Research shows we're stronger than we think, especially as we age

April 10, 2018 by Adrienne Berard, The College of William & Mary
Research shows we’re stronger than we think, especially as we age
Alberto Salazar was one of the world’s greatest distance runners during the early 1980s. Credit: The College of William & Mary

Alberto Salazar won the first marathon he entered. He was 22. In 1980, he won the New York City Marathon and went on to win it again in 1981, finishing with a time of 2:08:13 and setting a new course record.

The following spring, at the Boston Marathon, he outsprinted Dick Beardsley by two seconds in one of the most exciting distance races in American history—the "duel in the sun."

Under glaring sun and 70-degree temperatures, the two men were neck and neck for the entire 26.2 miles. Despite the heat, Salazar never drank water, fearing the extra weight would slow him down. After crossing the finish line, he collapsed. Salazar would never race the same again.

"He should have been the greatest marathoner of all time," said Michael Deschenes, chair of William & Mary's Department of Kinesiology and Health Sciences. "Salazar started out by winning the New York and Boston, which was incredible, but he had to stop. He kept on having to have his last rites read to him at races, because he was pushing himself too hard."

By the age of 27, Salazar's career as a runner was over. He had worked his body to its breaking point. Salazar developed chronic health problems that a doctor eventually linked to the extreme conditions he forced on himself during the "duel in the sun." Salazar's downfall showcases a uniquely human attribute, Deschenes explained, the dangerous disconnect between a motivated mind and its bodily host.

"No other animal will do that to itself," Deschenes said. "We're the only ones that will say 'I'm gonna keep going and keep going.' We push ourselves to death. You can always try to push yourself a little harder, but you have a physiological limit."

It's that limit Deschenes has spent his career working to understand. He specializes in the neuromuscular system, the network of nerves that connects our brains to our muscles. He is particularly focused on the neuromuscular junction, the synapse where the message goes from the to tissue, the precise location where the muscle receives its marching orders.

In a recent study published in Experimental Gerontology, Deschenes and a team of four W&M undergraduate co-authors—Shuhan "Sherry" Li, Matthew Adan, Jane Oh and Hailey Ramsey—examined the neuromuscular system during with the goal of learning how its response varies with age.

They found the two components of the neuromuscular system, nerves and muscles, do not respond in tandem to either aging or exercise training. It was previously thought the two parts of the system worked in concert, but the team's research indicates that nerves and muscles aren't quite the partners experts once thought.

In fact, the neural component of the system, the pathways the brain uses to communicate with the body, tired before the actual physical muscle. The loss of strength in their subjects was linked to "fatigue-related impairments in neuromuscular transmission," the study read.

"What we call muscle fatigue is a lot more likely to be neural fatigue," said Deschenes. "It's not that the muscle isn't capable of generating more force—it's that the nerve isn't capable of instructing the muscle to do the best it can. When you say, 'my muscles are tired,' it's more likely your nerves are tired. They can't activate your muscles as well as they did in the beginning."

We are, Deschenes explains, quite literally stronger than we think.

The research team conducted a series of ex vivo experiments by stimulating both nerve endings and muscular tissue and gauging the force produced. The researchers used animal models of various ages and in various stages of endurance training.

Whenever the researchers bypassed the nerve ending and stimulated the muscle directly, they saw an increase in force. For example, muscles from the younger control group produced about 46 grams of force when stimulated indirectly, through the nerve ending. By contrast, the same muscles produced about 69 grams of force when stimulated directly through the .

The researchers found that stimulating the nerve produced roughly two-thirds the force of what the muscle tissue was physically capable of producing. Deschenes and his team used the data to conclude the neural half of the system was tiring before the muscular one—and there could be an evolutionary reason for that.

"There's a physical limitation. You get to the point where you just can't do it anymore," Deschenes said. "That's for good reason, so we don't damage ourselves."

Salazar was case in point. But the team's most interesting finding, Deschenes said, had to do with age. When it came to young muscles, the greater part of their strength was neural rather than muscular at the outset of endurance training. The younger control group started with the strongest neuromuscular transmission efficiency, but after five minutes of stimulation, as the synapses fatigued, muscles from the youngest models began to resemble muscles from the oldest.

"We found out there's a big difference between aged and young in the very beginning," Deschenes said. "When you get the end of the five-minute protocol, the young tired muscles are behaving like old tired muscles."

The researchers found that young tired muscle produces the same amount of force as old tired muscle after continual stimulation or exercise.

"That whole aging thing disappears when the muscle gets tired. It's no longer a factor," Deschenes said. "After looking at all of this evidence, we find that when a young muscle gets tired it's no better than old muscle. It's the same. So if you're older, you don't have an excuse not to exercise. Our research demonstrates that."

Explore further: Muscle protective systems could reduce frailty in old age

More information: Michael R. Deschenes et al. Muscle fibers and their synapses differentially adapt to aging and endurance training, Experimental Gerontology (2018). DOI: 10.1016/j.exger.2018.03.010

Related Stories

Muscle protective systems could reduce frailty in old age

March 8, 2018
New research published today helps explain why people experience muscle loss in old age, increasing the prospects of reversing the condition in the future.

Step up your strength training

March 1, 2018
(HealthDay)—Strength training is an essential part of a complete workout program. But whether you use free weights, machines or resistance bands, keep challenging your muscles by stepping up your routine as you progress.

Therapeutic antibodies protected nerve–muscle connections in a mouse model of Lou Gehrig's disease

February 20, 2018
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, causes lethal respiratory paralysis within several years of diagnosis. There are no effective treatments to slow or halt this devastating disease. Mouse ...

Muscle regeneration compromises stability in muscular dystrophy

March 1, 2018
A new study finds that muscle fibers in Duchenne muscular dystrophy (DMD) split during regeneration to such an extreme that the muscle is weakened beyond repair. The article is published ahead of print in the American Journal ...

Endurance training helpful in recovery from muscle inflammation, new study shows

November 8, 2017
Endurance training can actually be helpful in dealing with muscle inflammation, according to a new paper co-written by faculty at Binghamton University, State University of New York, and Karolinska Institutet and Karolinska ...

Eye muscles are resilient to ALS

January 26, 2017
Amyotrophic lateral sclerosis, commonly known as ALS, is an incurable neurodegenerative disease that affects all voluntary muscles in the body leading to paralysis and breathing difficulties. Eye muscles, in contrast to other ...

Recommended for you

Genes may control how tough it is to stop drinking

September 25, 2018
(HealthDay)—When they give up booze, some alcoholics have more severe withdrawal symptoms than others. This discrepancy may come down to genetics, researchers say.

Why industry influence on research agendas must be addressed

September 25, 2018
Industry influence on the research agenda—and the tactics employed by tobacco, pharmaceutical, food, mining, chemical and alcohol companies to drive questions away from those most relevant to public health—is the focus ...

Study analyzes numbers, trends in health care data breaches nationwide

September 25, 2018
Health plans—entities that cover the costs of medical care—accounted for the greatest number of patient records breached over the past seven years, according to an analysis of U.S. health care data conducted by two Massachusetts ...

New study finds concurrent use of prescription drugs and dietary supplements could pose health risks

September 25, 2018
A new University of Hertfordshire study found that using certain over-the-counter herbal medicines and dietary supplements alongside prescription drugs could pose serious health risks, especially amongst older adults.

It's not just for kids—even adults appear to benefit from a regular bedtime

September 21, 2018
Sufficient sleep has been proven to help keep the body healthy and the mind sharp. But it's not just an issue of logging at least seven hours of Z's.

Most nations falling short of UN targets to cut premature deaths from chronic diseases

September 21, 2018
People in the UK, US and China have a higher risk of dying early from conditions like cancer, heart disease and stroke than people in Italy, France, South Korea and Australia.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Apr 10, 2018
This is not actually true, there are a range of animals including fish, ruminants etc that will run to death, usually when pursued by a predator.

There are some African tribes than can hunt by simply chasing a ruminant to death ~ the beast can run faster, but only in relatively short bursts and then must rest.

Humans are the only beast that does this for fun or in competition with others, but the motivation may well be similar neurologically if they fear career ruination, social 'death and disgrace etc.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.