively. Both, young and old subjects exhibited after VT significant increases in MVC +16% and +42% respectively. %VMA and RT in old subjects were increased by +8 and +26%, respectively. Similarly, %VMA and RT were increased in young individuals (+9% and +38%).ConclusionsThe results of the current study, suggest that the CC has a primary role to determine improvement of MVC, especially in old subjects. In fact, after the training period, the greater force ameliorations were retrieved in the consequences of VT. These changes were coupled with increases in central (%MVC) and peripheral (RT) components of force. While, the lack of improvements in %VMA after ES in old subjects suggest that the force amelioration was primarily due to peripheral factors.Support or Funding InformationThis project was supported by the Department of Excellence Grant ‐ Molecular and functional basis of successful aging and frailty SAFe (Successful Aging Frailty) ‐