title: Quadriceps strength assessed by magnetic stimulation of the femoral nerve in normal subjects.
abstract: Magnetic stimulation of the femoral nerve is a new technique for assessment of quadriceps strength by measurement of twitch tension (TwQ), a test that is independent of subject motivation. In this study, we sought to establish better define normal values by measurement of TwQ in 45 normal subjects. Supramaximal stimulation, as judged by TwQ, was achieved in 43 of 45 subjects at a mean of 90% of maximum stimulator output. The mean TwQ was 7.3 kilograms force (kgf) (SD 2.3) for women and 9.8 kgf (SD 2.5) for men. The mean maximal voluntary contraction (MVC) force was 48.0 kgf (SD 9.2) for women and 70.1 kgf (15.2) for men. The mean TwQ/MVC ratio was 0.15 for both women and men. Significant correlations were observed between TwQ and weight (r = 0.33, P<0.03) and height (r = 0.32, P<0.03) but these were weak and only partially explained observed variance. Our data confirm that magnetic femoral nerve stimulation is generally acceptable to naive subjects. Values are provided as a function of weight in normal subjects.
authors.affiliation: Department of Respiratory Medicine and Allergology, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden. chh@lungall.gu.se
authors.forename: Carl-Hugo
authors.initials: CH
authors.lastname: Hamnegård
authors.forename: Margareta
authors.initials: M
authors.lastname: Sedler
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: Björn
authors.initials: B
authors.lastname: Bake
mesh_terms: D000328:Adult; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D005267:Femoral Nerve / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D010808:Physical Examination / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity