Hello Reader,

A question I often get is:

Should I use pace, power or heart rate to guide my training sessions? This topic is being discussed currently on our new forum so I thought I'd expand a bit.

As so often is the case, the answer is, it depends. Context.

Let’s start with a bit of background and some general rules on when and why you should choose heart rate, and when and why you should choose pace or power for your training session to get the most out of it.

• Heart rate: When you measure your heart rate during steady-state exercise, you’re taking an internal glimpse into your body’s physiological stress. But heart rate doesn’t respond quickly to changes in pace or power. You know this intuitively. If you go from rest to a sprint, your heart rate doesn’t respond immediately. There’s a lag. So heart rate isn’t a very useful marker for short duration high intensity exercise. Conversely, it is an excellent gauge of internal stress over more prolonged exercise, like Zone 2 training, when hills are involved across a strength-endurance session, or for environmental conditions like altitude or heat. It also takes hydration and training fatigue into account. For all of these conditions and contexts, keeping within your prescribed heart rate for the session is typically best. When you do so, you can let your pace or power drift around in accordance with the conditions. But the internal stress for the session should stay about the same. And that's the goal of these sessions — prolonged durability generation, fat burning, aerobic development. Here’s a nice heart rate guided example with key points illustrated.

• Run pace: Run pace recorded typically using GPS is useful as a target for our high-intensity key session paces over relatively flat terrain. Anything from 400m to 2k in a session where you are really going after it applies. Here, pace can be the target and we can observe the heart rate response later. Remember that pace is what we call an ‘external’ load marker, so your internal stress (i.e., heart rate) could be relatively high or low. But we can check that later, not during. Here we won't use heart rate for any sort of guidance. A nice heart rate guided example follows with key points illustrated.

• Cycling power: Cycling power meters are exceptional training tools. Like run pacing, these measurements of power (force x rpm) occur external to our physiology, and, like movement speed, considered as an ‘external’ load (stress) marker. Notwithstanding minor differences in power you might observe in flat vs hilly terrain, the measurement is fairly robust. Like run pace, keep tabs on your power output for your shorter key sessions at threshold or above. Anything from 5 seconds to 20 min along the moderate to high intensity spectrum on the bike — power should be your target. As above, check the heart rate later. Here’s a nice bike power target example to consider.

Application in Athletica — Smart Coach has you covered

This subject falls in alignment nicely with a new Athletica release you can find in your settings page. Here you now have the option to automatically sync your bike and run workouts to Garmin in three different ways in accordance with your preference:

1. Prescribe workout by pace (run) or power (bike)
2. Prescribe workout by heart rate
3. Let our Smart Coach choose the best option

The Athletica Smart Coach option follows the guidelines mentioned above, with sub-threshold workouts pushed to guide you by heart rate and threshold workouts and above pushed to guide you by pace or power. I’m using the Smart Coach option myself.

Let me know what you think.

Train smarter, not harder,

Paul Laursen, PhD

​​​​​​