The left hand is the dominant working hand in sawing, the right hand acting more to direct the saw during the operation. The vibration level in the hands is directly proportional to the cube root of the grip force. The vibration level is about twice as high in the right hand than in the left but the grip force is greater in the left hand, which increases the transmission of the vibration into the left hand. Thus there are factors enough to cause the symptoms of CTS in both hands.
The ulnar nerve is anatomically more superficial, unsheltered by muscles, and has more stretch during sawing than the median nerve. Therefore, it is also liable to damage in forestry work. In the present study exposure to vibration correlated significantly with motor NCV in the ulnar nerve of the left hand. Seppalainen has also observed decreased conduction velocities in the ulnar nerve in men with exposure to vibration.