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Experimental Physiology 90.3 pp 393-401
DOI: 10.1113/expphysiol.2004.029595
© The Physiological Society 2005
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Dynamics of skeletal muscle oxygenation during sequential bouts of moderate exercise

Leonardo F. Ferreira1, Barbara J. Lutjemeier1, Dana K. Townsend1 and Thomas J. Barstow1

1 Departments of Kinesiology and Anatomy and Physiology, Kansas State University, 66506-0302, Manhattan, KS, USA

In rat muscle, faster dynamics of microvascular PO2 (approximately blood flow{eph_122_mu1}to O2 uptake{eph_122_mu2}ratio) after prior contractions that did not alter blood [lactate] have been considered to be a consequence of faster{eph_122_mu3}kinetics. However, in humans, prior exercise below the lactate threshold does not affect the pulmonary{eph_122_mu4}kinetics. To clarify this apparent discrepancy, we examined the effects of prior moderate exercise on the kinetics of muscle oxygenation (deoxyhaemoglobin, [HHb]{alpha}{eph_122_mu5}) and pulmonary{eph_122_mu6}in humans. Eight subjects performed two bouts (6 min each) of moderate-intensity cycling separated by 6 min of baseline pedalling. Muscle (vastus lateralis) oxygenation was evaluated by near-infrared spectroscopy and{eph_122_mu7}was measured breath-by-breath. The time constant ({tau}) of the primary component of{eph_122_mu8}was not significantly affected by prior exercise (21.5 ± 9.2 versus 25.6 ± 9.7 s; Bout 1 versus 2, P= 0.49). The time delay (TD) of [HHb] decreased (11.6 ± 2.6 versus 7.7 ± 1.5 s; Bout 1 versus 2, P < 0.05) and {tau}[HHb] increased (7.0 ± 3.5 versus 10.2 ± 4.6 s; Bout 1 versus 2, P < 0.05), while the mean response time (TD +{tau}) did not change (18.6 ± 2.7 versus 17.9 ± 3.9 s) after prior moderate exercise. Thus, prior moderate exercise resulted in shorter onset and slower rate of increase in [HHb] during subsequent exercise. These data suggest that prior exercise altered the dynamic interaction between{eph_122_mu9}and{eph_122_mu10}following the onset of exercise.

(Received 3 December 2004; accepted after revision 26 January 2005; first published online 11 February 2005)
Corresponding author T. J. Barstow: Department of Kinesiology, 1A Natatorium, Kansas State University, Manhattan, KS, 66506-0302, USA. Email: tbarsto{at}ksu.edu






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