A musculoskeletal model of wrist flexors comprising musculoskeletal dynamics and limb anatomy was experimentally validated with healthy subjects during maximum voluntary contractions. Electromyography signals recorded from flexors were used as input, while measured torques exerted by the hand were compared to the torques predicted by the model. The root mean square error and the normalized root mean square error calculated during estimation and validation phases were compared. In total, six subject-specific musculoskeletal parameters were estimated, while biomechanical indexes such as the operating range of the flexors, the stiffness of the wrist flexion musculotendon actuators, and the contribution of the muscle fibers to the joint moment were computed. Results are in agreement with previously published data.