Some experts believe that power meters and speed and distance devices have made heart rate monitors irrelevant.
Written by: Matt Fitzgerald
Heart rate monitors took the endurance sports world by storm in the early 1990s. The practice of heart rate monitoring appealed to cyclists, runners and triathletes as a way to make their training more precise and scientific. By the late ‘90s a majority of cyclists and triathletes (if not the majority of runners, who always lag behind in terms of adopting new technologies) used heart rate monitors in every workout and race, heart rate-based training systems dominated systems based on other intensity metrics, and coaches such as Sally Edwards had made healthy careers as heart rate training gurus.
But then the backlash began. Skeptical coaches and exercise scientists pointed to the limitations of heart rate monitoring and the dangers of over-relying on it. With the advent of power meters for cycling, some coaches and experts began to argue that proper use of a power meter makes heart rate monitoring pointless. And with the advent of run speed and distance devices, the same argument is now being made to runners.
My position is not quite so extreme. I believe that there is potential value in heart rate monitoring, but that heart rate should be used as an intensity metric secondary to power or pace. First let me make the case against heart rate monitoring, then the case for it, and then let you decide what to do.
The Case against Monitoring Heart Rate
Heart rate is not a super-reliable metric of exercise intensity. Strap on a heart rate monitor and ride a rollercoaster. As your fly along with a death grip on the safety bar, your heart rate will climb near its maximum. Does that mean you’re getting a great workout? No, it means your sympathetic nervous system is highly stimulated, just as it is likely to be during races, which is why heart rate is often 10+ BPM higher in races than it is at the same work output level in workouts. For this reason, you can’t trust heart rate to properly control your pacing in races. My greater point is that your heart rate is affected by a variety of factors besides exercise intensity, so it’s a dubious choice as the metric by which to measure and control exercise intensity.
Heart rate training formulas are iffy. Every heart rate-based training system relies on the use of formulas to establish target heart rate zones for different types of workouts. Even the best of these formulas are too one-size-fits-all to establish truly custom-fitting intensity targets. For example, some systems assume that every athlete who has a threshold heart rate of 168 has a VO2max heart rate of 175-179, but that’s not true. Heart rate profiles are very different from one athlete to the next, even when there is some overlap, making the use of one-size-fits-all formulas dubious.
Heart rate monitoring is useless at very high intensities. You can’t effectively use heart rate to monitor and control the intensity of very fast intervals, because the heart rate climbs throughout them. Anytime there is a sudden, drastic increase in exercise intensity, there is a substantial cardiac lag that makes the numbers on your HR monitor display not worth paying attention to.
Heart rate is not performance-relevant. In my opinion, the greatest flaw of heart rate monitoring as a means of monitoring and controlling workout intensity is that heart rate is not performance-relevant. You can’t set heart rate goals that will help you race better. For this reason, heart rate is not a very motivating type of workout feedback. Pace and power are. When you train sensibly with pace or power output as your primary form of feedback, you tend to push a bit harder in an effort to beat your previous standards. The introduction of this self-competitive aspect into training leads to faster progress.
The Case for Monitoring Heart Rate
Heart rate monitoring helps keep intensity in check. Perhaps the most valuable effect that heart rate monitors have had on endurance sports is that they have familiarized endurance athletes with the idea that there is an appropriate intensity level for each type of workout, and exceeding that intensity level is as counterproductive as falling below it. One of the most common errors that endurance athletes make with respect to intensity is pushing too hard in workouts that are intended to be easy or moderate. The use of target heart rate zones is a very effective way to prevent athletes from getting carried away with themselves.
Heart rate-power and heart rate-pace relationships provide very useful information. While heart rate monitoring on its own is admittedly of little value to the endurance athlete, simultaneous monitoring of heart rate and pace in running and of heart rate and power on the bike is very useful in helping the athlete track changes in fitness, fatigue and performance.
For example, as you gain fitness your heart rate at any given power output or pace should gradually decrease, and your power output or pace at any given heart rate should gradually improve. Tracking both power output or pace and heart rate allows you to follow these trends as they unfold. Another useful way to use these relationships is to track heart rate decoupling in long endurance workouts. When such workouts are performed at a steady intensity, your heart rate will hold steady for a while and then begin to increase as you fatigue. The better your endurance, the longer you can go before heart rate decoupling occurs.
Specific models of run speed and distance devices with integrated heart rate monitors have useful proprietary features based on heart rate-pace relationships. Polar’s RS800 speed and distance device has a feature called Running Index that scores every run you perform by quantifying your fitness level with calculations based on the relationship between your pace and heart rate. It translates roughly as an indicator of your current VO2max and is therefore a help tool for tracking changes in your fitness.
This article was adapted from the book, The Runner’s Edge, by Stephen McGregor, PhD, and Matt Fitzgerald.