112 Acute effect of vibration stimulus around shoulders on sensorimotor control. (3rd March 2020) - Morikawa, Masanori
Abstract : Background: Recent researches showed that vibration stimulus around shoulders temporally increased muscle activity and strength of shoulders at almost same vibration frequencies (30Hz or 35Hz). However, there was no study to investigate whether vibration stimulus around shoulders improves the sensorimotor control, which can be assessed with static and dynamic stability test, at different vibration frequency. Objective: To investigate the effect of vibration stimulus on the sensorimotor control around shoulders and the effective frequency of vibration stimulus. Design: Case-crossover study. Setting: Research laboratory. Patients (or Participants): Ten healthy collegiate men without orthopedic disease. Interventions (or assessment of risk factors): Participants placed both hands on a vibration platform with partial weight bearing in push-up position during a vibration protocol. Vibration protocol included 6 sets and rest for 30 seconds at 0Hz (control), 30Hz, and 50Hz frequencies. Main outcome measurements: 1) The center of pressure (COP) velocity during 30 seconds in the push-up position with their hands on the force platform as static stability test and 2) Upper Quarter Y Balance Test (UQYBT) composite score as dynamic stability test were collected before and after intervention. Results: For COP velocity, two-way repeated measures ANOVA showed a significant main effect for the time (pre vs post) (p<0.05). Paired t-test as post hoc analysis showed COP velocity was significantly faster from pre to post only at 0Hz (9.74±0.97 mm/s vs 10.12±0.98 mm/s, p<0.05), meant to become instable. In the UQYBT, there were significant main and interaction effects for the time and vibration frequency (p<0.05). Bonferroni test showed the amount of change for composite scores were significantly greater in 30Hz (5.28±3.53% vs -1.00±3.36%, p<0.01) and 50Hz (4.27±3.68% vs -1.00±3.36%, p<0.05) than 0Hz and not significant between 30Hz and 50Hz. Conclusions: The vibration stimulus maintained static stability and improved dynamic stability test for the shoulder. There was no effect in these tests between vibration frequencies.