Upper limb muscle forces during a simple reach-to-grasp movement: a comparative study.

Muscle force knowledge during reaching is an important research field and tools development for measuring those forces is a challenging task, especially for clinical routines. The purpose of this study was, during a simple reach-to-grasp movement, to compare forces estimation from a Hill-type model and from the EMG-to-Force Processing (EFP) method. Ten healthy male volunteers were tested. Surface EMG signals were recorded from deltoid scapular, deltoid clavicular, triceps brachii, and biceps brachii. Ten repeated measures of right upper limb kinematics had been recorded. Three reaching distances were tested: 20, 30, and 40 cm. Muscle activations were calculated and forces were estimated by the two methods. Correlations and low RMS error found between the two methods indicate that EFP is a good way to estimate muscle forces for this kind of movement. This knowledge is essential in order to integrate these forces in reaching models developed nowadays in robotic, rehabilitation, and ergonomics field of research.