METHODS: Forty healthy individuals were included and randomly assigned into the experimental group and control group. All subjects performed a preferential activation of the LM and/or TrA (maintained the constraction of LM and/or TrA for 30 s and then relaxed for 2 min), while those in the experimental group also received visual feedback provided by RUSI. The thickness of LM and/or TrA at rest and during contraction (Tc-max, T15s, and T30s) were extracted and recorded. The experiment was repeated three times.
RESULTS: No significant differences were found in the thickness of LM at rest (P > 0.999), Tc-max (P > 0.999), and T15s (P = 0.414) between the two groups. However, the ability to recruit LM muscle contraction differed between groups at T30s (P = 0.006), with subjects in the experimental group that received visual ultrasound biofeedback maintaining a relative maximum contraction. Besides, no significant differences were found in the TrA muscle thickness at rest (P > 0.999) and Tc-max (P > 0.999) between the two groups. However, significant differences of contraction thickness were found at T15s (P = 0.031) and T30s (P = 0.010) between the two groups during the Abdominal Drawing-in Maneuver (ADIM), with greater TrA muscle contraction thickness in the experimental group.
CONCLUSIONS: RUSI can be used to provide visual biofeedback, which can promote continuous contraction, and improve the ability to activate the LM and TrA muscles in healthy subjects.