A common functionality that happens to be shared by most wearables and fitness trackers out there is the ability to measure heart rates. So much so, that this feature is actually making its way to even mobile devices. Heart rate trackers have more than carved a niché for themselves, and are now the most mainstream characteristic of any fitness tracker worth its salt.
This brings about the question: why heart rate? Fitness is directly related to the heart rate patterns, but how can a user make sense of the readings in order to bring about a more quantified fitness regime?
This major question shall be the crux of this article, wherein this author tries to go over the basics of heart rate monitoring systems and how they are useful for a fitness program.
EASING INTO THE BASICS: HEART RATE TYPES
So before we actually go into the wearable part of the equation, let’s just skim over the basics of heart rates, and perhaps the most important factor to consider – the heart rate types.
Heart rate, simply put, is the rate at which the heart beats per minute. Building up the heart rate would lead to more calories being burnt and more effective workout routines – which somewhat explains the importance of cardio regimes before active weight training in a workout.
There are two major types of heart rate: Resting Heart Rate, and Maximum Heart Rate. Resting heart rate is the measure of the heartbeats when the body is in a still environment – which implies the state when the body is completely calm and there’s no exertion. The average resting heart rate is 60-80 beats per minute, but it’s lower for physically fit people. The average resting heart rate also increases with age, and has also been interestingly found to be more when the body is asleep, than in awake conditions.
Maximum heart rate is the maximum number of heartbeats per minute, and can be calculated via different formulae. While the most common one is [220 – (the age of the individual)], some additional formulae include [208 – (0.7 * the age of the individual)] for runners under 40, and [205 – (0.5 * the age of the individual)] for runners over 40.
The maximum heart rate, or MHR, is important since it helps the runner better understand the next major concept in heart rate patterns – heart rate zones.
HEART RATE ZONES
Heart rate zones give a clearer understanding to the individual, regarding the pulse rates correlated with the workout regimes. Five major heart rate zones can be listed out, which give a good idea of where you need to be in order to achieve more running goals.
Zone 1: 50 – 60% of MHR
This Zone is defined for comfortable activities. This can be a pre warm up zone, and is the precursor to getting to the next zone.
Zone 2: 65 – 70% of MHR
This is also a part of the easy rest and recovery zone, and helps in vital activities such as muscle and tissue repair, removal of waste products, reducing inflammation and restoration of energy and nutrients.
Zone 3: 70 – 80% of MHR
This is the endurance aerobic zone, which increases the aerobic capacity of the lungs, and the overall endurance of the body.
Zone 4: 80 – 90% of MHR
The threshold zone improves upon the maximum performance capacity, develops the lactic acid system and also vastly improves the aerobic capacity of the lungs – the organs of primary importance for a long distance runner.
Zone 5: 90 – 98% of MHR
This is the anaerobic threshold, and is also called race pace. It requires maximum amounts of effort with low volume.
Zone 6: 98 – 100% of MHR
This is where true blue athletes meet their biggest challenges – the max aerobic level, or the VO2 max training level.
For more quantified running, athletes generally measure the heart rate zones that would be suitable for their running paces.
MEASURING HEART RATE – THE SENSORS INVOLVED
When it comes to fitness trackers measuring heart rates, different types of equipment follow different modus operandi. For example, the Apple Watch relies on photoplethysmography which is based on a simple fundamental : Blood appears to be red because it reflects red light and absorbs green light.
[The] Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through the wrist at any given moment. When your heart beats, the blood flow in the wrist — and the green light absorption — is greater. Between beats, it’s less.
By flashing its LED lights hundreds of times per second, the Apple Watch can calculate the number of times the heart beats each minute — your heart rate. In addition, the heart rate sensor is designed to compensate for low signal levels by increasing both LED brightness and sampling rate.
To measure the heart rate in the background, the Apple Watch relies on Infra-red light rather than the green ones.
Fitbit trackers on the other hand use PurePulse LED lights, which reflect onto the skin to detect blood volume changes through the expansion / contraction patterns of the capillaries.
MAKING SENSE OF THE DATA
Now more specialised heart rate trackers out there can give a plethora of information regarding the running patterns and the body’s response frameworks. So information such as VO2 max levels, blood flow volume, and even running dynamics such as cadence, ground contact and vertical oscillation can be measured.
The key is to exert yourself, as long as your heart rate tracker is giving a thumbs-up. Exertion includes running at faster speeds, or with more gusto. Once you step from zone to zone, there’s really no looking back, and the body automatically habituates itself to burn more calories.
At the end of the day, correlation is the name of the game, so gathering the data taken from the heart rate sensors and accordingly getting workout routines suggested by professional fitness practitioners would undoubtedly achieve fitness goals in a more quantified manner!
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