During an incremental cycling exercise, cerebral oxygenation thresholds occurred concomitantly with both ventilatory thresholds, whereas muscle oxygenation and electrical activity thresholds occurred only at or after the second ventilatory threshold.
Observational (n=25)
No
Metabolic and ventilatory events characterizing the second cardiopulmonary threshold may affect both cerebral and muscle oxygenation levels and muscle recruitment responses during incremental cycling exercise.
The aim of this study was to locate the breakpoints of cerebral and muscle oxygenation and muscle electrical activity during a ramp exercise in reference to the first and second ventilatory thresholds. Twenty-five cyclists completed a maximal ramp test on an electromagnetically braked cycle-ergometer with a rate of increment of 25 W/min. Expired gazes (breath-by-breath), prefrontal cortex and vastus lateralis (VL) oxygenation Near-infrared spectroscopy (NIRS) together with electromyographic (EMG) Root Mean Square (RMS) activity for the VL, rectus femoris (RF), and biceps femoris (BF) muscles were continuously assessed. There was a non-linear increase in both cerebral deoxyhemoglobin (at 56 ± 13% of the exercise) and oxyhemoglobin (56 ± 8% of exercise) concomitantly to the first ventilatory threshold (57 ± 6% of exercise, p > 0.86, Cohen's d 0.8). We identified one threshold only for muscle parameters with a non-linear decrease in muscle oxyhemoglobin (78 ± 9% of exercise), attenuation in muscle deoxyhemoglobin (80 ± 8% of exercise), and increase in EMG activity of VL (89 ± 5% of exercise), RF (82 ± 14% of exercise), and BF (85 ± 9% of exercise). The thresholds in BF and VL EMG activity occurred after the second ventilatory threshold (p 0.6). Our results suggest that the metabolic and ventilatory events characterizing this latter cardiopulmonary threshold may affect both cerebral and muscle oxygenation levels, and in turn, muscle recruitment responses.
Racinais et al. (Fri,) conducted a observational in Healthy cyclists (n=25). Incremental cycling exercise (ramp test) was evaluated on Location of breakpoints in cerebral and muscle oxygenation and muscle electrical activity relative to ventilatory thresholds. During an incremental cycling exercise, cerebral oxygenation thresholds occurred concomitantly with both ventilatory thresholds, whereas muscle oxygenation and electrical activity thresholds occurred only at or after the second ventilatory threshold.