Everything You Need to Know About Heart Rate Training
Illustration by Dalbert B. Vilarino for phantastic
There’s a million and one articles out there about heart rate (HR) training. None of them have lent themselves to share with our athletes without referencing multiple others, so we wrote one of our own. This article is designed to capture the essence of heart rate training: the what, the why, and the how. This is meant to be the only article you will ever need to read about heart rate training.
Most athletes want to swim, bike, or run faster. To maximize the benefits of training, our bodies need to train at a range of effort levels. It’s no good to exercise at maximum effort at all times, but you shouldn’t be plodding along at the same moderate pace all the time either. You need to change it up, and keeping track of your heart rate is the best way to objectively measure exercise intensity.
Professional athletes track their heart rates, but it is not just for the pros. Anyone who wants to be faster can use this method to elevate their performance. Using heart rate makes your training more targeted towards what you want to achieve. It allows you to calibrate your body to better understand the effort and corresponding pace you can produce.
Heart rate might as well be the holy grail of endurance training metrics. In essence, it measures the number of the heart’s contractions per minute (beats per minute, or bpm). With every beat, the heart pumps blood carrying oxygen around the body, helping the muscles that propel our body forward to burn the energy to function.
Basically, your heart is your body’s engine. How much energy and oxygen are “demanded” by your muscles depends on the effort level or intensity of exercise. Most people’s resting heart rates (their heart rate when they sleep or lie down) are anywhere from 50–70 bpm. At higher effort levels, the heart needs to beat faster to deliver more oxygen to our working muscles. The key to unlocking your body’s potential lies in understanding this relationship.
People have quite different heart rates, so rather than compare this metric across a large group of different people, it’s most useful to look at an individual. The harder you push yourself, the more oxygen your heart has to provide to your body, and the faster it beats. As a result, for a given person, heart rate is the basic measure of effort or workout intensity, and, when compared over time, it can be an indication of changing fitness level.
That is, if, at the same heart rate, you are able to perform better, e.g., run, cycle, or swim faster (generating same speeds is costing the body less “effort”), congratulations, you just became fitter!
To make it easier to define comparable effort of training, humans have designated heart rate “zones,” which are different effort levels that range from taking it easy to pushing yourself super hard. There are three important “anchor points” used to define these zones, and it’s important to understand why they matter. These are: Max Heart Rate (MHR), VO2max, and Lactate Threshold (LT).
What it is?— The maximum rate at which your heart can pump blood carrying oxygen to your muscles, expressed in beats per minute (bpm).
Why it matters?— It is a reference point to define your effort levels — essentially it is your maximum effort. Together with resting heart rate (RHR), it puts the bookends of your scale — your minimum and maximum effort. Other zones are expressed as percentages of your maximum HR.
How to measure?— The best way is to get on a treadmill, set it to 2–3% incline, and gradually increase the pace every 60 seconds until you are pushing yourself the hardest you can go. Take that HR as your max. Another rule of thumb is to subtract your age from 220. It gets less accurate after 50, as, generally speaking, max HR goes down with age.
How to improve? — It is mostly genetically predefined, though fitter individuals tend to have higher MHR.
For reference— While there is no good or bad maximum heart rate, at his peak, Lance Armstrong had an MHR of 201 bpm, and an RHR of 32–34.
What it is?— Your body’s ability to consume oxygen. VO2 max measures the maximum volume of oxygen that can be delivered to working muscles, expressed in volume of oxygen per kilogram per minute (ml/kg/min). Many factors impact this metric: the number of blood cells you have, your muscle efficiency, your heart’s ability to pump blood, etc. Your VO2 max effort usually corresponds to a pace that is a little faster than 5K pace, so a very strenuous effort that leaves you out of breath.
Why it matters? — To go faster, you need more energy delivered to your muscles. For you to get more energy, more oxygen needs to “burn more fuel” (i.e., calories). At VO2 max, you are at the maximum rate at which oxygen can be delivered to your muscles, which means it is the maximum rate at which energy can be created. A higher VO2 max means you can operate at higher intensity. It’s like having a bigger car engine.
How to measure? — The proper way is to do it in a lab. In a laboratory, VO2 max is calculated by measuring the volume (V) of oxygen (O2) that you consume while running on a treadmill or indoor trainer. In a VO2 max test, you’re hooked up to a breathing mask while you undergo a progressively more difficult treadmill test. The alternative is to estimate it as ~ 90% of your max HR (statistically falling into the population). Popular consumer heart rate monitors like Garmin will also estimate your VO2 max, but those readings are a similar rough guess.
How to improve?— Even though VO2 Max is largely genetic, it can be influenced by training (research estimates say by 15–20%). To see your VO2 max improve, try interval training at close to VO2 max intensity. This will increase your stroke volume (the amount of blood heart pumps with each contraction) and therefore allow you to deliver more oxygen to your muscles.
For reference — VO2 Max ranges
What it is?— The effort level at which your muscles accumulate lactic acid. Too much acid in your blood will make you feel like throwing up. If trained, this is close to the highest effort level at which you could run a half-marathon. Afterwards, you’d quickly start fading.
Why it matters? — Performance is all about the ability to a) deliver oxygen to muscles, while at the same time b) clean them from the lactic acid that accumulates as the byproduct of burning fuel. Our bodies have the ability to clean out the lactic acid at a certain rate. When lactic acid accumulates faster than it can be cleaned out, it starts accumulating in the blood, and you’ll eventually have to stop or slow down.
The point at which lactic acid starts accumulating exponentially in the blood is called the Lactate Threshold (LT). It corresponds to a certain effort level (heart rate as well as pace), and knowing this point is critical to knowing the amount of effort you can put in before lactic acid starts accumulating faster than it can be flushed. Once you reach that point, acid starts growing exponentially. As endurance athletes, we don’t want to be in this zone for very long. Hence, endurance running is often about walking that thin line and not crossing this threshold.
How to measure?— You can get it from a finger prick test where lactic acid is measured every minute as you increase effort. Alternatively, you can estimate it as a percentage of your max HR. If your max HR is 190, your LT would typically be around 85–90% of that, so 160 bpm.
LT is often expressed as a percentage of VO2 max, and increasing that percentage is a sign of improving fitness. It’s narrowing the gap of effort at which you can efficiently burn fuel (VO2 max) without accumulating lactic acid in your muscles (LT). Higher LT means you can work at a higher intensity for a longer time.
How to improve? — Exercise at a steady effort just below your LT. It is a “comfortably hard” pace.
In order to easily measure and standardize different levels of effort as well as consider different objectives, people have defined training zones. Everyone’s exact HR will be different, so rather than define these training zones in terms of precise HRs, we use scalable percentages instead. There are many different definitions, but we will look at a 5-grade scale.
Note, this is a simplified version of how the body uses energy, and the zones are more of a fluid continuum — as you run faster, the amount of fat to carbs you use for energy gradually changes.
There is no single best zone to train in. You will need to train in each zone for different reasons throughout the season. But depending on your typical racing distance, you will spend more time in one zone than the others. Here is an illustrative split in training plans for varying distances:
You will notice that sprinters spend a lot more time simulating sprint efforts at or above their LT. On the other hand, endurance athletes spend a lot more time in Zone 2, training their bodies to efficiently consume fat as a source of energy over a long period of time. Most training instructions from coaches these days are prescribed in terms of training zones linking back to training objectives.
It’s not as straightforward, as most plans are periodized with a different focus during each stage (e.g., building endurance in one and building speed in another) thus changing the ratios over time. It might be easier to think about this ratio spread out over the course of the season.
Finally, arguments against using training zones and heart rate. As with any tool or methodology, there’s a fair amount of debate about HR. Critics cite things like inaccuracy or over-reliance on HR making athletes unable to listen to their body as potential negatives.
It is true that an individual’s HR can vary based on factors like altitude, heat, or how well they’ve slept. For instance, heat increases blood flowing to the skin for cooling, which raises cardiac output. Dehydration reduces blood volume and also requires an increase in heart rate to make up the difference.
Furthermore, we can’t effectively use heart rate to monitor and control the intensity of very fast intervals since heart rate takes time to react to sudden intensity increases. This substantial cardiac lag can make the numbers on your HR watch meaningless.
All of the above considered, it is still one of the best metrics to look at. And put simply, it is one of the few inputs we can measure. Hence, it’s hands down one of our favorites.
About the author
phantastic is a superhuman performance lab, on a mission to help athletes reimagine the possible and realize their potential. We are a team of athletes, coaches, and scientists. But more importantly hackers, tinkerers and experimenters, obsessed with chasing faster.
About the illustrator
Dalbert B. Vilarino is an editorial illustrator based in Toronto, Canada. His illustrations appeared in The New York Times, WIRED, The Wall Street Journal, The Globe & Mail, Johns Hopkins Health Review et al.
© 2020 phantastic
