The Thumb-Forefinger Grip and the Shape of Handles of Certain Instruments: An Electromyographic Study of the Muscle-Load

An electromyographic investigation of the contribution of muscle interosseus dorsalis I in some thumb—forefingor grips has been made. Objects with different shapes, which were held in a thumb-forefinger grip, were prossed against a power-plate. The investigation showed that the more powerful the pressure, the greater was the activity in the muscle. When applying the same pressure the activity increased with decrease in the diameter of the tool. When applying the same pressure with objects of the same diameter, that is when the distance between the finger tips was the same, the muscle activity became greater the smaller the contact area was.