## 4 Discussion
### Muscle Contribution  
From the results, we observe certain associations between recorded areas/muscles and grasps. Broadly speaking, wrist extensors showed the highest activation levels across all grasps, while wrist flexors also exhibited significant activation, acting as synergistic muscles. Furthermore, when comparing both wrist extensors, the ECR presented higher muscle activity, which could highlight the predominance of a radial deviation during these grasps, probably to counteract the gravitational force exerted to keep the wrist in the grasping position. Finger flexors were highly activated during cylindrical and oblique-palmar grasps, but we also found high level of contraction of the finger extensors, indicating their role as synergistic muscles. Thumb muscles showed higher activation during grasps involving thumb opposition (cylindrical, pad-to-pad pinch and lumbrical grasps). It is worth noting that the main distinction between two-finger and three-finger pad-to-pad pinches was that, in the latter case, the thumb muscles exhibited values more similar to finger flexors. Spot 2 (FCR) showed the lowest muscle activity during the performed grasps. Nevertheless, it could play a crucial role in distinguishing between various power grasps. Although no spot showed significant differences between the oblique-palmar and intermediate power-precision grasps (Table 3), spot 1 and spot 2 displayed different behaviors between these grasps: spot 2 seemed to be more associated with the thumb muscles and finger extensors in the oblique-palmar grasp, while, in the intermediate power-precision grasp, it demonstrated different values, compared to other spots (Table 2). FCU (spot 1) played a key role in distinguishing between the intermediate power-precision grasp and the three-finger pad-to-pad pinch, as well as lumbrical grasp, while ECR (spot 6) was crucial in distinguishing between the lateral pinch and the two/three-finger pad-to-pad pinch, as well as the lumbrical grasp and the three-finger pad-to-pad pinch. The ECU (spot 7) and finger flexors (spot 3) were crucial in distinguishing between the cylindrical grasp and the oblique palmar grasp, and between the cylindrical and intermediate power-precision grasps, respectively. Table 5 summarizes the primary findings, regarding which muscles were most activated during each kind of grasp. FCU (spot 1), FDS, FDP, and FPL (spot 3) and ECU, BR, and PT (spot 7) presented the highest activity levels during the cylindrical, intermediate power-precision, and oblique-palmar grasps. This observation was in accordance with the existing literature [32], as FCU has been identified as responsible for stabilizing the wrist during activities such as slicing meat (intermediate power-precision grasp) and using a hammer (cylindrical and oblique-palmar grasps). The FDS, FDP, and FPL muscles are finger flexors [33] and these power grasps require flexion of metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints of the fingers, together with the thumb joints. The BR, PT, and ECR act as wrist extensors and radial deviators [34], appearing to function as wrist stabilizers during power grasps, acting as antagonists to the FCU (spot 1). FCR and PL (spot 2) were the muscles with the least muscle activity throughout all the grasps, with the highest value for the cylindrical grasp. According to the literature, FCR is more activated when simultaneously performing a movement of flexion and radial deviation of the wrist [32]. In this case, the grasps considered did not require the wrist exerting any flexion-radial torque, so no activation higher than 20% was observed. Lateral pinch exhibited low activity in all extrinsic muscles, likely due to the significant contribution of the thenar and intrinsic muscles, which account for up to 80% of the grasp force [35]. EDC (spot 5) and APL, EPL, and EPB (spot 4, thumb muscles) presented high activity values during all grasps, with the highest values during the power grasps.