Runner's Dilemma #22 — My Legs Feel Heavy — Should I Still Run?

 

Runner's Log | Runner's Dilemma #22

My Legs Feel Heavy — Should I Still Run?

With a sub-4 marathon target on October 10th, I've been training pretty seriously lately.

I climb about 80 floors of stairs when I get to the office, and run about 5 days a week.

Each run is at least 10km, usually 15km. On weekends I do an LSD run over 20km.

But lately, I keep having the same thought.

My legs feel heavy.

It's not pain, not bad enough to stop me from running. Just this constant heavy, stiff feeling.

So I started wondering:

Should I keep running through this heavy feeling?

Or would it be better for my training to rest until it goes away?

So I looked into it.

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Getting Tired From Training Is Only Natural

What I found first was surprisingly simple.

Fatigue building up from heavy training is a natural thing.

Train hard, and of course your body gets tired — your performance can even dip temporarily.

Exercise physiology has a concept for this: functional overreaching.

Your training load goes up, your condition or performance drops for a while, but once you've recovered enough, it comes back stronger.

So:

Training and being tired ≠ training wrong

That's not how it works, apparently.

But there are a few things worth paying closer attention to here.

So Is This Fatigue Normal, or Too Much?

Heavy legs is a pretty subjective feeling.

So rather than judging by leg feel alone, it helps to look at a few things together.

For example:

Are you sleeping well?

Do you feel unusually reluctant to train, more than normal?

Does the same pace feel much harder than usual?

Is your heart rate consistently running higher than normal?

And has your mood been more irritable or down than usual?

You look at all of these together.

So it's not just "my legs feel a bit heavy today." It's:

"My legs are heavy, I'm not sleeping well, I don't feel like running, and the same pace feels unusually hard."

You're supposed to check whether several of these show up together.

If several of these symptoms appear at once, that's apparently different from simply having tired legs.

So Here's What I've Landed On

Heavy legs alone doesn't mean I absolutely need to rest. But it doesn't mean I should just grit my teeth and run through it either.

What matters is looking at sleep, mood, motivation to train, and how hard my usual pace feels — together.

In the end,
it sounds like heavy legs alone is no excuse — I'm still running today.

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Except There's an Exception

Two days ago.

I'd just eaten, and was getting ready to go run along the Anyang stream with my wife, when my younger kid said:

"Dad, how can you run after eating like that? I genuinely don't get it."

I hate leaving food on my plate, so I'd eaten every last bit of it... to the point where just standing up straight was uncomfortable.

And of course, that was the day I'd planned to jog 3km and then push a fast 10km.

So I pushed myself into it anyway.

And past the 5km mark, my heart rate shot up way more than usual, I couldn't find any rhythm, and even lifting my legs felt hard.

All sorts of thoughts started creeping in.

"Man, I thought I trained hard all summer... is this why I can't hit sub-4?"

I even started feeling down about it.

So I got curious:

"Does running right after overeating actually make it harder than usual?"

I asked AI, and turns out there's real backing for this.

When digestion and exercise happen at the same time, blood flow gets redistributed in your body, and right after a big meal, the digestive load can make exercise feel harder than usual. Apparently it's a pretty common experience among runners.

So, on a day you've eaten a ton and then run — feeling down, unmotivated, with your heart rate running higher than normal —

if you're thinking

"Ugh, I guess I've been overtraining. I should probably rest."

don't just settle into that and rest easy.

"That day, you just ate a lot. That's all."

Haha.

References: Functional overreaching and post-exercise parasympathetic reactivation study (11 male runners, light training–heavy training–taper comparison) · Cumulative fatigue and running gait coordination monitoring study (15 trained distance runners, overload training–taper comparison) · Literature review on training load and subjective wellbeing monitoring · Research on blood flow redistribution between digestion and muscle, and related GI symptoms during post-meal exercise.

The interpretations here reference these findings from a runner's perspective and are not a substitute for medical diagnosis. If symptoms don't resolve over time, consulting a professional is recommended.