Influence of crank rate on the slow component of pulmonary O2 uptake during heavy arm-crank exercise

Paul M. Smith, Eilidh McCrindle, Mike Doherty, Michael J. Price, Andrew M. Jones

    Research output: Contribution to journalArticle

    9 Citations (Scopus)

    Abstract

    The principal aim of this study was to examine the influence of variations in crank rate on the slow component of the pulmonary oxygen uptake (V̇O 2) response to heavy-intensity arm-crank ergometry (ACE). We hypothesized that, for the same external work rate, a higher crank rate would elicit a greater amplitude of the V̇O2 "slow component". Eleven healthy males (mean (± SD) age, 25 (±6) y; body mass, 89.1 (±10.7) kg; ACE V̇O2 peak, 3.36 (±0.47) L·min-1) volunteered to participate. The subjects initially completed an incremental exercise test for the determination of V̇O2 peak and peak power on an electrically braked arm ergometer. Subsequently, they completed "step" transitions from an unloaded baseline to a work rate requiring 70% of peak power: 2 at a crank rate of 50 r·min-1 (LO) and 2 at a crank rate of 90 r·min-1 (HI). Pulmonary gas exchange was measured on a breath-by-breath basis and V̇O2 kinetics were evaluated from the mean response to each condition using non-linear regression techniques. In contradiction to our hypothesis, the V̇O2 slow component was significantly greater at 50 r·min-1 than at 90 r·min-1 (LO: 0.60 ± 0.30 vs. HI: 0.47 ± 0.21 L·min-1; p < 0.05). The mean value for the localized rating of perceived exertion was also higher at 50 r·min-1 than at 90 r·min-1 (LO: 16.7 ± 1.4 vs. HI: 15.2 ± 1.3; p < 0.05), but there was no significant difference in end-exercise blood lactate concentration. It is possible that differences in muscle tension development and blood flow resulted in a greater contribution of "low-efficiency" type II muscle fibres to force production at the lower crank rate in ACE, and that this was linked to the greater V̇O 2 slow component. However, other factors such as greater isometric contraction of the muscles of the trunk and legs at the lower crank rate might also be implicated.

    Original languageEnglish
    Pages (from-to)292-301
    Number of pages10
    JournalApplied Physiology, Nutrition and Metabolism
    Volume31
    Issue number3
    DOIs
    Publication statusPublished - 1 Jun 2006

    Keywords

    • Fibre recruitment
    • O kinetics
    • Oxygen uptake
    • V̇O slow component

    ASJC Scopus subject areas

    • Endocrinology, Diabetes and Metabolism
    • Physiology
    • Nutrition and Dietetics
    • Physiology (medical)

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