title: Endurance training of trunk extensor muscles.
abstract: OBJECTIVE
  The purpose of this study was to assess the effects of an endurance exercise protocol on the isometric holding time of the trunk extensor muscles (mechanical fatigue measure) and on the recorded median frequency (MF) measurements from the surface electromyogram (physiological fatigue measure).
  
  
  METHODS
  Twenty-eight healthy female volunteers were selected to participate in the study.
  
  
  METHODS
  The subjects were stratified by activity level and then assigned to an exercise or a control group and tested at weeks 0, 3, and 6. Reliability (r) of the measurements, established by testing each subject twice at week 0, was .87. Exercise group subjects trained at home twice daily for 6 weeks, progressing by established protocol.
  
  
  RESULTS
  The exercise group subjects increased their isometric holding time by 22% after 6 weeks. The control group showed no significant changes.
  
  
  CONCLUSIONS
  The home program was believed to be effective for increasing isometric endurance of the trunk extensors, measured by holding time. The MF measurements prior to and just after a fatiguing contraction remained stable over time. The change in the slope of the MF with fatigue did not reach statistical significance. This physiologic measure of fatigue did not show commensurate changes with training in this group of subjects. Possible reasons for the results are discussed.
authors.affiliation: Department of Physical Therapy, University of Vermont, Burlington 05401.
authors.forename: M T
authors.initials: MT
authors.lastname: Moffroid
authors.forename: L D
authors.initials: LD
authors.lastname: Haugh
authors.forename: A J
authors.initials: AJ
authors.lastname: Haig
authors.forename: S M
authors.initials: SM
authors.lastname: Henry
authors.forename: M H
authors.initials: MH
authors.lastname: Pope
mesh_terms: D000328:Adult; D000886:Anthropometry; D001415:Back; D004576:Electromyography; D015444:Exercise; D005221:Fatigue / Q000503:physiopathology; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008905:Minicomputers; D010807:Physical Endurance; D012815:Signal Processing, Computer-Assisted