Summary of muscle parameters for Hill-based muscle modeling in the human lower limb

A summary is presented of five mechanical parameters from human lower limb skeletal muscles critical for Hill-based muscle modeling: the optimal fiber length, the fiber pennation angle, the physiological cross-sectional area (PCSA), the unloaded tendon length, and the fast-twitch fiber fraction. The data presented are drawn from a total of 29 publications including human cadaver studies, in vivo imaging studies of live humans, musculoskeletal modeling studies, and combinations of these methods. Where possible, parameter values were adjusted from the referenced data to present them with consistent definitions (normalization of measured fiber lengths to optimal sarcomere length, and calculation of PCSA as the ratio of fiber volume to fiber length). It is seen that within a specific muscle, optimal fiber lengths are fairly consistent between studies, pennation angles and PCSAs vary widely between studies, and data for unloaded tendon length are comparatively sparse. Few studies have reported fiber type fractions for a large number of muscles. Guidelines for implementing these parameter values in muscle modeling and musculoskeletal modeling are suggested.\n\nUpdate HistoryO_LIDecember 2, 2016: original submission\nC_LIO_LIDecember 3, 2016: discussion on maximum isometric force and specific tension added\nC_LIO_LIDecember 6, 2016: minor edits for typos, clarity, and missing references\nC_LIO_LIDecember 7, 2016: Tirrell et al. (2012) study added\nC_LI