Revista de medicina deportiva y estudios de dopaje

Effects of Resistance Exercise on Intramuscular Oxygenation and Muscle Fiber Composition

Abstract

Fumio Aida, Shukoh Haga, Shogo Sato, Takuya Sakurai, Kazuki Esaki, Takafumi Hamaoka, Masao Mizuno, Koji Toshinai, Hiromi Miyazaki, Tohru Takemasa, Noboru Hashimoto, Junetsu Ogasawara, Toshihito Katsumura, Takako Kizaki and Hideki Ohno

Determining the oxygenation level of skeletal muscle is an effective non-invasive method of evaluating its physiological changes. Nevertheless, the relationship between muscle fiber composition and intramuscular oxygenation is still unclear. In the present study we examined the differences in muscle fiber composition and their relationship to muscle oxygenation levels by comparing power lifters (Training group), who regularly engaged in muscular resistance training, with ordinary healthy people (Control group). The vastus lateralis muscle oxygenation level was measured via near infrared continuous wave spectroscopy, and muscle tissues were collected and used for histochemical analyses in order to calculate muscle fiber compositions. When the rate of decrease in muscle oxygenation after performing a single squat at 50 and 80% of the participants’ maximal lifting weight (MLW) was examined, the rate of decrease was significantly higher at 80% of MLW than at 50% of MLW in Training group, and was significantly higher in the Training group than in the Control group. Moreover, after performing multiple squat movements at 80% of MLW, compared with the Control group, the Training group showed a significant delay in the time it took for their muscle oxygenation level to recover to 50% of its original level at resting time (T_1/2). A significant correlation between the occupancy of Type IIa fiber and T_1/2, or between an average cross-sectional area of muscle fibers and T_1/2 was noted. The present study demonstrated that in the Training group, in a cross-sectional area of Type IIa fiber that had increased, the decreased muscle oxygenation level due to performing squat exercises exhibited a delay in recovery at the resting time, suggesting that the amount of oxygen consumption was increased in the Training group because the crosssectional area of Type IIa fiber was larger, compared with the Control group.