You're doing 2x20 at what your training app calls sweet spot, three times a week, and by Friday your legs are concrete. FTP hasn't moved in months. So you push harder — surely more effort means more adaptation. It doesn't. You're five watts above the zone ceiling, and you've crossed from the most efficient training intensity in cycling into threshold territory. Same session on paper. Three times the fatigue cost in practice.
Hunter Allen coined the term sweet spot to describe 88-93% of FTP — the narrow band where training stimulus is high but fatigue stays low enough to repeat the session 36 hours later. The reason it works is not because it's hard. It's because it's specifically, precisely, carefully not too hard. Miss that distinction by even a few watts and you turn a brilliantly efficient workout into something that digs a hole you spend the rest of the week climbing out of.
What sweet spot actually is
The term was coined by Hunter Allen, co-author of Training and Racing with a Power Meter and one of the people who did more than almost anyone to bring power-based training to amateurs. Allen identified a narrow band — 88 to 93 percent of your functional threshold power — where something interesting happens. The training stimulus is very high, close to what you'd get from riding at threshold, but the physiological cost is meaningfully lower. Not slightly lower. Meaningfully lower. The fatigue you accumulate in twenty minutes at 91 percent of FTP is a different animal from the fatigue you accumulate in twenty minutes at 100 percent. And that gap is the whole point.
Allen called it the sweet spot because it's the zone where the ratio of stimulus to fatigue is at its best. You're getting a large training effect per minute of work, but you're not burying yourself so deep that you need two days off the bike to absorb it. Below 88 percent you're in tempo, which is fine but doesn't stress the aerobic system as aggressively. Above 93 percent you're into threshold and the fatigue cost climbs sharply with every watt. Sweet spot sits in the narrow window between those two worlds, and that's what makes it so useful.
Why the physiology makes sense
It works like this. When you're riding at sweet spot intensity, you're working your aerobic system hard. Mitochondrial respiration is close to its maximum rate. You're producing lactate, but not so much that it spirals — your body can still clear it roughly as fast as it's being produced, or close to it. The metabolic stress is real, the cardiovascular demand is high, and the muscular tension is significant enough to drive peripheral adaptations. All the ingredients for aerobic improvement are present.
But here's where it gets really interesting. At threshold — 100 percent of FTP — you're right at the tipping point where lactate production and clearance are balanced on a knife edge. Stay there long enough and you'll accumulate fatigue that takes 48 to 72 hours to fully clear. At sweet spot, you're close enough to that tipping point to get most of the aerobic benefit, but far enough below it that the fatigue clears faster and you can do the same session again in two days. That repeatability is the real advantage. It's not that one sweet spot session is magic. It's that you can stack three of them in a week without your body falling apart, and the cumulative training load over a block adds up to something substantial.
The adaptations you're chasing — increased mitochondrial density, improved fat oxidation, greater capillary density, stronger cardiac output — all respond to accumulated time near the aerobic ceiling. Sweet spot lets you accumulate more of that time per week than threshold does, because threshold wrecks you and sweet spot doesn't. Same adaptations. Less wreckage. More sessions. Better block.
The polarised counterpoint
Now, I need to be fair here, because there's a strong and well-argued position that says sweet spot is exactly the wrong place to train. Professor Stephen Seiler, whose research into the training intensity distribution of elite endurance athletes has been as influential as anything in the last two decades, argues that sweet spot falls squarely in the grey zone — too hard to be easy, too easy to be hard. His polarised model says you should spend roughly 80 percent of your time at low intensity and 20 percent at high intensity, and the middle ground where sweet spot lives should be mostly avoided.
Seiler's logic is sound. When he studied elite cross-country skiers, rowers, and runners, most avoided the moderate zone. Easy was easy. Hard was hard. The middle was thin. And his experimental data backed it up — polarised distribution outperformed threshold-heavy distribution in several well-designed studies.
So who's right? Both, depending on when and how you use the tools. The mistake is treating this as a binary. When I had Dan Lorang on the podcast, he talked about periodisation as the organising principle that sits above any single training philosophy. Sweet spot has a place in the year. So does polarised training. So does threshold work. The question isn't "which model?" — it's "which model, right now, for this rider, at this point in their season?" The coaches who get the best results are the ones who stop arguing about camps and start sequencing training blocks in the right order.
How the best coaches use it
Tim Kerrison's approach at Ineos is the most visible example of sweet spot done well at the highest level. During the base phase — the months-long build that precedes the race-specific preparation — Kerrison loaded his riders with sweet spot volume. Long blocks at 88 to 93 percent, accumulating time at intensity without generating the deep fatigue that threshold and VO2max work produce. The idea was to build an enormous aerobic platform first, so that when the sharper, more fatiguing work was layered on top, it had something to land on. The base phase was where the engine was built. The specificity phase was where it was tuned.
This sequencing is what most amateurs miss. They throw sweet spot, threshold, and VO2max into the same week, every week, all year round, and wonder why nothing moves. Kerrison's riders did sweet spot when it was sweet spot time, and then they moved on. The block had a start date and an end date, and the intensity that followed was different.
When I had John Wakefield on the podcast, he talked about the practical design of these sessions at Bora-Hansgrohe. The durations were chosen for a reason. The recovery between intervals was calibrated to maintain quality without letting the rider cool down so much that the next effort became a fresh start. It's not complicated, but it is precise, and that precision separates a well-designed sweet spot block from a rider just pedalling sort-of-hard for an hour and calling it training.
The sessions that work
The classic sweet spot session — and the one most coaches start with — is two blocks of twenty minutes at 88 to 93 percent of FTP, separated by five to ten minutes of easy spinning. The 2x20 has been a staple of endurance training since before the term sweet spot existed, and there's a reason it persists: twenty minutes is long enough to drive real aerobic adaptation, the two-interval structure lets you maintain quality across both efforts, and forty minutes of total time at intensity generates a meaningful stimulus without wrecking you for the next day. If you're new to sweet spot work, this is where you start. Nail the power range, stay smooth, and resist the urge to push the second interval harder than the first. Consistency across both blocks matters more than peak power in either one.
Once 2x20 feels manageable, the next progression is 3x15 minutes at the same intensity with five minutes of recovery between each interval. The total time at intensity is forty-five minutes, and the three-interval structure introduces a different kind of challenge — the third effort arrives on legs that have already done thirty minutes of real work, and holding the power range through that final block is where the session earns its keep. The shorter intervals also let you hold the top end of the sweet spot range more comfortably, so you can push closer to 93 percent without the effort collapsing at the end.
For riders who've been training consistently and have a solid base, the single 30-minute block at sweet spot is a brutally effective session. No recovery. No mental reset. Just thirty minutes of sustained pressure at 88 to 93 percent, which teaches you to manage effort, control breathing, and maintain form when everything in your body is asking you to ease off. This is not a beginner session. If you can't hold a clean 2x20 without the power drifting, you're not ready for this one.
The session that adds another dimension entirely is the over-under sweet spot variation. You ride ten minutes at 90 percent of FTP, then surge for two minutes at 105 percent — just above threshold — then drop back to 90 percent for another ten, surge again, and repeat for a total of three cycles. The overs stress the lactate clearance system and the unders teach your body to recover while still working hard. It builds the kind of resilience that shows up in road races and sportives when the pace surges on a climb and you need to clear the lactate and settle back into rhythm. Around 36 minutes of work, and the combination of sustained pressure and sharp surges makes it one of the most complete sweet spot sessions you can do.
Building a four-week sweet spot block
Here's where it gets really practical. A well-structured sweet spot block runs three weeks of progressive loading followed by one week of recovery. The structure is simple, but the discipline to follow it — particularly the recovery week — is where most riders fail.
In week one, you ride two sweet spot sessions: a 2x20 on Tuesday and a 3x15 on Thursday. The remaining rides are genuine Zone 2 endurance work — not tempo, not "easy but with a few efforts thrown in," but actual easy riding where you can hold a conversation in full sentences. If you have a fifth day available, that's an endurance ride too. Total sweet spot volume for the week is about 85 minutes of time at intensity, and the rest is aerobic foundation work.
Week two adds volume. The Tuesday session becomes a 3x15, the Thursday becomes a 2x20, and you add a single VO2max session on Saturday — something like 5x4 minutes at 110 to 115 percent of FTP with equal recovery. That VO2max session keeps the top end sharp while sweet spot does the base-building work. Sweet spot volume stays around 85 minutes, but the overall training stress climbs because of the added intensity and slightly more endurance volume.
Week three is the peak. Tuesday is the over-under session — three cycles of ten minutes at 90 percent with two-minute surges at 105 percent. Thursday is the single 30-minute sustained block. Saturday is another VO2max session. The remaining days are endurance rides. This is the hardest week of the block, and you should feel it by Friday. If you don't, your sweet spot power is probably set too low. If you feel it by Wednesday, it's set too high.
Week four is recovery, and let me be really clear about this: recovery means recovery. You cut volume by 40 to 50 percent, you drop all intensity, and you ride easy. No sweet spot. No VO2max. No chasing segments. The adaptation you've been loading for three weeks happens during this week, not during the hard weeks. The hard weeks are the stimulus. The recovery week is the response. Skip it and you've done three weeks of digging without ever letting the body fill the hole back in stronger. Same sessions. Same errors. Same plateau.
When not to do sweet spot
Sweet spot is a base-building tool. It builds the aerobic engine. What it doesn't do is raise the ceiling — that's VO2max work. And it doesn't sharpen race-specific fitness — that's threshold and above. If you're in a dedicated VO2max block, where the training focus is on driving up your maximum aerobic capacity, sweet spot sessions compete for recovery resources without contributing to the primary goal. You'd be spending adaptation currency on the wrong thing.
During a taper before a target event, sweet spot is also the wrong call. You want to shed fatigue while maintaining fitness, and sweet spot generates enough training stress to interfere with that process. The taper is about arriving fresh, and freshness means backing off, not maintaining intensity.
And if you're already carrying significant fatigue — from a heavy block, bad sleep, a stressful stretch at work, or all three — adding sweet spot on top is pouring water into a full glass. The session might look right on paper, but the body can't absorb it. You're training, technically, but you're not adapting.
Putting it in the calendar
The riders who get the most from sweet spot are the ones who use it at the right time and then move on. A four-week sweet spot block in the early base phase, followed by a transition into threshold and then VO2max work as the target event approaches — that's the sequence the best coaches use. Dan Lorang talked about this layering on the podcast: you build the base, then you sharpen it, and the order matters because each phase creates the platform the next one stands on. Build the aerobic engine first. Then raise the ceiling. Then sharpen the point.
John Wakefield made a similar observation about the riders at Bora-Hansgrohe. The sessions are chosen for where they sit in the plan. A sweet spot session in November is doing a completely different job than the same session in June, and the coach who doesn't know the difference is just prescribing hard riding and calling it periodisation.
That's the principle most amateur plans get wrong. They default to sweet spot year-round because it feels productive and completable, and the rider never moves through the phases that would actually make them faster. The fix is to use it deliberately, load it progressively, recover from it properly, and then put it away and move on to the next block.
Where to go from here
If you want the structure around this — a periodised plan, coaching input, and a community of riders who are serious about getting faster — that's what the Not Done Yet community on Skool is for. The conversations there go deeper than any article can, and the riders holding each other accountable to the recovery week are worth more than any session design.
You're not done yet. The sweet spot block is just the start.