It's hard to believe and it seems counterintuitive but running "slow" will make you fast and it is important to do most of your miles at a TRULY easy and conversational pace. Here’s why!
I will start off with a personal example: In 2021, I spent the whole year training for Indiana 100, which involved A LOT of easy training miles and maybe one speed session a week. My paved, flat miles were done around a 9-9:15 min/mile pace. That year, I PRrd my 5k by 45 seconds (from 20:36 to 19:51 minutes) and 100-mile time by over 1 hour (from 23:23 to 22:21 hours)!
So how does running at a truly easy effort lead to us getting faster? And why are they the MOST important running miles that we do?
1. Easy miles add total weekly volume to our training:
More volume each week is highly correlated with faster race times from a 5k distance all the way up to full marathons. This is true for both recreational and elite runners. Research is still working on learning more about ultras and what helps with performance, but since easy running is very similar to the paces run on race day during an ultra, it is very likely that this finding applies to ultra marathons too!
2. Doing most of our training at an easy effort allows us to run more frequently:
By keeping most of our miles easy, we put less stress on the body when we run. This allows the body to recover quickly so that we can run more often! Think about other new things you have learned to do in the past. We tend to learn faster if we do something more often. This is true with running too! Repetition is key. By doing something more often, it tells our brains that it is important, it needs to pay attention, and it needs to adapt to what we are doing because we are going to do it again very soon in the future! So, we want to spread our miles out over many days during the week vs cramming them into 2-3 days a week.
3. Running at an easy pace increases capillary density in our muscles:
This is super important! If we have more capillaries in our muscles, that means we can deliver more oxygen to the muscles, which means it can create more energy and work harder for longer periods of time! This DOES NOT happen to the same degree with fast running!
4. Keeping our pace easy allows us to recover quickly:
Recovering quickly is very important so that every training run can be a quality run vs junk miles. This is especially true with speed training! If you run too fast all of the time, this contributes to people performing worse during key speed training days and increases the risk for injury. If you are going into a speed session feeling fatigued, you won't be able to hit your upper limits. Regarding injuries, training errors are the number one cause of running-related injuries and running too fast all of the time is one of the most common errors made in training.
How do you know if you are running easy enough?
Your easy miles should be slow enough that you can hold a full conversations or even sing without feeling breathless. The effort level is between a 3-4/10 or 70-75% heart rate max.
A common training error
Many runners do their easy miles (easy runs, long runs, rest periods during speed training) too fast because they feel it will lead to improved race benefits. In reality, it leads to adaptations to incorrect systems in our bodies from the metabolic systems (how our body creates and uses energy) all the way down to the types of muscle fibers that are being trained (slow twitch vs fast twitch muscle fibers). By training the wrong systems, we become WORSE endurance athletes rather than better ones! So, keep your easy miles at a truly conversational pace and 80-90% of your weekly volume should be done at this pace.
What happens if we spend too much time training in the middle?
“The middle” is considered to be a pace between a “conversational pace” and your critical speed (around a 1-hour or 10k pace). Training in the middle is a less effective place to train because it is too slow to get faster and too fast to allow for quick recovery.
What gets in the way of people slowing down?
Not understanding how the body works and adapts to training is part of the issue, but I feel like social pressure and general negative messages about running "slow" in the running community is even more of an issue. As a running coach and PT, this is something I feel like I am constantly battling. People want to look fast on Strava to impress their followers, be at the front of their group runs, speed past random strangers who are also doing their Saturday long run, and we better not get passed! The general community doesn’t praise or idolize easy-paced running, which is unfortunate since this messaging leads to people making ineffective training decisions and getting injured at a higher rate.
Here is a great podcast if you want to learn more about the science of easy-paced miles!