From uterine mechanics to motor control: a personal perspective on biomechanics across scales

This paper offers a personal perspective on a lifetime of research in biomechanics, organized around the mechanical principles that connect muscle, joint, tissue, limb, and whole-body function. The narrative begins with uterine biomechanics during labor, where in-vivo strain measurements and shell modeling were used to examine contraction patterns, deformation, pacemaker activity, and the transition from near-isotropic to anisotropic behavior. It then turns to joint mechanics, including hip incongruity, acetabular contact pressure, implant fixation, knee arthroplasty, and the gliding index, followed by studies of rehabilitation biomechanics at the Loewenstein Rehabilitation Center. These sections examine gait recovery, stepping and jumping, postural control, bilateral force-platform measurements, and mathematical modeling of body sway across neurological, orthopedic and amputee populations. Subsequent sections address articular cartilage mechanics and cartilage tissue engineering, surgical modifications of the musculoskeletal system, impact loading and fatigue in running, mechanical impedance as a task-dependent expression of motor control, and Functional Electrical Stimulation (FES) for rehabilitation. The FES work includes muscle recruitment, fatigue monitoring using ³¹P magnetic resonance spectroscopy, fatigue modeling, EMG-based monitoring, hybrid activation and bioelectric field modeling. The final sections consider bone quality, osteoporosis, metastatic weakening, vertebral fragility, and biomechanical indeterminacy. Across these topics, the central theme is that biomechanics is most powerful when experiment, modeling, and clinical observation are integrated. The concluding section reflects on how indeterminacy, redundancy, adaptation, and structure-function relations unify seemingly diverse problems in biomechanics.