We often get the question of what metric is best for tracking intensity, referring to heart rate, power, pace, and rating of perceived exertion (RPE). This is a great question so I thought I would cover this in today’s message.
The quick response is that neither of them are best. The best metric is using them all in collaboration with each other. Together, they are extremely powerful. Separate, there are gaps in their information.
Power, which can be used while cycling and running, gives an instantaneous value of effort. Its immense value is that it is a leading indicator of effort and instantaneous. What this means is that you know instantly whether you are at the right intensity rather than several minutes later. For this reason, it is ideal for pacing efforts. Additionally, power provides a lot of valuable information post workouts due to its instant nature. You can see exactly where you sprinted to catch a pack, fell off that interval, or put in that massive effort that ultimately left you too tired to continue.
Pace is another leading indicator but unfortunately impacted by terrain, wind, and environmental conditions. These downsides make it less than ideal for cycling and running where terrain and wind can greatly vary though running is more manageable. Pace is a valuable metric for swimming and track running where conditions are more controlled.
Heart rate, on the other hand, is a lagging indicator. Heart rate tells you how much an effort (usually that occurred a couple minutes ago) took out of you physically. This has its downsides but also some benefits. For judging intensity on the spot, especially for short high intensity efforts, heart rate is not very valuable. With that said, heart rate is extremely valuable when combined with other metrics. For example, let’s say you rode 300 watts (power) one week at 160 bpm and then several weeks later rode the same 300 watts at 165 bpm. This would tell us that the 300 watts took more out of your body the second time. This could be that your fitness has decreased, it was possibly a hotter day, or that you are tired or have not gotten enough sleep lately. On the other hand, if your heart rate goes down at the same wattage, we know the opposite of each of these could be true. In short, heart rate gives us a fuller picture of your workout, race, and fitness.
Rating of perceived exertion is also valuable because we should always seek to be super in-tune with our bodies. The goal is to be able to know where your wattage, pace, and heart rate are even if not looking at them. This is valuable in so many ways, especially if your technology malfunctions in a race.
So, in summary, I encourage you to utilize every metric possible but also stay very in-tune to your internal metric.