Assessment of ventilatory threshold using near-infrared spectroscopy on the gastrocnemius muscle during treadmill running

This study was designed to investigate the efficacy of the near-infrared spectroscopy (NIRS) methodology in exploring the relationship between ventilatory (VT) and NIRS-determined threshold on the gastrocnemius muscle during running. Seventeen healthy participants, 11 males and 6 females performed an incremental exercise test until volitional exhaustion on a treadmill. Initial speed was set at 8 km/h with increments of 0.5 km/h per minute. Tissue oxygen saturation (StO2) was obtained from the belly of the left gastrocnemius muscle. Running velocity at the NIRS threshold was evaluated with StO2–velocity plots, employing two different models: linear (NTlin) and Dmax (NTD). Significant difference in velocity was observed between NTD (11.7 ± 0.9 km/h) and VT (11.2 ± 1.2 km/h). However, no difference in velocity was observed between VT and NTlin (11.6 ± 0.8 km/h, p > 0.05), and between the two NIRS methods (p > 0.05). VT velocity was significantly correlated (p < 0.05) to NTlin (r = 0.86) and NTD (r = 0.84). Time duration at NIRS threshold as assessed with StO2-time plots employing a linear model (NT), did not differ from VT (8.5 ± 1.8 min vs. 7.9 ± 2.5 min respectively, p > 0.05). Furthermore, small but significant differences (p < 0.05) were found between VO2 and heart rate at VT and NT, expressed in either relative or maximum percentage values. Both NIRS-derived models were well correlated with VT and did not differ from each other. NIRS methodology applied on the gastrocnemius muscle was found to provide a useful means of detecting VT during treadmill running and to be practically appropriate in prescribing exercise training in running.Relevance to industryHuman performance assessment is useful in the field of occupational health or industry. Ventilatory threshold along with NIRS methodology could be used in the field or a simulated environment to evaluate performance of professionals involved in physically demanding activities, such as firefighting and construction.