Put your heart into exercising
There are many benefits of monitoring your heart rate when training. Sergeant Rob Orr looks at a few of them.

Monitoring your heart rate as part of your exercise routine is a good way to keep track of your fitness level.

Photo illustration by PTE John Wellfare

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DID YOU KNOW?

If your heart worked at only 99.9 per cent efficiency it would stop beating more than 100 times per day.

ALTHOUGH many fitness enthusiasts will be familiar with the use of heart rates to determine training intensity – using the formula 220 minus age times intensity – few are aware of the other benefits monitoring heart rates can provide.

Monitoring heart rates can be used to monitor changes in fitness levels and even predict overtraining and heart disease.

Consider the following equation.

Stroke volume times heart rate equals cardiac output Stroke volume is the amount of blood pumped out of the heart with each beat. When this is multiplied by the amount of times the heart beats in a minute, the result is the cardiac output – the amount of blood pumped from the heart in a one-minute period.

The stroke volume is largely determined by the structure of the heart and the heart manipulates the heart rate to alter the cardiac output to meet specific demands.

Two key fitness changes to the structure of the heart, and hence stroke volume, occur through physical training – an increase in muscle and an increase in cavity size of the left ventricle of the heart. These structural changes lead to an increase in stroke volume, so the heart does not have to beat as fast to maintain a given workload, which means a decreased heart rate at rest and for a given workload.

Resting rates
The first method of monitoring heart rates as a measure of fitness uses resting heart rates.

• Measure resting heart rates weekly, for example every Saturday and Sunday, upon waking naturally (as opposed to an alarm clock) and find your average for the week.

  
  With an increase in fitness, the resting heart rate should decrease. A progressively increasing resting heart rate should also be noted as this is often a sign that the body is overtrained or over-reaching.
  

Sub-maximal rates
This method is readily available on many cardio training machines, but anyone can draw up a simple plot of heart rates at a given intensity as a means of monitoring improvement.

• Run for 10 minutes on a treadmill at a set speed.
  
• Record the average heart rate over the last minute (if using a heart rate monitor) or just measure your heart rate for the first and last 15 seconds of the tenth minute.
  
• Repeat this exercise a month into the training program.
  If the training is having an effect, the heart rate at the same intensity will decrease, because the work has become easier.
  

Watch the drop
The speed at which the heart recovers from a training session can help predict heart disease.

Doctor Michael Lauer, a cardiologist at the Cleveland Clinic Foundation, claims that studies have found that an average person can expect a decrease of about 20 beats a minute, one minute after finishing exercise. A fitter person can experience a drop of more than 50 beats in the first minute.

The study found that people whose heart rates dropped less than 12 beats in a minute after vigorous exercise have a higher risk of morbidity than those whose heart rates dropped more than 13 beats.

• Measure your heart rate for the last minute of your high intensity exercise.
  
• If you have a heart rate monitor, check your heart rate again after a minute. Otherwise, wait 45 seconds, then use the last 15 seconds of the minute to count the number of heartbeats and multiply that number by four.
  
• Use either the number of beats recovered as an indicator of fitness or as a general measure of heart disease risk, using the figures from above.
  

In the genes
It’s true that maximal heart rates are genetically determined and, although free from gender bias, are influenced by age. But even if this means that the heart may have a finite amount of beats, using more beats per minute during exercise may not actually decrease life expectancy.

If, for example, a person’s maximal heart rate was 200 beats a minute, and they were able to train every day for an hour at maximal heart rate, this would mean that – considering the average resting heart rate is about 76 beats a minute – each week their heart would beat an extra 52,080 times.

Thus decreasing life expectancy by 11.4 hours each week. But, if their fitness training decreased their resting heart rate by six beats a minute, over a 23-hour period, this would save 65,520 beats a week, thus adding 2.6 hours of life to your heart every week. This equates to gaining an extra day of life every nine and a half weeks.

What if, as can happen, your resting heart rate drops by 20 or more beats per minute following continuous training adaptation? How much more life can your heart gain?

Sergeant Rob Orr is an Army Physical Training Instructor.

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