Comparing muscle VO $_textrm2$ from near-infrared spectroscopy desaturation rate to pulmonary VO $_textrm2$ during cycling below, at and above the maximal lactate steady state


Muscle oxygen uptake (V̇O 2m ) evaluated from changes in the near-infrared spectroscopy oxygen desaturation slope during a 5-s arterial blood flow occlusion has been proposed as an estimation of the actual V̇O 2m . However, its correspondence with pulmonary oxygen uptake (V̇O 2p ) during exercise remains unknown. Purpose: to investigate the V̇O 2m and V̇O 2p relationship in females and males in response to prolonged constant-load cycling exercise at different intensities. Methods: Eighteen participants (8 females) visited the laboratory on six occasions: 1) ramp incremental test; 2-3) 30-min constant power output (constant-PO) exercise bout to determine the maximal lactate steady state (MLSS); 4-6) constant-PO exercise bouts to task failure at (i) 15% below MLSS (MLSS -15% ); (ii) MLSS; (iii) 15% above MLSS (MLSS +15% ). V̇O 2m was estimated at baseline, at min 5, 10, 20, 30, and at task failure. V̇O 2p was continuously recorded during the constant-PO bouts. Results: V̇O 2p and V̇O 2m significantly increased from min 5 to min 30 in MLSS condition (all p textless 0.05) and from min 5 to min 10 in MLSS +15% condition (all p textless 0.05). V̇O 2p and V̇O 2m were correlated (r 2 adj range of 0.70-0.98, all p textless 0.001) amongst exercise intensities in both females and males. Additionally, both variables were also correlated when expressed as percent (r 2 adj range of 0.52-0.77, all p textless 0.001). Conclusion: V̇O 2p and V̇O 2m responses were similar when exercising below, at, and above the MLSS independently of sex. Most importantly, V̇O 2p and V̇O 2m were correlated regardless the exercise intensity and sex of the participants.

Journal of Applied Physiology