DETECTION OF VENTILATORY THRESHOLD USING NEAR-INFRARED SPECTROSCOPY IN MEN AND WOMEN

The onset of anaerobic (lactate) metabolism during incremental exer ci se, which may be a result of an imbalance between tissue oxygen supply and demand, has been associated with the gas exchange ventilatory thr eshold (VT). This study was designed to examine whether near infrared spectroscopy (NIRS) could be used to detect the VT in healthy subjects . Twenty-one men and 19 women completed incremental cycle ergometry du ring which NIRS measurements were obtained from the right vastus later alis and gas exchange measurements were monitored simultaneously using a metabolic cart. The VT was identified from the metabolic data by th e V-slope method and from MRS data as the intensity at which tissue ab sorbency crossed the resting baseline value observed immediately prior to the initiation of exercise. Pearson correlations for the relative oxygen uptake and power output observed for the two methods of detecti ng VT were 0.90 and 0.88, respectively, in men and 0.89 and 0.86, resp ectively, in women (P < 0.01). No significant differences were observe d between the two methods of detecting VT for any of the physiological responses (P > 0.05). No significant (P > 0.05) gender differences we re observed in muscle oxygenation values at the VT, 32% in men and 38% in women. These results validate the use of NIRS as an alternate noni nvasive method for detecting VT during cycle exercise in healthy subje cts.