Elevated baseline VO2 per se does not slow O2 uptake kinetics during work-to-work exercise transitions.
We investigated whether the characteristic slowing of pulmonary oxygen uptake (VO2) kinetics during "work-to-work" exercise is attributable to elevations in baseline metabolic rate (VO2) as opposed to the elevated baseline work rate, per se. We hypothesized that a step transition to a higher work rate from "unloaded" cycling, but with elevations in VO2 [and heart rate (HR)] reflective of a work-to-work transition, would result in a lengthened phase II time constant (τ(p)). Seven male subjects (mean ± SD age 27 ± 10 yr) completed 1) transitions to a high-intensity work rate from a moderate-intensity work rate (M→H) and 2) two consecutive bouts of high-intensity exercise (U→H and E→H, respectively) initiated from unloaded cycling, with the time separating the exercise bouts chosen such that the baseline VO2 for the second transition was similar to the baseline VO2 for the M→H transition. The τ(p) for M→H (48 ± 16 s) was significantly greater (P < 0.05) than the τ(p) for U→H (28 ± 8 s) and E→H (27 ± 6 s), which did not differ significantly. These findings suggest that the altered VO2 dynamics that are observed during work-to-work exercise are not related to the elevated baseline VO2 (or HR) per se; rather, these effects appear to be linked to the elevated baseline work rate, which would be expected to dictate the subsequent muscle fiber recruitment profile.
DiMenna
Fred J
FJ
School of Sport and Health Sciences, St. Luke's Campus, Univ. of Exeter, Heavitree Rd., Exeter, Devon EX1 2LU, UK.
Bailey
Stephen J
SJ
Vanhatalo
Anni
A
Chidnok
Weerapong
W
Jones
Andrew M
AM
D000293:Adolescent; D000328:Adult; D001642:Bicycling; D015444:Exercise; D006339:Heart Rate; D006801:Humans; D007700:Kinetics; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D055815:Young Adult
D019344:Lactic Acid