Attenuated activation of knee extensor muscles during fast contractions in older men and women

Min Hyuk Kwon, Jonathon W. Senefeld, Sandra K. Hunter

Research output: Contribution to journalArticlepeer-review


Aim: Reduced physical function and increased risk of falls in older adults are accompanied by age-related reductions in torque development of leg muscles, although the mechanisms and potential sex differences are not understood. Purpose: To determine the mechanistic origins (neural vs. muscular) for the age-related reduction in torque development, we compared the peak rates of torque development (RTD) during electrically-evoked and fast voluntary contractions of the knee extensors between young and older men and women. Methods: Sets of single- and double-pulse electrical stimulations evoked contractions of the knee extensor muscles in 20 young (23.0 ± 0.8 years; 10 women) and 20 older adults (78.2 ± 1.5 years; 10 women), followed by voluntary isometric knee extension contractions with torque development as fast as possible that matched the torque during electrically-evoked contraction (10–40% maximal torque). Results: Peak RTD during fast-voluntary contractions was 41% less than electrically-evoked contractions (p < 0.001), but more so for older adults (44%) than young (38%, p = 0.04), with no sex differences. Peak RTD during fast-voluntary contractions was more variable between contractions for the older than young adults (77%MVC s−1 vs. 47%MVC s−1, p < 0.001). Additionally, older women exhibited greater variability than older men (81%MVC s−1 vs. 72%MVC s−1, p = 0.04) with no sex-related differences within the young adults. Conclusion: Older adults had slower and more variable RTD during voluntary contractions than young adults, particularly older women. The limited age-related differences in electrically-evoked RTD suggest the primary mechanism for the slower torque development of the knee extensor muscles in older men and women involve reduced neural activation.

Original languageEnglish (US)
Pages (from-to)2289-2299
Number of pages11
JournalEuropean Journal of Applied Physiology
Issue number10
StatePublished - Oct 1 2020


  • Aging
  • EMG
  • Neural activation
  • Rate of torque development
  • Sex differences

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)


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