Abstract
The aims of this study were to compare physical activity (PA) behavior and physical fitness in patients with JIA who were diagnosed in the era of biologics with controls from the general population, and to examine if disease variables were associated with PA behavior and physical fitness. Further, to investigate the measurement properties of a submaximal treadmill test for use in both clinical practice and research settings.
The thesis has a comparative cross-sectional design, including a test-retest design to evaluate the reliability of the submaximal treadmill test. PA behavior was examined by objective and subjective measurements. Physical fitness was assessed with state-of-the-art methods. Additionally, the participants performed a submaximal treadmill test for the evaluation of criterion validity and reliability.
The overall PA levels were comparable between patients and controls, but patients had lower levels of vigorous PA. Patients participated in similar types and amounts of both organized and unorganized PA as controls. Both patients and controls reported enjoyment as the most important PA facilitator.
Patients and controls had comparable cardiorespiratory fitness and body composition, while patients had lower muscle strength and endurance and bone mineral density. The use of biologic medication was a correlate for higher overall PA levels and lower sedentary time. No other disease variables were identified as correlates for PA or physical fitness. Higher vigorous PA was a correlate for higher cardiorespiratory fitness and muscle strength in patients.
The submaximal treadmill test was valid and reliable for research purposes on group level in patients, but not optimal for estimation of VO2peak in individual patients.
Our findings are encouraging regarding PA behavior and physical fitness in patients with JIA. The results suggest that patients also should perform vigorous PA and bone- and muscle-strengthening activities at least three times per week according to PA recommendations for children in general, preferably through enjoyable activities.