New research provides a window into how, on a cellular level, exercise can improve muscle health and, ultimately, exercise capacity, which is “the best predictor of mortality in the general population.”
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“Whether muscle is healthy or not really determines whether the entire body is healthy or not,” says lead researcher Prof. Zhen Yan, of the University of Virginia School of Medicine in Charlottesville.
“And exercise capacity, mainly determined by muscle size and function,” he adds, “is the best predictor of mortality in the general population.”
According to the new study, exercise improves muscle health by renewing its cellular powerhouse: the mitochondria. Mitochondria are crucial to the good functioning of our bodies, as well as to our overall health and longevity.
These tiny parts of the cell turn the food we eat into energy. Mitochondria transform proteins, fats, and sugars into the fuel that the body needs to live.
So, how does exercise affect the mitochondria in the muscles?
The answer given by the new study is through “mitophagy.”
In the case of muscles, mitophagy contributes to keeping skeletal muscle healthy and strong. And to show how exercise induces mitophagy, Prof. Yan and team genetically modified mice to carry a gene that helps to report on the effects of physical activity.
This gene is called pMitoTimer. It makes mitochondria fluorescent, allowing the researchers to study mitophagy in vivo, after the mice engaged in 90 minutes of treadmill running.
Three to 12 hours after the running session, the researchers observed that mitochondria showed signs of stress. After 6 hours, they saw signs of mitophagy.
Prof. Yan explains the effect of exercise on mitochondria through an analogy that includes a vehicle inspection, the purpose of which is to remove defective cars from the streets.
“Aerobic exercise removes damaged mitochondria in skeletal muscle. If you do it repeatedly, you keep removing the damaged ones. You have a better muscle with better mitochondrial quality. We clean up the clunkers, now the city, the cell, is full of healthy, functional cars.”
Prof Zhen Yan
.Chemical reaction in mitophagy identified
The researchers also identified the molecular mechanism behind the process. The treadmill workout seemed to activate a kinase called AMPK.
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kinase is an enzyme that modifies other proteins through a process called phosphorylation. In this biochemical process, phosphate groups are added to proteins.The researchers determined that, in a biochemical chain reaction, AMPK triggers another kinase called Ulk1.
Prof. Yan continues the vehicle inspection analogy, saying, “When [it’s] turned on, Ulk1 activates other components in the cell to execute the removal of dysfunctional mitochondria.”
“It’s analogous to a 911 call where a tow truck removes the clunkers. However,” he says, “we still do not know how these activities are coordinated.”
To confirm their discovery – that Ulk1 plays a critical role in mitophagy – the team created a mouse model lacking the Ulk1 gene. These mice were also subjected to treadmill exercise, but the ensuing mitophagy was considerably inhibited.
“Mice that were unable to do mitophagy did not have the benefit of exercise,” explains study co-author Joshua Drake, a postdoctoral fellow in Prof. Yan’s laboratory.
“Even though, from an exercise standpoint, they still were able to run just as far as normal mice, they didn’t benefit metabolically with training,” he adds.
“These findings provide direct evidence of exercise-induced mitophagy and demonstrate the importance of Ampk-Ulk1 signaling in skeletal muscle,” the authors conclude.
Adding weightlifting to cardiovascular exercise reduces risk of all-cause mortality
- A new study suggests that adding weightlifting to aerobic exercise can further reduce the risk of all-cause mortality.
- The study finds that weightlifting is associated with an additional 9% decrease in the risk of all-cause mortality, while aerobic training alone reduces it by 32%.
- Weightlifting alone was also associated with a 15% reduced risk of cancer mortality.
- While the findings show that aerobic training was associated with a 30% lower risk of cancer mortality when meeting guidelines levels, there was no overall additional benefit for weightlifting.
- According to experts, it’s never too late to get started with weight training to receive the benefits, and positive effects may be seen with even modest amounts.
A new study explored the benefits of two types of exercise on all-cause mortality: aerobic exercise and lifting weights.
For the study, researchers defined aerobic exercise as moderate-to-vigorous physical activity (MVPA) and weightlifting as muscle-strengthening exercise (MSE).
There isn’t much available research on MSE’s effect on mortality as there is on MVPA’s, so the study’s authors explored the effects of each on mortality separately and together. They also investigated the effects of both forms of exercise on cardiovascular disease (CVD) and cancer.
“Weightlifting and [aerobic exercise] were associated with a lower risk of all-cause and CVD mortality, but not cancer mortality. Adults who met recommended amounts of both types of exercise appeared to gain additional benefit,” the study authors wrote.
The study was recently published in the British Journal of Sports Medicine.
Researchers analyzed data from questionnaires filled out by 154,897 men and women ages 55 to 74 in the National Cancer Institute’s 1993
Following that, 99,713 of the participants described their weightlifting activity in a follow-up survey that did not capture what type of weightlifting was done but did ask about frequency in broad categories.
Next, the researchers summarized these categories into any weightlifting in the last 12 months or none. Those who performed muscle-strengthening exercises (MSE) reported lifting weights:
- less than once per month
- 1 to 3 times per month
- 1 to 2 times per week
- 3 to 7 times per week
In 2006, the same group of participants described their weightlifting activity in a follow-up survey that did not capture whether the type of weightlifting or its frequency adhered to current recommended guidelines for strength training. Researchers continued to track their health — and mortality — until 2016.
Based on the findings from the follow-up survey and health monitoring that continued for nearly 10 years, the study concluded:
- There was a 32% lower risk of all-cause mortality associated with people who met the recommended levels of MVPA but did not weight-lift.
- The risk of all-cause mortality decreased by 9% for people who had done any weightlifting in the last 12 months after taking into account any benefit from MVPA.
- Those who met MVPA recommendations and had engaged in any weightlifting in the last year had a 41% reduction in the risk of all-cause mortality, with no interactive bonus in risk reduction.
Study lead author, Jessica Gorzelitz, assistant professor in the department of health and human physiology at the University of Iowa, explained to Medical News Today:
“Older adults who participated in weightlifting exercise had significantly lower mortality before and after accounting for aerobic exercise participation, and importantly, those who did both types of exercise had the lowest risk.”
Linda S. Pescatello, Ph.D., a professor of kinesiology at the University of Connecticut, not involved in the study, told MNT:
“I no longer think one modality [or] type of exercise is better than the other. I prefer aerobic training over resistance training, personally. Rather, they both result in overlapping, but in some cases, distinct benefits from the other.”
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“If you can talk as you exercise but not sing, you have achieved a moderate level of exertion. If you cannot speak more than a few words before taking a breath, you are engaged in vigorous physical exercise.”
Experts recommend engaging in both moderate- and vigorous-intensity exercise on a regular basis, with at least two strength training sessions a week on non-consecutive days.
Dr. Christopher Cooper, professor emeritus of medicine and physiology at the University of California, Los Angeles, not involved in the study, explained to MNT:
“The way muscle-strengthening works is by resistance training. You actually break down muscle at a cellular level, and then it rebuilds itself and reconstitutes itself stronger, but you’ve got to allow time for recovery in between.”
Emmanuel Stamatakis, professor of physical activity and population health at the University of Sydney, not involved with the study, noted: “The American College of Sports Medicine recommends 2 to 4 sets of 8–15 repetitions of each strength-promoting exercise, with 2–3 minutes rest between sets.”
Though the study was observational, finding associations in data rather than causal connections, Gorzelitz suggested some possible causes for the reduction in mortality risk from lifting weights:
“Weightlifting is associated with improvements in strength, which are related to function both in performance contexts and activities of daily living. As a committed weightlifter, going to the gym to see my regular crew is not only motivating, but it’s a great social activity for myself.”
Prof. Stamatakis told Medical News Today:
“Weightlifting is one of many types of muscular strength-promoting exercises. As we age, regular strength-promoting exercise has myriad health benefits, including maintenance or increase of muscle mass, maintenance of functional capacity to carry out day-to-day tasks, and prevention of musculoskeletal problems and falls.”
“The maintenance of muscle mass is extremely important not only for functional strength but for glucose control and prevention of type 2 diabetes since muscle is a metabolically very active tissue.”
– Emmanuel Stamatakis, professor of physical activity and population health at the University of Sydney
As to the study’s findings, Dr. Cooper noted: “This is an older population — the age at the time of the questionnaires was 71. So, it’s likely that [fewer] falls could have been a major factor” in the reduction of all-cause deaths.
Gorzelitz agreed and said that “weightlifters have better neuromuscular coordination, which can be associated with lower risk of injury or falling.”
The results refer specifically to people who have done any weightlifting, not any other form of muscle strength training.
The benefits were similar for any weightlifting in the last year (less than once a month), as they were for people reporting weightlifting 1 to 2 times a week, a reduction in risk of all-cause mortality of 18% compared to 24%.
This suggests that some of the effects may not be simply due to an increase in muscle strength but could include the desire to increase and the means to do so.
“People may be unfamiliar with weightlifting and not know how to get started,” Gorzelitz noted.
“Our results suggest that some is better than none, and it’s OK to get started slowly and progress as strength and confidence increase. It is important to work all the major muscle groups of the body — the legs, hips, back, abdomen, chest, shoulders, and arms.”
“Perhaps the most feasible and accessible for most middle-aged and older adults type of strength exercise is own-body weight exercises without any equipment such as push-ups, squats, sit-ups, chin-ups, or even static exercises like planks,” Prof. Stamatakis noted.
“When executed correctly and regularly, [planks] can be as effective as weightlifting, and [they] can be done at home or in the park, settings that appeal to many people more than gyms,” he added.
Daniel Griffin, a physical therapist at Resilience Physical Therapy and Wellness in Agawam, MA, not involved in the study, suggested to MNT:
“3 exercises I commonly prescribe for people who are new to lifting weights and who do not have any musculoskeletal conditions are deadlifts (picking a weight up off the ground), isometric push-ups or planks (with the hands elevated if needed), and inverted rows (which can be performed at home using a suspension trainer). Combined, these three exercises can strengthen all the major muscle groups of the body.”
Dr. Cooper recommended: “For someone who is unaccustomed to muscle strength, [try] simple exercises with therabands, the elastic bands. Those types of exercises are graded in elasticity, so you can start easy and work up.”
“Things like sit-to-stand, sit-to-stand with small handheld weights, all of these are better than nothing in someone who’s just starting out with muscle-strengthening exercises,” he added.
“As people get stronger, [weightlifting] needs to be more structured and address the major muscle groups in the arms and legs, both the extensor and the flexor. You get into more complex kind of exercise training routines for which people go to health clubs and pay trainers to supervise them. Or they do circuits on weight machines and so on, self-designed circuits.”
– Dr. Christopher Cooper, professor emeritus of medicine and physiology at UCLA
Source - Medical News Today
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