Estimation of hand preshaping during human grasping

EMG-based decoding of grasp gestures in reaching-to-grasping motions

“…It was shown that the hand's pre-shaping occurs from 60% to 80% of the reach-to-grasp motion, which corresponds to the time instant when the distance between the thumb and the index reached its maximum [21,33]. Our analysis with normalized time suggested that hand's preshape occurs after the 30% with respect to the completion time of the task.…”

“…In natural self-paced motion the hand spontaneously opens and closes while being in the reaching phase [21][22][23]16]. The preshape of the hand is defined as the formation of the fingers before they take the final configuration, and it takes place during the reaching cycle [33]. More particularly, the fingers extend to a maximum before they start closing (continuously flex) around the object with respect to its characteristics.…”

“…In this work, we employed two criteria to identify the occurrence of the hand preshaping [21,33]. The first criterion was based on the distance between the fingertips of the thumb and the index finger, which are considered the fingers participating in most of the grasp types.…”

“…Thus, the area criterion could be more informative of the motion of the fingers, as it encapsulates the behavior of all the fingers involved in the grasp [33]. In order to examine the general trends of the motion of the fingers, we computed the two criteria in normalized time and present the results in Fig.…”

Evaluation of Human Prehension Using Grasp Quality Measures

“…For the five fingers of the human hand, it can be extended using the method proposed by [18]. The contact plane is generated by selecting three fingers.…”