Dynamic Evaluation of Skeletal Muscle Voluntary Contraction Function Using Pulsed Wave Doppler Imaging: An Exploratory Study Based on Wearable Ultrasound

To develop dynamic monitoring and quantitative analysis of voluntary skeletal muscle contractions. A novel micro wearable ultrasound system was evaluated in 40 healthy female participants. Using pulsed wave Doppler imaging, we captured the muscle bundle contraction of the flexor digitorum superficialis in dominant hands during repeated isotonic contractions for 8 seconds, in a cycle of five rounds. Waveform patterns and derived peak systolic velocity (PSV) and muscle systolic time (MST) were recorded and analyzed. Participants with low skeletal muscle mass index (SMI < 5.7 kg/m²) or first-quartile handgrip strength (HS) exhibited a split waveform with bidirectional systolic patterns and reduced PSV stability (PSV was 10.24–11.31 cm/s and 10.12–11.71 cm/s for subjects with low-SMI or low-HS in the first round, and was 9.04–11.29 cm/s and 9.86–10.72 cm/s in the last round). In contrast, subjects with higher muscle mass and strength had regular muscle contraction waveforms and higher PSV, which decreased with increasing grip counts and recovered after rest (PSV was 11.11–15.47 cm/s and 11.21–14.88 cm/s for subjects with normal-SMI or normal-HS in the first round, and was 10.63–13.94 cm/s and 10.09–13.97 cm/s in the last round). The micro wearable ultrasound device enables continuous imaging of voluntary skeletal muscle contraction, and the waveforms and their derived quantitative indicators vary among individuals with different muscle mass and strength.