title: Motor-neuron pool excitability of the lower leg muscles after acute lateral ankle sprain.
abstract: BACKGROUND
  Neuromuscular deficits in leg muscles that are associated with arthrogenic muscle inhibition have been reported in people with chronic ankle instability, yet whether these neuromuscular alterations are present in individuals with acute sprains is unknown.
  
  
  OBJECTIVE
  To compare the effect of acute lateral ankle sprain on the motor-neuron pool excitability (MNPE) of injured leg muscles with that of uninjured contralateral leg muscles and the leg muscles of healthy controls.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Ten individuals with acute ankle sprains (6 females, 4 males; age= 19.2 ± 3.8 years, height= 169.4 ± 8.5 cm, mass= 66.3 ± 11.6 kg) and 10 healthy individuals(6 females,4 males; age= 20.6 ± 4.0 years, height = 169.9 ± 10.6 cm, mass= 66.3 ± 10.2 kg) participated.
  
  
  METHODS
  The independent variables were group (acute ankle sprain, healthy) and limb (injured, uninjured). Separate dependent t tests were used to determine differences in MNPE between legs.
  
  
  METHODS
  The MNPE of the soleus, fibularis longus, and tibialis anterior was measured by the maximal Hoffmann reflex (H(max)) and maximal muscle response (M(max)) and was then normalized using the H(max):M(max) ratio.
  
  
  RESULTS
  The soleus MNPE in the ankle-sprain group was higher in the injured limb (H(max):M(max) = 0.63; 95% confidence interval [Cl],0.46, 0.80) than the uninjured limb (H(max):M(max) = 0.47; 95%Cl, 0.08, 0.93)(t(6) = 3.62,P =.01).In the acute ankle-sprain group, tibialis anterior MNPE tended to be lower in the injured ankle (H(max):M(max) =0.06; 95% Cl, 0.01, 0.10) than in the uninjured ankle (H(max):M(max) =0.22; 95%Cl, 0.09, 0.35),but this finding was not different (t(9) =-2.01, P =.07). No differences were detected between injured (0.22; 95% Cl, 0.14, 0.29) and uninjured (0.25; 95%Cl, 0.12, 0.38) ankles for the fibularis longus in the ankle-sprain group (t(9) =-0.739, P =.48). We found no side-to-side differences in any muscle among the healthy group.
  
  
  CONCLUSIONS
  Facilitated MNPE was present in the involved soleus muscle of patients with acute ankle sprains, but no differences were found in the fibularis longus or tibialis anterior muscles.
authors.affiliation: Physical Therapy at Atlantic Coast Athletic Club, Charlottesville, VA, USA.
authors.forename: Lindsey W
authors.initials: LW
authors.lastname: Klykken
authors.forename: Brian G
authors.initials: BG
authors.lastname: Pietrosimone
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Ingersoll
authors.forename: Jay
authors.initials: J
authors.lastname: Hertel
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000842:Ankle / Q000503:physiopathology; D016512:Ankle Injuries / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007593:Joint Instability; D035002:Lower Extremity; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018908:Muscle Weakness; D018482:Muscle, Skeletal / Q000502:physiology*; D013180:Sprains and Strains / Q000503:physiopathology*; D055815:Young Adult