Easy runs are indispensable for any runner - it doesn’t matter if you are training for a 1-mile or a 100-mile race! Any good training plan will have you running a lot of easy miles, but easy is a pretty broad term and athletes often have a lot of questions about what their easy runs should look like. Why does easy running matter so much and how exactly do we pace them?
Most of Your Training Runs Should Be Easy
The term easy running is an all-encompassing term for anything below your aerobic threshold (Zone 1 in a 3-Zone Model, Zone 2 in a 5-Zone Model). Below this threshold, the body utilizes fatty acids and carbohydrates to produce the energy we need. There is little–to-no anaerobic metabolism underneath this threshold, which basically means that there is minimal lactate production. This produces less stress on the body and also paves the way for a lot of good adaptations to happen in our bodies: increased mitochondrial density (more energy production), increased capillary density (quicker oxygen transport and waste removal), and increased myoglobin content (more oxygen for muscles), to name a few big ones.
When we run too fast on easy days, it inhibits these desired adaptations. Instead, running too fast causes lactate to accumulate more than we’d like. We do want some lactate accumulation to happen some days, but only on specific workouts, not on our easy days. Producing too much lactate too often can hinder adaptation to our training and slow down our recovery.
Generally, the consensus amongst exercise physiologists says that approximately 70-90% of training should be done at an easy pace.
So How Easy Should “Easy” Be?
Your easy pace should vary week-to-week depending on where you are in the training cycle, and even should vary day-to-day. The fatigue you bring into a run, whether that’s from training, weekly volume, or even life stresses will affect the pace of your easy runs. Because of this, I never recommend that athletes use pace to guide their easy runs. We have a few better ways we can gauge our easy runs:
<85% of your lactate threshold HR (LTHR) or <75% of max HR
You can calculate your LTHR doing a 30-minute time trial - the average HR of the last 20 minutes of the time trial is approximately your LTHR.
It’s very hard to measure your true max HR, so LTHR is a better route for this.
*Caveat: Wrist-based HR is often pretty inaccurate, so I recommend using a chest strap if you want to do these calculations. Because of this inaccuracy with wrist-based data, the LTHR estimations from watches are also usually inaccurate. You can use the below bullet points to gauge your easy runs really well without this!
2-4 out of 10 on the Rate of Perceived Exertion Scale
You can carry on a full conversation or sing a song. Breathing is not labored. Labored breathing is a sign that we are producing lactate.
You feel comfortable and relaxed and finishing is not a concern. You don’t feel like you are straining or working against your body.
The big takeaway: The fresher your legs are, your pace will be faster, and the more fatigue or stress you have, your pace will be slower. Easy is a feeling and an effort, not a specific number or pace.
There is Individual Variation in Easy Running
Our easy paces can vary GREATLY. Even if two athletes are training for the same exact time at the same exact race, their easy paces may look very different. This is primarily due to our muscle fiber typology. Athletes who have more slow-twitch muscle fibers (aka oxidative or Type I) burn fat at higher intensities and fatigue slower, which allows them to run faster at a lower percentage of their VO2max. Athletes with primarily fast-twitch fibers (aka fast glycolytic or Type IIB) will need to run slower on easy days as these fibers are recruited quickly and produce more lactate.
How Slow is Too Slow?
It’s really hard to go too slow on easy days, but it’s very easy to go too fast. Generally, there’s no such thing as going too slow on an easy run. However, an easy run should still maintain good running form. If you feel your form breaking down, you might be going too slow. If this is the case, try picking up your cadence but keeping the effort still easy. If that feels too hard, it’s likely that you are in need of a rest day and should stop the run.