Muscle oxygenation and pulmonary gas exchange kinetics during cycling exercise on-transitions in humans

Bruno Grassi, Silvia Pogliaghi, Susanna Rampichini, Valentina Quaresima, Marco Ferrari, Claudio Marconi, Paolo Cerretelli

Research output: Contribution to journalArticlepeer-review


Near-infrared spectroscopy (NIRS) was utilized to gain insights into the kinetics of oxidative metabolism during exercise transitions. Ten untrained young men were tested on a cycle ergometer during transitions from unloaded pedaling to 5 min of constant-load exercise below (VT) the ventilatory threshold. Vastus lateralis oxygenation was determined by NIRS, and pulmonary O2 uptake (Vo2) was determined breath-by-breath. Changes in deoxygenated hemoglobin + myoglobin concentration {Δ[deoxy(Hb + Mb)]} were taken as a muscle oxygenation index. At the transition, Δ[deoxy(Hb + Mb)] was unmodified [time delay (TD)](TD)l for 8.9 ± 0.5 s at VT (both significantly different from 0) and then increased, following a monoexponential function [time constant (τ) = 8.5 ± 0.9 s for VT]. For >VT a slow component of Δ[deoxy(Hb + Mb)] on-kinetics was observed in 9 of 10 subjects after 75.0 ± 14.0 s of exercise. A significant correlation was described between the mean response time (MRT = TD + τ) of the primary component of Δ[deoxy(Hb + Mb)] on-kinetics and the τ of the primary component of the pulmonary Vo2 on-kinetics. The constant muscle oxygenation during the initial phase of the on-transition indicates a tight coupling between increases in O2 delivery and O2 utilization. The lack of a drop in muscle oxygenation at the transition suggests adequacy of O2 availability in relation to needs.

Original languageEnglish
Pages (from-to)149-158
Number of pages10
JournalJournal of Applied Physiology
Issue number1
Publication statusPublished - Jul 1 2003


  • Functional evaluation
  • Near-infrared spectroscopy
  • Oxidative metabolism
  • Oxygen uptake kinetics
  • Skeletal muscle

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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