What is the most important muscle in the body? Your first answer may be to suggest your legs, abdominals or even your tongue, but however great a well-defined six-pack looks, the most important muscle is in fact the heart! It doesn’t just pump blood around our body, but also has a vital role in shuttling hormones and transporting the nutrients consumed from food to our working tissues and muscles.

Like any muscle, if we want it to grow bigger, stronger and more efficient, we need to exercise it, just as we train our legs, abdominals and arms to be stronger.

So, how we do this?

Well, we apply the same theory as we do to other muscles in the body. Take skeletal muscle for example; the load (weight) and number of reps we use can influence how that muscle develops. If you wanted to focus solely on getting a muscle strong, then you would typically train it across a 1-5 repetition bracket, but people looking for bigger muscles would focus on training between 6-12 reps using a variety of exercises. 

Our heart (or rather our cardiovascular system) can also be trained in a similar way to elicit specific training outcomes, such as strength, size or stamina. When it comes to the cardiovascular system, we have three different adaptive abilities or “energy systems”. Let’s take a look at them:

1. The Alactic System – great for supplying us with instant bursts of speed and power
2. The Anaerobic System - great for delivering speed and power for a short period of time
3. The Aerobic System - not a great one for expressing power or speed, but will keep you going for hours on end

Unless you’re an athlete, don’t worry too much about developing the alactic system. For everyday life, your focus should be on building up the anaerobic system and even more importantly, the aerobic system as these are the ones that’ll have the greatest impact on your health and fitness goals.

In the same way we use repetition brackets as a guide for individual training responses (i.e. strength, hypertrophy or muscular endurance), our heart also has its very own set of ‘rep ranges’ called ‘zones,’ and each zone helps to develop one of those three energy systems. 

So, how do we know which zone we’re working in?

Let’s think about weight training again. We often estimate the load we should lift based on a percentage of your one rep max for that lift. It works just the same with heart rate training. 

Heart rate zones are set as a percentage of maximum heart rate, which can be calculated using the formula 220 – age, or for a more accurate measurement, performing the Cooper Test, a 12-minute maximal running test (which is a bit less fun…)

Once a max heart rate has been established the zones can be set and you can confidently exercise for your desired training outcome: 

Zone 1 - 0-65% of Max HR
Helps to improve overall health by driving the recovery process in the body

Zone 2 - 66-75% of Max HR
Works on developing your aerobic fitness

Zone 3 - 76-85% Max HR
Helps to increase the amount of time and power you can work aerobically

Zone 4 - 86-95% Max HR
Helps to develop your anaerobic fitness

Zone 5 - 96-100% Max HR
Helps to develop the power you can express anaerobically and the ability to function at max capacity

These five zones provide the structure required to train cardiovascular fitness to its full capacity. Thanks to modern day fitness apps, we have complete access to what our heart is doing while we’re exercising.

Keep an eye out for my next blog - I’ll explain why it’s important to train your heart, and how you can use technology to train your cardiovascular system to achieve a stronger, healthier and happier future.