James A. Ashton-Miller and Ronald F. Zernicke
Steven J. Obst, Lee Barber, Ashton Miller and Rod S. Barrett
This study investigated reliability of freehand three-dimensional ultrasound (3DUS) measurement of in vivo human Achilles tendon (AT) moment arm. Sixteen healthy adults were scanned on 2 separate occasions by a single investigator. 3DUS scans were performed over the free AT, medial malleolus, and lateral malleolus with the ankle passively positioned in maximal dorsiflexion, mid dorsiflexion, neutral, mid plantar flexion and maximal plantar flexion. 3D reconstructions of the AT, medial malleolus, and lateral malleolus were created from manual segmentation of the ultrasound images and used to geometrically determine the AT moment arm using both a straight (straight ATMA) and curved (curved ATMA) tendon line-of-action. Both methods were reliable within- and between-session (intra-class correlation coefficients > 0.92; coefficient of variation < 2.5 %) and revealed that AT moment arm increased by ∼ 7 mm from maximal dorsiflexion (∼ 41mm) to maximal plantar flexion (∼ 48 mm). Failing to account for tendon curvature led to a small overestimation (< 2 mm) of AT moment arm that was most pronounced in ankle plantar flexion, but was less than the minimal detectable change of the method and could be disregarded.
Ronald F. Zernicke, Grant C. Goulet, Peter R. Cavanagh, Benno M. Nigg, James A. Ashton-Miller, Heather A. McKay and Ton van den Bogert
As a field, biomechanics comprises research from the molecular and cellular levels, to tissues, to organs, to organisms and their movements. In the past 50 years, the impact of biomechanics research on society has been amplified dramatically. Here, we provide five brief summaries of exemplar biomechanics results that have had substantial impact on health and our society, namely 1) spaceflight and microgravitational effects on musculoskeletal health; 2) impact forces, soft tissue vibrations, and skeletal muscle tuning affecting human locomotion; 3) childbirth mechanics, injuries, and pelvic floor dysfunction; 4) prescriptive physical activity in childhood to enhance skeletal growth and development to prevent osteoporotic fractures in adulthood and aging; and 5) creative innovations in technology that have transformed the visual arts and entertainment.