How Hard Should You Run? Follow Your Heart.

I think sometimes I sound like a broken record talking about how and why to use heart rate-based training for runners and triathletes. But I wanted to beat that drum a little bit more and give a quick example from my own training with a couple runs I did last week. I also wanted to show that, even though I’ve trained like this for years now, I still have seemingly “bad” runs with the approach, but that’s okay. I keep plugging along and trust the process. 

I’m showing an image comparing two runs from last week, four days apart, nearly identical route, similar conditions, with more-or-less the same heart rate. But I was about 30 seconds per mile slower in the second run shown on the right, and for a shorter distance. Bad run right? Nope! I was patient. I executed the run just as planned. I followed my heart. And it wanted me to have a slower run on that particular day. 

Running by heart rate…

Heart rate training is all about listening to your body. Wearing a heart rate monitor while you run and workout is the most objective way we have to gauge effort level and understand the stress your body is under. There is also a lot of research and different approaches to tell you the specific training effect that running in different heart rate zones will produce. So, I argue that (in most cases) we should set target heart rate zones for our runs, and let the pace be what it may. Rather than setting a target pace for our runs, and letting your heart rate, workout stress/effort, and resulting physiological impact be what it may. 

Running by pace…

Sure – running according to a specific pace is probably the first and simplest approach most runners use when they’re starting out; and one that many people stick with through their running career because it’s so simple (and because it’s fun to show off how fast our long run was :-P). For example, “I want to do all of my long training runs at 10:00 min/mile for this upcoming marathon”. But, how does that 10:00 min/mi pace feel to you when it’s 40 degrees out versus say, 85 degrees? With/without the Virginia summer humidity? Or running on the flat road versus up the side of a mountain on a trail? Or when you’re well-rested versus sleep-deprived and recovering from a cold? You get the point. A difference in conditions like these can turn a leisurely afternoon stroll into an near all-out effort. So are you still getting the the training effect you intended on with your long run in those cases. Probably not. 

Running according to heart rate takes these conditions into account. When it’s hot, heart rate is elevated, naturally slowing your pace to level out the effort and training stress. Same thing with hilly terrain or humidity. It’s also known that higher heart rate can be a leading indication of a pending cold or sickness. Your heart rate will also naturally be higher when you’ve missed sleep or if you’ve been stressed. This is your body asking you to slow down. And following your heart rate monitor for your run will meet that request. It’s a more direct reflection of effort. 

Running by feel…

Alternatively, you could run by feel instead of by pace or heart rate. And for many seasoned runners, this is a valid option. However, what’s going on in your head and in the rest of your body can be completely different. How many times have you surged out of the starting line of a race fueled by adrenaline. Only to crash and burn a couple miles after you realized you’re running wayyy too fast. 

Running according to heart rate can also be a great pacing tool for these situations. The more you become aware of the connection between your heart rate and effort level, the more you understand how much longer your body can continue to run at a certain heart rate. So, when race day comes – you’ll have your heart rate monitor as an objective voice yelling “slow down!!” after you shoot out of the gate. 

Wrapping it up…

Back to my “bad” run on the right. I don’t know the exact cause of the slower pace. I hadn’t slept quite as much as I would’ve liked over the few days in between, maybe that was it. Maybe I wasn’t fully recovered from the run on the left (my farthest in quite a while). Maybe my body was feeling more stress than my head was leading me to believe.

I do know that my 8:09 min/mi pace was exactly what it should’ve been for that day though. Because pace is the result of my run, not a set target I’m aiming for. Yeah, I’d like for all of my runs to be “fast” and increasingly fast, but I’m in it for the long haul. I just want incremental progress over time. And I nailed the target heart rate to get the training effect I’m looking for to keep that progress rolling, and that’s what counts. 

Published by

Jim Warner Fitness & Endurance Training

*USA Triathlon Certified Coach *ACE Certified Personal Trainer *NPTI Kettlebell Certification *NPTI TRX Suspension Training Certification *Conditioning Coach at Jungle Gym Strength & Conditioning, Newport News, VA *Amateur Endurance Athlete -Boston Marathon Qualifier -Ironman Triathlete -Cross-country Cyclist

6 thoughts on “How Hard Should You Run? Follow Your Heart.”

    1. Hi Debbie! The short answer is there are a couple different approaches & it depends on the type of run you are doing …

      The simplest approach applies primarily to doing long/endurance-building runs. In this case, your target heart rate equals 180 minus your age (plus some small, optional modification), and you should try to maintain as close to that target heart rate or lower throughout your run. You can read more details here: I find that many of my clients complain that it feels too slow at first, but with practice their bodies adapt to go faster and faster and that relatively low heart rate.

      A more involved way to determine target heart rates is to follow the 5 Zones approach, mentioned here: In this case, you would perform a 30 minute “test” or time trial of running as hard as possible and record your average heart rate over the duration. This average heart rate can be used to determine Zones 1-5 by taking percentages of it (see link for more details). Zone 2 here is a good target for long runs; Zone 3 for tempo runs; Zone 4/5 for longer/shorter intervals.

      I find in practice that Zone 2 from this second approach can be very similar to the MAF heart rate in the first approach for long runs. And since a majority of training should be done at lower intensities, either of these approaches should be helpful for starters.

      Hopefully that helps! If you have other questions, feel free to email me:


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