CyclingThreshold and sweet spotIntermediate 73 min

Over-under intervals (3 × 12 min)

Over-unders: three 12-minute blocks alternating 2 minutes at 94–96% of FTP and 1 minute at 104–106%, with no real recovery. 36 minutes around threshold in 73 minutes. For learning to absorb changes of pace in races.

Written by Pierre Halloo · Updated 25 October 2026

Session profile30 blocks

At a glance

Duration: 73 min
Main target: 94–106%FTP4 Z4 · Threshold
Time at target: 36 min
Estimated load: 77
Structure: 3 × (4 × (2′ at 94–96% FTP / 1′ at 104–106% FTP)), 6′ between sets
Level: Intermediate
Equipment: Power meter · Smart trainer

The session in detail

FTP

Time in zone

Z127 min
Z210 min
Z436 min

What the targets mean

The session's targets, in watts for three reference FTPs
Target	Zone	Time	FTP 200 W	FTP 250 W	FTP 300 W
104–106%	4Threshold	12 min	208–212 W	260–265 W	312–318 W
94–96%	4Threshold	24 min	188–192 W	235–240 W	282–288 W
50–60%	1Recovery	12 min	100–120 W	125–150 W	150–180 W

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What this session is for

Over-unders teach you to stay efficient through surges: a climb that kicks up, the bunch accelerating, a harder turn on the front. Each 'over' minute, just above threshold, builds fatigue; the two 'under' minutes that follow, just below, aren't a recovery: you keep riding hard, and your body has to absorb the extra without you easing off.

The explanation often given, a better 'lactate shuttle' from one muscle to another, remains a hypothesis: no trial has tested this exact format. Its value is mainly practical. Racing is never ridden at constant power.

Who it's for

Intermediate to advanced riders, after several threshold sessions in steady blocks, such as 2 × 20. They suit riders who race in a bunch or on rolling courses. You need a recently measured FTP: a per cent either way changes both targets.

When to do it

One session of this kind a week at most during a build, in place of a threshold session. Keep at least one easy day before and after, and avoid the day before a race. To progress, lengthen the blocks from 8 to 15 minutes, then move to more contrasting alternations, such as the criss-cross.

How to do it

Warm-up
15 min
5′ at 45–55% FTP + 5′ at 56–65% FTP + 5′ at 66–75% FTP
15 minutes building from 45 to 75% of FTP, in 5-minute steps. On a smart trainer, ERG mode copes well with changes every 1 to 2 minutes: it's on your side here.
Main set
48 min
3 × (4 × (2′ at 94–96% FTP / 1′ at 104–106% FTP)), 6′ between sets
Three 12-minute blocks, each made of 4 × (2 minutes at 94–96% of FTP, then 1 minute at 104–106%), with 6 easy minutes at 50–60% between blocks. For an FTP of 250 W: 235 to 240 W, then 260 to 265 W. Each block finishes on an 'over', as Carmichael's version intends. Keep a steady cadence through the changes, and don't exceed the 'over' target: a few watts too many make the 'unders' impossible.
Cool-down
10 min
10′ at 40–55% FTP
10 very easy minutes at 40–55% of FTP. If the third block went badly, keep the same targets next time with 8-minute blocks.

How it should feel

The 'overs' aren't the hardest part: it's coming back down only to 95% afterwards, without the relief of a proper recovery. The 'under' phase is very badly named. Guide: 8 to 9 out of 10 at the end of each block.

Common mistakes

Overshooting the 'overs'

A minute at 115% instead of 105% seems harmless. But the 'unders' that follow become impossible, and the block falls apart. The session doesn't ask for heroic 'overs', it asks for 'unders' you can hold.

Turning the 'unders' into recovery

Dropping to 85% for a breather removes the point of the session: carrying on hard just under threshold, with the fatigue of the previous minute.

Copying CTS's numbers as they are

The original version refers to Carmichael's own field test: 86–90% and 95–100% of its power. Those numbers don't carry over to % of FTP. Here, it's about 95% and 105% of your FTP.

Adding them on top of a threshold session

Over-unders replace a threshold session in your week, they don't add to it. Two sessions at this level within a few days is a lot of fatigue for little extra benefit.

When to skip it

Before you start

A recently measured FTP.
Several threshold sessions in steady blocks already done.

Skip it if

You're tired, or a race is planned for the next day.
You have doubts about your health: get medical advice before sustained hard efforts.

Origin and evidence

Level of evidence

Established practice, no dedicated studyLevel 1 of 5

A format popularised by Chris Carmichael ('OverUnder Intervals', CTS), who insists every interval ends on an 'over'. The original version refers to CTS's own field test: 'under' at 86–90% and 'over' at 95–100% of that test's power, numbers that don't carry over as they are to % of FTP. The common version, widespread on training platforms, sits at about 95% and 105% of FTP. No scientific trial of this exact format has been found; the explanation usually given, the 'lactate shuttle', remains a hypothesis. The 6-minute recoveries between blocks, the warm-up and the cool-down are Wattson choices. Bottom line: very widely used, moderate confidence.

Sources

Carmichael C., OverUnder Intervals, CTS (Carmichael Training Systems)

Frequently asked questions

What power should I ride over-unders at?

At 94–96% of FTP for the 'unders' and 104–106% for the 'overs'. For an FTP of 200 W, 188 to 192 W then 208 to 212 W; for 300 W, 282 to 288 W then 312 to 318 W. That's the common version, around 95 and 105%.

Why finish each block on an 'over'?

It's the instruction from Chris Carmichael, who popularised the session: finishing above threshold, already tired, is like the top of a climb or a surge in a race. It also forces you to keep something in reserve to accelerate right to the end of the block.

Over-unders or threshold 2 × 20?

Two by twenty first: constant power, simpler to hold. Over-unders add the changes of pace and are better preparation for rolling or bunch races. They replace a threshold session in your week rather than adding to it.

Do over-unders improve lactate clearance?

That's the usual explanation, but it remains a hypothesis: no scientific trial has tested this exact format. The value of over-unders is mainly practical: learning to hold threshold through surges, as in a race.

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