Background: Why Do We Use Heart Rate Monitors?
We here at SEA define “training” as the systematic use of exercise to improve capability. Through the science-based cyclical application of stress (exercise) and rest, the body adapts to those stressors, resulting in improved ability to go faster or farther. The intensity of that exercise is very important for training for two main reasons. First, the specific structures and functions which exercise stresses are highly dependent upon intensity itself. For example, certain changes in our metabolism of carbohydrates don’t happen unless the intensity is quite high.
Second, the amount of stress applied to the body is directly tied to the amount of workload (the multiple of volume and intensity) used in training and if you don’t know the intensity of that training, you don’t know the workload. To put it simply, as a coach I need to know how tired you are going to be from one training session in order to plan when and how hard the next session will be. If you tell me “I trained really hard today,” then my next question will be “For how long?” Obviously the amount of fatigue generated by that workout varies greatly if that “really hard” workout was two hours, as opposed to 20 minutes. The converse is also true. If you tell me you went for an hour, the fatigue generated from that workout is very different between a “walk” and “as hard as I could go.”
In some sports, like road running, or cycling with a power meter, it’s extremely effective to use what I call “output” measures of intensity. In road running this would be measuring intensity by pace, and in cycling with a power meter, this would be measuring the watts applied to the pedals. However, in most of the sports I coach, we don’t have reliable output metrics. You can’t really measure power or pace in a mountain running/skiing race where the grade, surface, and technicality of a climb can vary drastically. However, thanks to the advent of the portable heart rate monitor in the late 80’s/early 90’s, we CAN measure what I call an “input” measure of intensity, in heart rate (HR). While most of our metrics that we care about are output measures (speed and distance), we know that the relationship between input and output metrics is stable and reliable in most situations. Thus, when training for sports where output metrics are not available, training with HR is the next best thing (and indeed, because HR is actually a measure of the stress that a given workload is enacting on the body, even when you have output metrics it’s also best-practice to also measure HR).
Which Type of Heart Rate Monitor Should You Use?
Broadly, there are currently three main methods of measuring HR. The first, and gold standard, is the clinical Electrocardiograph, or ECG (often called an EKG from the German spelling of Kardio). This measures, from several points, the total electrical activity of the heart, giving us the most accurate measurement of HR.
A close second is the Chest Strap ECG. While a clinical ECG may use up to 12 leads to measure total heart electrical activity, a 3-lead ECG is considered the gold standard for simply measuring the rate of contractions. A chest strap ECG (from here simply called a chest strap), is simply a two-lead ECG built into a strap that you can wear around. As a result, the accuracy of a chest strap is somewhere between 99.8% and 99.9%. The chest strap is commonly paired with a watch or a cycling computer so that you can monitor your heart rate during workouts.
The third, and an increasingly popular, option is Photoplethysmography (PPG). PPG’s were initially used in pulse oximeters, but now you will likely be familiar with the technology from its ubiquity in wrist-based fitness trackers such as the Apple Watch, Fitbit, Garmin, etc. Also called “optical heart rate sensors,” PPG’s measure the heart rate through shining light into a blood vessel and measuring the way that the volume of the blood vessel changes the reflections in light with each heartbeat. The accuracy of PPG’s can be as high as 92% in more advanced models like the Apple Watch, but varies significantly by brand, use, and exercise intensity.
So what do we recommend? For checking the health of your heart, use a 12-lead ECG. While you’re not training, monitor your activity with a PPG. However, we highly recommend a chest strap for training because we have found:
- The chest strap is more accurate at higher intensities and capturing intervals.
- The chest strap stays put during workouts, securing accuracy.
- You can wear a chest strap under your clothes, so in the winter this allows you to wear your watch outside your jacket, thus getting great HR data without cold wrists. And who likes cold wrists? Nobody.
Want to do additional reading about Heart Rate Monitors? Click below for sources used in this Blog Post:
