title: Specificity of a back muscle exercise machine in healthy and low back pain subjects.
abstract: OBJECTIVE
  To determine whether dynamic back muscle endurance exercises in a semisitting position induce more fatigue in back muscles than that in hip extensors in healthy controls as well as in patients with nonspecific chronic low back pain.
  
  
  METHODS
  Sixteen healthy volunteers and 18 volunteers with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion at 60% of their strength in a machine designed for back exercise in a semisitting position with knees' angle at 135 degrees . The number of cycles and perceived muscle fatigue (Borg CR-10 scale) at five areas (upper and lower back, gluteus, hamstrings, and quadriceps) were used as fatigue criteria. EMG signals were recorded bilaterally on four back muscles, two hip extensors (gluteus maximus and biceps femoris), and the vastus medialis. The slope values of the instantaneous median frequency values computed over time were retained as EMG indices of fatigue.
  
  
  RESULTS
  The number of cycles was equivalent in healthy controls (n = 23 +/- 13) and patients with back pain (n = 27 +/- 16). EMG indices of fatigue disclosed evidence of muscle fatigue in all the back muscles and the vastus medialis, contrary to hip extensors. EMG revealed significantly more muscle fatigue of lower back muscles, which was further corroborated by the Borg scale assessment. No between-group difference was obtained in any EMG comparison.
  
  
  CONCLUSIONS
  These results showed that this type of exercise machine can specifically train the back muscles, and this as much in subjects with nonspecific chronic low back pain as in healthy controls. This has implications for the training of back muscle endurance, especially in patients with back pain for whom poor back muscle endurance is sometimes of concern.
authors: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada. lariviere.christian@irsst.qc.ca
authors: Christian
authors: C
authors: Larivière
authors: Rubens A
authors: RA
authors: DA Silva
authors: A Bertrand
authors: AB
authors: Arsenault
authors: Sylvie
authors: S
authors: Nadeau
authors: André
authors: A
authors: Plamondon
authors: Roger
authors: R
authors: Vadeboncoeur
mesh_terms: D000328:Adult; D004576:Electromyography; D004867:Equipment Design; D005080:Exercise Test; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal; D010807:Physical Endurance / Q000502:physiology; D011792:Quebec; D011795:Surveys and Questionnaires; D055815:Young Adult