The Effects of Radius Bone Density on the Resting Myoelectrical Activity of Contralateral Wrist Flexors in Subjects Exposed to Unilateral Forearm Vibration

Abstract

Objective: To investigate whether bone mineral density or bone mineral content of the ultradistal radius has any effect on the resting muscle activity of contralateral wrist flexor muscles during unilateral forearm vibration. Material and Methods: Ninety healthy adult volunteers (33 women, 57 men) were included in this study. The mean age of participants was 34.2 (20-52) years. The right forearm was exposed to vibration for 1 minute. The frequency of vibration was 46 Hz. The resting myoelectrical activities of the right and left wrist flexor muscles were simultaneously measured by surface electromyography before, during and after vibration. The right ultradistal radius bone mineral density and bone mineral content were measured by dual-energy X-ray absorbtiometry. Results: The resting myoelectrical activity of the left wrist flexor muscles significantly increased during vibration (from 2.0 +/- 0.8 microvolts to 4.5 +/- 2.2 microvolts, p=0.0001). It decreased to 1.8 +/- 0.9 microvolts after vibration (p=0.0001). Multiple linear regression analysis revealed that the right ultradistal radius bone mineral density was an independent predictor of the resting myoelectrical activity of the left wrist flexor muscles measured during vibration. However, age, gender, body mass index, the right ultradistal radius bone mineral content and, the right and left wrist flexor muscles' resting myoelectrical activity measured before vibration were not predictors (R2=0.772, F=301.8, p = 0.0001). Conclusion: It is suggested that the ultradistal radius bone may affect the resting myoelectrical activities in the contralateral wrist flexor muscles, based on its bone mineral density during unilateral forearm vibration.