Takafumi HAMAOKA^1,2,*, Takuya OSADA¹, Norio MURASE¹, Takayuki SAKO³, Hiroyuki HIGUCHI¹, Yuko KUROSAWA¹, Mitsuharu MIWA⁴, Toshihito KATSUMURA¹ and Britton CHANCE⁵

¹Department of Preventive Medicine and Public Health, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, Japan
²National Institute of Fitness and Sports, 1 Shiromizu-cho, Kanoya, Kagoshima, Japan
³Exercise Physiology, Department of Food & Nutrition, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo, Japan
⁴Hamamatsu Photonics, 5000 Hiraguchi, Hamakita City, Shizuoka Prefecture, Japan
⁵Department of Biochemistry and Biophysics, University of Pennsylvania, D501 Richards Building, Philadelphia, USA

(Received March 10, 2003; Accepted April 22, 2003)

The forearm muscles of five healthy males were monitored for changes in microvessel hemoglobin saturation (SO_2-TRS) by near infrared time-resolved spectroscopy (NIR_TRS) and changes in phosphorus metabolites by magnetic resonance spectroscopy (³¹P-MRS) during 12 min of resting arterial occlusion. Muscle oxygenation and phosphorus metabolites were also measured during grip exercises at varying intensities. Upon the initiation of occlusion, SO_2-TRS fell progressively until it reached a plateau in the latter half of the occlusion. Phosphocreatine (PCr) began to decrease around 6 min after the initiation of arterial occlusion. The resting O₂ store and O₂ consumption were 295 μM and 0.95 μM/sec, respectively-values which reasonably agree with the reported results. A significant correlation was observed between the changes in SO_2-TRS and PCr during exercise (r² = 0.80, p < 0.001). These results indicate that NIR_TRS is able to provide reliable information about resting metabolism and oxidative rate during exercise. NIR_TRS and MRS are useful to monitor oxygenation and energetics noninvasively in the human muscle.

Key words: muscle oxygenation; O₂ gradient; basal O₂ consumption; phosphocreatine (PCr); near infrared

^*E-mail address: kyp02504@nifty.ne.jp