Why do we bother measuring and using heart rate?

It’s effectively a way of looking at the effort we’re making so we know how hard we’re working and, ultimately, how hard we can work. Use of heart rate training zones lets us make efficient use of our training time and gives us a measure of improvement. We generally split training zones by looking at percentage heart rates based on maximum heart rate alone, or maximum and minimum heart rates. The information below shows the convention of heart rate zones, the uses of that particular zone, and the percentage heart rates used to bracket these zones. Heart rate training zones are calculated by taking into consideration your Maximum Heart Rate (MHR) and your Resting Heart Rate (RHR). Within each training zone, subtle physiological effects take place to enhance your fitness.

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**Calculating training zones using heart rate**

Firstly, we need to find out your estimated Maximum Heart Rate (MHR) and your Resting Heart Rate (RHR). Your MHR can be established through laboratory tests or estimated by this formula: 220bpm – Age. For a person who is 50 years old, his/her estimated heart rate is 220-50 = 170bpm. This formula, may have a standard deviation of 7-11 beats/min but is used because it is simple to remember. Other formulas would include **HR _{max} = 217 − (0.85 × age)** (Miller et al.) and

**HR**.

_{max}= 205.8 − (0.685 × age)As for the RHR, find somewhere nice and quiet, lie down and relax. Position a watch or clock where you can clearly see it whilst lying down. You may simply determine your pulse per 10 seconds and multiply by 6, or use a heart rate monitor and look for the lowest value. After 20 minutes determine your resting pulse rate (beats/min). Use this value as your RHR.

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**Training/Target Heart Rate (THR)**

Based on your personal fitness goals, you can bring your heart rate into the different zones aforementioned to achieve your desired results. One of the methods you may use is the ‘Karvonen Method’.

The *Karvonen method* factors in resting heart rate (HR_{rest}) to calculate target heart rate (THR), using a range of 50–85% intensity:

THR = ((HR_{max} − HR_{rest}) × % intensity) + HR_{rest}

*Example for someone with a HR _{max} of 180 and a HR_{rest} of 70:*

50% intensity: ((180 − 70) × 0.50) + 70 = 125 bpm

85% intensity: ((180 − 70) × 0.85) + 70 = 163 bpm

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**Calculating calories burnt using heart rate**

For males, estimate the calories that you burned during your exercise session. This is given by the equation C = (0.6309 x H + 0.09036 x W + 0.2017 x A — 55.0969) x T / 4.184. C is the number of calories that you burned, H is your average heart rate, W is your weight, A is your age and T is the length of your exercise session in minutes.

For females, derive the calories that you burned. This is given by the equation C = (0.4472 x H — 0.05741 x W + 0.074 x A — 20.4022) x T / 4.184. Assume that you’re a 28-year-old female weighing 146 pounds. Your average heart rate during an exercise session that lasted 36 minutes was 138 bpm. You burned C = (0.4472 x 138 — 0.05741 x 146 + 0.074 x 28 — 20.4022) x 36 / 4.184 = 301 calories.

Hence, your training zones are important to ensure that you are actually putting in an optimal effort to achieve your fitness goals and to plan your workouts better.

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Resources:

Wikipedia (2011) *Heart Rate *Retrieved from, http://en.wikipedia.org/wiki/Heart_rate#Formula

Brian Mackenzie *Heart Rate Training Zones *Retrieved from, http://www.brianmac.co.uk/hrm1.htm

Royal Air Force Triathlon *Heart-rate Training Zones *Retrieved from, http://www.raf.mod.uk/raftriathlon/rafcms/mediafiles/498BDA28_1143_D71E_4627EBDF0F3C498A.pdf

Allan Robinson (2011) *How to Estimate Calories Burned by Heart Rate *Retrieved from, http://www.livestrong.com/article/78365-estimate-calories-burned-heart-rate/