Reliability of Quadriceps Femoris Muscle Strength Assessment Using a Portable Dynamometer and Protocol Tolerance in Patients With Chronic Obstructive Pulmonary Disease.

OBJECTIVE This study aimed to evaluate the intrarater and interrater reliability of isometric quadriceps femoris strength (IQS) using a portable dynamometer in patients with chronic obstructive pulmonary disease (COPD) and to verify their tolerance to the protocol. METHODS A cross-sectional reliability study was conducted with 50 patients with stable COPD (34 men and 16 women; mean age = 69 7 [SD = 8]). The main outcome measure was obtained using a portable dynamometer (Microfet 2®) to assess IQS. Two blind raters performed 2 assessments in the dominant lower limb in 2 nonconsecutive days. The intraclass correlation coefficient (ICC) was used to verify the intrarater and interrater reliability, and it was considered excellent when ICC > 0.90, with a 5% significance level. RESULTS Rater 1 and 2 intrarater reliability was as follows: ICC = 0.96 (95% CI = 0.94 to 0.98) and ICC = 0.97 (95% CI = 0.95 to 0.98), respectively. The interrater reliability was as follows: ICC = 0.96 (95% CI 0.93 to 0.98). The minimum detectable difference (MDD) was 4 to 5 kgF, in mean, for intrarater and interrater reliability. Not all patients presented relevant changes in physiological responses, dyspnea and lower limb fatigue. CONCLUSION There was an excellent intrarater and interrater reliability for IQS, and the patients tolerated the protocol. IMPACT This tool can be used to assess quadriceps strength in clinical practice in patients with COPD.