Quadriceps muscle properties in rheumatoid arthritis: insights about muscle morphology, activation and functional capacity

Abstract

Background Rheumatoid arthritis (RA) is an inflammatory and chronic autoimmune disease that leads to muscle mass loss and functional capacity impairment, potentiated by physical inactivity. Despite evidences demonstrate neuromuscular impairments in RA patients, aging effects may have masked the results of similar previous studies. The aim of study was to verify (i) the effects of RA on functional capacity and muscle properties in middle-aged patients and (ii) the association between age, clinical characteristics, quadriceps muscle properties and functional capacity. Methods Thirty-five RA women and 35 healthy age-matched women were compared with the following outcomes: (i) physical activity level through the International Physical Activity Questionnaire (IPAQ); (ii) timed-up and go (TUG) test; (iii) isometric knee extensor muscular strength; and (iv) vastus lateralis muscle activation and muscle architecture (muscle thickness, pennation angle and fascicle length) during an isometric test. An independent Student t-test and partial correlation (controlled by physical activity levels) were performed, with p < 0.05. Results Compared with healthy women, RA presented (i) lower physical activity level (− 29.4%; p < 0.001); (ii) lower isometric knee extensor strength (− 20.5%; p < 0.001); (iii) lower TUG performance (− 21.7%; p < 0.001); (iv) smaller muscle thickness (− 23.3%; p < 0.001) and pennation angle (− 14.1%; p = 0.011). No differences were observed in muscle activation and fascicle length. Finally, the correlation demonstrated that, with exception of TUG, muscle strength and muscle morphology were not associated with age in RA, differently from healthy participants. Conclusion Middle-aged RA patients’ impairments occurred due to the disease independently of the aging process, except for functional capacity. Physical inactivity may have potentiated these losses.

Morphological Parameters in Quadriceps Muscle Were Associated with Clinical Features and Muscle Strength of Women with Rheumatoid Arthritis: A Cross-Sectional Study

“…Our findings of mean VL muscle thickness and VL pennation angle were higher. However, RA patients of the Blum et al (2020) study [34] had moderate mean disease activity, while our RA patients had low disease activity. In fact, our VL muscle thickness findings (1.61 ± 0.43 cm) were lower than those from the healthy group in this same study [34].…”

“…There are limited data on muscle morphology assessment by ultrasound in RA patients. Blum et al (2020) [34] recently found mean muscle thickness and pennation angle in patients with RA of 1.37 ± 0.34 cm and 8.65 ± 2.36 • , respectively. Our findings of mean VL muscle thickness and VL pennation angle were higher.…”

“…If all images collected for a given location did not meet established technical standards that location was considered "absent", and the patient was excluded from the analysis. For the assessment of the muscle thickness, the distance between deep and superficial aponeuroses was considered, and it was calculated through the mean value of three parallel lines drawn at right angles between the superficial and deep aponeuroses along each ultrasonography image [34]. In addition, the fascicle with the best visualization of each image was used for pennation angle analysis.…”

“…In addition, the fascicle with the best visualization of each image was used for pennation angle analysis. Pennation angle was calculated as the angle between the muscle fascicle and the deep aponeurosis [34] (Figure 1A-C).…”

“…The angle of pennation is defined as the angle between the insertion of the muscle fascicle and the deep aponeurosis [31,32], and is related to the muscle's capacity to generate force [33]. More recently, Blum et al (2020) also demonstrated that RA patients showed smaller muscle thickness (−23.3%) and pennation angle (−14.1%), which is the angulations of muscle fibers relative to the line of action of muscle in pennate muscles, compared with healthy women [34].…”