Validity and reliability of strain gauge measurement of volitional quadriceps force in patients with COPD

Fernanda Machado Rodrigues, Heleen Deyemer, Miek Hornikx, Carlos Augusto Camillo, Ebru Calik-Kutukcu, Chris Burtin, Wim Janssens, Thierry Troosters, Christian Osadnik

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This study investigated the validity and reliability of fixed strain gauge measurements of isometric quadriceps force in patients with chronic obstructive pulmonary disease (COPD). A total cohort of 138 patients with COPD were assessed. To determine validity, maximal volitional quadriceps force was evaluated during isometric maximal voluntary contraction (MVC) manoeuvre via a fixed strain gauge dynamometer and compared to (a) potentiated non-volitional quadriceps force obtained via magnetic stimulation of the femoral nerve (twitch (Tw); n = 92) and (b) volitional computerized dynamometry (Biodex; n = 46) and analysed via correlation coefficients. Test-retest and absolute reliability were determined via calculations of intra-class correlation coefficients (ICCs), smallest real differences (SRDs) and standard errors of measurement (SEMs). For this, MVC recordings in each device were performed across two test sessions separated by a period of 7 days (n = 46). Strain gauge measures of MVC demonstrated very large correlation with Tw and Biodex results (r = 0.86 and 0.88, respectively, both p < 0.0001). ICC, SEM and SRD were numerically comparable between strain gauge and Biodex devices (ICC = 0.96 vs. 0.93; SEM = 8.50 vs. 10.54 N·m and SRD = 23.59 vs. 29.22 N·m, respectively). The results support that strain gauge measures of quadriceps force are valid and reliable in patients with COPD.

Original languageEnglish
Pages (from-to)289-297
Number of pages9
JournalChronic Respiratory Disease
Issue number3
Publication statusPublished - 1 Aug 2017


  • assessment
  • chronic obstructive pulmonary disease
  • Isometric force measurement
  • muscle testing
  • rehabilitation

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