Muscles, Strength & Aging - How Aging Affects Your Muscles, Nerves , Bones and Movement
Unless you've been living under a rock, you've seen articles in the media about the importance of strength training for older adults.
This year, I've fielded a number of enquiries from men and woman aged 60 and above who’ve been prodded into action through the media, or by popular podcasters like Peter Attia (author of the bestselling book, Outlive) and Andrew Huberman.
What's with that? Why does the media - and these podcasters - want you to lift weights all of a sudden?
Is this really such a big deal, or is it being driven by silicon valley longevity fanatics who want to live until they're 200, then upload their brains into the matrix?
Well, it is a big deal. And it isn't. Simultaneously.
It isn't a big deal because we've known for a long time that exercise, in particular strength training, is really important as you get older. Nothing new to see here. Plus, death still awaits us all. No amount of tech will sort that out, sorry.
And yet, it is a big deal, too.
Here's some reasons why:
The data about the importance and promise of exercise keeps rolling in year after year. It is the one silver bullet we have for reliably improving our health.
Many people are living longer due to Western medicine. But they're often kept alive by medication with a poor quality of life. Unsurprisingly, people want to actually be able to do stuff throughout the duration of their long life.
In my opinion, we're waking up to the fact that pharmaceuticals often come with severe trade-offs. "Yes, we can give you a pill for that back pain and osteoporosis, but you'll have severe migraines once a week." People are very motivated - more so than ever - to avoid that sort of thing.
The ageing population is creating a very large demand for medical services (with fewer working age people to staff the system). Older people are rightly concerned to minimise their reliance on the Australian medical system, knowing a stay in hospital could be pretty horrible. Plus, it would not surprise me one bit if state and federal governments were asking the ABC (and other outlets) to run more stories about this subject. Which is a fair thing to do, in my view.
So, with that said. I'm embarking on a project.
A project to create a short ebook for this cohort (older adults looking to improve their health through strength training). It will be called "Strength, Muscles & Aging: The Why and How of Strength Training For People 60+".
I'll be assembling the content over several weeks via my blog and my email list.
Today I want to set the scene. What happens to your muscles, bone, nerves and movement capacity as you get older? And how can exercise, in particular strength training, influence these processes?
Muscles
As you advance in years, your muscles shrink.
Scientists evaluate this in different ways in a research setting - via cross sectional area and muscle volume - using MRI and other tools.
In a clinical setting, lean body mass (which is muscles PLUS non-fat tissues - organs etc) can be determined via DEXA scan.
It can be a little surprising just how much they shrink, as body weight typically stays the same or increases with age - hiding the muscle loss to some degree.
But it can be seen when measures of body composition are taken - the proportion of your weight that is due to bone, muscle, fat and other tissues.
If you're living a sedentary lifestyle and not exercising enough, you will accumulate fat and lose muscle as you age.
According to Dr Peter Attia (in "Outlive"), muscle mass begins to decline as early as our thirties. And then the rate of that decline picks up after the age of 60.
The decline is especially noticeable in your "fast twitch" muscle fibres (each muscle contains a blend of fast and slow twitch) - those responsible for high speed and high force movement.
This goes part of the way towards explaining why you lose certain functional abilities - and not others - as you age.
It becomes harder to jump or hop, to right yourself quickly if you stumble, or to step up onto a high surface. Rapid, powerful movements are affected first via loss of fast twitch muscle function. And your maximum strength can decline, too, affecting your ability to do things like move a heavy wheelbarrow, or lift a big rock off the ground in your garden.
One important implication of muscular decline is that your muscles become less adept at taking in glucose. Another way of putting it is that they are more insulin resistant (insulin being the hormone responsible for pushing glucose out of the blood and into the tissues - with the liver and the muscles being the main storage sites for glucose).
Note: this is why exercise (especially strength training) can help people who have pre-diabetes or diabetes. You can re-train your muscles to take up glucose through exercise. And increasing your total muscle mass increases the size of your "sink" for glucose.
An implication of this muscle loss for older people is that they may have trouble bouncing back physically from illnesses or injuries requiring a hospital stay. Muscle can waste very easily if you're flat on your back in a hospital bed for a time. It's better to have muscle in reserve, as it were, so that you have some margin to work with in case you get sick or have an accident.
Nerves
Aging is accompanied by a decrease in the connections between brain and muscle via motor neurons (nerves responsible for activating your muscles).
These are continually being turned over but as you age the rate at which motor nerves are broken down exceeds the rate at which they are replaced.
And what can happen is when a fast twitch muscle fibre loses its nerve connection, a nearby nerve supplying a slow twitch fibre may pick up the slack. Only then the muscle behaves like a slow twitch fibre - with reduced capacity for rapid force production.
Bones
Through your life, bone is continually being turned over, just like all the cells in your body.
(Here's an interesting fact I remember learning when I was at uni studying Physio: your oldest cell is 7 years old. That blows my mind because in one sense aging is a meta phenomenon - is exists outside our cells. But back to your bones...)
When you're younger, the rate of bone growth matches the rate of bone loss, so that your net bone mass stays constant. But as you get older, the rate of loss outpaces the rate of new deposits, and your total bone mass declines.
This means you're at greater risk of fracture, because weaker bones are broken more easily. If you can prevent severe fractures, or severe consequences from a fracture, it makes sense to do so. If you're 65 years or older, and you break your hip in a fall, the odds of you being dead within a year (from consequences of the fracture) are between 15% and 36% (Outlive, page 254). If you're doing strength and fitness training, your odds of preventing the fall or recovering well are much better.
Just as with muscle, you can lose bone mass if you're laid low in hospital from sickness or injury. Going into these situations (especially a time in intensive care) with muscle or bone to spare increases the chance you can emerge on the other side with fewer long term implications. It can also be a gruelling experience that's physically taxing. It's better if you can be physically prepared to face that challenge.
Bone loss can also bring about painful physical deformities like a thoracic kyphosis (hunchback). These can be painful in themselves and also cause secondary issues like breathing difficulties. Genetics play a big role in this but exercise can have a potent preserving effect on bone mass, and this can limit the extent of such postural deformities, and the resultant pain, discomfort and secondary issues.
Movement/Physical function
As you age, you typically experience a decline in these physical abilities:
Balance
Fitness (your ability to run, walk, swim, bike (etc) at a fast pace)
Power (the ability to generate force rapidly)
Maximum Strength (the ability to generate lots of force - whether rapidly or slowly)
Mobility (your ability to execute functional tasks - like reaching down to tie your shoe laces, or looking over your shoulder in the car)
These losses in functional mobility reflect a multifaceted degradation in mind and body systems. Your balance is an expression of your brain, muscles and bone. Your strength is influenced by your psychology.
This is all really depressing, Tim. Why the long list of the ways we fall apart as we age?
It's important to say that we observe these things occurring as people age, but it's not totally cut and dried as to what is the main driver of these processes - whether its inactivity or aging. Often people will “slow down” quite early on in life, before the effects of aging set in.
And then they attribute physical decline to age when it’s due to a sedentary lifestyle.
When we ask what's driving physical decline on an individual level, aging or inactivity, the answer is very often "both".
But to what degree?
What proportion of the decline is an inevitable by-product of getting old, and what proportion can be mitigated by activity?
I don’t have an exact answer to that but the good news - and the reason for setting the scene so elaborately - is that these things can be substantially mitigated (or even reversed) for a very long time. That means there's a great deal of potential to enjoy a long healthspan (again, to borrow from Peter Attia, who to the best of my knowledge coined that phrase) - the proportion of your life where you can be healthy and active.
Plus, mitigating the decline in muscles, bones, nerves and functional movement does not require a very large time investment.
With a reasonably modest time commitment of three hours per week, older adults can expect to make very substantial improvements to their health. The process of getting fitter and stronger through exercise can be very enjoyable, and it does not need to cause pain, soreness or injury. Furthermore, many people who are over 60 years of age are at a stage in life when they DO have the time and resources needed to develop their strength and fitness.
Let it be known to this cohort of people that I'm aggressively competing with your overseas holiday plans to wrestle that budget towards your strength and fitness as a first priority. (You can have holidays with the leftovers! ;) )
What can exercise do for you?
Let's look at it based on the framework of this article. How can exercise affect your muscles, nerves, bones and movement capacity?
1 - Muscle
Physical training helps you preserve muscle mass. Strength training - done safely and sensibly, but with resistance that's quite heavy in relation to your capacity - can work wonders in not just maintaining muscle, but actually gaining more.
More muscle means you move better, have better balance, and have more physical padding ("body armour") to protect you from fracture if you fall. And, your ability to take up glucose is helped. Every gram of muscle you already have becomes more sensitive to insulin, meaning that metabolic dysfunction and diabetes (or pre-diabetes) can be allayed - or the severity (and need for medication) reduced.
Exercise - especially strength training - can preserve your type II fibres, meaning your strength need not decay as fast and you'll have the ability to do things like righting yourself quickly if you stumble, or climb up onto a high step, or push a loaded wheelbarrow.
In summary: More muscle mass, that can create more force (and do so quickly) helps you to move well for longer and plays an important role in preserving health.
2 - Nerves
Structured training - especially strength and power based - helps maintain the nerve connections between brain and muscle.
The repeated strong firing of the nerves helps preserve them for longer, maintaining optimal "innervation" (nerve connection/supply) for longer. (Remember: one of the reasons muscle wasting occurs with aging is the loss of innervation).
Exercise also has potent affects at preventing or alleviating age-related disorders which cause cognitive decline, such as Dementia, Parkinson's Disease and Alzheimer's.
In summary: Exercise delays the degeneration of the nervous system, and this happens in the central nervous system (brain and spinal cord) plus the peripheral nervous system (all nerves outside the brain and spinal cord).
3 - Bones
The loading associated with physical training makes bones denser and stronger. The best results are achieved through weight bearing activities which exert compressive forces on the body (like walking, hiking, or doing squats) as well as exercises which create pulling forces on the bones via muscular tension (resistance training).
In summary: exercise strengthens your bones, making them harder to fracture and reducing postural deformities (as well as secondary issues) arising from bone loss. Serious fractures - like those affecting the neck of the femur - are often a big deal, leading to a curtailed lifespan with a poorer quality of life.
4 - Movement Capacity / Skill / Functional Ability
If you're over 60 years of age, you can preserve or even expand your movement capacity. A slow decline in movement is not inevitable.
Your body is incredibly adaptive; your nervous system plastic and responsive.
Here's some quotes from participants who took part in the BELL trial, a six-week in-person (and then six weeks at home) strength training intervention using kettlebell based resistance exercises. It took place just prior to, and during, the covid19 pandemic in Australia.
Their reflections on the experience, and what it did for them, can be found in this article by Neil J. Meigh et al.
The participants were all "insufficiently active older adults" aged between 59 and 79.
“I’m walking, going out with the wife, doing things, and I’m confident in myself as I walk around that I’m not an ‘old’ person, I’m [an older person] that looks healthy and I’m quite enjoying that. …Having the opportunity to do something, seeing it through, finishing it, being able to challenge myself; I’m a different [man]” - Alan, 70-74 years old.
“I can carry three loads of groceries up the stairs and… they’re quite steep, whereas before with my knee I couldn’t do it”. - Abigail, 65-69 years old.
“My migraines, they’re less frequent and less severe… to me, wellbeing is not feeling sick with a headache or not having the same nagging pain in my hips… [my] overall well-being is much better… I used to have to go and have massages nearly every week, and I haven’t been once since I’ve been doing kettle bell [training]… I’m not constantly looking down to see that I’m not going to trip over… I’m not feeling as unsteady… I’ve had such a good response to it… I sleep like a baby” - Janice, 60-64 years old.
“When I was getting out of bed before I started the trial, [I] always worried about [my] back going or something, but now I just can’t believe how much stronger my back is now. I’ll get up in the morning, get out of bed and there’s just not one bit of pain in there… It’s definitely one hundred percent better than what it was before I started the trial. It’s just unreal, I can’t believe it.” Robert, 70-74 years old
“I’m thrilled! I’m fit as a fiddle, I feel good, I sleep well, and I have no more back problems. I used to have once a month a physio come here to maintain my back [ ] I think I don’t need him [any more], I’m fine.” - Georgina, 70-74 years old.
I find that all pretty inspiring.
What’s more, I don’t think such results are especially unusual. The degree of inactivity in our society is very, very high. It makes sense that health declines when movement is relegated to the extent it is in modern Australia.
Reversing that on an individual level IS achievable in many cases!
It’s no surprise to me, that when a healthier approach to movement is adopted, the benefits flow pretty quickly.
If you’re an older adult looking to improve your health through movement, and in particular strength training, then please do get in touch with me :)