Muscle Contraction Duration and Fibre Recruitment Influence Blood Flow and VO2 Independent of Contractile Work during Steady-State Exercise in Humans

Jennifer C. Richards, Colorado State University - Fort Collins
Anne R. Crecelius, University of Dayton
Brett S. Kirby, Duke University Medical Center
Dennis G. Larson, Medical Center of the Rockies Foundation
Frank A. Dinenno, Colorado State University - Fort Collins

This is the peer-reviewed version of the following article:

Richards, J.C., A.R. Crecelius, B.S. Kirby, D.G. Larson and F.A. Dinenno. “Muscle contraction duration and fibre recruitment influence blood flow and VO2 independent of contractile work during steady-state exercise in humans.” Exp Physiol. 97:750-761. 2012.

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We tested the hypothesis that, among conditions of matched contractile work, shorter contraction durations and greater muscle fibre recruitment result in augmented skeletal muscle blood flow and oxygen consumption (O2) during steady-state exercise in humans. To do so, we measured forearm blood flow (FBF; Doppler ultrasound) during 4 minutes of rhythmic handgrip exercise in 24 healthy young adults and calculated forearm O2 via blood samples obtained from a catheter placed in retrograde fashion into a deep vein draining the forearm muscle. In Protocol 1 (n = 11), subjects performed rhythmic isometric handgrip exercise at mild and moderate intensities under conditions in which tension time index (TTI; isometric analog of work) was held constant but contraction duration was manipulated. In this protocol, shorter contraction durations led to greater FBF (184 ± 25 vs. 164 ± 25 ml·min-1) and O2 (23 ± 3 vs. 17 ± 2 ml·min-1; both PPper se during steady-state exercise in humans.