title: Method to Reduce Muscle Fatigue During Transcutaneous Neuromuscular Electrical Stimulation in Major Knee and Ankle Muscle Groups.
abstract: BACKGROUND
  A critical limitation with transcutaneous neuromuscular electrical stimulation as a rehabilitative approach is the rapid onset of muscle fatigue during repeated contractions. We have developed a method called spatially distributed sequential stimulation (SDSS) to reduce muscle fatigue by distributing the center of electrical field over a wide area within a single stimulation site, using an array of surface electrodes.
  
  
  OBJECTIVE
  To extend the previous findings and to prove feasibility of the method by exploring the fatigue-reducing ability of SDSS for lower limb muscle groups in the able-bodied population, as well as in individuals with spinal cord injury (SCI).
  
  
  METHODS
  SDSS was delivered through 4 active electrodes applied to the knee extensors and flexors, plantarflexors, and dorsiflexors, sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. Isometric ankle torque was measured during fatiguing stimulations using SDSS and conventional single active electrode stimulation lasting 2 minutes.
  
  
  RESULTS
  We demonstrated greater fatigue-reducing ability of SDSS compared with the conventional protocol, as revealed by larger values of fatigue index and/or torque peak mean in all muscles except knee flexors of able-bodied individuals, and in all muscles tested in individuals with SCI.
  
  
  CONCLUSIONS
  Our study has revealed improvements in fatigue tolerance during transcutaneous neuromuscular electrical stimulation using SDSS, a stimulation strategy that alternates activation of subcompartments of muscles. The SDSS protocol can provide greater stimulation times with less decrement in mechanical output compared with the conventional protocol.
authors.affiliation: University of California, Los Angeles, CA, USA.
authors.forename: Dimitry G
authors.initials: DG
authors.lastname: Sayenko
authors.affiliation: Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Nguyen
authors.affiliation: Toronto Rehabilitation Institute-University Health Network, Toronto, Ontario, Canada.
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Hirabayashi
authors.affiliation: Toronto Rehabilitation Institute-University Health Network, Toronto, Ontario, Canada University of Toronto, Toronto, Ontario, Canada.
authors.forename: Milos R
authors.initials: MR
authors.lastname: Popovic
authors.affiliation: Toronto Rehabilitation Institute-University Health Network, Toronto, Ontario, Canada University of Toronto, Toronto, Ontario, Canada k.masani@utoronto.ca.
authors.forename: Kei
authors.initials: K
authors.lastname: Masani
mesh_terms: D000328:Adult; D000368:Aged; D000842:Ankle; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007717:Knee; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000534:rehabilitation*; D004561:Transcutaneous Electric Nerve Stimulation / Q000009:adverse effects / Q000379:methods*; D055815:Young Adult
keywords: muscle fatigue; spinal cord injury; transcutaneous neuromuscular electrical stimulation