Background Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease of unknown etiology, affecting not only the joints but also other tissues such as skeletal muscle [1]. Muscle loss is a secondary manifestation that impairs the function and quality of life of patients with RA [1]. Physical exercise is associated with reduced morbidity and other beneficial effects inseveral diseases [2, 3].

Objectives To evaluate the effect of aerobic exercise on muscle loss of animals with collagen-induced arthritis (CIA).

Methods CIA was inducedin male mice DBA/1J asdescribed by Brand, 2010 [4]. The animals were divided into two CIA groups: (i) animals with exercise (protocol: walking for 30 min, from 9 to 15 m.min^-1, three times a week for 4 weeks after the onset of the disease), (ii) animals without exercise. Clinical score and paw swelling were assessed daily during all the experimental period. The weight of the animals and spontaneous exploratory locomotion were evaluated weekly. After death, the myofiber area of the tibialis anterior and gastrocnemius muscles were evaluated as well as ankle joint histopathology. For statistical analysis, t-test were performed and statistical significance was considered for p values p<.05.

Results No significant difference was observed in clinical parameters of disease activity (clinical score, paw swelling and animal weight) and spontaneous locomotion in the walking group compared with the group without exercise. Although not significant, exercise slightly decreased joint inflammation (1.6 ± 0.17 and 1.9 ± 0.20 arbitrary value, p=.16) and bone erosion (1.3 ± 0.26 and 1.8 ± 0.23 arbitrary value, p=.12), besides that, cartilage erosion were significantly reduced in exercised joint (1.3 ± 0.26 and 1.8 ± 0.23 arbitrary value, p<.05). However, there was significant difference in the myofiber sectional area: exercised CIA showed greater myofiber cross-sectional area compared to the group without exercise (598 ± 58 μm² and 481 ± 63 μm², respectively, p<.05), representing a difference of 24%.

Conclusions This is the first intervention study with forced walk in the experimental model CIA. According to results, aerobic exercise applied from the first clinical signs showed benefit over cartilage erosion and muscle atrophy in an experimental model of arthritis, observed mainly by the reduction of myofiber area, but does not seem to impact in the process of arthritis.

1. McInnes IB, Schett G. New England Journal of Medicine 2011, 365(23).

2. Navarro F et al. Cell Biochemistry and Function 2010, 28(4):266-273.

3. Nader GA, Lundberg IE. Current Opinion in Rheumatology 2009, 21(6):599-603.

4. Brand DD et al. Nature Protocols 2007, 2(5):1269-1275.

Disclosure of Interest None Declared