title: Effects of fatiguing constant versus alternating intensity intermittent isometric muscle actions on maximal torque and neuromuscular responses.
abstract: To determine the effects of constant versus alternating applications of torque during fatiguing, intermittent isometric muscle actions of the leg extensors on maximal voluntary isometric contraction (MVIC) torque and neuromuscular responses.
  
  
  
  Sixteen subjects performed two protocols, each consisting of 50 intermittent isometric muscle actions of the leg extensors with equal average load at a constant 60% MVIC or alternating 40 then 80% (40/80%) MVIC with a work-to-rest ratio of 6-s on and 2-s off. MVIC torque as well as electromyographic signals from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) and mechanomyographic signals from the VL were recorded pretest, immediately posttest, and 5-min posttest.
  
  
  
  The results indicated that there were no time-related differences between the 60% MVIC and 40/80% MVIC protocols. The MVIC torque decreased posttest (22 to 26%) and remained depressed 5-min posttest (9%). There were decreases in electromyographic frequency (14 to 19%) and mechanomyographic frequency (23 to 24%) posttest that returned to pretest levels 5-min posttest. There were no changes in electromyographic amplitude and mechanomyogrpahic amplitude.
  
  
  
  These findings suggested that these neuromuscular parameters did not track the fatigue-induced changes in MVIC torque after 5-min of recovery.
authors.affiliation: Department of Nutrition and Health Sciences Human Performance Laboratory, University of Nebraska-Lincoln, Lincoln, NE 68505, United States.
authors.forename: C M
authors.initials: CM
authors.lastname: Smith
authors.forename: T J
authors.initials: TJ
authors.lastname: Housh
authors.forename: E C
authors.initials: EC
authors.lastname: Hill
authors.forename: K C
authors.initials: KC
authors.lastname: Cochrane
authors.forename: N D M
authors.initials: NDM
authors.lastname: Jenkins
authors.forename: R J
authors.initials: RJ
authors.lastname: Schmidt
authors.forename: G O
authors.initials: GO
authors.lastname: Johnson
mesh_terms: D004594:Electrophysiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D055815:Young Adult