The jog between intervals is the part of the session that matters

Coaches obsess over rep pace and then let athletes stand around, which quietly changes what the workout trains.

Two runners do the same session on paper. Twelve times four hundred at the same pace, ninety seconds recovery. One jogs the ninety seconds. The other walks to the fence, chats, and starts the next rep from standing. Those are not the same workout. They are not even close, and the difference sits in what happens to lactate in the gap.

Lactate does not sit still. It moves out of the working muscle, into the blood, and gets taken up and used by other tissue, including the heart and less active muscle fibres. That uptake runs faster when the tissue is working. A gentle jog keeps the pump going, keeps the muscle demanding fuel, and clears lactate meaningfully faster than standing does. Stand still and clearance slows, so each subsequent rep starts from a higher baseline and the athlete accumulates through the session.

Which of those you want depends on what you are training, and that is the point. Neither is wrong. A session where you deliberately let the baseline climb is a tolerance session. A session where you jog and hold the baseline flat is a session about running well at a hard pace repeatedly. Both are legitimate. Choosing accidentally is the failure.

And it is almost always accidental. I have watched squads where the recovery was written on the plan as ninety seconds and observed at anything from sixty seconds to three minutes depending on who was talking to whom. The prescribed variable in the session, the one written in the training diary, is the one nobody controls.

There is a knock on effect coaches underrate. Once the baseline climbs, running mechanics degrade, and the last three reps get run with the form of a tired athlete. If those reps are held at pace anyway, you have spent thirty minutes practising bad mechanics under fatigue. Sometimes that is exactly what you want, because races end that way. Sometimes it is just damage.

So write the recovery as a pace, not a duration. Jog at whatever number the athlete can actually hold, and hold it. If the athlete cannot jog the recovery, the rep pace was wrong, and that is useful information a stopwatch on the reps alone will never give you.

The reps are the part that gets recorded. The gaps decide what got trained.