June 1, 2001Journal of Applied Physiology109 citations

V˙o 2 and heart rate kinetics in cycling: transitions from an elevated baseline

Q: What is the clinical evidence from this study?

Study design: Other. Population: Healthy (n=8). Intervention: Repeated bouts of heavy square-wave cycling from an exercising baseline vs. First bout. Primary outcome: VO2 and heart rate kinetics (mean response time).

SBShawn E. BeardenIdaho State University RMRobert J. MoffattFlorida State University

Key Result

Repeated bouts of heavy square-wave cycling from an exercising baseline resulted in a smaller mean response time in the second bout due to a greater fast-component amplitude.

Structured PICO

How do VO2 and heart rate kinetics change during repeated bouts of heavy square-wave cycling from an exercising baseline in healthy males?

Population

8 healthy, male volunteers

Intervention

Moderate and repeated bouts of heavy square-wave cycling from an exercising baseline (leg ergometry above and below the gas exchange threshold separated by recovery cycling at 35% VO2 peak)

Comparator

First bout vs. second bout

Outcome

Oxygen consumption (VO2) and heart rate kineticssurrogate

Repeated heavy exercise from an elevated baseline alters VO2 kinetics, suggesting a role for local oxygen delivery limitation in heavy exercise transitions with unloaded baselines.

Abstract

The purpose of this study was to examine oxygen consumption (VO2) and heart rate kinetics during moderate and repeated bouts of heavy square-wave cycling from an exercising baseline. Eight healthy, male volunteers performed square-wave bouts of leg ergometry above and below the gas exchange threshold separated by recovery cycling at 35% VO2 peak. VO2 and heart rate kinetics were modeled, after removal of phase I data by use of a biphasic on-kinetics and monoexponential off-kinetics model. Fingertip capillary blood was sampled 45 s before each transition for base excess, HCO and lactate concentration, and pH. Base excess and HCO concentration were significantly lower, whereas lactate concentration and pH were not different before the second bout. The results confirm earlier reports of a smaller mean response time in the second heavy bout. This was the result of a significantly greater fast-component amplitude and smaller slow-component amplitude with invariant fast-component time constant. A role for local oxygen delivery limitation in heavy exercise transitions with unloaded but not moderate baselines is presented.

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