Runner coming into the finish line
September 30, 2022

George Epley



Most running training plans when preparing for a 70.3 triathlon will indicate a specific pace or heart rate (HR) to establish the desired amount of intensity of a workout. There is often great debate between pace or HR and the best matrix to maximize training benefits and race day performance. For many athletes, pace is a quantifiable matrix to judge their performance during a workout. The athlete will compare paces between runs and evaluate the quality of the activity solely based on this information. However, many factors will affect an athlete’s run pace on a given day, such as wind, rain, humidity, hills, the workout the day before, and GPS accuracy, to name a few. Thus, giving them results that may not represent the actual intensity of the workout. Factors that affect the validity of HR training include dehydration, sleep, caffeine, cardiac drift, and the accuracy of the heart rate monitor. Choosing between HR or pace when determining training intensity could significantly impact your physiological benefit and performance goals. Whether using pace or HR, it is vital to establish the correct training zones to match the proper amount of stimulus for each prescribed workout.

Typically, I will have an athlete perform a running time trial to determine lactic threshold (LT) pace and LT heart rate. The hard effort must be constant without a drop in intensity to establish a heart rate defection point to determine the lactic threshold and create accurate training zones. Below are examples from a run test to set both pace and HR training zones. I will repeat the testing several times to confirm the results and will regularly repeat testing during a racing season to update the training zones.

For several reasons, most of my 70.3 run training plans are in heart rate. First, if we look at the pace chart above and view zone 3 (tempo), we see a pace of 6:01 to 6:29 min/mile. We established this pace zone with minimal fatigue in the athlete. Generally, the run test is conducted after a rest day or at the beginning of a training block, where fatigue is not a prominent variable in the results. When we retest after a training block, the same conditions are established to determine if we have made performance gains. It would be challenging to develop pace training zones when fatigued since fatigue is a complex variable to replicate. Fatigue is also a challenging variable to measure. We train to build fatigue resistance.

The more fatigue resistance an athlete has, the faster they will go. An example of a workout to build fatigue resistance would be a morning Bike 4 x 10 min. @ 95 – 100% FTP, evening Run 4 x 15 min. @ 6:29 -7:20 pace (zone 2). After a high-intensity bike workout in the morning, it may be difficult for the athlete to maintain the correct pace zone, and they will commonly run at a higher intensity than required. However, suppose the same run workout is written in HR as 4 x 15 min. @ 85-89% of HR LT. Now, we focus on the correct physiological stimulus based on the prescribed workout, and the pace becomes arbitrary. However, monitoring pace and HR together is a great tool to monitor aerobic endurance with a matrix called aerobic coupling, where HR and pace are coupled with a less than five percent separation. If the separation between pace and HR is greater than five percent, this is decoupling. For example, if you do a two-hour run-in zone 2 HR and your HR and pace remain consistent, your fitness is optimal, and you’re ready to increase intensity. Another reason I prefer HR over pace is the training environment and weather conditions. On page ten in Daniels’ Running Formula by Jack Daniels’, the author states, “switch days to accommodate weather” if your workouts are based on pace, that may be a viable option but not very practical for the triathlete.

However, when your workouts are based on HR, a very windy day has little impact on your training. During the winter months, many of us utilize a treadmill during training. Since GPS on your watch cannot measure pace indoors, you then become dependent on the accuracy of the treadmill. Unless you can calibrate the treadmill, the chances are the pace numbers will be erroneous. Again, in this scenario, training with HR is a better option. As a coach, the more data I collect from an athlete’s workout, the better. This data set includes HR, pace, temperature, and other valuable data points. So, the more information you can record from your workout, the better. There are also times when workouts written in pace are appropriate for an athlete’s training. Still, I generally reserve those types of workouts when working on specific goals or when we can limit the variables that could affect the results. I will also use pace training when I need to see an immediate response to an increase in intensity where HR will lag.


An example may be a high-intensity track workout consisting of 400m intervals where HR may not reach its peak until well into the interval. Also, pace training is valuable when doing workouts above LT, where achieving a specific response may be difficult since there may be only a few heartbeats between zones. The gap between zones above LT is significant because our max HR will continue to decline as we age. However, HR is also beneficial in this scenario, providing information on how quickly the athlete is recovering from the effort and is valuable in determining the volume of future workouts at that intensity. A good training plan will have workouts written to address detailed training zones to achieve a specific physiological response. HR training provides a prodigious option to complete your training with optimal results. Good luck with your training and racing. Hard work does pay off.

Coach Geroge Epley has a passion for knowledge and believes it’s the key to maximizing your potential. He keeps abreast of the latest scientific studies, always trying to find more efficient and validated means of coaching his athletes. Knowledge in the form of communication is just as important. The more he knows about his athletes and the sooner he knows of changes in circumstances, lifestyle, or training, the greater resource he can be.

Coach George is a USA Triathlon Level II Certified Coach, USA Triathlon Youth & Junior Elite Certified, USA Cycling Elite Level, USA Cycling Cyclocross Certified, ACSM – Certified Personal Trainer, MBSC – Certified Functional Strength Coach, Training Peaks Coach and WKO4 Certified

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