Relationship between physical and psychosocial status and irisin level in individuals with knee osteoarthritis performing brisk walking exercise

Objective: The aims to investigate the effect of brisk walking exercise on irisin level and physical and psychosocial parameters such as pain, muscle strength, functional capacity, sleep quality, depression, fatigue, quality of life and the relationship between irisin level and these parameters in individuals with knee osteoarthritis. Method: Individuals between the ages of 40-65 diagnosed with knee osteoarthritis were included in the study. Participants were randomly divided into control (n=20) and intervention groups (n=20). Both groups received a home exercise program including progressive strengthening exercises for 8 weeks, and the intervention group additionally performed brisk walking exercise. Participants' knee pain was assessed with the 'Visual Analog Scale', joint range of motion with the 'goniometer', muscle strength with the 'Manual Muscle Strength Measuring Device', functional capacity with the '6-Minute Walk Test', depression severity with the 'Beck Depression Inventory-II', sleep quality with the 'Pittsburgh Sleep Quality Index' and fatigue level with the 'Fatigue Severity Scale'. In addition, the Knee Injury and Osteoarthritis Outcome Score and the Osteoarthritis Knee and Hip Quality Of Life Scale were used to assess participants' symptoms, functional status and quality of life. Serum irisin levels were measured using an ELISA kit. All evaluations were made before and after the exercise program and blood samples were taken from the participants to determine the irisin level. Results: As a result of our study, it was determined that the serum irisin levels of the participants in the intervention group decreased significantly after the 8-week exercise program (p=0.012) and this decrease was found to be statistically significant compared to the control group (p=0.039). In within-group comparisons of other parameters, both groups showed statistically significant improvements after the exercise program in pain level, range of motion, quadriceps muscle strength, functional capacity, depression severity, sleep quality, fatigue level, all subdimensions of the Knee Injury and Osteoarthritis Outcome Score, physical activity, mental health, and pain subdimensions of the Knee and Hip Osteoarthritis Quality of Life Scale (all p<0.05). However, a statistically significant decrease in body mass index (p=0.009) and a statistically significant improvement in the social support subdimension of the Knee and Hip Osteoarthritis Quality of Life Scale were detected only in the intervention group (p=0.013). In the between-group comparison after the exercise period, no statistically significant difference was found in other parameters except for the irisin level. Furthermore, no statistically significant correlation was found between the irisin level and any of the physical and psychosocial parameters after the 8-week brisk walking exercise program. Conclusion: This study demonstrated that a regular brisk walking program led to a reduction in irisin levels in individuals with knee osteoarthritis. Although the brisk walking program had various positive effects on physical and psychosocial parameters, it did not result in additional improvements compared to the control group. Furthermore, no significant relationship was observed between irisin levels and physical or psychosocial parameters among patients who regularly engaged in brisk walking. Further research is warranted to assess how different exercise programs (planned with consideration of type, duration, and intensity) affect irisin levels and how these effects translate into clinical outcomes in individuals with osteoarthritis.