All exercise is beneficial but for cell health, train longer

Endurance exercise improves metabolic health and prevents many age-related chronic diseases, but researchers have not been clear on why.

A new study suggests that the explanation may lie in specific cellular changes that give a 50-year-old a similar ageing profile to a 25-year-old.

Endurance exercise fires up the engines of the body and prevents the accumulation of harmful cells. Credit: Getty

The research, published in Nature journal NPJ Aging, was sparked by a chance conversation between colleagues.

Longevity expert Professor Luigi Fontana was working at Washington University in St. Louis at the time, studying the effect of calorie restriction on cell senescence, which is the process where cells stop dividing but do not die. Instead, senescent cells secrete pro-cancer and pro-inflammatory proteins. As we age, we accumulate more of these cells, a process which is hastened by smoking, exposure to pollution, UV damage, alcohol, excessive calorie intake, and decreased physical activity.

He was discussing his research with a colleague, Marco Demaria, who is one of the world’s leading experts in cell senescence. They decided to collaborate and, in 2018, found that eating less is associated with a reduced accumulation of these cells.

Demaria was particularly interested in the control group of Fontana’s research: middle-aged men who did not calorie restrict but were lean because they regularly engaged in endurance exercise.

He asked Fontana if he could look at some of the samples he had collected – including colon mucous biopsies – to see what effect endurance exercise had on senescent cells.

So, for the study, they examined the biopsies of 11 lean master athletes aged between 47 and 67, who ran about 77 kilometres a week. They compared their biopsies to a control group of 11 non-obese sedentary men of the same age and a group of young, lean men in their 20s who were sedentary but otherwise healthy.

They found that markers of cell senescence were much higher in the middle-aged men than in young sedentary men, but this increase was “significantly blunted” in the middle-aged, age-matched endurance runners. In fact, among the 50- and 60-year-old runners, the levels of cell senescence markers were similar to the group in their 20s.

Longer runs and rides can lead you to a more youthful self. Credit: Getty

“This study shows that, apart from the usual powerful metabolic effects of exercise such as improved insulin sensitivity, glucose metabolism, blood pressure, lipid profile and [brain-derived neurotrophic factor] BDNF, this is a more molecular effect,” explains Fontana, who is now the Scientific Director of the Charles Perkins Centre RPA Clinic at the University of Sydney.

“So for the first time we show that endurance exercise, at a molecular level, is preventing the accumulation of senescent cells that are secreting pro-inflammatory cytokines [proteins] and pro-cancer molecules.”

Keefe Chan, a senior researcher investigating cell senescence at the Peter MacCallum Cancer Centre, says: “One possible anti-ageing strategy is to target the key hallmarks of ageing and so the thought of high-intensity endurance exercises in humans [to do that] is pretty new.”

While he notes the researchers only looked at one marker of cell senescence, it was skewed towards men. Though he would like to see a larger sample size, the findings are encouraging.

“This is adding to that saying that high-intensity exercise throughout the duration of your life will add to the benefits of ageing in a healthy fashion,” he says, adding that starting at any point in life will still delay the further accumulation of these cells.

The researchers didn’t study why exercise has this effect, but suggest it may be the result of lowering insulin and increasing DNA and antioxidant repair pathways, and more autophagy (our body’s process of clearing old and damaged cells).

As for the type of exercise, resistance training is excellent for building muscle, among its many other benefits, but it is not as powerful for improving insulin sensitivity.

“When you do regular endurance exercise, you markedly increase GLUT4 in your skeletal muscle fibres. GLUT4 is a glucose transporter that is essential to improve insulin sensitivity and glucose tolerance, therefore lowering the risk of developing type 2 diabetes,” says Fontana, who cycles for an hour at least three days a week, swims in the ocean and lifts weights at home.

But more endurance is not more, at least when it comes to the cellular ageing effects. One British study from last year suggested running regular marathons could age men by a decade.

Excessive endurance training over years can “overwhelm the system”, Fontana explains. Running for three hours a day or cycling for five hours a day regularly leads to a sustained activation of the sympathetic nervous system (stress response) which can ultimately have a detrimental effect on the heart and the ageing process, he says.

Not so damaging as other factors, however. Separate research published in The Journals of Gerontology last week found among the top factors that accelerate epigenetic ageing were smoking, followed by alcohol intake; increased waist size; excess body fat; inflammation; high triglycerides; childhood obesity; and type 2 diabetes.

On the flipside, quality diet and not eating too much are among the factors that slow ageing, Fontana says. The findings of Fontana’s new study are preliminary and the sample size was small but suggest in more ways than one: “Exercise is an extremely important component of this healthy ageing puzzle.”

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