title: Muscle redundancy does not imply robustness to muscle dysfunction.
abstract: It is well-known that muscle redundancy grants the CNS numerous options to perform a task. Does muscle redundancy, however, allow sufficient robustness to compensate for loss or dysfunction of even a single muscle? Are all muscles equally redundant? We combined experimental and computational approaches to establish the limits of motor robustness for static force production. In computer-controlled cadaveric index fingers, we find that only a small subset (<5%) of feasible forces is robust to loss of any one muscle. Importantly, the loss of certain muscles compromises force production significantly more than others. Further computational modeling of a multi-joint, multi-muscle leg demonstrates that this severe lack of robustness generalizes to whole limbs. These results provide a biomechanical basis to begin to explain why redundant motor systems can be vulnerable to even mild neuromuscular pathology.
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA.
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Kutch
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Valero-Cuevas
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D002490:Central Nervous System / Q000473:pathology; D004594:Electrophysiology; D005385:Fingers / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology* / Q000502:physiology*; D012984:Software; D013710:Tendons / Q000473:pathology