Muscles Remember Inactivity at Molecular Level
New research reveals that muscles retain molecular memory of repeated inactivity, leaving lasting changes that explain why regaining strength after layoffs becomes more difficult with age. The findings underscore the importance of regular activity, especially for older adults or anyone recovering from illness, injury, or extended breaks from training.
- The study, published in *Advanced Science*, involved researchers from the Norwegian School of Sport Sciences who used a model of repeated lower-limb immobilization on young adults and aged rats to compare the effects of inactivity. - In young adults, a second period of inactivity resulted in a "protective" molecular response where oxidative and mitochondrial gene pathways were less disrupted, demonstrating resilience. - Conversely, in aged muscles, repeated inactivity created a "detrimental" memory, leading to greater muscle loss, an exaggerated suppression of genes related to aerobic metabolism, and the activation of DNA-damage pathways. - The molecular "memory" is believed to be epigenetic, where periods of inactivity leave lasting chemical marks on the DNA, such as hypermethylation, that regulate gene activity without altering the genetic code itself. - A co-author of the study, Professor Adam P. Sharples, noted that these findings are crucial for developing better recovery strategies after illness, injury, or age-related decline. - Previous research has shown that even short periods of disuse can have a significant impact; one study found that just five days of immobilization led to a 3.5% decrease in quadriceps muscle size and a 9% loss of strength in young men. - Future research, supported by the Novo Nordisk Foundation, will explore how different types and intensities of exercise can create a positive molecular memory to counteract the effects of inactivity, especially in older adults.
