How Does a Heart Rate Monitor Work?

When the heart beats, an electrical signal is transmitted through the heart muscle in order for it to contract. The transmitter picks up this signal and sends it to the wrist receiver, which displays the data.

Heart Rate Monitors used to consist of a transmitter attached to a chest strap and a receiver in form of a watch. Nowadays there are models that have a built-in optical heart rate monitor, which means – as long as the watch fits correctly – there's no need to wear a chest strap. There are features that you won’t get from optical reading, but there is an option to use the chest strap monitor with these models too.

Why Use a Heart Rate Monitor?

A heart rate monitor shows you how hard you are working and measures the intensity of your workout. Optimal intensity is when you are working hard enough to positively affect your health by burning fat and building muscle. It will help you to achieve optimised training in which you don't overwork yourself or work out too easily. Once you figure out your limits you will have clearer targets, be more focused, and you will achieve better results more easily.

Identifying Your Training Target

What is your goal? Do you want to improve your aerobic fitness, lose weight, are you coming back from a long break or do you have specific race goals in mind?

Calculating Your Heart Rate Limits

The advanced monitors have the capacity to calculate most of this data for you. For those of you who don't have these features, the following formulas will guide you.

1. Resting heart rate
   Do this by counting your pulse for one minute while still in bed. Your resting hr may vary each morning. For better measurement, count it over 3 mornings, then add the measurements and divide by three (number of days). Find your resting heart rate as soon as you wake up (preferably do the counting when woken up naturally not by alarm). (ie Sunday=65, Monday=69, Tuesday=67; 65+69+67=201/3=67
2. Maximum heart rate
   220 minus your age (e.g. 220-36=184)
3. Heart rate reserve
   Subtract your heart rate reserve from your maximum heart rate (based on the maximum heart rate example: 184-67=117)
4. Lower limit of your threshold
   Maximum heart rate multiplied by 60% (184x0.60=110.4)

Heart Rate Zones

There are four main heart rate zones:

1. Recovery or energy efficient zone 60-70%
   Training in this zone improves the ability of your heart to pump blood and improve the muscles' ability to utilize oxygen. The body becomes more efficient at feeding the working muscles, and learns to metabolize fat as a source of fuel. You will burn fat, may lose weight, and you will be allowing your muscles to re-energize with glycogen.
2. Aerobic or target heart rate zone 70-80%
   Training in this zone will develop your cardiovascular system. Your ability to transport oxygenated blood to the muscle cells and carbon dioxide away from the cells will be developed. It is also effective for increasing overall muscle strength.
3. Anaerobic zone 80-90%
   Training in this zone will develop your lactic acid system. In this zone the amount of fat being utilized as the main source of energy is greatly reduced and glycogen stored in the muscle is predominantly used. One of the by-products of burning this glycogen is lactic acid. There is a point at which the body can no longer remove the lactic acid from the working muscles quickly enough. This is your anaerobic threshold. Training in this zone helps to increase the lactate threshold, which improves performance. Training in this zone is hard: your muscles are tired and your breathing is heavy.
4. VO2Max or Red line zone 90-100%
   Training in this zone will only be possible for short periods. It effectively trains your fast twitch muscle fibres and helps to develop speed. This zone is reserved for interval running and only the very fit are able to train effectively within this zone.

Choosing a Heart Rate Monitor

It's incredible how quickly technology changes nowadays. Almost all of the GPS running watches have a wrist-based heart rate monitor. How to choose the most suitable model?

A basic model of the GPS watch with HR is a great option if you need to track pace, distance, time and obviously the heart rate. Some of the models like Garmin Forerunner 35 and Polar M200 have wrist-based heart rate, which is really convenient to use. They have smart notifications – you will see the messages and phone calls on your watch screen. They will also track you daily steps, distance and calories. Not bad for entry level 'basic' GPS watches!

The more advanced the GPS watch, the more features you get, so consider this if you not only run, but also swim or cycle. The Polar M430 is a great watch with plenty of useful features – VO2 estimation, race finish predictor, it can even record your heart rate underwater! If you are going for a long distance runs consider the Garmin Forerunner 935 or Fenix 5. Battery life in these watches lasts up to 50 hours in GPS mode, so it's a great option for ultra running or multi days races.

Most of the Garmin watches can be purchased in a bundle – with a HR chest strap – even if they include wrist-based HR. Why would you need a strap if you have a heart rate measured from your wrist? The heart rate chest strap gives you running dynamics – cadence, stride length, vertical ratio, vertical oscillation, ground contact time and balance. It's very useful information if you are training for a race and you want to measure your running technique and performance!

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