The hands are essential for our ability to complete tasks. Quantifying the many forces acting on the entire hand is important to improve our understanding of hand function and hand-related musculoskeletal disorders. Biomechanical models of the hand used to compute internal tissue loads typically simplify the applied forces into a single point of force applied at the centre of mass of the distal phalanx. Accounting for the distributed loads across the hands and fingers is a needed step in understanding the loads acting on and inside the body. Therefore, the purpose of this thesis was to use a pressure mapping system to examine the effects of distributed loads on net joint moments and muscle activations in the hands during common tasks. Twenty-three right-handed participants completed a series of finger presses, power grips, and pinch tasks. A pressure mapping system measured pressure on 17 regions of the hand. Three- dimensional hand kinematics was collected using a 72-marker setup. Forces were also measured with a six degrees of freedom force transducer to ensure participants matched specified exertion levels. Pressure distribution, kinematics, and kinetics were used to calculate internal net joint moments at the fingers (distal phalangeal flexion, proximal phalangeal flexion, metacarpal flexion, metacarpal abduction) and muscle activations for 22 forearm and hand muscles using an OpenSim model. External loads were represented in three manners: (1) Centre of Mass Model (COM) distributed the forces over segments that contributed to the force production and placed loads at the centre of mass; (2) Centre of Pressure Model (COP) distributed the forces over segments that contributed to the force production and placed loads at the centre of pressure; (3) Single Point Model (SP) placed a single load at the distal phalanx or the centre of mass of the hand. Results of equivalence tests indicate differences in all net joint moments between COM-SP and COP-SP comparisons. There were no differences between COM and COP. COM and COP moments during all tasks were larger in digits with a larger percentage of total force compared to SP. Due to the larger moments in those conditions, COM and COP calculated larger muscle activities compared to SP. Both internal net joint moments and muscle activations were most affected by the pressure distribution and hand posture. Overall, these findings indicate that representing external forces using distributed loads provide increased fidelity of forces at the hand and fingers. Distributed loads provide more information on internal loads of the hand and digits, and in turn, quantify individual differences that can lead to injury in occupational settings. / Thesis / Master of Science in Kinesiology
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29394 |
| Date | January 2023 |
| Creators | Chhiba, Ryan |
| Contributors | Keir, Peter, Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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