Why Training With a Power is Better Than Heart Rate

Power meters have become much more prevalent in bike equipment in the past five years. Prices have come down significantly as the market has become more competitive. Manufacturers are making bikes with power meters as a stock option. Companies like SRAM are even setting up their components as “power ready,” alleviating the need to buy an entire crankset, ultimately reducing costs.

Power meters have been simmering in the background since SRM power meters were first spotted on athletes’ bikes at the 1984 Olympics. However, even though they were initially utilized for professional athletes is not a reason that you can not benefit from the same great technology that a power meter provides. Three of the key reasons a power meter can help you include:

Precision: Due to cardiac drift*, training with heart rate is often challenging when trying to do longer sustained efforts. Utilizing power provides the precision to ensure your first effort will create the same physiologic load as your last effort. You can see the variability in heart rate (red) and power (pink) in the image below. Note the climb of heart rate during the intervals and the peak heart rate increase from one interval to the next.

Accuracy: Heart rate has variability. Fatigue, stress, sleep, illness, and even hydration affect your heart rate. These changes are essential to note, understand and influence your training decisions, but we do not want the inconsistency to impact the workout metrics from one day to the next. On the other hand, barring some malfunction or change in your power meter, power will be the same today, tomorrow, and two years from now, which means that any changes result from improvements in your physiology and fitness.

Caloric Tracking: Last but not least is power’s more accurate caloric tracking. The improved accuracy of calories is because, unlike heart rate, power measures the actual work. If you have been around anyone using power, you may have heard them talk about their “kJs.” When they say this, they are referencing the number of kilojoules burned during their workout, which is a direct reference to energy. This information can help you in your diet planning and fueling strategies for training and racing.

Ultimately, if you will not utilize the data to guide your training, a power meter will be a paperweight for your bike. However, if you do choose to use the data, it can be a tool to propel you to never achieved fitness levels quickly! If you are still trying to figure out where to begin with your power meter search, here are our thoughts on power meters.

*cardiac drift – The body’s natural phenomenon of increasing heart rate caused during exercise lasting more than five minutes. This “drift” is caused by factors such as increased core temperature, the fight-or-flight response, dehydration, muscle activation, and many other factors