Abstract

Aim We hypothesize that training-induced changes in muscle oxygen saturation (StO(2)) assessed by near-infrared spectroscopy (NIRS) during constant work rate cycling exercise (CWRE) may be a useful marker of the effects of training at 'vastus medialis' of the quadriceps in patients with chronic obstructive pulmonary disease (COPD). Methods Incremental exercise [peak oxygen uptake (VO2)] and CWRE at 70% pretraining peak VO2, before and after 8-w training, were done in 10 healthy age-matched subjects (H) [80% men, 65(11) years, FEV1 105(14)%] and 16 COPD patients [94% men, 70(5) years, FEV1 46(11) %] encompassing the entire spectrum of disease severity, recruited in the outpatient clinics. NIRS was used to assess StO(2) in the 'vastus medialis' of the left quadriceps. Results Pretraining CWRE decreased StO(2) (P0 center dot 05) and generated marked StO(2) rebound (P0 center dot 001) after unloading in the two groups. After training, VO2 peak increased in H [253(204) ml min(-1)] (P0 center dot 01) and in COPD [180(183) ml center dot min(-1)] (P = 0 center dot 01) and blood lactate fell [-4 center dot 4 (2 center dot 7) and -1 center dot 6(2 center dot 3) mmol center dot m(-1)] (P0 center dot 05 each). Training generated a further fall in StO(2) during CWRE [-10(12)% and -10(10)%, P0 center dot 05] and increased StO(2) rebound after unloading [8(7)% and 5(9)%, PCWRE, similarly in both groups, likely due to training-induced enhancement of muscle O-2 transfer and utilization. Training-induced StO(2) fall during CWRE may be useful individual marker for non-invasive assessment of enhanced muscle aerobic post-training function.