Resistance exercise training increases the expression of irisin concomitant with improvement of muscle function in aging mice and humans

We investigated the effect of resistance training on irisin expression with improvement in muscle strength and function in aged mice and human. In the mice study, 19 months old male C57BL/6 mice were randomly assigned into two groups; control group and resistance exercise group. Ladder climbing exercise with tail weight was performed 3 days per week for 12 weeks. In the human study, participants (aged over 65 years) were randomly assigned into exercise group or control group. Elastic band exercise program consisted of 12 weeks of 1-h session 2 days per week. In the mice study, we found an increase of irisin in serum and soleus muscle as well as improvement in muscle strength (p = 0.02) and muscle quality (p = 0.03) without body composition change in training animals. In the human study, isokinetic leg strength and grip strength were improved in the exercise group compared to the control group without change of body composition. In addition, the level of circulating irisin level was increased. It had a positive correlation with grip strength (R = 0.526, p = 0.002) and leg strength (R = 0.414, p = 0.003) in the exercise group. Thus, resistant training might be an efficient intervention method to increase irisin levels and prevent age-related decline in muscle function.