Understanding neuromusculoskeletal interactions underlying biomechanics and control of the human hand

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Dexterous hand function is a defining feature of the human identity. The hand is vitally important in nearly all activities of daily living, from getting dressed in the morning to preparing dinner in the evening. The fully opposable thumb is especially crucial to hand function, enabling interaction with objects and tools via gripping or pinching. While the hand's versatility is a central theme in modern human ingenuity, its complex anatomy challenges our understanding of mechanical function and neuromuscular control. Successful performance of a hand-intensive task ultimately relies on the seamless interaction of neurophysiological (e.g. sensory and motor nerves) and biomechanical apparatus (e.g. muscles and tendons). However, there is an immense need to investigate how these systems interact with each other to preserve hand function, especially during complex occupational tasks that require online control of postures and grip forces. My research will use an innovative, inter-disciplinary approach to investigate hand biomechanics and neuromuscular control. This research will be organized in three themes: (1) Determining mechanical interactions; (2) Elucidating links between biomechanics and neurophysiology by experimentally manipulating sensorimotor pathways; (3) Developing a computer model capable of representing neuromusculoskeletal coupling within the hand.The first theme will investigate mechanical inter-relationships between musculoskeletal structures of the hand. Participants will perform occupationally relevant hand activities. Measurements will include grip forces using a force sensor, joint angles via motion capture, and muscle activity from fine-wire EMG, with a focus on load sharing between the extrinsic (large) and intrinsic (small) hand muscles. Additional studies will use electrical stimulation to elicit thumb muscle contractions. Ultrasound will assess concurrent changes in the size and shape of the carpal tunnel (wrist) as well as mechanical properties of the anatomical structures passing through the wrist. The second theme will focus on sensorimotor integration and adaptation when neurophysiological mechanisms are altered for a short time. Specifically, biomechanical hand function will be assessed before, during, and after a compressive force is applied to the wrist. Studies in this theme will also experimentally manipulate visual feedback to determine the integrated effects of sensory input on biomechanical function and neuromuscular control. The third theme will develop a computer model of the hand to combine data gathered from the first and second research themes. This innovative research will assess redundancies across biological systems, informing several important areas such as industrial engineering and ergonomics (e.g. tool design) to improve work performance and efficiency.