Lack of exercise leads to significant and reversible loss of scale invariance in both aged and young mice

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 8; pp. 2320 - 2324
• Main Authors: Gu, Changgui, Coomans, Claudia P., Hu, Kun, Scheer, Frank A. J. L., Stanley, H. Eugene, Meijer, Johanna H.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.02.2015; National Acad Sciences
• Subjects: Aging - physiology; Animal behavior; Animals; Behavior, Animal; Biological Sciences; Circadian rhythm; elderly; Exercise; Fluctuations; Humans; lifestyle; Male; Mice; Mice, Inbred C57BL; Physical Conditioning, Animal; Physical Sciences; risk factors; Rodents; Time Factors; World Health Organization; behavioral activity; wheel running; aging; circadian rhythms; multiple timescales
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1424706112

Significance Healthy systems are characterized by scale invariance across multiple timescales. We investigated whether loss of scale invariance that occurs with aging and disease can be counteracted by exercise, in four age groups of mice. Surprisingly, we observed that lack of exercise was detrimental not only in old but also in young mice, raising the possibility of an unforeseen role of behavioral activity for health in aged and young subjects alike. Moreover, we show that scale invariance could be restored by high levels of exercise, even in old animals. The World Health Organization has pinpointed lack of exercise and a sedentary lifestyle as a major risk factor for various diseases. Our measures may guide health programs. In healthy humans and other animals, behavioral activity exhibits scale invariance over multiple timescales from minutes to 24 h, whereas in aging or diseased conditions, scale invariance is usually reduced significantly. Accordingly, scale invariance can be a potential marker for health. Given compelling indications that exercise is beneficial for mental and physical health, we tested to what extent a lack of exercise affects scale invariance in young and aged animals. We studied six or more mice in each of four age groups (0.5, 1, 1.5, and 2 y) and observed an age-related deterioration of scale invariance in activity fluctuations. We found that limiting the amount of exercise, by removing the running wheels, leads to loss of scale-invariant properties in all age groups. Remarkably, in both young and old animals a lack of exercise reduced the scale invariance in activity fluctuations to the same level. We next showed that scale invariance can be restored by returning the running wheels. Exercise during the active period also improved scale invariance during the resting period, suggesting that activity during the active phase may also be beneficial for the resting phase. Finally, our data showed that exercise had a stronger influence on scale invariance than the effect of age. The data suggest that exercise is beneficial as revealed by scale-invariant parameters and that, even in young animals, a lack of exercise leads to strong deterioration in these parameters.