Biomechanical Comparison of the Validity of Two Configurations of Simulators for Body-Powered Hand Prostheses

Simulators are often used in prosthesis research to evaluate new devices or characterize aspects of prosthesis use, so as to recruit participants without amputations. Simulators, in general, must locate the prosthesis somewhere other than where the intact biological limb exists. In this study, we compared two configurations of simulators for hand prostheses to determine which leads to more natural elbow and shoulder kinematics, and in turn, which is the more valid simulator. One configuration located the prosthesis in-line with the forearm, beyond the biological hand; the other located it beside the hand. We measured the kinematics of 12 non-amputee participants during three clinical tests of hand-arm dexterity, which were completed 1) using each simulator configuration with a body-powered Hosmer 5X hand prosthesis and 2) using the biological hand with a wrist brace. The beside-the-hand configuration resulted in kinematics that were more similar to those measured with the biological hand, particularly during the Box and Blocks Test, which involved the largest range of arm motion of those studied. Therefore, we concluded that simulators with the beside-the-hand configuration are likely to better emulate the use of hand prostheses for activities involving a wide variety of arm movement. We suggest using this configuration in general, except when arm movement is of secondary importance and when this configuration would be obstructive, visually or otherwise

Optimization of Motor Performance

According to the OPTIMAL (Optimizing Performance Through Intrinsic Motivation and Attention of Learning) theory of motor learning, enhanced expectancies (EE), autonomy support (AS), and external focus (EF) augment the coupling of a person’s actions to intended movement goals. This goal-action coupling is postulated to boost a person’s focus on goal-related aspects of the motor task while reducing the person’s self-related thoughts, resulting in enhanced performance of skilled movements as well as in improving the acquisition outcomes for the learning of motor skills. The three studies in this compilation report were aimed at providing empirical evidence for the motor performance benefits of the combinatory implementation of the three key motivational (i.e., EE and AS) and attentional (i.e., EF) factors of the OPTIMAL theory. In addition, a preliminary investigation of the neuromechanistic influence of such an implementation on the human motor system was carried out. Using a between-participants design, the first study employed a maximal-effort countermovement jump task to examine the additive effects of the consecutive (or serial) implementation of EE, AS, and EF on motor performance. Results indicated that optimized group participants produced greater relative jump heights than control group participants. The second study used a within-participants design involving a clinical-applied balance test to determine the immediate effects of implementing EE, AS, and EF simultaneously (in parallel) on motor performance. The results showed that participants experienced greater postural stability in terms of making fewer balance errors and producing lower center-of-pressure velocity in the optimized condition than the control condition. Finally, a simple visuomotor task involving the rhythmic production of force via isometric finger abduction was used in the third study with a between-participants design. The neurophysiological and behavioral effects of a simultaneous implementation of EE, AS, and EF in relation to motor performance were examined using a novel TMS-force experimental protocol. The corticospinal excitability of all participants remained stable throughout the experiment. Additionally, the force-accuracy performance of participants in the optimized group was similar to that of participants in the control group