Reproducibility and sensitivity of muscle reoxygenation and oxygen uptake recovery kinetics following running exercise in the field.

The purpose of this study was to assess the reliability of postexercise near-infrared spectroscopy (NIRS)-derived measurements and their sensitivity to different exercise intensities in the field. Seventeen athletes (24·1 ± 5·6 year) repeated, on three occasions, two 2-min submaximal shuttle-runs at 40% and 60% of V(IFT) (final speed of the 30-15 intermittent fitness test) and a 50-m shuttle-run sprint (Sprint), with (OCC) or without (CON) repeated transient arterial occlusions of the medial gastrocnemius during the postexercise period. NIRS variables (i.e. oxyhaemoglobin [HbO(2)], deoxyhaemoglobin [HHb] and their difference [Hb(diff)]) were measured continuously for 3 min after each exercise. Half-recovery (½Rec) and mean response (MRT; monoexponential curve fitting) times of muscle reoxygenation and muscle oxygen uptake (mVO(2)) recovery were calculated. Reliability was assessed using the typical error of measurement, expressed as a coefficient of variation (CV). Postexercise recovery of muscle reoxygenation revealed CVs ranging from 16·8% to 37·3%; CV for mVO(2) recovery ranged from 6·2% to 20·9%, with no substantial differences shown between NIRS variables and exercise intensities. While running, intensity did not affect MRT or ½Rec for muscle reoxygenation, and differences were found for mVO(2) recovery (e.g. [Hb(diff)]-mVO(2) MRT = 28·7 ± 5·2, 34·2 ± 5·1 and 37·3 ± 6·2 s for 40%, 60% and Sprint, respectively, P<0·01). To conclude, the kinetics of postexercise NIRS measurements showed CV values ranging from 6% to 37%, with no substantial differences between exercise intensities or NIRS-derived variables. However, exercise intensity did influence mVO(2) recovery kinetics, but not that of muscle reoxygenation in an occlusion-free condition.