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

Abstract

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.

Inter-day test–retest reliability and feasibility of isokinetic, isometric, and isotonic measurements to assess quadriceps endurance in people with chronic obstructive pulmonary disease: A multicenter study

“…For example, the isometric protocol can be performed with a cheaper strain-gauge system or a fixed hand dynamometer. 5,27 Nevertheless, further research is needed to evaluate the protocols and measurements construct validity, strategies to reduce the systematic bias, and responsiveness to change.…”

“…4 Isometric (sustained) contractions have been recommended for measuring quadriceps strength. 3,5 Several protocols (including different measurements within isokinetic, isometric, and isotonic protocols) have been used to assess quadriceps endurance in the COPD population, 2 but there is still no consensus on which protocol and outcome measure that is preferable in this context. 3 Before the use of any protocol could become a reality in clinical practice several aspects, including but not limited to, the feasibility and reliability of measurement protocols needs to be determined.…”

Fatigue in Chronic Respiratory Diseases: Theoretical Framework and Implications For Real-Life Performance and Rehabilitation

“…One of the main advantage is the low cost of an isometric set-up (i.e., custom chair and strain gauge), as compared to computerized dynamometry (i.e., at least 10 times cheaper). Strain gauge measures of quadriceps force are valid and reliable, in both healthy and CRD populations (Bachasson et al, 2013b ; Machado Rodrigues et al, 2017 ). Isometric test have often been criticized on the basis that this muscular contraction regime is not the best reflect of daily activities of the patients.…”

Assessment of Peripheral Muscle Function in Cystic Fibrosis: Why and How?

“…Not only are commercially available or custom-built chairs with strain gauges (which allow isometric strength measurements) much cheaper than computerized dynamometry (usually ϳ$5,000 -$7,000), but strain gauge measures of quadriceps strength also show excellent validity (ie, vs computerized dynamometry) and are highly reliable (as much as are Biodex values 6 ) in both healthy individuals 7 and those individuals with chronic respiratory disorders. 6 Moreover, normative data are available when using standardized procedures. 8 Such chairs are also easily transportable and can be used to assess muscle function in other chronic respiratory conditions.…”