2021 Volume 20 Issue 1 Pages 19-29
The effects of stretching the skin over the anterior surface of the thigh with application of various pressures at the stimulation site while standing, on the movements of the subcutaneous tissue (Experiment 1) and direction of the postural response (Experiment 2) were investigated. Subjects in each experiment were 16 different healthy young adults. In both experiments, the skin around the muscle-tendon junction of the rectus femoris was stretched proximally with an amplitude of 7.5 mm and velocity of 10 mm/s. The pressure was set from 0 to 200 g in steps of 25 g in Experiment 1, and from 0 to 350 g in steps of 50 g in Experiment 2. In Experiment 1, skin stretching was performed with the subject's body fixed. Using an ultrasonic scanner, the resulting movements of the deep skin, superficial fascia, and deep fascia were analyzed. Movements of the deep skin and superficial fascia were apparent in all subjects at all pressures. For deep fascia, the proportion of subjects showing movement increased as the pressure increased beyond 50 g. In Experiment 2, the subjects were instructed not to resist any postural responses and the direction of the postural response to skin stretching was measured. All subjects showed forward leaning at 0 g. The proportion of subjects showing backward leaning increased as the pressure increased. These results suggest that forward leaning might occur by stretching of the skin and subcutaneous tissue, and backward leaning might occur with stretching of the fascia in addition to these tissues.
