title: Muscle force production and functional performance in spastic cerebral palsy: relationship of cocontraction.
abstract: OBJECTIVE
  To determine cocontraction's relation to strength and motor function in children with spastic cerebral palsy (CP).
  
  
  METHODS
  Prospective evaluation with a convenience sample of 10 subjects.
  
  
  METHODS
  Pediatric rehabilitation center at a tertiary care hospital.
  
  
  METHODS
  Ten ambulatory children with spastic CP, mean age 5 to 14yrs.
  
  
  METHODS
  A single comprehensive assessment of hamstring and quadriceps muscle strength; gait analysis while monitoring electromyographic (EMG) activity in those muscles; administration of the Gross Motor Function Measure (GMFM); heart-rate monitoring during quiet rest versus gait to compute an energy expenditure index (EEI). Cocontraction ratios and magnitudes were determined for the gait and strength testing trials using the EMG data.
  
  
  RESULTS
  Cocontraction ratios during strength tests correlated directly with those during free gait. Cocontraction magnitude and total EMG magnitude had an inverse relationship to EEI; children with more muscle activity in the agonist and antagonist tended to be more energy efficient. Knee extensor muscle strength correlated positively with the GMFM and gait velocity. Neither cocontraction ratio nor magnitude during gait was related to strength.
  
  
  CONCLUSIONS
  Children with CP used a similar muscle activation strategy across two different motor tasks. Strength and cocontraction were uniquely related to different aspects of motor function. Further research is needed to quantify more precisely cocontraction and force to EMG relations in this population.
authors.affiliation: Department of Orthopaedics, University of Virginia Health System, Charlottesville, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Damiano
authors.forename: T L
authors.initials: TL
authors.lastname: Martellotta
authors.forename: D J
authors.initials: DJ
authors.lastname: Sullivan
authors.forename: K P
authors.initials: KP
authors.lastname: Granata
authors.forename: M F
authors.initials: MF
authors.lastname: Abel
mesh_terms: D000293:Adolescent; D002547:Cerebral Palsy / Q000503:physiopathology* / Q000534:rehabilitation; D002648:Child; D002675:Child, Preschool; D004576:Electromyography; D005684:Gait / Q000502:physiology; D006801:Humans; D009119:Muscle Contraction; D009128:Muscle Spasticity / Q000503:physiopathology; D011446:Prospective Studies; D013647:Task Performance and Analysis