Why Slower Runs Makes You Faster

Everybody tells you slow running makes you faster, but nobody tells you why. Most runners feel guilty running slow. It feels unproductive, like you're wasting a workout. But, easy running is actually where most of your physiological gains happen.

​​First, what actually counts as easy

​Easy means conversational. You should be able to hold a full sentence without gasping. If you're working too hard to talk, you've already crossed out of easy territory. Most runners, when left to their own devices, run their easy days too hard. It feels more productive, but it's actually working against you, and we'll get to why.

​​What's happening in your body at easy effort​

When you run at an easy, aerobic effort, your body is quietly making a lot of changes that don't show up on your watch, but absolutely show up in your racing.

​​Mitochondrial density. Mitochondria are your cells' energy factories, responsible for converting oxygen into usable fuel. Easy running is one of the most effective ways to increase the number of mitochondria in your muscle cells. More mitochondria means your body can produce energy more efficiently, which means you can run faster for longer before things start to fall apart.​

Capillary development. Your body responds to easy, sustained aerobic work by growing more capillaries, the tiny blood vessels that deliver oxygen to your muscles. More capillaries means better oxygen delivery, which directly supports your ability to hold a pace.​

Cardiac adaptations. Over time, easy running increases your stroke volume, which is how much blood your heart pumps with each beat. A more efficient heart means more oxygen delivered with less effort. This is part of why trained runners have lower resting heart rates because their heart just doesn't have to work as hard.​

Fat oxidation. Easy running trains your body to use fat as a fuel source more efficiently. This matters a lot for anything longer than a 5k. The better you are at burning fat, the longer you can sustain effort before you start depleting your carbohydrate stores.

​​The problem with running everything at a medium effort​

Most recreational runners end up spending a lot of time in a middle zone: not hard enough to really challenge their fitness, but not easy enough to drive the adaptations above. It's the worst of both worlds. You accumulate fatigue without getting the full benefit of either end of the spectrum.

​Elite runners actually do the majority of their training at easy effort. The concept isn't new, coaches have been preaching it for decades. The idea is simple, protect your easy days so your hard days can actually be hard. When your easy runs aren't easy enough, your hard runs suffer for it.

​​Why the gains take time​

This is where people get frustrated and give up. It takes weeks to months for mitochondrial development, capillary growth, and cardiac adaptations. You're not going to feel faster after one easy week. But runners who commit to it consistently almost always find that their easy pace gradually gets faster without feeling harder. That's the whole point. That's running economy improving in real time.

Slowing down on your easy days is not a sign that you're not working hard enough. It's one of the highest-leverage things you can do for your running. The adaptations that make you a better runner are largely built at lower intensities, over time, with consistency.

​So the next time an easy run feels almost too easy, that's probably a good sign.

​-Eliana

​P.S. Feel like you’re not sure when to run easy or when to run hard? Having trouble figuring out how slow is slow and how fast is fast? Book a free consult call here.