Perceptions and trunk movements elicited by trunk muscle vibration in young adults in static position

The present study aimed to investigate whether proprioceptive stimulation by means of multiple muscle vibration (MV) can induce perceptual and actual trunk responses that may differ according to the stability of the body position during stimulation. Fifteen healthy young adults (25.2 ± 4.3 years old) were recruited. Muscle vibration at 80 Hz was applied to multiple abdominal and spinal muscles in sitting and standing positions with the eyes closed in order to see whether position could affect trunk responses. Perceptions and actual trunk movements were assessed using a numeric rating scale (0: no movement perception - 10: vivid movement perception) and a 3D movement analysis system (VICON), respectively. Statistical tests were used to compare different MV conditions in sitting and standing positions and correlations between outcomes. MV induced perceptions of trunk movements, with same median scores (inter-quartile range) of 5.5(3.5)/10 in both sitting and standing positions. Perception of movement in most MV conditions was mostly (37.5-75%) directed toward the direction of concentric contraction of the stimulated muscles, contrary to what is usually expected. The actual movement direction of the trunk aligned with the perceived movement, with average amplitudes in sitting and standing positions between 1.0 and 5.0° depending on the planes of movement and conditions. Amplitude of actual movement and perception scores were moderately correlated, in sitting and standing positions (ρ = 0.38, p < 0.001, both). Findings confirm that MV can temporarily modify the perception and the actual trunk posture in healthy individuals and warrant further investigation in individuals with altered trunk postures.