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Loose your heart rate monitor, we have a better way to measure fitness

February 26, 2010

What is a heart rate monitor? A heart rate monitor is a device that allows a user to measure their heart rate during training. It usually consists of two elements: a chest strap transmitter and a watch/wrist receiver. The chest strap has electrodes in contact with the skin to monitor the electrical voltages in the heart. A radio signal is transmitted, which measures the users heart beat. The receiver then translates this into beats per minute or percentage of a theoretical maximum heart rate.

What is your heart rate and what affects it? Your heart rate is the rate at which your heart beats. Your heart has an intrinsic rate, which is how fast it would beat if you took it out of your body. This rate changes with age. Additionally, sympathetic nerves speed it up, and parasympathetic nerves slow it down. Exercise causes the parasympathetic nerves to be less active, which increases your heart rate during activity. Intense exercise further causes the sympathetic nerves to speed it up even more. But, heart rate is affected by more than just your activity. Numerous other factors come into play, including medicines you are taking, diseases or conditions you may have, the amount of sleep you get, caffeine intake, startling noises or actions, your age, your fitness level, the humidity, the temperature, your mindset, etc.

 Clearly, your heart rate is comprised of many variables. This makes heart rate difficult to analyze, especially when it comes to fitness. Unfortunately, for many athletes and trainers, they believe that the heart rate is a magical marker of fitness. They dutifully measure and record their heart rates and base their training and self worth on this number. Frequently, the importance of heart rate is overemphasized in training programs and the quest for actual, real fitness is lost.

The problem with calculating “maximum” heart rate

The problem with heart rate begins with the elusive maximum heart rate calculation. This is the value from which all training “zones” are calculated.  The most popular equation to find your maximum heart rate is:

 220 – your age = HRmax

 However, when they found that this wasn’t very accurate, Dr. Hirofumi Tanaka came up with a new formula:

 208 – .7 x (your age) = HRmax

The results of Tanaka’s study state that “HRmax is predicted, to a large extent, by age alone and is independent of gender and habitual physical activity or lack thereof” and that their findings “have the effect of underestimating the true level of physical stress imposed during exercise testing and the appropriate intensity of prescribed exercise programs.”

 Now, what good is a formula that doesn’t work? What they are proposing in the above formulas are that everyone of the same age should have the same maximum heart rate. Looking at the wide range of health and fitness of all 25 year olds, or all 45 year olds, this logically can not be true. Everyone’s heart will have a different capacity and, therefore, different maximum heart rate. The size of your heart and strength of your muscles surrounding your heart will have a great impact on what your heart is capable of, and this will be different for everyone. If we can’t accurately calculate our maximum heart rate, and hence our “heart rate zones”, are we chasing something intangible?

What’s the real problem with heart rate monitors? Let’s take a look at some basic problems with using heart rate as a measure of intensity. When was the last time you watched a suspenseful movie? Or got pulled over for speeding? Or got caught surfing the internet at work? How high was your heart rate then? It was likely pretty high, but were you actually doing any work? Runners frequently go out for training runs with their monitors faithfully strapped on. But how good is their interpretation of the results? Maybe they were chased by a dog for half a mile or almost got hit by a car. Maybe the humidity was higher or they didn’t get as much sleep the night before. Multiple factors could cause an abnormal spike in heart rate values, rendering them useless.

There is also a mental aspect of wearing a heart rate monitor. Every once in a while you may realize you are below your 60-70% range and up the intensity. But, how many people set the ranges on their monitor so that it beeps if their heart rate gets to high? Then, thinking they are overdoing it (even though they don’t feel tired), slow down. They just drastically reduced the effectiveness of their workout.

Why do people use heart rate monitors anyway?

The reason athletes and trainers like to measure fitness and intensity using a heart rate calculation is because they have not defined fitness and performance in any real way. This allows them to make pretty graphs and charts and, heck, you can even download information from your monitor onto your computers these days and come up will all sorts of cool stuff. But, does it really tell you anything about your fitness level? Being able to say that you “were in your ‘target’ heart rate for 20 minutes” or “I put forth such a great effort, I nearly ‘maxed out’ my heart rate” does not translate into improved fitness or greater work capacity.

Heart rate monitors may have a place in training for special populations, such as pregnant women and people who have had serious heart trouble in the past, but many people strap on their monitors for somewhat of a false safety blanket. To them, staying in their “heart rate zone” means they aren’t pushing too hard and aren’t pushing too little. This causes them to ignore how they are actually feeling and rely on an electronic device and arbitrary limits to tell them when to slow down or speed up.

How am I going to measure my workouts without my heart rate monitor? Heart rate monitors do not measure quality or productivity. Riding your bike on the same course, in the same amount of time, will produce different heart rates on different days, due to all of the extrinsic factors affecting the measurement. Measuring how far and how fast you can move is a much better measure of fitness and performance. Here’s a great article on intensity and how to measure your workouts using power output.

What is comes down to is this: push yourself every workout. If you’re lallygagging, go faster. It doesn’t matter if you’re at 50% or 90% of your max heart rate (because we already know that’s speculative and inaccurate). If your purpose of training is to waste your time and complicate your training, by all means, strap that sucker on and stay between 60-70%. But, if your purpose is to perform better, to get fitter, and improve your athleticism, then measure your times, your distances, and your weights. Strive to be faster, go farther, and lift more.

In real life, you must be able to function without the feedback of a heart rate monitor. At CrossFit, we’re training for sport, as well and the unknown and unknowable things life throws at us. If we’re carrying our buddy in combat or trying to get out of a burning house, are we going to slow down because our heart rate is too high? Of course not. We need to know our limits without relying on an inaccurate electronic device to feed it to us.

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