Why Training With Heart Rate is Still Relevant

Heart Rate Training Is Not Dead

Like so many areas in our lives, the pace of innovation in cycling is accelerating. Power meters were once a rare sight anywhere outside of the pro or Olympic team ranks; now they are ubiquitous at the Saturday coffee shop ride. But this has led to a few misconceptions, both for athletes with power meters and those without.

Misconception #1: Heart rate is not a good indicator of intensity
Heart rate is not as good or as precise an indicator of intensity, compared with power, but there are a lot of athletes who are unwilling to pay upwards of $1000 for a power meter. Can you train effectively with only heart rate? Yes. You just need to understand what a heart rate monitor is telling you and how you can use that information.

During exercise your heart rate is your body’s response to the work you are doing (power is a direct measure of that work). After more than 20 years of working with power meters we know a lot more about the nature of that response, and that has improved the efficacy of heart rate training. For instance, heart rate data from the field test that CTS uses with athletes (two 8-minute time trials separated by 10 minutes of easy spinning. Click here for CTS Field Test Instructions and Workout Descriptions) correlates strongly with power data from the same test. This means that the following calculations using the higher of the two average heart rates from your time trial will establish training intensity ranges that are equally effective for targeting your aerobic system, sustainable pace at lactate threshold, and repeatable efforts at VO2 max.

Misconception #2: If you have a power meter, you don’t need to monitor heart rate.
A lot of power meter users no longer wear heart rate monitor straps even though every power meter is equipped with heart rate monitor technology. But without heart rate, you’re gathering power data out of context. Heart rate data informs you about your body’s response to producing power. Today you might complete SteadyState intervals at 250 watts, an average heart rate of 165 beats per minute, and a perceived exertion of 7 on a scale of 1-10. Tomorrow you might be able to complete the exact same intervals at 250 watts, but at average heart rates of 160 bpm. If perceived exertion is still 7-8, I’d tell you to keep training. The power and PE are right, and the decreased HR is likely due to an increase in plasma volume as a response to yesterday’s workout. However, if PE is 9-10 and you feel like you’re in a time trial to produce 250 watts at 160bpm, the heart rate and RPE are indicators of significant fatigue and a need for more recovery.

Perceived exertion – and even pace – can provide context for heart rate for athletes without power meters. If HR is decreased to 160bpm (which can happen from increased plasma volume, interval workoutson back-to-back days, etc.) but your perceived PE and pace are normal for SteadyState intervals, continue at 160bpm. One mistake athletes often make is to push harder in an effort to achieve their goal of 165bpm. PE goes off the charts, but what they don’t realize is that power output does too. Instead of 250 watts they’re doing intervals at 260-270 watts, which is higher than they can sustain for those intervals. Instead of 3 high-quality intervals, they’re fried after one.

Heart rate response during intervals can also tell you whether you should continue with your workout or change your plans. When an athlete has recovered from previous training and is ready for today’s workout, heart rate will increase quickly as an interval begins (you should reach your target heart rate within 30-45 seconds). If your heart rate is slow to respond initially and stays elevated longer than normal into your recovery period, it’s a sign of fatigue. More often than not, you’re better off saving your hard interval sessions (SteadyState or harder) for another day.

Additional guidelines for heart rate training

1. Be aware of cardiac drift: heart rate will gradually creep upward during a workout, especially in hot weather or indoors in a warm environment. This is a response to dehydration and an increase in core temperature; your heart beats faster at a given power or effort level. The increase can be 5-10 bpm in a hard one-hour workout, or up to about 15bpm during a 3+ hour ride.
2. Heart rate is not a good indicator of intensity for some workouts: Sprints and 1-3 minute PowerIntervals (max efforts) are so short that heart rate doesn’t respond quickly enough to provide meaningful information during the actual effort. But since they are also maximal efforts, there’s no need to worry about data during the interval. Just dig in and go!