title: Muscle oxygen consumption at onset of exercise by near infrared spectroscopy in humans.
abstract: In this study, we tried to continuously measure muscle oxygen consumption (m-VO2) by near infrared spectroscopy (NIRS) without arterial occlusions. We used an intermittent isometric exercise at high intensity, which elicits a spontaneous occlusion of the blood flow to the muscle due to an increase in intramuscular pressure. Changes in muscle oxygenation and phosphocreatine (PCr) concentration were monitored in 5 subjects during an intermittent isometric exercise (5 sec. contraction/5 sec. relaxation) at 50% of maximum voluntary contraction for 3 minutes. The rate of deoxygenation was measured from the 2nd sec. to the 3rd sec. of each muscle contraction. The rate of deoxygenation at the onset of exercise followed an exponential time course with a time constant of 42.0 +/- 12.5 sec. (mean +/- SD). This value agreed with the time constant of the decrease in PCr (48.2 +/- 10.2 sec.). This result suggests that m-VO2 was successfully monitored with a time resolution of 10 sec. by NIRS during exercise without arterial occlusion.
authors.affiliation: Department of Preventive Medicine and Public Health, Tokyo Medical University, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Hamaoka
authors.forename: Toshihito
authors.initials: T
authors.lastname: Katsumura
authors.forename: Norio
authors.initials: N
authors.lastname: Murase
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sako
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Higuchi
authors.forename: Motohide
authors.initials: M
authors.lastname: Murakami
authors.forename: Kazuki
authors.initials: K
authors.lastname: Esaki
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Kime
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Homma
authors.forename: Akiko
authors.initials: A
authors.lastname: Sugeta
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kurosawa
authors.forename: Teruichi
authors.initials: T
authors.lastname: Shimomitsu
authors.forename: Britton
authors.initials: B
authors.lastname: Chance
mesh_terms: D000328:Adult; D015444:Exercise; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D010100:Oxygen