title: Effects of botulinum toxin type A on non-injected bi-articular muscle include a narrower length range of force exertion and increased passive force.
abstract: BACKGROUND
  The goal of this study was to test the hypothesis that botulinum toxin type A (BTX-A) injection in rat tibialis anterior (TA) muscle affects the mechanics of its bi-articular synergist, both actively and passively.
  
  
  METHODS
  Two groups of Wistar rats were tested: control (no BTX-A) and BTX (0.1 U of BTX-A) animals were injected exclusively to the mid-belly of TA. Extensor digitorum longus (EDL) muscle isometric forces were measured after proximal and distal lengthening.
  
  
  RESULTS
  Five days after injection, BTX-A administration changed EDL mechanics: (1) active forces decreased (proximal muscle length dependently); (2) length range of active force exertion decreased both proximally and distally; and (3) passive muscle forces increased.
  
  
  CONCLUSIONS
  Effects of BTX-A appear to not be limited to decreased active muscle tone, but may cause also a narrower active range of movement and increased passive resistance. Through spread of BTX-A to a bi-articular muscle, such effects are plausible for both joints spanned.
authors.affiliation: Biomedical Engineering Institute, Boğaziçi University, Çengelköy Istanbul, 34684, Turkey.
authors.forename: Filiz
authors.initials: F
authors.lastname: Ateş
authors.forename: Can A
authors.initials: CA
authors.lastname: Yucesoy
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects / Q000528:radiation effects; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000494:pharmacology*; D007273:Injections, Intramuscular; D007537:Isometric Contraction / Q000187:drug effects* / Q000502:physiology; D008297:Male; D023421:Models, Animal; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D005082:Physical Exertion / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019274:Botulinum Toxins, Type A
keywords: bi-articular muscle; botulinum toxin type A; muscle force length; passive force; range of force exertion; rat extensor digitorum longus muscle; spread of BTX-A