Fig 1.
Schematic illustration of Cost of Transport (CoT) and gait speed (v) at normoxia and hypoxia.
(a) Upward and leftward shifts of the U-shaped CoT-v relationship in walking and an upward shift of the linear CoT-v relationship in running result in a slower energetically optimal transition speed (EOTS, circles) and economical speed (ES, triangles) at hypoxia. (b) Upward shifts of both CoT-v relationships result in unchanged ES and EOTS. Solid and dotted lines mean normoxia and hypoxia, respectively. Both red arrows indicate a possible ‘shifting model’ for explaining slower ES and EOTS at hypoxia.
Table 1.
Summary of experimental conditions.
Fig 2.
U-shaped (walking) and linear (running) CoT-v relationships on different gradient slopes at normoxia and hypoxia.
The energetically optimal transition speed (EOTS; km·h-1) was 7.447 ± 0.311 km·h-1 at normoxia and 7.678 ± 0.324 km·h-1 at hypoxia, and the economical speed (ES; km·h-1) was 4.993 ± 0.185 km·h-1 at normoxia and 5.056 ± 0.210 km·h-1 at hypoxia on the level slope (Black panel). The EOTS was 7.679 ± 0.342 km·h-1 at normoxia and 7.653 ± 0.295 km·h-1 at hypoxia, and 5.198 ± 0.192 km·h-1 at normoxia and 5.133 km·h-1 ± 0.243 km·h-1 at hypoxia on the downhill slope (Blue panel). The EOTS was 7.412 ± 0.480 km·h-1 at normoxia and 7.516 ± 0.415 km·h-1 at hypoxia, and the ES was 4.984 ± 0.238 km·h-1 at normoxia and 5.082 ± 0.223 km·h-1 at hypoxia on the uphill slope, respectively. # downhill > uphill within normoxia or hypoxia. * downhill > level = uphill within normoxia and hypoxia. † (p < 0.05), ‡ (p < 0.01), and § (p < 0.001) indicated significant differences of the energy cost of transport per unit distance (CoT; J·kg-1·km-1) between normoxia and hypoxia on each slope. Data were shown as mean ± standard deviation (S.D.).
Fig 3.
Comparisons of muscle activities during walking or running at the EOTS.
Deep colors (black, blue, and red) and thin colors (grey, light blue, and pink) are normoxia and hypoxia, respectively. Solid and dotted bars are walking and running, respectively. WN, RN, WH, and RH mean walking at normoxia, running at normoxia, walking at hypoxia, and running at hypoxia, respectively. * walking > running within normoxia or hypoxia, § walking < running within normoxia or hypoxia, and † normoxia > hypoxia within walking or running, respectively. Data are mean ± S.D.
Fig 4.
Comparisons of mean power frequency during walking or running at the EOTS.
Deep colors (black, blue, and red) and thin colors (grey, light blue, and pink) are normoxia and hypoxia, respectively. Solid and dotted bars are walking and running, respectively. WN, RN, WH, and RH mean walking at normoxia, running at normoxia, walking at hypoxia, and running at hypoxia, respectively. * walk > running within normoxia or hypoxia and † normoxia < hypoxia within walking or running, respectively. Data are mean ± S.D.