Objective: A bi-directional interaction between muscle and bone functions may be assumed. However effects of muscle activity on bone structure and function have been investigated till today. Aim of this study was to determine whether bone mineral density (BMD) affected muscle strength gain.

Materials and Methods: Twenty three young-adult healthy males were included in this double-blind propective study. These volunteers were randomized into two groups. In EMS group, electrical muscle stimulation of the right wrist flexor muscles was applied; in healthy controls, transcutaneous electrical nerve stimulation was applied. Electrodes were placed over the flexor aspect of the right forearm in both groups. Electrical stimulation was applied for six weeks in both groups. Before trail, BMD of the rigth distal radius were measured in all participants.

Results: Isokinetic muscle torque measurements was revealed that increase in the wrist extensors strength was 67.2% in EMS group, and was 18.1% in controls (p=0.001). Strong correlation between baseline ultradistal radius BMD and muscle strength gain of the wrist extensors were found in EMS group. Regression analysis revealed that ultradistal radius BMD may be an important determinant of the muscle strength gain of the wrist extensors.

Conclusion: Current study suggests that bone can regulate muscle activity, based on its BMD. This result implies that there may exist a mechanism that bone sensing mechanical stimuli can send the signals to central nervous system and neuronally regulate muscle activity. It is well known that bone subjected to loading neuronally regulates bone formation. Taken together, a possible new mechanism, bone reflex, may be defined that bone subjected to loading can neuronally regulate bone formation and muscle activity.

Bone Muscle strength Exercise Electrical muscle stimulation Bone mineral density