A preliminary study on the relationship between grip force and muscle thickness

In this study, we propose a novel method to explore the relationship between grip force and forearm muscle thickness during isometric contraction. One-directional ultrasound was used to detect the depth of muscle-bone interface. By tracking the movement of this interface, the change of muscle thickness can be calculated. A dynamometer was used to measure force. Three able-bodied subjects were asked to gradually increase grasping force from 0% to 40% maximum voluntary contraction (MVC) and decrease grasping force from 40% to 0% MVC following the guiding patterns on the screen, 4 channels of one-directional ultrasound signals on the forearm were recorded in the meanwhile. The relationship between extensor digitorum muscle and grip force was analyzed and the results showed that the relationship between this muscle and grip force can be represented with two exponential functions, with averaged R2 value of 0.982. And the existence of hysteresis in the muscle thickness-force relationship is discovered. These relationships have potential importance on grip force estimation.