Rafaela Cavalheiro do Espírito Santo

The effect of contraction type on muscle strength, work and fatigue in maximal isokinetic exercise

This study investigated knee extensor muscle strength, work and fatigue level under maximal isokinetic concentric and eccentric exercise. Seventeen male athletes were randomized into two groups and performed 10 sets of 10 maximal isokinetic concentric (N = 8) or eccentric (N = 9) contractions. Knee extensor peak torque and mean torque values per set were 54-121% and 53-133% higher in eccentric compared to concentric exercise, respectively, whereas the percent fall of performance in these variables was more accentuated in concentric exercise. Total work was significantly higher in eccentric exercise (19475 J) than concentric exercise (15758 J), while fatigue index was greater in concentric (36%) than eccentric (18%) exercise. In conclusion, maximal isokinetic eccentric exercise promotes larger overload to knee extensor muscles than its concentric counterpart due to higher torque produced by the muscle group and also thanks to minor muscle fatigue effects.

Collagen-induced arthritis as an animal model of rheumatoid cachexia: CIA as an animal model of RA

Rheumatoid arthritis is characterized by chronic polyarticular synovitis and presents systemic changes that impact quality of life, such as impaired muscle function, seen in up to 66% of the patients. This can progress to severely debilitating state known as rheumatoid cachexia—without loss of fat mass and body weight—for which there is little consensus in terms of diagnosis or treatment. This study aims to evaluate whether the collagen‐induced arthritis (CIA) animal model also develops clinical and functional features characteristic of rheumatoid cachexia.

Prevalence of rheumatoid cachexia in rheumatoid arthritis: a systematic review and meta-analysis: Systematic Review of RA cachexia prevalence

Low muscle mass occurs in patients with rheumatoid arthritis without weight loss; this condition is referred as rheumatoid cachexia. The aim of the current study was to perform a systematic review with meta‐analysis to determine the rheumatoid cachexia prevalence.

AB0135 Aerobic Exercise in Inclined Treadmill Reduce Fatigue in Collagen-Induced Arthritis

Background Rheumatoid arthritis (RA) patients suffer from joint pain and decreased physical capacity, like muscle wasting and fatigue. Fatigue is a clinical manifestation reported by 40-80% of patients with RA and is regarded as an important feature of the disease. Aerobic exercise may be beneficial for treating this feature in RA patients, however the mechanisms involved are still unclear. Objectives To evaluate the effect of aerobic exercise training on the endurance exercise performance in collagen-induced arthritis (CIA) mice. Methods Male DBA1/J mice with CIA [1] were randomly divided into 3 groups: wildtype with exercise (WT-EXE, n=4), CIA exercised (CIA-EXE, n=5) and CIA non-exercised (CIA, n=4). Endurance exercise performance test (fatigue) was analyzed in all groups prior to booster injection and each 15 days after protocol started. Eighteen days after the disease induction (booster), WT and CIA-EXE were submitted to training on an inclined treadmill (θ=5°), 45 minutes a day, 5 days per week for 6 weeks at 60% of their own endurance exercise performance. Variables analyzed were disease score, hindpaw nociception, body weight (g), fatigue (by endurance exercise performance in min) and relative muscle weight (muscle weight in mg divided by total animal weight in g). Data was analyzed with ANOVA Two-Way followed by Bonferroni and independent sample t-test and p<0.05 was considered significant. All data are represented as Mean ± SEM. Results Body weight was significantly higher in WT-EXE compared with CIA after 4 and 6 weeks of exercise. At week 6 of exercise, CIA-EXE had higher body weight than CIA. Fatigue test at 4 and 6 weeks of experiment was significantly different among all experimental groups; WT-EXE and CIA had, respectively, the highest and the lowest fatigue velocity. Gastrocnemius muscle weight was significantly heavier in control group than in CIA-EXE and CIA. Nociception and clinical score of arthritis did not differ between CIA-EXE and CIA. Conclusions Inclined aerobic exercise appears as an interesting intervention in RA to treat decreased physical capacity. Collagen-induced arthritis animals demonstrated decreased endurance, and consequently increased fatigue, characteristics of a good animal model to study fatigue. The exercise protocol used in this study was able to improve this feature, demonstrating that interventions used to treat physical disabilities in RA are also valid in this model. Further studies are necessary to clarify the mechanisms behind fatigue, especially when combining exercise training and common treatments of RA. References Rosloniec EF, et al. Curr Protoc Immunol 2010; Chapter 15: Unit 15.5.1-25. Acknowledgements Financial support: CAPES, CNPq, FAPERGS, FIPE-HCPA. Disclosure of Interest None declared

AB0117 Collagen-Induced Arthritis in Mice as a Model of Rheumatoid Cachexia

Background Rheumatoid arthritis (RA) extra-articular features frequently involved metabolism alterations which in a context are known as rheumatoid cachexia. Loss of lean muscle mass, reduction of grip strength and fatigue are the most common signs in RA. Loss of body weight and reduction in food intake are not usually part of human rheumatoid cachexia, but have been demonstrated before in animal models of arthritis. Recently, Evans et al1 published a definition for cachexia that seems to fulfil rheumatoid condition. Therefore a better elucidation of rheumatoid cachexia is needed and an animal model that mimics human condition may be useful. Objectives To explored the possibility of using collagen-induced arthritis in mice as an animal model of cachexia. Methods 8-12 weeks male DBA/1J mice were separated in two groups: control (CO) and collagen-induced arthritis (CIA). CIA animals were immunized by intradermal injection of bovine type II collagen with complete Freunds adjuvant followed by a booster. Immunization protocol and clinical signs (arthritis score and paw edema) evaluation occur as previous described by Brand et al 20072. Animals were followed by 65 days with evaluations made in day zero and at 18, 25, 35, 45, 55 and 65 days after immunization. Rheumatoid cachexia was evaluated by body weight change (%), food intake (g), fatigue (by endurance exercise performance in minutes), grip strength (g), locomotion (cm) and relative muscle weight (muscle weight in mg divided by total animal weight g). Statistical analysis includes repeated measures analysis of variance (ANOVA) for variables with variation between time and group and t-test for variables with variation only between groups. Difference was assumed when p value were lower than 0.05. Results Arthritis score and paw edema confirm disease in CIA group. Fatigue was higher in CIA group (lower time in endurance exercise) at the same time that grip strength and locomotion was lower (after 35 days until the end of the experiment). Relative gastrocnemius muscle weight was also lower in CIA group 3.9±0.57mg/g vs 5.0±0.61mg/g (CO). Body weight change and food intake were not statistical different within groups, however in days 25 and 35 CIA animals lost more weight than CO animals. Conclusions These data demonstrate firstly that CIA animals show metabolic extra articular events that mimics human pathophysiology arthritis. Even though there were no difference in body weight change and food intake it reinforces the similarity among CIA animal model and human RA once this variables have the same behavior in humans. Also considering the lack of studies involving rheumatoid cachexia and the obstacle that involve this study design in humans it is essential to have a solid animal model to evaluate prospectively mechanism of rheumatoid cachexia. References Evans WJ, et al. 2008. Cachexia: a new definition. Clinical Nutrition 27(6):793-9. Brand DD, Latham KA, Rosloniec EF. 2007. Collagen-induced arthritis. Nature protocols 2(5):1269-75. Disclosure of Interest None declared