Effect of acute hypoxia on muscle blood flow, VO2p, and [HHb] kinetics during leg extension exercise in older men

Livio Zerbini, Matthew D. Spencer, Tyler M. Grey, Juan M. Murias, John M. Kowalchuk, Federico Schena, Donald H. Paterson

Research output: Contribution to journalArticlepeer-review


The adjustment of pulmonary oxygen uptake (VO2p), heart rate (HR), limb blood flow (LBF), and muscle deoxygenation [HHb] was examined during the transition to moderate-intensity, knee-extension exercise in six older adults (70 ± 4 years) under two conditions: normoxia (FIO2 = 20.9 %) and hypoxia (FIO2 = 15 %). The subjects performed repeated step transitions from an active baseline (3 W) to an absolute work rate (21 W) in both conditions. Phase 2 VO2p, HR, LBF, and [HHb] data were fit with an exponential model. Under hypoxic conditions, no change was observed in HR kinetics, on the other hand, LBF kinetics was faster (normoxia 34 ± 3 s; hypoxia 28 ± 2), whereas the overall [HHb] adjustment (τ' = TD + τ) was slower (normoxia 28 ± 2; hypoxia 33 ± 4 s). Phase 2 VO2p kinetics were unchanged (p <0.05). The faster LBF kinetics and slower [HHb] kinetics reflect an improved matching between O2 delivery and O2 utilization at the microvascular level, preventing the phase 2 VO2p kinetics from become slower in hypoxia. Moreover, the absolute blood flow values were higher in hypoxia (1.17 ± 0.2 L min-1) compared to normoxia (0.96 ± 0.2 L min-1) during the steady-state exercise at 21 W. These findings support the idea that, for older adults exercising at a low work rate, an increase of limb blood flow offsets the drop in arterial oxygen content (CaO2) caused by breathing an hypoxic mixture.

Original languageEnglish
Pages (from-to)1685-1694
Number of pages10
JournalEuropean Journal of Applied Physiology
Issue number7
Publication statusPublished - Jul 2013


  • Blood flow
  • Hypoxia
  • NIRS
  • O kinetics
  • Older adults

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Orthopedics and Sports Medicine
  • Physiology (medical)


Dive into the research topics of 'Effect of acute hypoxia on muscle blood flow, VO2p, and [HHb] kinetics during leg extension exercise in older men'. Together they form a unique fingerprint.

Cite this