Effect of Resistance Training and Fish Protein Intake on Motor Unit Firing Pattern and Motor Function of Elderly

• Published in: Frontiers in physiology Vol. 9; p. 1733
• Main Authors: Watanabe, Kohei, Holobar, Aleš, Mita, Yukiko, Kouzaki, Motoki, Ogawa, Madoka, Akima, Hiroshi, Moritani, Toshio
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 04.12.2018
• Subjects: aging; countermeasures to aging; motor unit decomposition; multichannel surface electromyography; nutritional supplementation; Physiology; countermeasures to aging; motor unit decomposition; nutritional supplementation; aging; multichannel surface electromyography
• ISSN: 1664-042X; 1664-042X
• DOI: 10.3389/fphys.2018.01733

We investigated the effect of resistance training and fish protein intake on the motor unit firing pattern and motor function in elderly. Fifty healthy elderly males and females (69.2 ± 4.7 years) underwent 6 weeks of intervention. We applied the leg-press exercise as resistance training and fish protein including Alaska pollack protein (APP) as nutritional supplementation. Subjects were divided into four groups: fish protein intake without resistance training (APP-CN, = 13), placebo intake without resistance training (PLA-CN, = 12), fish protein intake with resistance training (APP-RT, = 12), and placebo intake with resistance training (PLA-RT, = 13). Motor unit firing rates were calculated from multi-channel surface electromyography by the Convolution Kernel. For the chair-stand test, while significant increases were observed at 6 weeks compared with 0 week in all groups ( < 0.05), significant increases from 0 to 3 weeks and 6 weeks were observed in APP-RT (18.2 ± 1.9 at 0 week to 19.8 ± 2.2 at 3 weeks and 21.2 ± 1.9 at 6 weeks) ( < 0.05). Increase and/or decrease in the motor unit firing rate were mainly noted within motor units with a low-recruitment threshold in APP-RT and PLA-RT at 3 and 6 weeks (12.3 pps at 0 week to 13.6 pps at 3 weeks and 12.1 pps at 6 weeks for APP-RT and 12.9 pps at 0 week to 13.9 pps at 3 weeks and 14.1 pps at 6 weeks for PLA-RT at 50% of MVC) ( < 0.05), but not in APP-CN or PLA-CN ( > 0.05). Time courses of changes in the results of the chair-stand test and motor unit firing rate were different between APP-RT and PLA-RT. These findings suggest that, in the elderly, the effect of resistance training on the motor unit firing rate is observed in motor units with a low-recruitment threshold, and additional fish protein intake modifies these adaptations in motor unit firing patterns and the motor function following resistance training.