Determination of Maximal Lactate Steady State in Healthy Adults: Can NIRS Help?.

• Autores: Cecilia Bellotti, Silvia Pogliaghi, Elisa Calabria, Carlo Capelli
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 45, Nº. 6, 2013, págs. 1208-1216
• Idioma: inglés
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• Resumen

  • AB Purpose: We tested the hypothesis that the maximal lactate steady state (MLSS) can be accurately determined in healthy subjects based on measures of deoxygenated hemoglobin (deoxyHb), an index of oxygen extraction measured noninvasively by near-infrared spectroscopy (NIRS). Methods: Thirty-two healthy men (mean +/- SD age = 48 +/- 17 yr, range = 23-74 yr) performed an incremental cycling test to exhaustion and square wave tests for MLSS determination. Cardiorespiratory variables were measured bbb and deoxyHb was monitored noninvasively on the right vastus lateralis with a quantitative NIRS device. The individual values of V[spacing dot above]O2 and HR corresponding to the MLSS were calculated and compared to the NIRS-derived MLSS (NIRSMLSS) that was, in turn, determined by double linear function fitting of deoxyHb during the incremental exercise. Results: V[spacing dot above]O2 and HR at MLSS were 2.25 +/- 0.54 L[middle dot]min-1 (76% +/- 9% V[spacing dot above]O2max) and 133 +/- 14 bpm (81% +/- 7% HRmax), respectively. Muscle O2 extraction increased as a function of exercise intensity up to a deflection point, NIRSMLSS, at which V[spacing dot above]O2 and HR were 2.23 +/- 0.59 L[middle dot]min-1 (76% +/- 9% V[spacing dot above]O2max) and 136 +/- 17 bpm (82% +/- 8% HRmax), respectively. For both V[spacing dot above]O2 and HR, the difference of NIRSMLSS from MLSS values was not significant and the measures were highly correlated (r2 = 0.81 and r2 = 0.76). The Bland-Altman analysis confirmed a nonsignificant bias for V[spacing dot above]O2 and HR (-0.015 L[middle dot]min-1 and 3 bpm, respectively) and a small imprecision of 0.26 L[middle dot]min-1 and 8 bpm. Conclusions: A plateau in muscle O2 extraction was demonstrated in coincidence with MLSS during an incremental cycling exercise, confirming the hypothesis that this functional parameter can be accurately estimated with a quantitative NIRS device. The main advantages of NIRSMLSS over lactate-based techniques are the noninvasiveness and the time/cost efficiency