title: Effect of repeated forearm muscle cooling on the adaptation of skeletal muscle metabolism in humans.
abstract: This study aimed to investigate the effect of repeated cooling of forearm muscle on adaptation in skeletal muscle metabolism. It is hypothesized that repeated decreases of muscle temperature would increase the oxygen consumption in hypothermic skeletal muscle. Sixteen healthy males participated in this study. Their right forearm muscles were locally cooled to 25 °C by cooling pads attached to the skin. This local cooling was repeated eight times on separate days for eight participants (experimental group), whereas eight controls received no cold exposure. To evaluate adaptation in skeletal muscle metabolism, a local cooling test was conducted before and after the repeated cooling period. Change in oxy-hemoglobin content in the flexor digitorum at rest and during a 25-s isometric handgrip (10% maximal voluntary construction) was measured using near-infrared spectroscopy at every 2 °C reduction in forearm muscle temperature. The arterial blood flow was occluded for 15 s by upper arm cuff inflation at rest and during the isometric handgrip. The oxygen consumption in the flexor digitorum muscle was evaluated by a slope of the oxy-hemoglobin change during the arterial occlusion. In the experimental group, resting oxygen consumption in skeletal muscle did not show any difference between pre- and post-intervention, whereas muscle oxygen consumption during the isometric handgrip was significantly higher in post-intervention than in pre-test from thermoneutral baseline to 31 °C muscle temperature (P < 0.05). This result indicated that repeated local muscle cooling might facilitate oxidative metabolism in the skeletal muscle. In summary, skeletal muscle metabolism during submaximal isometric handgrip was facilitated after repeated local muscle cooling.
authors.affiliation: Laboratory of Environmental Ergonomics, Faculty of Engineering, Hokkaido University, N13 W8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan. wakabayashi@eng.hokudai.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Wakabayashi
authors.affiliation: Department of Public Health, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: Department of Mechanical and Industrial Engineering, Gadjah Mada University, Yogyakarta, Indonesia.
authors.forename: Titis
authors.initials: T
authors.lastname: Wijayanto
authors.affiliation: Faculty of Design, Kyushu University, Fukuoka, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Watanuki
authors.affiliation: Faculty of Design, Kyushu University, Fukuoka, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tochihara
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D003080:Cold Temperature; D005542:Forearm / Q000502:physiology; D018737:Hand Strength; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply; D012881:Skin Temperature; D055815:Young Adult
keywords: Cold adaptation; Hypothermic skeletal muscle; Local cold exposure; Non-shivering thermogenesis; Tissue oxygenation