Correlation of cervical-inspiratory-muscle electromyography and oxygen uptake during treadmill walking

For measurements of exercise intensity, an individual's oxygen uptake (V̇O₂) is measured with an exhaled gas analyzer that involves a mask, but exercise coaching would benefit if an individual's V̇O₂ could be estimated with more easily obtained predictors. We investigated the predictability of V̇O₂ by electromyography (EMG) of the neck inspiratory muscles. We analyzed the EMG results of the sternocleidomastoid (EMGst) and scalene (EMGsc) muscles of 14 healthy adults who performed a treadmill exercise load test. Their V̇O₂, inspiratory flow rate, and heart rate were simultaneously recorded during the exercise. The exercise load test was performed twice at a ≥2-day interval. The first visit was an incremental exercise test, and the second was a repeated two-load exercise test at levels below and above the participant's ventilatory threshold (VT) as determined in the first test. We observed that the integrated EMG values for each exercise load showed partially significant positive correlations with the EMGst and EMGsc. However, the cervical inspiratory muscle EMGs did not show as high a correlation as the minute ventilation. These results indicate that (i) EMG of the cervical inspiratory muscles could be used to estimate V̇O₂, but (ii) these EMG parameters alone should be considered insufficient for estimating V̇O₂.