title: Vastus lateralis O2 desaturation in response to fast and short maximal contraction.
abstract: OBJECTIVE
  The purpose of this study was to investigate, in heavy-resistance strength-trained (N = 10) and untrained (N = 10) subjects, the vastus lateralis muscle oxyhemoglobin (O2Hb) desaturation time course in response to a brief, maximal, voluntary isometric contraction.
  
  
  METHODS
  The two groups were not statistically different physically. Mean (+/- SD) age, height, and body mass of all the subjects were 28.0 +/- 6.3 yr, 1.8 +/- 0.1 m, and 77.8 +/- 9.9 kg, respectively. Each subject performed five trials. Every trial consisted of 1) a 1-min rest period, 2) a leg press exercise of 2-4 s, and 3) a 5-min recovery period. Leg press exercise consisted of a static maximal voluntary contraction performed using the dominant leg only. Leg press strength was recorded using a load cell. Muscle O2Hb saturation (SmO2) was measured noninvasively by near-infrared spectroscopy (0.17-s sampling time).
  
  
  RESULTS
  Rate of force development was higher in the trained subjects than in the untrained ones (6897 +/- 1654 vs 5515 +/- 1434 N x s(-1); P < 0.05). Once the exercise began, the time to the onset of SmO2 decrease was consistently shorter in the untrained than in the trained subjects (2.81 +/- 0.40 vs 3.91 +/- 0.67 s, P < 0.01). In all the trained subjects and in two of the untrained ones, SmO2 started to decrease once the exercise was stopped. After the end of the exercise, SmO2 transiently decreased and reached its minimum value in 15.0 +/- 3.8 and 10.1 +/- 1.3 s in the trained and untrained subjects, respectively (P < 0.01).
  
  
  CONCLUSIONS
  These data suggest that the vastus lateralis muscle of heavy-resistance strength-trained subjects could have a late activation of the oxidative metabolic system, or greater stored oxygen available, during a very fast, short, isometric maximal contraction.
authors.affiliation: Department of Science and Biomedical Technologies, University of L'Aquila, L'Aquila, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cettolo
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Biasini
authors.forename: Valentina
authors.initials: V
authors.lastname: Quaresima
mesh_terms: D000328:Adult; D006801:Humans; D007558:Italy; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction; D010100:Oxygen / Q000378:metabolism*; D052097:Quadriceps Muscle / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared; D014891:Weight Lifting
chemical_list: D010100:Oxygen