title: Walking economy at simulated high altitude in human healthy young male lowlanders.
abstract: We measured oxygen consumption during walking per unit distance (Cw) values for 12 human healthy young males at six speeds from 0.667 to 1.639 m s-1(four min per stage) on a level gradient under normobaric normoxia, moderate hypoxia (15% O2), and severe hypoxia (11% O2). Muscle deoxygenation (HHb) was measured at the vastus lateralis muscle using near-infrared spectroscopy. Economical speed which can minimize the Cwin each individual was calculated from a U-shaped relationship. We found a significantly slower economical speed (ES) under severe hypoxia [1.237 (0.056) m s-1; mean (s.d.)] compared to normoxia [1.334 (0.070) m s-1] and moderate hypoxia [1.314 (0.070) m s-1, P<0.05 respectively] with no differences between normoxia and moderate hypoxia (P>0.05). HHb gradually increased with increasing speed under severe hypoxia, while it did not increase under normoxia and moderate hypoxia. Changes in HHb between standing baseline and the final minute at faster gait speeds were significantly related to individual ES (r=0.393 at 1.250 m s-1, r=0.376 at 1.444 m s-1, and r=0.409 at 1.639 m s-1, P<0.05, respectively). These results suggested that acute severe hypoxia slowed ES by ∼8%, but moderate hypoxia left ES unchanged.
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Kami-yoshida 5597-1, Fuji-yoshida-city, Yamanashi 4030005, Japan mhoriuchi@mfri.pref.yamanashi.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Horiuchi
authors.affiliation: Division of Human Environmental Science, Mt. Fuji Research Institute, Kami-yoshida 5597-1, Fuji-yoshida-city, Yamanashi 4030005, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Handa
authors.affiliation: Center for Health and Sports Science, Kyushu Sangyo University, Matsukadai 2-3-1, Higashi-ku, Fukuoka-city, Fukuoka 8138503, Japan.
authors.forename: Daijiro
authors.initials: D
authors.lastname: Abe
authors.affiliation: Faculty of Health and Sports Science, Doshisha University, Tatara 1-3, Kyotanabe, Kyoto 6100394, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuoka
keywords: Bipedal locomotion; Energy expenditure; Muscle O2 extraction; Optimal speed; Peripheral circulation