Muscles attach to bones via tendons that stretch and recoil, affecting muscle force generation and metabolic energy consumption. In this study, we investigated the effect of tendon compliance on the metabolic cost of running using a full-body musculoskeletal model with a detailed model of muscle energetics. We performed muscle-driven simulations of running at 2–5 m/s with tendon force-strain curves that produced between 1 and 10% strain when the muscles were developing maximum isometric force. We computed the average metabolic power consumed by each muscle when running at each speed and with each tendon compliance. Average whole-body metabolic power consumption increased as running speed increased, regardless of tendon compliance, and was lowest at each speed when tendon strain reached 2–3% as muscles were developing maximum isometric force. When running at 2 m/s, the soleus muscle consumed less metabolic power at high tendon compliance because the strain of the tendon allowed the muscle fibers to operate nearly isometrically during stance. In contrast, the medial and lateral gastrocnemii consumed less metabolic power at low tendon compliance because less compliant tendons allowed the muscle fibers to operate closer to their optimal lengths during stance. The software and simulations used in this study are freely available at simtk.org and enable examination of muscle energetics with unprecedented detail.
Software and data to reproduce publication results
We investigated the effect of tendon compliance on the metabolic cost of running using a full-body musculoskeletal model with a detailed model of muscle energetics. We performed muscle-driven simulations of running at several speeds and tendon compliances, and computed the average metabolic power consumed by each muscle. We used modeling and simulation to gain insight into the energy consumed by individual muscles throughout the gait cycle. We compared trends observed in muscle activations, metabolic power, and fiber mechanical power over a broad range of tendon compliances and at four running speeds.
Experimental data and simulation results underlying the results of this study, Matlab scripts that assemble the relevant simulation results and generate the figures appearing in the manuscript, OpenSim plug-ins for using the muscle energetics model in OpenSim 3.2, and OpenSim GUI scripts for adding metabolic probes to existing OpenSim models and changing the compliance of all tendons in a model.See all Downloads