title: Functional output improvement in FES cycling by means of forced smooth pedaling.
abstract: OBJECTIVE
  Investigation of the influence of forced smooth and normal (nonsmooth) pedaling on the functional output of outdoor functional neuromuscular electrical stimulation (FES)-propelled cycling of spinal cord-injured subjects.
  
  
  METHODS
  Twelve subjects with complete spinal cord injury (T4-T12) and limited previous FES training.
  
  
  METHODS
  Each subject participated in two separate outdoor sessions: once while pedaling a tricycle in a fixed gear, and a second time while free pedaling the same tricycle; both times with FES. Data on distance covered until exhaustion, cadence, and pedal forces were collected. Energy balance calculations led to evaluations of jerk loss and joint-related concentric/eccentric work.
  
  
  RESULTS
  First-trial and total session distances were 68 and 103% longer, respectively, in the forced smooth cycling session than in the free cycling session (P < 0.001). Significantly more additional crank work (accompanied by increased concentric work production) was generated in nonsteady cycling phases to overcome increased jerk losses during free than during fixed-gear pedaling. During fixed-gear pedaling, timing and joint location of muscle work generation were more similar to the cycling of able-bodied subjects than during freewheel pedaling, because most work was generated by knee extensors in the power phase during the former pedaling mode.
  
  
  CONCLUSIONS
  The superiority of forced smooth cycling to free cycling, as regards functional output distance, is based on less energy expenditure (less jerk loss and muscle tension) and on more efficient production of energy (more efficient timing and joint location of work production). Some energetic mechanisms that are advantageous for fixed-gear cycling act predominantly in unsteady phases; others work continuously during all phases of cycling.
authors.affiliation: Center for Sensorimotor Research, Department of Neurology, Ludwig-Maximillians University, Munich, Germany. jszecsi@nefo.med.uni-muenchen.de
authors.forename: Johann
authors.initials: J
authors.lastname: Szecsi
authors.forename: Phillip
authors.initials: P
authors.lastname: Krause
authors.forename: Siegbert
authors.initials: S
authors.lastname: Krafczyk
authors.forename: Thomas
authors.initials: T
authors.lastname: Brandt
authors.forename: Andreas
authors.initials: A
authors.lastname: Straube
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001696:Biomechanical Phenomena; D004599:Electric Stimulation Therapy; D005260:Female; D005858:Germany; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010264:Paraplegia; D010807:Physical Endurance; D013647:Task Performance and Analysis