title: Delayed blood reoxygenation following maximum voluntary contraction.
abstract: OBJECTIVE
  To characterize the total hemoglobin concentration ([THb]) and oxyhemoglobin saturation (%HbO2) time courses after brief dorsiflexion maximal voluntary contractions (MVC) and to determine whether these responses varied by gender.
  
  
  METHODS
  Eighteen healthy, moderately physically active subjects (nine male) lay supine and performed two or more 3-s dorsiflexion MVC. [THb] and %HbO2 were measured continuously in the tibialis anterior muscle using near-infrared spectroscopy (NIRS). The data from 0 to 150 s postcontraction were analyzed using single- and multicomponent exponential models.
  
  
  RESULTS
  The mean (standard error) precontraction [THb] and %HbO2 values were 78.5 (7.3) microM and 65.0 (0.8) %, respectively, and decreased during the contraction. After the contraction, [THb] grew exponentially, characterized by amplitude (A), 8.7 (1.3) microM; time delay (TD), 0.2 (0.2) s, and time constant (tau), 5.9 (0.6) s. Fifteen subjects had a secondary decay phase characterized by A, 1.9 (0.7) microM; TD, 59.2 (6.4) s; and tau, 12.4 (2.3) s. Eight subjects experienced an initial decay in %HbO2, characterized by A, 1.8 (0.8) %; TD, 0.0 (0) s; and tau, 4.2 (0.3) s. Then, %HbO2 grew exponentially, being characterized by A, 7.9 (0.9) %; TD, 10.1 (1.0) s; and tau, 9.7 (2.0) s. Finally, in 16 subjects, there was a secondary decay phase, characterized by A, 2.6 (0.4) %; TD, 54.4 (7.5) s; and tau, 18.9 (2.6) s. There were no gender differences in any kinetic parameter.
  
  
  CONCLUSIONS
  There are three phases to the post-MVC oxygen supply-demand coupling: 1) rising oxygen demand relative to supply; 2) rising oxygen supply relative to demand; and 3) restoration of precontraction oxygen supply-demand matching. These processes are unaffected by gender.
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, TN 37232-0675, USA.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Maguire
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Weaver
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Damon
mesh_terms: D000328:Adult; D005080:Exercise Test; D005260:Female; D006801:Humans; D006940:Hyperemia; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010108:Oxyhemoglobins / Q000032:analysis*; D010809:Physical Fitness / Q000502:physiology; D011446:Prospective Studies; D012737:Sex Factors
chemical_list: D010108:Oxyhemoglobins