Over-unders: the interval that teaches you to ride through lactate
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Most threshold work asks one question: can you hold a steady effort for a long time? Racing almost never asks that. It asks whether you can hold a hard effort, absorb a surge on a ramp, and then carry on at nearly the same pace without falling apart. That is a different ability, and over-unders are the interval built to train it.
They are also one of the most frequently botched sessions in cycling, usually because riders get the two halves the wrong way round in their heads. Here is what the session is actually doing, and how to run it so it works.
What an over-under is
You alternate between a few minutes just above your functional threshold and a few minutes just below it, with no rest in between. A typical block: two minutes at 105–110% of FTP, then two minutes at 90–95%, repeated three or four times, then a proper recovery before the next block.
The critical detail is that the "under" is not recovery. It is the work. Going over threshold produces metabolic by-products faster than you can clear them; dropping back under threshold — but only just — forces your body to do the clearing while still riding hard. That is the adaptation you are chasing, and it only happens if the under stays uncomfortable.
Stylised. The ratchet — never quite clearing before the next over begins — is the shape that matters, and it is why the last rep of a block hurts so much more than the first at identical watts.
Why the ratchet is the point
Look at the orange trace above. Each over pushes lactate up. Each under brings it partly down — but not all the way back. Across a block you climb a staircase, so that by the third or fourth over you are producing the same watts in a considerably worse internal environment.
That is a fair imitation of what a race does to you. A bunch surges over a rise, settles, surges again; nobody stops to let you recover to baseline. Training the clearing machinery under load is what turns "I blew on the third climb" into "I was there at the top". If you want the physiology underneath this, our piece on lactate threshold, LT1 and LT2 is the companion read, and critical power vs FTP explains why the line you are riding around is fuzzier than a single number suggests.
Four sessions, in order of difficulty
All of these assume a 15–20 minute warm-up with a couple of short openers, and a proper cool-down. Percentages are of FTP; if your FTP number is stale, fix that first — how to test and raise your FTP covers it.
First taste
3 × (2 min over / 3 min under)
Your first over-unders, or the first week of a block.
Short enough that the third rep is hard rather than ugly.
The standard
3 × (2 min over / 2 min under) × 3
The everyday version once you have done a few.
Twelve minutes of continuous work per block. This is the one most plans mean.
Long grind
2 × (3 min over / 5 min under) × 2
Fondo and long-climb preparation.
Fewer transitions, more time near threshold. Feels easier at the start and worse at the end.
Race sharpener
4 × (1 min over / 1 min under) × 4
Three to four weeks out from a hilly road race.
Rapid switching — closest to what a punchy bunch actually does to you.
The four ways riders ruin them
Riders treat the over as a VO2max effort. At 120% of FTP you will not survive to the fourth rep, and the under stops being recovery — it becomes a second hard effort. The over belongs at roughly 105–110% of FTP: clearly above, never heroic.
If you soft-pedal the under at 70%, you have built a normal VO2max session with long rests. The whole point is that the under stays at 90–95% of FTP — high enough that clearance has to happen while you are still working hard.
The over and under are one continuous effort. Coasting through the transition resets the thing you are trying to train. Change gear, do not change pedalling.
Over-unders are a sharpening tool, not a base. Four to six weeks of them in a build phase does far more than a token set every week from November.
Indoors is where they work best
Over-unders are unusually badly suited to the open road. The session depends on switching between two precise power targets on a schedule, and roads supply junctions, descents, wind and traffic lights instead. Most riders' outdoor over-unders are, in practice, a rough approximation with the overs too hard and the unders accidental.
On a trainer in ERG mode the machine holds each step for you, and all you have to do is keep turning the pedals and breathe. That is also the honest catch: ERG will hold the target right up until your legs stop, so pick the version you can finish rather than the one that looks impressive. If ERG is new to you, ERG mode explained covers how to ride it without the spiral of death.
Moveee Indoor runs the whole session in a browser tab — pair the trainer, load an over-under workout, and it steps the resistance through every over and under while you ride a real road in 3D. The ride saves with full power streams, so the next day you can look at whether the third block actually held its targets or quietly sagged. It is free while in alpha.
Where they fit in a week
Treat an over-under session as a hard day — the same budget as VO2max work, not an extra on top. Two quality days a week with easy riding around them is plenty for most riders; how many hard days a week makes the case in detail. In a build block, one over-under session and one shorter, sharper session works well, with the long ride left genuinely easy.
Run them for four to six weeks and the change you should notice is not a bigger FTP number — it is that the second climb of a group ride no longer costs you the day. That is the whole promise of the session, and it is a better one than most intervals can make.
Sources 6
Where this article summarises a study, the study itself is linked — not a write-up of it.
- 1 Faude O, Kindermann W, Meyer T Lactate Threshold Concepts: How Valid are They? · Sports Medicine · 2009
- 2 Brooks GA The Science and Translation of Lactate Shuttle Theory · Cell Metabolism · 2018
- 3 Jones AM, Burnley M, Black MI, Poole DC, Vanhatalo A The maximal metabolic steady state: redefining the 'gold standard' · Physiological Reports · 2019
- 4 Ebert TR, Martin DT, McDonald W, Victor J, Plummer J, Withers RT Power output during women's World Cup road cycle racing · European Journal of Applied Physiology · 2005
- 5 Seiler S What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes? · International Journal of Sports Physiology and Performance · 2010
- 6 Laursen PB, Jenkins DG The Scientific Basis for High-Intensity Interval Training · Sports Medicine · 2002
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