The acute response of irisin to resistance and endurance exercise at both lower and higher intensities in healthy older adults.

Exercise-induced release of irisin may contribute to the beneficial effects of exercise on brain health. Previous studies in healthy adults have shown ~15 % increase in short-term post-exercise irisin concentrations. However, previous research investigating the exercise-induced release of irisin in older populations is scarce and findings are highly variable. The present study investigated the effects of exercise mode and intensity on short-term acute post-exercise irisin concentrations in older adults. Thirty-two healthy older adults (women n = 18, men n = 14, age 72 ± 5 years), completed a randomised cross over study of four single-bout exercise sessions on separate days, consisting of either: lower-intensity resistance exercise (Low-RE), higher-intensity resistance exercise (High-RE), lower-intensity endurance exercise (Low-EE) or higher-intensity endurance exercise (High-EE) as well as a seated rest control (RC). Serum irisin concentrations were measured at pre- and 0-, 30-, and 60-min post-exercise. Body composition, peak oxygen consumption and one repetition maximum were evaluated to inform individual exercise intensities. Irisin concentrations were increased immediately after High-RE, High-EE, and Low-EE and remained elevated after Low-EE at 30 min post-exercise. Irisin concentrations were greater after Low-EE than High-EE at 30-min post-exercise, and greater after High-RE than Low-RE at 60-min post-exercise. Healthy older adults exhibit a short-term acute peak irisin response to exercise (~17 %) comparable to that previously observed in younger populations (~15 %), highlighting the potential for exercise-induced benefits on brain health irrespective of age. Given that resistance and endurance exercises at different intensities elicit distinct responses, intensity, resistance volume, endurance session duration and mode must be considered when designing optimal exercise prescriptions for improved brain health.