Validation of muscle oxygenation kinetics to predict aerobic fitness and exercise transition thresholds

The aim of this study was to validate previously developed equations to predict maximal oxygen uptake () from near‐infrared spectroscopy (NIRS) during and after a period of limb ischaemia. Moreover, NIRS recovery kinetics after steady‐state exercise (SSE) could be used to monitor and exercise intensity thresholds. Seventeen healthy adults completed a 3 min 300 mmHg pressure cuff occlusion to measure the occlusion slope, relative rate of muscle reoxygenation at 10 s (Rep 10s), baseline ( R bl ), peak ( R peak ) and area under the curve (AUC 2min ). SSE was performed at 100 W (SSE1) and 150 W (SSE2) to determine the relative rate of muscle reoxygenation ( R 1 bl and R 2 bl ). Thereafter, incremental maximal cycling was used to determine , ventilatory thresholds (VTs) and gross efficiencies (GEs). The values of Rep 10s ( r = 0.61, p = 0.02), R bl ( r = 0.53, p = 0.04), R peak ( r = 0.60, p = 0.02), AUC 2min ( r = 0.67, p < 0.01) and occlusion slope ( r = −0.68, p = 0.005) were correlated with absolute . After steady‐state cycling, SSE1 R bl was correlated with absolute ( r = 0.67, p = 0.01) and relative ( r = 0.60, p = 0.02), in addition to absolute VT1 ( r = 0.66, p = 0.01) and relative VT1 ( r = 0.61 p = 0.02). The SSE2 R bl was correlated with absolute ( r = 0.58, p = 0.02), relative ( r = 0.63, p = 0.02), absolute VT2 ( r = 0.56, p = 0.03), relative VT2 ( r = 0.62, p = 0.01) and GE2 ( r = 0.56, p = 0.03). Using previously defined prediction equations, could be predicted with a modest degree of typical error (Rep 10s, 521 mL min −1 ; R peak , 525 mL min −1 ; slope, 393 mL min −1 ). NIRS kinetic profiles during or after a period of ischaemia or after SSE are related to and exercise intensity thresholds. Nonetheless, their predictive validity is limited to a broad estimate of the aerobic fitness of an individual.