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

摘要

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 (StO_2) was obtained from the belly of the left gastrocnemius muscle. Running velocity at the NIRS threshold was evaluated with StO_2-velocity plots, employing two different models: linear (NT_(lin)) and D_(max) (NT_D). Significant difference in velocity was observed between NT_D (11.7 ± 0.9 km/h) and VT (11.2 ± 1.2 km/h). However, no difference in velocity was observed between VT and NT_(lin) (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 NT_(lin) (r = 0.86) and NT_D (r = 0.84). Time duration at NIRS threshold as assessed with StO_2-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 VO_2 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 industry: Human 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.