Ok let’s get a little sciency about cardiovascular fitness. It’s something we all talk about but what is it actually? It’s the ability of the heart, lungs and blood vessels to efficiently supply oxygenated blood to your muscles as you exercise and technically, also when you are just lazing about.
Cardiovascular fitness is measured by something called VO2max. VO2 max (Volume of oxygen – O2, maximum) is a number calculated in an exercise lab and measures the amount of oxygen you use while you run on a treadmill. I imagine it’s a really miserable test since your nose is plugged and you breathe through a tube taped in place in your mouth as you stumble along as fast as you can. All this to make sure they accurately measure oxygen-in and carbon dioxide-out. Then with some fancy mathematics the lab crew can calculate how much oxygen you burn, and from that infer how much energy you burn.
Suffice it to say, VO2max is a measure of your cardiovascular fitness.
In a paper published in 2018, looking at the association between cardiovascular fitness (as measured by VO2max) and death, researchers were trying to understand if habitual vigorous exercise is bad for you as you get older. Apparently, it has been observed that if you overdo it with cardiovascular exercise (like running or cycling) as you age, you can over-stress your heart and create a multitude of problems for yourself. Fortunately, these nasties of the heart are reversible, presumably if you stop exercising.
Now, I am interested in this because I cycle daily. I get my heart a-pumping, my brow a-sweating and my lungs a-puffing for a minimum of 30 minutes every morning. I do this because I believe it’s good for my brain. But am I sacrificing my heart?
This particular study looked at the VO2max of 122,000 individuals with an average age of 53y and their all cause mortality over one decade. That is, the risk of dying from something over 10 years as compared to others based on cardiovascular fitness. Individuals were grouped, based on their VO2max by percentile as low (<25th percentile), below average (25th – 50th), above average (50th – 75th), high (75th – 97th) or elite (>97th). To get a sense of their grouping the low group had a BMI of 31.7 (couch potato*); below average 29.8 (walk a bit*); above average, 28.0 (walk more than a bit*); high, 26.2 (run occasionally*); and elite 24.5 (run often*). (*Truthfully I made up these descriptions to make it easier to understand.)
Recall that BMI is a measure of body fat based on height and weight. Doctors use it to determine if you are thin, or obese or somewhere inbetween. A normal BMI is between 18.5 – 24.9. So only the elite group in this study sqeaked into the normal weight range, while everyone else was either overweight or obese. They also looked at other comorbidities, including diabetes, hypertension, coronary artery disease, smoking and death. But for the sake of this blog, I only included the total number of individuals in each percentile group, BMI and number of deaths and percentage deaths..
Below is a table showing the data in percentages for ease of comparison.
|VO2max||LOW||BELOW AVERAGE||ABOVE AVERAGE||HIGH||ELITE|
|CVF %ile||<25th||25th – 50th||50th – 75th||75th – 97th||>97th|
|Number participants||29,181||27,172||31, 897||30,187||3,570|
(walk a bit)
(walk more than a bit)
|Number deaths over 10 years||6,904||2,888||2,340||1,412||93|
Over the course of 10 years, individuals with LOW cardiovascular fitness have 23.7% risk of dying; whereas the ELITE cardiovascular fitness individuals have a 2.6% risk of dying.
So what does this mean?
It means those with poor cardiovascular fitness have a 10 times greater risk of dying than those with robust cardiovascular fitness. TEN times greater risk of dying.
After some really fancy statistics and number crunching, the researchers conclude “Cardiovascular fitness is inversely associated with long-term mortality with no observed upper limit of benefit.” Which means – as cardiovascular fitness goes up, your chance of dying goes down and you can’t over do it.
The researchers go on to suggest… “Health care professionals should encourage patients to achieve and maintain high levels of fitness.”
Well duh. Of course some thin dude with a normal BMI running on a treadmill with their nose plugged is going to perform better than another with a BMI over 31, who rarely, if ever, steps on a treadmill let alone run with his nose plugged.
Is this really a fair comparison? Perhaps not.
What is truly revealing about this study is the difference between the low group and the below average group. The couch-potato people compared to the walk-a-bit people. There is a MASSIVE improvement. Death in the low group is 23.7%,whereas death in the below average group is 10.6%. The risk of death over a decade is more than cut in half, simply by getting up off the couch and walking consistently. Even better, if you walk more than a bit, you can decrease that risk even further to 7.3%.
So, just a little bit of habitual cardiovascular exercise, cuts your risk of death over a decade by more than half. HALF! Incredible right? No marathon required. No expensive gym memberships required. Just go for a walk daily.
Whew. I can continue my daily cycling and not sacrifice my heart while I cut my risk of dying in the next 10 years in half, if not more as I get fitter and fitter. BOOM. Not only will your brain thank you, your heart and lungs will cheerily participate in your quest for longevity.