New evidence bolsters the brain-benefits of resistance/muscle exercise 05/06/2019
Note: This article first appeared in May 2019
Beyond being a way to look trimmer on the beach, exercise makes a powerful preventive and rehabilitative medicine.
Regular exercise — or vigorous physical activity of any kind — lowers the risk for diabetes, heart disease, high blood pressure, and even certain types of cancer.
And recent research reveals that both types of exercise — aerobic routines like running and muscle-building "resistance" workouts — can benefit, protect, and even physically alter our brains.
We summarized some of the relevant research in “Miracle-Gro” for Your Brain, Exercise as Brain-Saver, and Exercise May Protect Memory from Alzheimer's — and today’s report conveys the encouraging results of more recent evidence.
Both types of exercise build stronger brains
In addition to strengthening the cardiovascular system, aerobic exercise stimulates production of the brain's “growth factor”, called BDNF, thereby creating new cells in the brain's memory center (hippocampus) and improving memory.
Aerobic exercises are ones that raise your heart rate and cause you to breathe harder, and include things like brisk walking, running, cycling, jumping rope, swimming, and vigorous sports like tennis.
And while “resistance” strength exercises build stronger bones and muscles, emerging evidence suggests that it can also ease anxiety and depression (see “Muscle work and the anxious mind”, below).
Resistance exercises include things like weightlifting, body-weight exercises — e.g., push-ups, squats, and certain yoga poses — and working out with resistance machines or elastic bands. (To learn more about equipment-free body weight exercises, see Fixing the Harms of a Sedentary Past, Fast, and its links to related articles.)
Given their overlapping but distinct physical and brain benefits, it’s ideal to engage in both aerobic and resistance exercise.
Not everyone can participate in vigorous aerobic exercise due to physical limitations, medical conditions, or injuries.
However, almost anyone can engage in muscle workouts, if they start slowly and modify standard resistance exercises to account for any physical limitations.
And recent evidence suggests that resistance workouts can benefit the brain in multiple ways, from improving and protecting memory to lifting your mood and easing anxiety.
SMART evidence about muscle-work’s effects on the brain
Yorgi Mavros, PhD, of Australia’s University of Sydney studies the ways in which exercise can help treat and prevent disease.
Professor Mavros led the recently published SMART (Study of Mental and Resistance Training) trial, which was designed to examine the effects of muscle training on people aged 55 and older who’d been diagnosed with mild cognitive impairment (MCI).
MCI is characterized by minor thinking or memory problems that are noticeable, but not extreme enough to substantially disrupt daily activities.
However, MCI’s non-scary name belies the fact that eight out of 10 people with MCI will develop Alzheimer’s disease or another form of dementia within a few years.
While no known medication prevents dementia, the results of the Aussie SMART study — and other, similar ones — suggest that muscle-strengthening exercises might be a “prescription” that helps.
The 100 study participants were randomly assigned to one of four groups:
- Placebo exercise (stretching)
- Placebo cognitive training
- Computer-based cognitive training
- Muscle-strengthening resistance exercises with weights
The SMART participants who lifted weights worked out twice a week over the course of the study — starting out with light weights and gradually building up to at least 80 percent of their peak strength as their muscles got stronger.
After six months, the volunteers had their cognitive abilities tested again. The results showed that neither the “real” computer-based brain-training program nor either of the placebo programs (stretching and placebo brain training) boosted memory capacity.
(The lack of memory improvement from the computer-based brain-training program isn’t terribly surprising: see Do “Brain Games” Aid Memory or Mental Agility?.)
But the group assigned to muscle strengthening exercises showed substantial improvements in cognitive functions.
Importantly, this was the first study to show that resistance training can improve brain function in patients with MCI.
How often should you work on muscle strengthening exercises to potentially protect memory?
“The key is to make sure you are doing it frequently, at least twice a week, and at a high intensity so that you are maximizing your strength gains,” Dr. Mavros explained. “This will give you the maximum benefit for your brain.”
Muscle strengthening builds bigger, better brains
Additional research from the SMART trial used functional magnetic resonance (fMRI) scans to look for any changes in the brains of the volunteers assigned to lift weights regularly.
And the results were encouraging: the brain scans revealed that areas of the brain central to thinking and memory increased in size, significantly.
Next, the Australian scientists want to pinpoint the best exercise “prescription” for brain enhancement.
As study co-author Maria Fiatarone Singh, MD, said, “We want to find the underlying messenger that links muscle strength, brain growth, and cognitive performance, and determine the optimal way to prescribe exercise to maximize these effects.”
In what ways does muscle exercise benefit the brain?
What specific cognitive abilities — including attention, reasoning and memory — may be improved by resistance training?
To answer that question, researchers from Drexel University and the University at Alabama at Birmingham (UAB) conducted a meta-analysis of 20 published studies of muscle-strengthening exercises.
The joint Drexel/UAB team conducted a study designed to determine whether resistance exercise improves the participants’ cognitive abilities, including “executive” function (control and coordination of thinking abilities and behaviors) and working memory, which is the aspect of short-term memory that aids logic and reasoning.
The results showed that resistance training improved all cognitive screening scores, except for working memory.
The researchers noted that resistance training requires focus on the details of physical effort and body positioning and relies on executive function far more than working memory — which may explain why those capacities showed improvement.
The meta-analysis also revealed that the effects of resistance exercise on thinking abilities are highly variable. So, they called for more research designed to identify the optimal exercise duration, frequency, and intensity to boost cognitive health.
And an evidence review by an international team found evidence that resistance exercise can reduce anxiety in addition to depression: see Weighty Way to a Lighter Mood?.
Those findings fit with the conclusions of an international team of scientists who conducted a large meta-analysis of research on aerobic exercise, which found substantial evidence that it can help treat depression (Schuch F et al. 2016).
But for anxiety, which is often accompanied by depression, the best exercise prescription may be muscle-strengthening resistance exercises.
Indeed, a review of studies on muscle exercises by the American Psychological Association found substantial evidence that low-to-moderate intensity resistance exercises eased anxiety across a diverse range of people and ages — even after a single exercise session (Strickland JC et al. 2014).
Don’t delay treatment for serious depression
While exercise can clearly be beneficial, it’s not enough in some cases.
If you’re suffering from what feels like serious depression or anxiety, you need to seek professional help and treatment, which may include counseling, cognitive therapy, dietary supplements, drugs, and more.
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- Gordon BR, McDowell CP, Lyons M, Herring MP. The Effects of Resistance Exercise Training on Anxiety: A Meta-Analysis and Meta-Regression Analysis of Randomized Controlled Trials. Sports Med. 2017 Dec;47(12):2521-2532. doi: 10.1007/s40279-017-0769-0. Review. PubMed PMID: 28819746.
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