New research into weight lifting has revealed two insights: that the practice is able to strengthen the connections between nerves and muscles, and that this strengthening can still happen in the later years of our lives.

We actually start losing muscle mass before the age of 40, caused in part by a reduction in muscle fibres that happens as motor neurons – cells in the brain and spinal cord that tell our bodies to move – break down.

This decline can't be stopped, but the new study shows that it can be slowed down significantly. According to the study's results, weight training makes the connections between nerves and muscles stronger, protecting the motor neurons in the spinal cord – essential for a well-functioning body.

"Previously, researchers have been unable to prove that weight training can strengthen the connection between the motor neurons and the muscles. Our study is the first to present findings suggesting that this is indeed the case," says exercise physiologist Casper Søndenbroe from the University of Copenhagen in Denmark.

This is partly because of the challenges in sampling enough tissue at locations where muscle and nerve cells connect so meaningful measurements can be made. To overcome this, the researchers instead looked for biomarkers related to the stability of the junctions between neurons and muscles in the biopsy samples of participants.

The research involved 38 healthy, elderly men with an average age of 72, who were asked to undertake a 16-week course of fairly intensive weight lifting training involving leg presses, leg extensions, leg curls, and two upper arm exercises. Another group of 20 healthy, elderly men, again with an average age of 72, did no weight training and were used as a control comparison.

Weight training sessions happened three times a week, and after two months (halfway through the experiment), the differences in muscle size and fitness could be seen. Researchers collected muscle biopsies and found detectable changes in the biomarkers.

From twinges in the back to pain in the knees, the indication is that weight training can slow down some of this breakdown between muscles and the nervous system, without actually reversing it. The researchers suggest that starting earlier in life can build up 'reserves' that the body can fall back on.

"The study shows that even though you begin late in life, you can still make a difference," says Søndenbroe.

"Of course, the sooner you start, the better, but it is never too late – even if you are 65 or 70 years old. Your body can still benefit from heavy weight training."

Although this study was done in men, this applies to women, too: for example, older women, who are more prone to osteoporosis, benefit from resistance training just as much as men do.

As many populations around the world continue to live longer and longer, the issue of preserving a good quality of life in our twilight years becomes more and more important – and that includes keeping muscles working as well as possible.

While there are certain biological processes that cannot be stopped as the years go by, research has shown that diet, as well as exercise, can protect against some of the damage that old age can leave us vulnerable to.

The next stage in this particular area of research is to work out how strength training helps nerves and muscles stay together.

"Now we need to determine which specific mechanisms cause weight training to strengthen the connection to the nervous system," says Søndenbroe.

"To do that, we need to introduce different methods, though our goal continues to be to make sure as many senior citizens as possible not only live longer but also experience well-being."

The research has been published in the American Journal of Physiology: Cell Physiology.