The short answer is: Heart rate training is a valid training modality, but there are more effective ways to reach your best. For decades, coaches have been designing workouts based on heart rate.  In the 1980s, Mark Allen and others won Ironman World Championships using heart rate training.  Since then, several alternative technologies have emerged.  Cycling power meters and GPS watches have eclipsed heart rate monitors in popularity and effectiveness.   A mix of power-based and pace-based training will lead to speedy and consistent race results.

Determining Zones Can Be Difficult

Determining heart rate zones requires an athlete’s resting heart rate, maximum heart rate, and other heart rate information. Methods for determining resting heart rate and maximum heart rate can be unreliable.  Resting heart rates may be skewed by caffeine, activity levels, fatigue, etc. The standard formula for maximum heart rate (i.e., 220 – age) does not account for an athlete’s fitness and other characteristics. Determining maximum heart rate via stress testing can be problematic because many athletes do not exert to their true max heart rate.   If these foundational parameters are inaccurate, the resulting heart rate zones will be inaccurate.  As a result, training will be suboptimal.

Cycling with a Power Meter Leads to Consistency

Cycling power meters show exertion exactly and immediately.  That is, power meters indicate precisely how much power is being exerted at a given time.  Such precise and immediate feedback enables very precise training and racing.  As cyclists become fit, leg strength/endurance becomes the key factor.   When using heart rate, fit cyclists may inadvertently increase exertion without immediately causing a commensurate heart rate increase – particularly during long endurance rides.  These inadvertent increases in exertion can lead to early fatigue.  When racing, unwittingly increasing exertion can lead to diminished run capacity.  Training and racing with a power meter will lead to more consistent results.

Pace-based Run Training Challenges Runners

After some basic pace testing with a GPS watch, runners can set their training paces.  Despite factors that may affect heart rate (e.g., caffeine, lack of sleep, etc.), runners can typically match prescribed pace goals for a given workout.   Therefore, pace-based run training typically leads to better results.

Using Heart Rate Data

Heart rate monitors can be useful for triathlon training.  Wearing a heart rate monitor during training helps you understand how your heart rate correlates to running paces and cycling power.  As workout conditions change (e.g., unusually hot weather, altitude, etc.), heart rate data will inform deviations from prescribed workout paces and power ranges.  For example, on an unusually hot day, you may not be able to maintain prescribed run paces despite considerable effort.  At this point, you may ignore the prescribed pace/power and attempt to maintain a heart rate associated with the prescribed pace/power.   Similarly, if your power meter malfunctions, you may revert to heart rate.  After noticing a power meter malfunction, perform the remainder of your workout/race based on heart rate data associated with your prescribed power goals.