The Cardiac Muscle

Some people believe that the heart has a set number of beats;

“I believe every human has a finite number of heartbeats. I don’t intend to waste any of mine.” – Neil Armstrong

 So, is this true, and if so why would we want to waste them on exercise?

Well arguably, people do not die because their heart has simply used up all its allocated beats and simply stopped.  According to the World Health Organisation (2012) the top 4 killers are cardiovascular diseases, cancers, diabetes and chronic lung diseases.  At number 1 is cardiovascular diseases which killed 17.5 million people in 2012, that is 3 in every 10 deaths. Of these, 7.4 million people died of ischaemic heart disease, and 6.7 million from stroke.  There are other contributing factors such as diet, obesity, type-2 diabetes and smoking, but usually it is possible to modify these.

To put it simply ischaemic heart disease and stroke both indicate inadequate blood supply to the heart and the brain respectively, usually as they have become blocked by deposits of cholesterol.  So the heart muscle has not simply run out of beats and stopped; it has ironically, as it is the heart after all, been denied enough blood and oxygen for its own use, and become ‘injured’.  The cardiac muscle utilises a huge daily amount of energy to pump the blood around the body.  This requires the efficient supply, transport and use of oxygen carried within the blood, via the arteries and capillaries back to the heart muscle itself.

 So why does exercise help?

It’s well accepted that if you exercise, they say 3 x week of 20 minutes, but any exercise is better than nothing, then your resting heart rate will drop lower as the heart muscle adapts to the exercise regime.  It becomes bigger and stronger and more efficient and so is able to pump out more blood per beat, and with less beats.  The cardiac muscle also becomes more efficient at using the oxygen carried to it within the blood.

In addition;

The lungs also become more efficient with regular aerobic exercise, providing more oxygen for the blood to carry around.

Weight bearing exercise such as walking and weights also improve our bone strength reducing the risk of osteoporosis.

By exercising we also retain and improve our neuromuscular co-ordination, meaning we have better balance and controlled use of our body, and less likely to have falls.

There is also growing new evidence on improved cognitive function and functional capacity, and reduced risk of depression, anxiety, and dementia[1]

However despite this presumed evidence that exercise is good for our hearts we have still witnessed a rise in deaths from Ischemic heart disease and stroke between the years 2000 – 2012?

Why?

Maybe the message about these modifiable factors such as diet and exercise still haven’t been fully appreciated and practiced by the population.

But looking at the graph we can see that some causes of death, such as lower respiratory diseases, HIV/AIDS, Diarrhoeal diseases, pre-term birth and tuberculosis have decreased.  As people aren’t dying from these anymore they are now living longer; only now, arguably, to eventually die from cardiovascular diseases.  We have to die from something.

Or maybe, Neil is right and we do only have a finite number of heart beats after all, and if we are not dying from these other causes, then maybe we are now more likely to use up our allocated beats.

 

So, even if this theory of a finite number of heart beats is true – are we actually wasting them with exercise?

It seems not.

If we compare a non-exerciser, say with a resting heart rate of 70, to a recreational exerciser with a resting heart rate of 60 – what’s the effect on their daily heart rate?

Exerciser at rest:         60 beats per minute    x 60 minutes   x 23 hours       =          82,800

1 hour exercise:          120 beats per minute  x 60 minutes   x 1 hour           =            7,200

TOTAL:                       23 hours ‘rest’ and 1 hour exercise a day                  =          90,000

Non-exerciser:            70 beats per minute    x 60 minutes   x 24 hours       =          100,800                                                                                                                                   -10,800

So even with exercising for 1 hour per day, you actually have a net saving of 10,800 beats per day.

Sure this is a simple illustration, and in reality it takes maybe 2 to 3 months to reduce your heart rate by 10 beats per minute, so initially there will be an additional heart beat cost; where you have to add the exercising heart rate to the early ‘unfit’ and elevated resting heart rate.  And also the heart rate does not immediately return to its resting rate after exercise, but remains elevated for a while after exercise.

However both of these factors are temporary and the effect of each will reduce in time, especially as you exercise more and become more efficient at utilising the oxygen within the blood.

The example I have illustrated is also very conservative too, as with modest exercise you may get your heart rate down to even less than 60 beats per minute.

If you extrapolate that moderate daily saving out      over a week    7 x 10800 = 75,600

Over a month  4 x 75,600 = 302,400

And a year      12 x 302,400 = 3,628,800

That’s a saving of over 3.5 million heart beats a year….staggering!  So even if Neil is right and we do have this finite number of beats, then please do feel confident to expend some on exercise, it seems it adds up on all counts.

A 2006 study[2] found that exercising for 1 hour, 5 days a week, is associated with significant health benefits.

A study in 2011[3] provided even better news, 15 min a day or 90 min a week of moderate-intensity (ie brisk walking) exercise seems to also be of benefit, and even for individuals at risk of cardiovascular disease.

It just gets better in 2012[4] a study found that moderate physical activity, equivalent to brisk walking for up to 75 minutes per week was associated with a gain of 1.8 years in life expectancy relative to no leisure time activity.

Crucially it seems that the benefits can be achieved through structured or non-structured physical activity, and even accumulated (even through short 10 – 15 min bouts) throughout the day on most days of the week[5].

So get going, anything will do and it doesn’t even have to be that hard either, being able to hold a conversation throughout the exercise is a good guide.

Take that flight of stairs at work, get off the bus a few blocks short if the weather’s nice (or even if it isn’t), walk from the furthest carpark at the supermarket (you will be also guaranteed a park there!), walk to the local shops (when you run out of milk, eggs or butter), walk or play with the dog or the kids (if you have one) – whatever it takes, it all adds up….

But who’s really counting….

 

[1] Bauman, A., Merom, D., Bull, F. C., Buchner, D. M., & Singh, M. A. F. (2016). Updating the Evidence for Physical Activity: Summative Reviews of the Epidemiological Evidence, Prevalence, and Interventions to Promote “Active Aging”. The Gerontologist, 56(Suppl 2), S268-S280.

[2] Warburton, D. E., Nicol, C. W., & Bredin, S. S. (2006). Prescribing exercise as preventive therapy. Canadian Medical Association Journal, 174(7), 961-974.

[3] Wen, C. P., Wai, J. P. M., Tsai, M. K., Yang, Y. C., Cheng, T. Y. D., Lee, M. C., … & Wu, X. (2011). Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. The Lancet, 378(9798), 1244-1253.

[4] Moore, S. C., Patel, A. V., Matthews, C. E., de Gonzalez, A. B., Park, Y., Katki, H. A., … & Thun, M. (2012). Leisure time physical activity of moderate to vigorous intensity and mortality: a large pooled cohort analysis. PLoS Med, 9(11), e1001335.

[5] Hupin, D., Roche, F., Gremeaux, V., Chatard, J. C., Oriol, M., Gaspoz, J. M., … & Edouard, P. (2015). Even a low-dose of moderate-to-vigorous physical activity reduces mortality by 22% in adults aged≥ 60 years: a systematic review and meta-analysis. British journal of sports medicine, 49(19), 1262-1267.

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