Motor unit firing variability and synchronization during short-term light-load training in older adults

2009 ◽  
Vol 197 (4) ◽  
pp. 337-345 ◽  
Author(s):  
L. Griffin ◽  
P. E. Painter ◽  
A. Wadhwa ◽  
W. W. Spirduso
Keyword(s):  
Older Adults ◽  
Motor Unit ◽  
Short Term ◽  
Light Load ◽  
Motor Unit Firing

Motor unit firing rates during constant isometric contraction: establishing and comparing an age-related pattern among muscles

2021 ◽  
Author(s):  
Eric A. Kirk ◽  
Anita D. Christie ◽  
Christopher A. Knight ◽  
Charles L. Rice
Keyword(s):  
Older Adults ◽  
Motor Unit ◽  
Isometric Contraction ◽  
Voluntary Contraction ◽  
Age Related ◽  
Motor Unit Firing ◽  
Euclidean Distances ◽  
Intramuscular Electromyography ◽  
Related Pattern ◽  
Variance Explained

Motor unit (MU) firing rate (FR) frequency is lower in aged adults, compared with young, at relative voluntary contraction intensities. However, from a variety of independent studies of disparate muscles, the age-related degree of difference in FR among muscles is unclear. Using a standardized statistical approach with data derived from primary studies, we quantified differences in FRs across several muscles between younger and older adults. The dataset included 12 different muscles in young (18-35) and older adults (62-93 years) from 18 published and one unpublished study. Experiments recorded single MU activity from intramuscular electromyography during constant isometric contraction at different (step-like) voluntary intensities. For each muscle, FR ranges and FR variance explained by voluntary contraction intensity were determined using bootstrapping. Dissimilarity of FR variance among muscles was calculated by Euclidean distances. There were 3-fold differences in the absolute frequency of FR ranges across muscles in the young (soleus 8-16 and superior trapezius 20-49 Hz), but in the old, FR ranges were more similar and lower for 9 out of 12 muscles. In contrast, the explained FR variance from voluntary contraction intensity in the older group had 1.6-fold greater dissimilarity among muscles than the young (p < 0.001), with FR variance differences being muscle dependent. Therefore, differences between muscle FR ranges were not explained by how FRs scale to changes in voluntary contraction intensity within each muscle. Instead, FRs were muscle dependent but were more dissimilar among muscles in the older group in their responsiveness to voluntary contraction intensity.

Unusual motor unit firing behavior in older adults

1989 ◽  
Vol 482 (1) ◽  
pp. 136-140 ◽  
Author(s):  
Gary Kamen ◽  
Carlo J. De Luca
Keyword(s):  
Older Adults ◽  
Motor Unit ◽  
Firing Behavior ◽  
Motor Unit Firing

scholarly journals EFFECTS OF SHORT-TERM STRENGTH TRAINING ON MOTOR UNIT FIRING RATE IN OLDER MEN AND WOMEN

1998 ◽  
Vol 30 (Supplement) ◽  
pp. 194
Author(s):  
B. L. Tracy ◽  
R. A. Conwit ◽  
M. McHugh ◽  
E. J. Metter ◽  
B. F. Hurley
Keyword(s):  
Strength Training ◽  
Firing Rate ◽  
Motor Unit ◽  
Older Men ◽  
Term Strength ◽  
Short Term ◽  
Men And Women ◽  
Motor Unit Firing ◽  
Short Term Strength ◽  
Older Men And Women

scholarly journals Fish Protein Ingestion Induces Neural, but Not Muscular Adaptations, Following Resistance Training in Young Adults

2021 ◽  
Vol 8 ◽  
Author(s):  
Kohei Watanabe ◽  
Aleš Holobar ◽  
Kenji Uchida ◽  
Yukiko Mita
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Resistance Training ◽  
Motor Unit ◽  
Muscle Mass ◽  
Knee Extension ◽  
Fish Protein ◽  
Motor Unit Firing ◽  
Isometric Knee Extension ◽  
Protein Ingestion

Purpose: Nutritional supplementation in conjunction with exercise is of interest for the prevention or improvement of declines in motor performances in older adults. An understanding of the effects on both young and older adults contributes to its effective application. We investigated the effect of fish protein ingestion with resistance training on neural and muscular adaptations in young adults using interventions and assessments that have already been tested in older adults.Methods: Eighteen young adults underwent 8 weeks of isometric knee extension training. During the intervention, nine participants ingested 5 g of fish protein (n = 9, Alaska pollack protein, APP), and the other nine participants ingested casein as a control (n = 9, CAS) in addition to daily meals. Before, during, and after the intervention, the isometric knee extension force, lower extremity muscle mass, and motor unit firing pattern of knee extensor muscles were measured.Results: Maximum voluntary contraction (MVC) was significantly increased in both APP and CAS groups from 0 weeks to 4, 6, and 8 weeks of intervention (p &lt; 0.001), but there were no significant differences between the groups (p = 0.546–0.931). Muscle mass was not significantly changed during the intervention in either group (p = 0.250–0.698). Significant changes in motor unit firing rates (p = 0.02 and 0.029 for motor units recruited at 20–40% of MVC and at 40–60%) were observed following the intervention in the APP but not CAS (p = 0.120–0.751) group.Conclusions: These results suggest that dietary fish protein ingestion changes motor unit adaptations following resistance training in young adults.

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