Tempo isn't a slow sprint

An athlete came to me recently with a sore Achilles after her tempo runs.

Not after sprinting. After the easy stuff, the part of the week that's meant to be gentle.

That's backwards. Tempo is the session that's supposed to keep you healthy, so pain coming out of it usually means something about how it's being run is wrong.

When I watched her, it was obvious within a few seconds. She was running her tempo right up on the balls of her feet, bouncing off the ground like she was sprinting.

Same technique she'd use at full speed, just at a much slower pace.

And that was what kept hammering her Achilles.

To see why, it helps to think about what tempo actually is.

At full speed, running on the ball of your foot is exactly right. The contact is hard and over in under a tenth of a second.

The calf and Achilles load and release almost instantly, and the heel barely needs to come down, because you're not on the ground long enough for it to matter.

The Achilles is built for that. A quick stretch and snap back that springs you off the ground. What it doesn't like is being held under load for long stretches at a time.

Tempo is the opposite. You're on the ground longer each step, you take far more steps, and the whole session is about volume rather than effort.

Stay up on your toes through all of that and the calf and Achilles never get a break.

Every step keeps them loaded. The heel never comes down to take any of it. And the load just adds up rep after rep until the back of the ankle starts hurting.

At that point you're not really running. The calf is working the whole time without a rest, and that constant load is what the Achilles ends up paying for.

That was the whole problem with her. Right technique for sprinting, wrong pace to be doing it at.

As you slow down, the foot is meant to come down with you.

The contact point moves back through the foot the slower you go. A sprinter is up on the ball of it, a 400 runner lands more through the arch, someone jogging uses almost the whole foot.

Tempo sits down that end. You want it to look like how you'd run if you weren't thinking about it, relaxed, with the heel actually coming down each step.

Not a big heel-first plod either. Just letting the foot land naturally so the calf gets a rest between steps instead of working the whole way through.

You can feel which one you're doing without filming it.

On a relaxed tempo rep the heel should touch down lightly each stride, and your calves shouldn't be the first thing to tire. If your lower legs are burning before you're even out of breath, you're running it too high on the foot.

The fix with her wasn't to stop tempo. It was just to get her off her toes and let the heel come down, so the calf wasn't holding the whole time.

If your lower legs are already sore, doing tempo on grass helps too. The softer surface takes some of the impact out and gives the tendon an easier time while you sort the foot out.

Her foot was the trigger, but there's a bigger habit underneath it, which is running tempo too hard in the first place.

Tempo sits at 70 to 75 percent. An easy, conversational pace where you can still get a sentence out between breaths.

The pull is always to go faster than that. The reps feel like nothing early on, so the pace creeps up, and before long it's closer to a sprint session than a recovery one.

Push past 75 percent and you end up in the worst place to be. Too hard to recover from, too easy to make you any faster.

You lose the recovery the easy day was supposed to give you, and you take something off your next hard day as well.

Going too fast has a simpler cost too. You don't finish.

Run the first few flat out because they feel easy and you won't get through the volume, which is the whole point of the session.

Because the volume is what does the work.

Tempo is there to move blood around, keep your aerobic base ticking over, build general fitness, and load the tendons and connective tissue gently and often, without taxing your nervous system.

The number on the watch barely matters in these sessions. What matters is that you get through it relaxed and finish looser than you started.

So run the easy days easy, and remember tempos aren’t sprints. Ease the pace back until you could talk through it, and let the heel come down.