Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia

Nathaniel D.M. Jenkins; Terry J. Housh; Ty B. Palmer; Kristen C. Cochrane; Haley C. Bergstrom; Glen O. Johnson; Richard J. Schmidt; Joel T. Cramer

doi:10.1002/mus.24505

Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia

Nathaniel D.M. Jenkins, Terry J. Housh, Ty B. Palmer, Kristen C. Cochrane, Haley C. Bergstrom, Glen O. Johnson, Richard J. Schmidt, Joel T. Cramer

Nutrition & Health Sciences

Research output: Contribution to journal › Article › peer-review

21 Scopus citations

Abstract

Introduction: We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s^-1 in younger versus older men. Methods: Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Results: Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s^-1 were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Conclusions: Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.

Original language	English (US)
Pages (from-to)	120-130
Number of pages	11
Journal	Muscle and Nerve
Volume	52
Issue number	1
DOIs	https://doi.org/10.1002/mus.24505
State	Published - Jul 1 2015

Keywords

EMG
Normalization
Power-velocity
Reliability
Sarcopenia
Torque-velocity

ASJC Scopus subject areas

Physiology
Clinical Neurology
Cellular and Molecular Neuroscience
Physiology (medical)

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title = "Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia",

abstract = "Introduction: We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s-1 in younger versus older men. Methods: Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Results: Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s-1 were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Conclusions: Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.",

keywords = "EMG, Normalization, Power-velocity, Reliability, Sarcopenia, Torque-velocity",

author = "Jenkins, {Nathaniel D.M.} and Housh, {Terry J.} and Palmer, {Ty B.} and Cochrane, {Kristen C.} and Bergstrom, {Haley C.} and Johnson, {Glen O.} and Schmidt, {Richard J.} and Cramer, {Joel T.}",

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year = "2015",

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doi = "10.1002/mus.24505",

language = "English (US)",

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T1 - Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia

AU - Jenkins, Nathaniel D.M.

AU - Housh, Terry J.

AU - Palmer, Ty B.

AU - Cochrane, Kristen C.

AU - Bergstrom, Haley C.

AU - Johnson, Glen O.

AU - Schmidt, Richard J.

AU - Cramer, Joel T.

PY - 2015/7/1

Y1 - 2015/7/1

N2 - Introduction: We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s-1 in younger versus older men. Methods: Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Results: Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s-1 were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Conclusions: Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.

AB - Introduction: We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s-1 in younger versus older men. Methods: Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Results: Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s-1 were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Conclusions: Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.

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KW - Reliability

KW - Sarcopenia

KW - Torque-velocity

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Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia

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