To our knowledge, this study is the first to assess exercise’s effect on people with JIA based on high-quality RCTs. We pooled the results of five randomized controlled trials involving 306 individuals for this study to comprehensively assess the effect of exercise on quality of life and exercise capacity in JIA. Interestingly, our findings suggest that exercise did not significantly improve the exercise capacity, health, and quality of life of people with JIA compared to controls. However, exercise significantly improved pain in JIA. According to the GRADE method, the quality of the outcome evidence was very low (very low to moderate), and the results should be interpreted with caution.

Two quality-of-life scales were pooled for this study, including the QoL and PedsQL. The PedsQL is a health-related QoL (HRQoL) scale for rheumatic diseases designed to assess health-related quality of life in children and adolescents with rheumatic diseases such as juvenile idiopathic arthritis, systemic lupus erythematosus, and juvenile-type fibromyalgia, high reliability and validity [32, 33]. Our pooled analysis of QoL and HRQoL revealed that exercise could improve the quality of life in JIA, consistent with the literature [21]. JIA often presents with unique signs and symptoms such as altered body joint structure, limited range of motion in joints, drowsiness, and fatigue [1, 5]. Lack of exercise and disease-related disability have certain psychosocial implications, which may lead to changes in QoL and HRQoL in JIA [34, 35]. However, exercise can change the body composition of people with JIA, with a decrease in fat mass and an increase in bone and lean mass [36], leading to healthy body composition in people with JIA. Exercise also increases self-esteem and self-efficacy and improves sleep quality, thereby increasing QoL in people with JIA [37]. QoL and HRQoL are important factors associated with personal well-being, and the management of JIA should focus on the potential benefits of exercise. Although there was a trend for exercise to improve quality of life in JIA, the results were not statistically significant, suggesting that the results may change with the inclusion of new studies. Given the limited evidence, it is essential to conduct more high-quality RCTs in the future to confirm the effect of exercise on the quality of life in JIA.

The Child Health Assessment Questionnaire is used to score a child’s disability on a scale from 0 to 3, with higher scores representing more severe disability [38]. One of the main findings of the study was the assessment of CHAQ, and our results suggest that exercise improves the health status of people with JIA. However, contrary to a previous study, the difference was not statistically significant [20]. Given the limitations of previous research, we place greater confidence in the results of our study. It is now understood that exercise can improve the state of the body in several ways, such as by reducing adiposity, developing the muscular and cardiovascular systems, and improving bone density, balance, and coordination [39,40,41]. However, exercise did not significantly change the health status of JIA patients. It is noteworthy that exercise also did not significantly worsen the health status of JIA patients.

Four outcome indicators, VO2peak, 6mwt, EPM, and HRmax, were used to assess exercise capacity in JIA patients, with VO2peak, 6mwt, and HRmax showing similar trends and exercise improving these indicators in JIA patients. Interestingly, the magnitude of the benefits of exercise on these indicators was different, with similar benefits for VO2peak (SMD: 0.21; 95% CI: -0.10, 0.52) and 6mwt (MD: 0.29; 95% CI: -0.05, 0.62) and the most significant benefit for HRmax (SMD: 0.77; 95% CI: -0.26, 1.80). VO2peak has been widely used as an indicator to assess cardiac health [42]. Usually, the VO2peak increases with age and maturity [43], and our study demonstrated that exercise significantly increases the benefits of this process through effective heart stimulation in JIA patients. Theoretical indications suggest that improvements in HRmax and VO2peak would contribute to an increase in 6mwt, a commonly used measure of exercise capacity. Interestingly, our results indicated that the association between HRmax and 6mwt may be weaker compared to the association between VO2peak and 6mwt. However, contrary to expectations, exercise did not lead to a significant improvement in the Exercise Performance Measure (EMP) (SMD: -0.26; 95% CI: -0.62, 0.09) and even showed a negative trend. Exercise is known to improve joint range of motion by building muscle strength and increasing ligament flexibility [44, 45], and our results contradict conventional knowledge. This discrepancy might be discouraging, but it is essential to consider that exercise could improve specific motor abilities in JIA while potentially having different effects on the overall progression of the condition. Unlike rheumatoid arthritis (RA), exercise improves the ability of joints, such as the joints of the hands, to perform movement 46]. This may be because RA affects not only the joints but also other parts of the body, including the eyes, the skin, the heart, the lungs, the nerves, and the bloodstream 47]. The effect of exercise is superimposed on the various parts of the body, which in turn exhibits an amplification of the effect. In addition, the studies included in our analysis did not show any worsening of JIA, and due to limited original research and the variety of exercise types, we could not characterize the relationship between exercise and JIA progression.

The significant outcome of the study was the improvement in pain among JIA patients, validating the positive effect of exercise in this population, consistent with the literature [20], which provides the theoretical basis for promoting exercise to this patient population. First, it is well known that physical exercise reduces functional pain by acting on the central mechanisms of pain perception and produces pressure changes at the stress site, which can cause changes in pain perception [48]. Some studies have found that seriously injured soldiers in combat are virtually pain-free, and dancers and athletes who continue to perform strenuous exercise in the face of serious injury feel no pain [49, 50]. Second, an increase in pain threshold and tolerance and a decrease in pain rating occur after exercise [51]. A person’s pain threshold increased immediately after 40 min of running, and cycling continuously for 8 min between 200 and 250 W loads significantly increased the threshold for dental pain [52, 53]. Additional studies have found that exercise alters mechanisms related to the release of adrenocorticotropic hormone and growth hormone, thereby improving symptoms of the disorder and reducing pain [54, 55]. However, these possible mechanisms are not specific to JIA and are equally applicable to various chronic diseases. Moreover, we resolved the previous conflicting results regarding the impact of exercise on pain [21]. Notably, Tarakci’s study [31] had a higher number of participants drop out, which may affect the credibility of the results. However, adopting the appropriate exercise is undoubtedly associated with a reduction in disease-induced pain [56]. In the present study, all RCTs included in this meta-analysis had an exercise intervention period of more than twelve weeks. Accordingly, future studies are needed to confirm the effect of short-term exercise on JIA.

This study has several important clinical implications for the management of JIA. First, this study found that although long-term exercise intervention did not significantly improve the overall quality of life and overall health of adolescents with JIA, long-term exercise did not lead to worsening health status in adolescents. This suggests that long-term exercise is safe for JIA. Second, long-term exercise intervention decreases pain levels in patients with JIA, and clinical practitioners should consider prescribing and encouraging exercise interventions for patients with JIA, alongside medication management, taking into account individual circumstances. In summary, regular physiotherapy is essential to JIA management to promote muscle and bone health, optimize body function, and slow disease progression. In the future, it may be necessary to incorporate the natural increase in the exercise capacity of JIA patients themselves, enriching the form of exercise while increasing the intensity to counteract the adverse features of JIA. We also recommend that exercise be an integral part of JIA and other standard care for arthritis.

This study possesses several strengths. First, as of May 1, 2023, we included all high-quality RCTs that met strict inclusion and exclusion criteria. Second, we comprehensively included multifaceted outcome indicators, enabling a thorough analysis of the impact of exercise on JIA across multiple levels. Finally, we systematically assessed the quality of evidence for relevant outcomes using the GRADE methodology and provided a strength of recommendation. These strengths enhance the study’s rigor, completeness, and high reference value.

In addition, there were several limitations to the study. The most significant one was the small number of RCT trials available. Despite conducting a comprehensive and systematic database search, only 16 controlled trials related to JIA were identified. Out of these, only five trials met the criteria for inclusion due to issues such as the control group being the intervention itself or the intervention group being mixed with other measures, as well as poor experimental design. The limited number of RCTs hindered a more in-depth analysis, and we could not perform regression and subgroup analyses, which could have provided a better understanding of the heterogeneity in the results. Due to the limitations of the included articles, we were unable to assess publication bias using methods such as funnel plots. Lastly, due to limitations in the primary literature, we may not be able to pool other endpoints, such as biomechanical measures for adolescents. This may affect the comprehensiveness of the results.