title: Oxygenation and neuromuscular activation of the quadriceps femoris including the vastus intermedius during a fatiguing contraction.
abstract: BACKGROUND
  The purpose of this study was to assess oxygenation and neuromuscular activation of the quadriceps femoris muscle group, including the vastus intermedius (VI), during a fatiguing contraction.
  
  
  METHODS
  Eleven healthy men performed an isometric knee extension at 50% of the maximum voluntary contraction until failure. Near-infrared spectroscopy was used to measure tissue oxygen saturation (StO2), and surface electromyography was used to quantify the median frequency (MF) of the four individual quadriceps femoris muscles.
  
  
  RESULTS
  A significant decrease in StO2began at 25% of time to exhaustion in all four muscles, and StO2of the VI was significantly higher than StO2of the vastus medialis (VM) from 25% of time to exhaustion until 95% of time to exhaustion. The MF of the VI did not significantly decrease during the fatiguing task. We found a significant correlation between ∆MF and ∆StO2in the VI (r = 0·745, P<0·01) and a significant correlation between StO2and time to exhaustion in the VM and rectus femoris (RF) (VM, r = 0·684, P<0·05; RF, r = 0·635, P<0·05).
  
  
  CONCLUSIONS
  These results suggest that muscle O2saturation in the VI is associated with neuromuscular fatigue during a fatiguing isometric contraction, and the level of oxygenation in the VM and RF is a key to sustaining a fatiguing contraction.
authors.affiliation: Research Center of Health, Physical Fitness & Sports, Nagoya University, Nagoya, Japan.|Graduate School of Education & Human Development, Nagoya University, Nagoya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akima
authors.affiliation: Graduate School of Education & Human Development, Nagoya University, Nagoya, Japan.|Japan Society for the Promotion of Science, Chiyoda, Tokyo, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Ando
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D009469:Neuromuscular Junction / Q000502:physiology*; D010101:Oxygen Consumption; D052097:Quadriceps Muscle / Q000294:innervation* / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D055815:Young Adult
keywords: blood volume; fatigue; near-infrared spectroscopy; oxygenation; quadriceps femoris