Runner's Dilemma #37 — How to Find the Interval Pace That Fits You
Runner's Log | Runner's Dilemma #37
How to Find the Interval Pace That Fits You
I still remember the day of my first interval session.
I think it was 400m fast, then 200m of walking or jogging, for 6 sets.
Looking back, it may have been risky.
I wasn’t even halfway through when I made a promise to myself.
‘One more lap, then I’m done.’
After that lap, I thought again.
‘Okay, just one more.’
With the last lap ahead, I struck a deal.
‘Just 200m more, then I quit.’
In the end, I made it through that final 200m by counting only to 20, then deciding to stop.
Finally, the session was over.
‘I didn’t give up!’
I felt proud.
But at the same time, another thought crossed my mind.
‘This is not something a human should be doing.’
That was my first impression of intervals.
After that, on interval days I skipped club runs or made every excuse to run away.
Then I fell apart on the Hwadae ridge traverse, and I failed my sub-4 full marathon attempt too.
I felt it was time to change.
On interval days, I will show up.
Every Tuesday, we do interval training at Anyang Stadium.
And today is that day.
Deciding to “just do it” doesn’t mean the fear is gone.
Until now, I just ran whatever our club president told us to run.
But suddenly I got curious.
Why do we even do intervals?
How fast should I run them?
And am I actually doing them right?
Today I want to look into these three questions.
I. Why Do Intervals Make You Faster?
Interval training alternates fast running with recovery, over and over.
But why split it up like this?
Why not just run fast from start to finish?
According to the sources I found,
intervals repeat high-intensity running several times, which helps improve cardiorespiratory fitness, meaning the body’s ability to use oxygen more efficiently.
Intervals are usually run at an intensity you can hold for about 3–5 minutes.
In Jack Daniels’ approach, the target is an effort close to what you would run in a 3,000–5,000m race.
Through this kind of training, aerobic fitness can improve.
Of course, the effect depends on your training method and current fitness.
As for why we split it up, I think it’s probably this:
by resting and then running again, you can accumulate more time at high intensity than by running once for a long stretch.
I didn’t confirm this in the sources. It’s my guess.
So the next question comes up.
II. How Are Intervals Done?
There turned out to be several kinds of intervals.
You can fix a distance, like 400m or 1,000m, and repeat it. Or you can fix a time, like 3 or 4 minutes, and repeat that.
Here are the examples from the sources.
| Workout example | Recovery | Pace reference |
|---|---|---|
| 1,000m × 5 | 2 min jog | 5,000m pace |
| 400m × 10 | 60 sec jog | 3,000m pace |
| 1,600m × 5 | 2 min jog | 10K pace |
A few guidelines worth remembering:
- Each fast rep usually lasts 2–5 minutes.
- Recovery is about half the time you ran. (Ran 4 minutes? Rest 2 minutes.) When recovering with an easy jog, anywhere from half to the same amount of time is used. (Ran 4 minutes? Rest 2–4 minutes.)
- If it’s too hard, first lengthen recovery to around 2 minutes, and if it’s still too hard, lower the pace.
Of course, this table is just an example of training formats. It doesn’t mean everyone should run the same speed for the same number of reps.
In Jack Daniels’ approach, you set your training paces from a recent race result, then build the reps and distances around those paces.
What matters isn’t simply running fast.
Start too fast, and you may slow down more and more toward the end.
Run too relaxed, and you may not reach the intensity you planned.
Thinking back, even 400m at speed was tough for me in my first interval session.
I didn’t know why I was running at that speed, or why I was repeating it six times.
I just ran what the club president said to run.
So how can I find the speed that fits me now?
III. Finding the Interval Pace That Fits Me
My first question was this:
“If someone normally runs an easy 6:30 per km, how fast should they run intervals?”
The AI answered that you should set training paces based on a recent 5K or 10K race result, not on your everyday running speed.
One well-known method is Jack Daniels’ VDOT.
It estimates your current running ability from a recent race result and sets training paces to match.
So I asked the AI.
It gave me other information too, as in the table below.
| Workout type | Pace per km (approx.) |
|---|---|
| Easy | 5:46 ~ 6:54 |
| Tempo | 5:01 ~ 5:16 |
| Interval | 4:32 ~ 4:43 |
My usual easy 6:30 falls within the easy range.
The tempo range also roughly matches a speed I feel I could hold for about an hour.
VDOT is better than I expected.
Of course, these numbers aren’t necessarily the right answer.
Still, it’s better than vaguely wondering “how fast should I run?” Now I have a concrete starting point.
So, I asked again.
I asked it to organize distance, rest, and number of sets based on this table.
This table is based on my own result, so anyone else should recalculate with their own.
Here is what it gave me.
| Workout | Fast segment | Pace per km | Recovery | Sets | Total fast distance |
|---|---|---|---|---|---|
| 400m intervals | 400m (about 1:49–1:51) | 4:32 ~ 4:38 | 60 sec jog | 8–10 | 3.2 ~ 4km |
| 800m intervals | 800m (about 3:40–3:44) | 4:35 ~ 4:40 | 2 min jog | 5–6 | 4 ~ 4.8km |
| 1,000m intervals | 1,000m (about 4:38–4:43) | 4:38 ~ 4:43 | 2 min–2:30 jog | 4–5 | 4 ~ 5km |
| Timed intervals | 3 min (about 650m) | 4:35 ~ 4:40 | 1:30 jog | 5 | about 3.3km |
The sources often set recovery at about half the running time.
It can vary with rep length and intensity, so I’ll treat the recovery times in this table only as a starting point.
The total fast distance is around 4km.
Start with fewer sets; if it’s hard, lengthen recovery first, and if it’s still hard, lower the pace.
Of course, this is only the AI’s suggestion. I’ll have to run it myself to see if it fits my body.
Until now I just ran what the club president said. But now I feel like I’m slowly learning why I run at that speed.
I’m heading to Anyang Stadium again this evening.
I’m still scared of intervals.
But now that I know a bit about why I’m running at this speed, rather than just gritting my teeth, my thinking seems to be shifting from ‘just survive’ to ‘let’s do this.’
References: VDOT running paces (athletedata) · VO2max Interval Training (Shuichi Running)
