Are You A Fast Or Slow Walker?

Let's go for a walk

Walking seems like such a simple thing. We usually do not think about it until you cannot walk properly. My patient who had a recent ACL reconstruction literally had to learn how to walk again Pictured below).

Walking actually relies on quite a few body systems working together. Your eyes to help you see where you are going.  Your muscles and bones working together to get you places, your heart and lungs to circulate oxygen. Of course you need your brain and nerves to coordinate everything.

Previous studies have shown that walking speed is a significant predictor of life expectancy in older adults. Pooled results from 9 studies involving 34,000 adults aged 65 and older showed that walking speed was significantly associated with lifespan. Men with the slowest walking speeds at age 75 had a 19 percent chance of living for 10 years compared to those with the fastest walking speeds who had 87 percent chance of survival.

Another study found that even amongst healthy adults aged above 65, participants with slower walking speed were 3 times more likely to die of cardiovascular disease compared to those who walked faster.

Did you know that if you are a slow walker you may have a smaller brain compared to a faster walker? Research has shown that how fast you walk to the shops, MRT, or your local coffee shop can predict your chance of a heart attack, being hospitalised or even dying. Your walking speed can even reveal your rate of cognitive ageing.

As we age, these systems start to slow down. Studies show that walking speed is a significant predictor of life expectancy in older adults. This does not just apply to older adults as Rasmussen and colleagues (2019) found that even amongst 45 year olds, a person's walking speed can predict the rate at which their brain and body were ageing.

In that study (Rasmussen et al, 2019) had 904 subjects, all 45 years old born between 1972 and 1973 living in New Zealand. Their health and cognitive function were assessed regularly over their entire lifespans. 

There was fairly huge variation in walking speed among the subjects. You would think that these 45 year olds would have similar walking speeds but some walked as quickly as healthy 20 year olds while others walked as slowly as much older adults.

The 45 year olds with slower walking speeds showed signs of "accelerated ageing" with their lungs, teeth and immune systems were in poorer shape compared to those who walked faster. They also had 'biomarkers' associated with a faster ageing rate such as higher blood pressure, raised cholesterol and lower cardiorespiratory fitness. 

The slow walkers also had a weaker hand grip strength and found it more difficult to get up from a chair. Other signs of cognitive ageing include lower IQ test scores, worse memory test scores, processing speed, reasoning and other cognitive functions. MRI scans showed they had smaller brains and a thinner neocortex - the outermost brain layer which controls thinking and higher information processing.

Even the faces of the slow walkers were rated as ageing faster than the faster walkers!

The research suggests that the slow walkers' brains and bodies age at a faster rate compared to the quick walkers. There were already signs that these health differences were present from an early age  as researchers were able to predict the walking speed 45 year olds based on intelligence, language and motor skills test taken when the participants were just 3 years old. 

Wow, I am so surprised that there is a link between how fast people walked at 45 years old and their cognitive abilities all the way back to when they were 3 years old. Perhaps walking speed is not only a sign of ageing but a clue to lifelong brain health.

Reference

Rasmussen LJH, Caspi A, Ambler A et al (2019). Association Of Neurocognitive And Physical Function With Gait Speed In Midlife. JAMA Netw Open. 2:2(10): e1913123. DOI: 10.1001/jamanetworkopen.2019.13123.

Strength Matters More Than Size

Pawel Poljanski's legs at the Tour De France

My colleague was wondering why I was not 'big' (or muscular) despite exercising regularly. I explained to her I was more Type I muscle dominant (or slow twitch muscle) as most endurance athletes are. Those who have predominantly Type I muscle fibers are lean, not big and muscular.

Her obesrvation is accurate. I actually lift weights twice a week and even though I can squat 90 kg, my thighs are still skinny.

I also explained to her that it is better to be strong than have big muscles. Weight training can make you stronger and your muscles bigger. They are both related since bigger muscles are usually stronger. However, they are not identical. You can get stronger without adding muscle bulk. 

This happens when the signaling from your brain to your muscles become more efficient and how effectively your muscle fibers are recruited. You can add muscle without getting stronger, this typically happens when you gain weight.

Strength is also a much better predictor of cognitive performance than muscle mass. Storoschuk and colleagues (2023) studied 1424 adults above 60 years of age between 1999 and 2002 in a health and nutrition examination study (NHANES). These subjects had DEXA scans to assess body composition, leg strength tests, a digit symbol substitution test (cognitive test) and questionnaires that assessed physical activity habits. The DEXA scan is used to determine how much muscle one has in their arms and legs and fat-free mass index (FFMI), which shows total muscle to height.

The figure above presents the benefits of different variables on cognitive performance. The farther on the right each square is, the greater the cognitive benefits. You can see that low FFMI (low muscle mass) has no significant effect on cognitive scores, while peak leg force (a measure of strength) definitely have a significant benefit. Those who did resistance training (or weight training) for at least once a week has an even stronger effect.

Strength explained about 5 percent of the variance in cognitive scores, while muscle mass explained only 0.5 percent. Low strength levels raised the risk of premature death, but low muscle mass did not. In contrast, another study by Tessier et al (2022) found that low muscle mass predicted more rapid cognitive decline over a 3 year follow up period, after accounting for differences in strength. Perhaps it would be premature to conclude that muscle mass (being big) does not matter.

Confused? Storoschuk et al (2023) explained that there is a difference between the muscle you get from physical activity and muscle you get in the process of gaining weight. Greater muscle mass may just be a larger body size rather than greater strength, which does not seem to translate into protection from cognitive decline and other health benefits.

Moreover the conflicting results from the 2 studies are possible due to different popolulations, different cognitive tests and different sample sizes. 

My take on this? It is good if you have big muscles and I will still lift weights twice a week to at least maintain and avoid losing what I have. Getting stronger is much better, and that is the main reason why I do weight training. Even though I do not seem to gain muscle I am able to increase the reps and quality of the exercises I perform. 

So, to ward off cognitive decline, strength training is just as important as aerobic exercises.

References 

Tessier A, Wing SS, Rahme E et al (2022). Association Of Low Muscle Mass With Cognitive Function During A 3-Year Follow-up Among Adults Aged 65 To 86 Years In The Canadian Longitudinal Study On Aging. JAMA Netw Open. 5(7): e2218826. DOI: 10.1001/jamanetworkopen.2022.19926

Storoschok KL, Gharios R, Potter GDM et al (2023). Strength And Multiple Types Of Physical Activity Predict Cognitive Function Independent Of Low Muscle Mass In NHANES 1999-2002. Lifestyle Med. 4: e90. DOI: 10.1002/lim2.90

Can Exercise Prevent Memory Loss?

My son was watching me go through my Prezi slides for my talk on running next Wednesday when I came across an interesting article on the last page of the Business Times (below).

BT 301021

The author, a medical doctor was writing on preventing memory loss, about how when we find ourselves forgetful, we should not pass it off as aging.

He goes on to talk about how high blood pressure increases in mid life and this appears to be an important risk factor for developing dementia later in life.

There also seems to be a detrimental effect on our health if resting heart rate (HR) is high. The author quoted a Prevention Regimen for Effectively Avoiding Second Strokes (PRoFESS) study, where those with a prior stroke who had a higher resting HR than 67 beats per minute had an accelerated cognitive decline.

So a high HR may be considered as a risk factor for cognitive decline and dementia.

Wow, straight away I thought that this definitely serves as a huge incentive to keep exercising and keep my blood pressure and resting HR low.

So here's good reason for you to attend my Zoom talk on running next Wednesday (3/11/21) so you can keep exercising to prevent memory loss and cognitive decline.

Here is the link to register.