You’ve stopped training for a few months, you’ve lost stamina, maybe even some muscle mass, and now the idea of starting again makes you feel like you have to start from scratch. Yet, your body may remember much more than you imagine. Some research shows that muscle cells retain biological traces of previous workouts, even when the most visible benefits of exercise begin to wane.
The so-called cellular memory of training could help the body recover some adaptations when returning to physical activity. And the interesting part is that this ability could also concern the liver, a fundamental organ for managing energy during exercise.
Also studying these mechanisms is a group of researchers from the University of Illinois Urbana-Champaign, who are trying to understand how cells retain traces of physical activity and what happens when, after a break, they are stressed again.
Muscles retain a memory of training
We are used to considering the results of physical exercise as something that requires continuous maintenance. We stop running and the resistance decreases. We stop strength training and, as time passes, some of the muscle mass gained begins to reduce.
The body, however, appears to retain some information even when these changes become evident. A study published in Scientific Reports has identified a form of epigenetic memory linked to training in human muscle. In essence, physical activity can leave changes in the way some genes are regulated, without directly altering the DNA sequence.
These changes can persist during a period of inactivity and influence the response to subsequent training. It’s a bit as if the muscle stored some instructions already used, ready to be recalled when you go back to work. Another research published onAmerican Journal of Physiology-Cell Physiology followed 20 healthy adults who underwent two months of high-intensity training, three months off and a subsequent recovery period.
Analyzes of muscle biopsies showed that some exercise-associated molecular changes were still present after three months without training. Part of the traces left by physical activity, therefore, had resisted suspension. The research helps to understand why the return to exercise can follow different dynamics compared to the first approach to training, even if the speed of recovery depends on numerous individual factors.
The liver also participates in exercise memory
When we run, lift weights or cycle, our muscles expend energy. To sustain that effort they need a continuous supply, and the liver does an important part of this job.
Research published in Molecular Metabolism has explored the relationship between training, liver and energy metabolism, identifying mechanisms that could help maintain the effects of previous periods of physical activity. The researchers focused their attention on a family of enzymes called carboxylesterases, involved in the transformation of lipids and the availability of fats that can be used as an energy source.
The activity of these enzymes appears to be affected by exercise. In the human component of the study, after six weeks of training, researchers observed changes in their blood activity, with differences also linked to previous physical fitness. These findings suggest that training history may help modulate how the body manages energy. An interesting mechanism also for understanding the relationship between physical exercise, blood sugar control and fat metabolism.
Cells can remember much more than we thought
For a long time we have associated memory almost exclusively with the brain, where neurons store and process information through their connections. The immune system in turn has a memory, which allows it to more quickly recognize some pathogens it has already encountered. Research in recent years is showing that other types of cells can also retain traces of previous biological experiences.
A study published in Nature showed, for example, that some skin stem cells can maintain a memory of inflammation, promoting a faster response to subsequent injury. Another research published in the same journal has identified a memory of obesity in adipose cells that can persist even after significant weight loss. A phenomenon that could help explain the tendency to regain lost weight.
Cellular memory of training fits into this line of studies: cells can modify their functioning in response to stimuli and retain some of these modifications over time. Researchers are now trying to understand how long this information can remain available, what mechanisms allow it to be preserved and how it can be reactivated.
What happens when we start training again after a break
The prospect is particularly interesting for those who have to stop physical activity due to an injury, illness, pregnancy or simply due to a particularly demanding period of work. Stopping training can cause a decrease in cardiovascular capacity, strength and some metabolic adaptations. The times depend on the type of exercise, the duration of the interruption and individual conditions.
Yet, some of the changes built with exercise can survive longer than the physical performance we are used to measuring. This could also become useful in the study of rehabilitation programs and physical activity aimed at people who have difficulty exercising regularly.
For now, scientists are trying to understand how long this biological memory lasts and whether it is possible to exploit it to promote recovery after prolonged periods of inactivity. In the meantime, those who return to the gym after a few months can at least treat themselves to some good news: the resistance will have to be rebuilt, the muscles will have to start working again, but part of the work done in the past could still be written in the cells.
