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The influence of age on isometric endurance and fatigue is muscle dependent: a study of shoulder abduction and torso extension.

Authors
Yassierli-Y; Nussbaum-MA; Iridiastadi-H; Wojcik-LA
Source
Ergonomics 2007 Jan; 50(1):26-45
NIOSHTIC No.
20031889
Abstract
The present study examined differences in isometric muscle capacity between older (55-65 years) and younger (18 - 25 years) individuals. A total of 24 younger and 24 older participants (gender balanced within each group) performed sustained shoulder abductions and torso extensions to exhaustion at 30%, 50% and 70% of individual maximal voluntary contraction (MVC). Along with endurance time, manifestations of localized fatigue were determined based on changes in surface electromyographic signals obtained from the shoulder (middle deltoid) and the torso (multifidus and longissimus thoracis) muscles. Strength recovery was monitored using post-fatigue MVCs over a 15-min period. Compared to the younger group, older individuals exhibited lower muscular strength, longer endurance time and slower development of local fatigue. Age effects on fatigue were typically moderated by effort level, while effects of gender appeared to be marginal. Non-linear relationships between target joint torque and endurance time were observed, with effects of age differing between shoulder abduction and torso extension. Overall, the effects of age on endurance and fatigue were more substantial and more consistent for the shoulder muscle than for the torso muscles and were likely related to differences in muscle fibre type composition. For strength recovery rates, no significant age or gender effects were found in either experiment. In summary, this study suggests that differences in isometric work capacity do exist between older and younger individuals, but that this effect is influenced by effort level and the muscle tested.
Keywords
Statistical-analysis; Ergonomics; Physical-stress; Physical-exercise; Musculoskeletal-system; Muscles; Muscle-stress; Muscle-tension; Muscular-disorders; Humans; Analytical-processes; Age-factors
CODEN
ERGOAX
Publication Date
20070115
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2007
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-004089
Issue of Publication
1
ISSN
0014-0139
Source Name
Ergonomics
State
VA; WA
Performing Organization
Virginia Polytechnic Institute and State University
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