Despite the rise of powermeters, many of our athletes still use heart rate as the metric by which we coach them. There are a number of reasons for this. Heart rate monitors are cheap and heart rate based training is still highly effective. As opposed to power, heart rate has some level of variability. Power is the gold standard, the numbers are exact and the training programs can be a little more precise (down to the watt). Heart rate however, can be affected by a number of factors. Say for example, you have 5 minute efforts at 200 watts. You may do these efforts on a Monday with a heart rate of 140bpm. You may do these efforts again on Friday but your heart rate is now 155bpm. What does this mean?
Athlete’s often comment on how their heart rate is too high or low relative to the effort level. This variability can be down to a number of factors, and it’s important to take these into account when choosing to train with heart rate.
Weather: Riding in the heat can cause your heart rate to be higher relative to effort level, especially if you’re not acclimatised to riding in the heat. It is important to factor in more recovery time after training in high temperatures.
Caffeine and food: Stimulants such as sugar and caffeine can raise your heart rate higher than what it should be relative to effort level. This isn’t too much of an issue, but more a consideration when staring at your heart rate data.
Stress and fatigue: Fatigue can come in many forms such as lack of sleep, a hard training block, work stress or overtraining. Your heart rate may be too high during easy efforts, or not high enough during hard effort.
Illness: A good early warning sign that you may be getting sick is a low heart rate during moderate to high level efforts. We see this in post ride comments all the time.
It is important to report all of the above to your coach. A good coach is adaptable. They will alter your program to take into account the reason as to why your heart rate isn’t in the prescribed zone. A good rule of thumb is that if your heart rate isn’t in line with your effort levels, and you haven’t been eating or drinking an unusual amount of sugar/caffeine, you should take it easy for the rest of the workout or stop the workout, and for a day or two post workout.
Even if you prefer to train with power, training with both power and heart rate can help paint an even greater picture of your performance. For example, the below images show the same workout done by an athlete at the start of a program, and then 5 weeks later. In the second image you can see the athlete has not had to work as hard to deliver the same (actually slightly higher) power output. At its most basic, this is what we train for: more power for less physiological cost.
Our bodies are smart, and they are trying to tell us something when we exercise. It is important to listen to your body. Your heart rate won’t improve mid-workout if you are sick, stressed or highly fatigued. Pushing harder and longer will only mean you’ll have to rest harder and longer when these factors catch up with you. Train smart, race smart and in the immortal words of Roxette, “Listen to your heart (rate)”.
