Spatial distribution of electromyographic activity in the vastus lateralis muscle during different contraction tasks in patients with heart failure.

Neuromuscular dysfunction might represent a key, yet underexplored, contributor to exercise intolerance in patients with heart failure (HF). The objective of this study was to investigate the magnitude of activity and the spatial distribution pattern of activation in the vastus lateralis muscle using High-density surface electromyography (HD-EMG) during various measurement tasks in HF patients. This study included hospitalized patients diagnosed with HF and age-matched elderly individuals without cardiac disease (control group). HD-EMG signals from the vastus lateralis muscle were recorded during isometric contractions at 20%, 40%, and 60% maximal voluntary contraction. HD-EMG signals from the vastus lateralis muscle were detected the root mean square (RMS), modified entropy, and coefficient of variation (CV). The generalized linear mixed-effects model revealed a did not differ significantly main effect of group (HF vs. control) on RMS and CV. In contrast, a significant group effect of group was observed for entropy, with HF patients showing higher entropy values than controls. Our results suggests that the temporal structure of motor unit activity is more monotonous and exhibits less variability in patients with heart failure. In other words, although the muscular output appears similar in patients with heart failure, the flexibility and diversity of their control strategies may be impaired. Entropy revealed differences in temporal and structured neural control that were not detectable by quantitative variability metrics such as CV.