Since the invention of the wireless heart rate monitor in the late 1970’s1, heart rates have been widely used by athletes, coaches and exercise enthusiasts as an important guide to training intensity. Heart rate training has been viewed in many ways over the years, from very precise to not so precise. Now, a growing number of coaches and exercise physiologists support the use of heart rates as an important part of biological feedback, as heart rates are a direct reflection of what is happening internally. In order to understand how heart rate plays a key role in training, you must understand the trends and variables that are associated with it.
The first step is to learn your “threshold” heart rate range. ”Threshold” or “lactate threshold” are terms that have been used for a long time to describe your maximum heart rate steady state, or the heart rate you can sustain at your highest level of output for an extended period of time – such as 10-20 minutes or longer. The science behind the lactate threshold has been greatly challenged in recent years. Studies are increasingly revealing that lactic acid is not the villain, but rather a good thing that helps prevent fatigue2. It is now believed that there is no “threshold” but rather a simple steady state of high end energy production at a specific heart rate range. For simplicity, I will still use “threshold” to describe this range.
The easiest way to determine your heart rate threshold range is to either perform a 10-20 minute time trial test, or study your 6-10+ minute peak heart rate averages from a race or a group ride. It is very important to test for heart rates when well rested and not fatigued. If you are too fatigued, your heart rate will not respond well and this will give you inaccurate results. This is a very common mistake. A good 10-minute average usually provides very accurate results but you want to retest over time to confirm this heart rate range. You can retest in the same way, with a 6-10+ minute effort while out riding or from a race, and again, only look at results when well rested.
With a good test and solid numbers, you can easily set up heart rate training zones
Next, in order to use these numbers to your benefit, you must consider the daily variables that affect heart rate, which will always be present to some degree, no matter how subtle. The best example of this is the weather. Every day brings a different temperature and humidity, but most days are similar as you go through each season. Weather becomes a bigger variable when you travel through the change of seasons. Any time you have a large swing in daily temperatures, especially when acclimated to the cold and experience a hot day, it is very common to see elevated heart rates. The same goes when traveling from a cold climate to warm weather to train or race. When traveling from low to high altitude, elevated heart rates are also the norm, but the opposite happens when traveling from high altitudes to sea level. Athletes living above 5000 feet adapt to less oxygen, so when they travel to sea level to compete, their heart needs to work less to provide the same amount of O2 to the muscles. Other variables include life stress, injury, nutrition and sickness.
Once you take into account daily variables and you have confirmed your threshold heart rate range, you can then start to learn re-occurring trends in heart rate through a training cycle. When well rested, heart rate will likely elevate fast, and into your threshold heart rate ranges. But as you become fatigued through a training period, heart rate will become increasingly harder to elevate consistently. How you perceive each daily effort will also change. Your perceived exertion when rested and with heart rates responding into your threshold ranges is usually low. As you train and build fatigue, it is very common to experience slow responding heart rates and higher than normal perceived exertions. The goal is to experience fatigue but to also recognize your level of fatigue through daily trends in heart rate to know when to rest and recover.
There is a lot to learn when it comes to learning the trends in heart rates. Whether you can train longer and harder or you have the ability to recover faster, heart rates will provide the bio feedback needed to allow you to make the best decisions on training moving forward.