Study shows that exercise rejuvenates muscle stem cells of old mice

Dr. Thomas Rando, Stanford University
Image Credit: Steve Fisch/Stanford University Website

While we’re all at home and practicing social distancing during this global pandemic, it has become a challenge to get in daily exercise. Aside from outward physical appearance, what other benefits does exercise hold? Dr. Thomas Rando and his team at Stanford University explored this question in more detail in a CIRM supported animal study.

The Stanford research team found that exercise played a key role in restoring the youthful properties in the muscle stem cells of old mice. Muscle stem cells play an important role in tissue regeneration. They are usually on standby alongside muscle fibers in a resting state known as quiescence until called upon to repair damage.

For this study, the researchers wanted to see if voluntary exercise had an effect on the muscle stem cells in mice. Older mice that were 20 months old, the equivalent of 60-70 human years, were given an exercise wheel where they were allowed to run at will. Younger mice that were 3-4 months old, the equivalent of 20-30 human years, were also given an exercise wheel and allowed to run at will. A separate group of younger and older mice were given a wheel that didn’t rotate to compare them with the groups of mice that exercised.

They found that the older animals that had exercised regularly were significantly better at repairing muscle damage compared to their counterparts that did not exercise. However, this exercise benefit was not observed between the younger group of mice.

The researchers also transplanted the muscle stem cells from the older mice that had exercised into younger mice that had not exercised. They found that the muscle stem cells from the older mice contributed more to the repair process than did those from the non-exercising mice.

What was also surprising is that injecting blood from an old mouse that had exercised into an old mouse that hadn’t created a similar benefit in the muscle stem cells. This finding suggests that exercise simulates the production of some factors that then circulate in the blood and enhance the function of older stem cells.

Lastly, the researchers were ably to identify a molecular pathway that activates the resting muscle stem cells in response to damage.

In a press release, Dr. Rando discusses how this discovery could potentially lead to the development of a drug that could rejuvenate muscle stem cells.

“If we could develop a drug that mimics this effect, we may be able to experience the benefit without having to do months of exercise.”

The full results of this study were published in Nature Metabolism.

Researchers cool to idea of ice bath after exercise

Have you ever had a great workout, really pushed your body and muscles hard and thought “You know what would be good right now? A nice plunge into an ice bath.”

No. Me neither.

Weightlifter Karyn Marshall taking an ice bath: Photo courtesy Karyn Marshall

Weightlifter Karyn Marshall taking an ice bath: Photo courtesy Karyn Marshall

But some people apparently believe that taking an ice bath after a hard workout can help their muscles rebound and get stronger.

It’s a mistaken belief, at least according to a new study from researchers at the Queensland University of Technology (QUT) and the University of Queensland (UQ) in Australia. They are – pardon the pun – giving the cold shoulder to the idea that an ice bath can help hot muscles recover after a hard session of strength training.

The researchers got 21 men who exercise a lot to do strength training twice a week for 12 weeks. One group then agreed – and I’d love to know how they persuaded them to do this – to end the training session by jumping into a 50 degrees Fahrenheit (10 Celsius) ice bath. The other group – let’s label them the “sensible brigade” – ended by doing their cool down on an exercise bike.

Happily for the rest of us at the end of the 12 weeks the “sensible brigade” experienced more gains in muscle strength and muscle mass than the cool kids.

So what does this have to do with stem cells? Well the researchers say the reason for this result is because our bodies use so-called satellite cells – which are a kind of muscle stem cell – to help build stronger muscles. When you plunge those muscles into a cold bath you effectively blunt or block the ability of the muscle stem cells to work as well as they normally would.

But the researchers weren’t satisfied just putting that particular theory on ice, so in a second study they took muscle biopsies from men after they had done leg-strengthening exercises. Again, half did an active cool down, the others jumped in the ice bath.

In a news release accompanying the article in the The Journal of Physiology, Dr Llion Roberts, from UQ’s School of Human Movement and Nutrition Sciences, said the results were the same:

“We found that cold water immersion after training substantially attenuated, or reduced, long-term gains in muscle mass and strength. It is anticipated that athletes who use ice baths after workouts would see less long-term muscle gains than those who choose an active warm down.”

The bottom line; if you strain a muscle working out ice is your friend because it’s great for reducing inflammation. If you want to build stronger muscles ice is not your friend. Save it for that nice refreshing beverage you have earned after the workout.

Cheers!