The Effects of a 28-Hz Vibration on Arm Muscle Activity during Isometric Exercise

MISCHI, M., and M. CARDINALE, The Effects of it 29-Hz Vibration oil Arm Muscle Activity during Isometric Exercise. Med. Sci. Spot-is Exerc., Vol. 41, No. 3, pp. 645-652, 2009. Purpose: The aim of this study was to evaluate activation and coactivation of biceps and triceps muscles (hiring isometric exercise performed with and Without Superimposing it vibration stimulation. Methods: Twelve healthy volunteers (age = 22.7 + 2.6 yr) participated in this study. The subjects performed five trials of isometric elbow flexion and five trials of elbow extension with increasing levels of force in two conditions: vibration (V) and normal loading (C). V stimulation was characterized by it frequency of 28 Hz. Surface EMG activity of biceps and triceps muscles was simultaneously measured by bipolar surface electromyography and assessed by the estimation of the root mean square (RMS) of the electrical recordings over a fixed 5-s interval. Frequency analysis was adopted to estimate the RMS related to muscle activation and to exclude the harmonics generated by movement artifacts due to V. Results: The analysis of the recordings revealed a significant EMG(RMS) increase when V was applied. On average, the EMG(RMS) Of biceps and triceps during elbow flexion was, respectively, 26.1% (P < 0.05) and 19.2% (P < 0.15) higher than C. During elbow extension, the EMG(RMS) of biceps and triceps was 77.2% and 45.2% (P < 0.05) higher than C, respectively. The coactivation was assessed as the ratio between the activation of antagonist and agonist muscles during arm flexion and extension tasks. The results revealed an increase of coactivation during V exercise, especially for lighter loads. Conclusion: This study shows that V exercise at 28 Hz produces an increase of the activation and the coactivation of biceps and triceps. This exercise modality seems therefore suitable for various applications.