Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue

Randy J. Schmitz, Brent L. Arnold, David H. Perrin, Kevin P. Granata, Glenn Gaesser, Bruce M. Gansneder

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t = pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC's and three maximal isotonic contractions, respectively. Following each exercise, strength and power were:assessed immediately after (t =: 00) and at 2.5 (t =: 02.5), 5 (t =: 05), 10 (t =: 10), and 15 (t =: 15) minutes. All strength and power measures were normalized to the respective t = pre value. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective t=pre value. Following isometric exercise, both strength and power at t =: 00 (68.7% ± 8.7% & 88.0% ± 8.7%) and t =: 02.5 (82.2% ± 17.8% & 95.2% ± 5.0%) significantly decreased from t=pre (100% ± 0.0%) (p < 0.05) with greater decreases in strength at each time point (p < 0.05). EMG analysis revealed a significant EMG amplitude decrease (p < 0.05) at t =: 00 and t =: 02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t =: 00 (68.0% ± 13.2% & 38.8% ± 10.7%) and t =: 02.5 (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t=pre (100% ± 0.0%) with a greater power decrease at t =: 00 (p < 0.05). The EMG amplitude of males was significantly less at t =: 00 than the respective EMG amplitude for females (p < 0.05) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed.

Original languageEnglish (US)
Pages (from-to)167-175
Number of pages9
JournalIsokinetics and Exercise Science
Volume10
Issue number4
StatePublished - 2002
Externally publishedYes

Fingerprint

Isotonic Contraction
Fatigue
Knee
Muscles
Quadriceps Muscle
Torque
Exercise
Population

Keywords

  • EMG
  • Gender
  • Power

ASJC Scopus subject areas

  • Rehabilitation
  • Physical Therapy, Sports Therapy and Rehabilitation
  • Orthopedics and Sports Medicine

Cite this

Schmitz, R. J., Arnold, B. L., Perrin, D. H., Granata, K. P., Gaesser, G., & Gansneder, B. M. (2002). Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue. Isokinetics and Exercise Science, 10(4), 167-175.

Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue. / Schmitz, Randy J.; Arnold, Brent L.; Perrin, David H.; Granata, Kevin P.; Gaesser, Glenn; Gansneder, Bruce M.

In: Isokinetics and Exercise Science, Vol. 10, No. 4, 2002, p. 167-175.

Research output: Contribution to journalArticle

Schmitz, Randy J. ; Arnold, Brent L. ; Perrin, David H. ; Granata, Kevin P. ; Gaesser, Glenn ; Gansneder, Bruce M. / Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue. In: Isokinetics and Exercise Science. 2002 ; Vol. 10, No. 4. pp. 167-175.
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N2 - This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t = pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC's and three maximal isotonic contractions, respectively. Following each exercise, strength and power were:assessed immediately after (t =: 00) and at 2.5 (t =: 02.5), 5 (t =: 05), 10 (t =: 10), and 15 (t =: 15) minutes. All strength and power measures were normalized to the respective t = pre value. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective t=pre value. Following isometric exercise, both strength and power at t =: 00 (68.7% ± 8.7% & 88.0% ± 8.7%) and t =: 02.5 (82.2% ± 17.8% & 95.2% ± 5.0%) significantly decreased from t=pre (100% ± 0.0%) (p < 0.05) with greater decreases in strength at each time point (p < 0.05). EMG analysis revealed a significant EMG amplitude decrease (p < 0.05) at t =: 00 and t =: 02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t =: 00 (68.0% ± 13.2% & 38.8% ± 10.7%) and t =: 02.5 (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t=pre (100% ± 0.0%) with a greater power decrease at t =: 00 (p < 0.05). The EMG amplitude of males was significantly less at t =: 00 than the respective EMG amplitude for females (p < 0.05) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed.

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