title: Differences in pedal forces during recumbent cycling in adolescents with and without cerebral palsy.
abstract: BACKGROUND
  We showed that subjects with cerebral palsy had greater transverse and frontal plane hip and knee motion, increased duration of muscle activity, increased cocontraction, and decreased efficiency during recumbent cycling than subjects with typical development. However, it is also important to understand the forces exerted on the pedals. The purpose of this report was to compare pedal forces during cycling between adolescents with and without cerebral palsy.
  
  
  METHODS
  Ten subjects (3 male, 7 female) with spastic diplegic or quadriplegic cerebral palsy (15.6 years, SD 1.8) and 10 subjects (3 male, 7 female) with typical development (14.9 years, SD 1.4) cycled on a stationary recumbent cycle at 30 and 60 revolutions per minute if able. Three-dimensional piezoelectric force transducers measured pedal forces. Data were analyzed using two-way ANOVAs.
  
  
  RESULTS
  Subjects with cerebral palsy spent a smaller percentage (P<.001, r2=.09, power=1.0) of the revolution applying positive force (pushing into the pedal during the extension phase) and a greater percentage (P<.001, r2=.09, power=1.0) of the revolution applying negative force (pulling away from the pedal during the flexion phase). There was no effect of cadence and no interaction effect.
  
  
  CONCLUSIONS
  These findings compliment our earlier findings of altered joint kinematics and muscle activity indicating that subjects with cerebral palsy and typical development have different cycling strategies. Methods to increase the duration of the positive force may allow subjects with CP to cycle more successfully and cycle vigorously enough to reach a heart rate necessary for improving fitness.
authors.affiliation: Shriners Hospitals for Children, 3551 North Broad Street, Philadelphia, PA 19140, USA. tjohnston@shrinenet.org
authors.forename: Therese E
authors.initials: TE
authors.lastname: Johnston
authors.forename: Laura A
authors.initials: LA
authors.lastname: Prosser
authors.forename: Samuel C K
authors.initials: SC
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001642:Bicycling / Q000502:physiology*; D001696:Biomechanical Phenomena; D002547:Cerebral Palsy / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology