Guides
What Is Sweet Spot Training on a Turbo? (88-94% FTP)
The short answer
- Sweet spot training means riding at 88-94% of your FTP (functional threshold power), the zone that sits between high tempo and full threshold.
- It gives you most of the fitness gains of threshold work for noticeably less fatigue, which is why it suits time-limited indoor riders.
- On a turbo it is the single most efficient way to build sustainable power, because the trainer holds the resistance steady and removes the excuse to coast.
- A simple starter session is 3 x 10 minutes at 90% FTP with 5 minutes easy between, inside a 60-minute ride.
- Do not live in the sweet spot all year: 2-3 sessions a week max, and you still need easy zone 2 and proper threshold or VO2 work.
Sweet spot training means riding at 88 to 94 percent of your FTP, the zone that sits just below your one-hour threshold and just above hard tempo. It is the most time-efficient way to build sustainable cycling power, because it stacks up a big training stimulus while staying repeatable through the week. On a turbo trainer it works even better than outdoors, because the trainer holds the resistance dead steady so you cannot coast, drift, or hide on a descent.
Sweet spot is the workout I prescribe more than any other for the riders I coach who only have a few hours a week. I have run these sessions on the turbo for years, and below I will explain exactly what the zone is, why it works, and give you a session you can ride today.
What does “sweet spot” actually mean?
The phrase describes the band of effort where the trade-off between fitness gain and fatigue is at its best, hence “sweet spot”. Push harder, into threshold and above, and the fatigue cost climbs faster than the benefit. Ease off into tempo and below, and you have to ride for much longer to get the same adaptation.
In numbers, that band is 88 to 94 percent of your FTP. If your FTP is 250 watts, your sweet spot is roughly 220 to 235 watts. It maps to the top of zone 3 and the very bottom of zone 4 in the standard model. If you want the full breakdown of where every band sits, I have written it up separately in my guide to understanding training zones on the turbo.
What it feels like on the bike
This matters more than the watts. Sweet spot should feel “comfortably hard”. You can hold it, your breathing is deep and steady but controlled, and you could speak a short broken sentence but would not want to hold a conversation. If you are gasping and counting down the seconds, you have drifted into threshold and the session will cost you more recovery than it should. If you are chatting away happily, you have slipped into tempo and you are leaving fitness on the table.
Why sweet spot training works so well on a turbo
The big benefit is repeatability. Threshold and VO2 max work is more potent minute for minute, but it batters you, so you can only do it once or twice a week before quality drops. Sweet spot sits far enough below threshold that you can do 2 to 3 sessions a week, week after week, and still recover. Over a training block that volume of quality work adds up to a serious lift in your sustainable power.
The turbo amplifies all of this for three reasons:
- Steady resistance. Indoors there are no descents, no junctions, no easing off over a crest. The trainer holds the load, so 10 minutes at 90 percent really is 10 minutes at 90 percent, not an average smeared across coasting and surging.
- ERG mode removes decisions. On a smart trainer, ERG mode pins the resistance to your target watts. You set 225 watts and the trainer makes you pedal at 225 watts whatever your cadence does. All you manage is keeping the pedals turning, which is perfect for sustained intervals.
- No wasted minutes. A one-hour turbo session is a full hour of training. The same hour outdoors usually includes traffic lights, freewheeling and faff. For time-limited riders that efficiency is the whole point.
A tested example sweet spot session
Here is the session I start almost every rider on. It fits in 60 minutes and is the right side of brutal. I have ridden this exact structure dozens of times and the numbers below are what it looks like for a 250-watt FTP rider.
| Block | Duration | Target (% FTP) | Watts at 250 FTP | Feel |
|---|---|---|---|---|
| Warm-up | 10 min | 50-65% | 125-160 W | Easy, building |
| Interval 1 | 10 min | 90% | 225 W | Comfortably hard |
| Recovery | 5 min | 55% | 140 W | Spin, breathe |
| Interval 2 | 10 min | 90% | 225 W | Comfortably hard |
| Recovery | 5 min | 55% | 140 W | Spin, breathe |
| Interval 3 | 10 min | 92% | 230 W | Hard but holding |
| Cool-down | 10 min | 45-55% | 115-140 W | Easy |
That is 3 x 10 minutes of work, 30 minutes in the zone, inside an hour. As you adapt, the progression is simple: lengthen the intervals before you raise the intensity. Go to 3 x 12, then 3 x 15, then 2 x 20. Only once you can comfortably hold 2 x 20 at 90 percent should you nudge the target toward the 94 percent top of the band.
Where sweet spot fits in your week
One session in isolation does very little. Sweet spot earns its keep when it sits inside a structured week alongside easy riding and recovery. I have laid out how to balance hard and easy days in my guide to creating a weekly turbo training plan, and if you want the building blocks for the session itself, see how to structure a basic turbo training session. For shorter, sharper work on your other quality day, short intervals on a turbo are a good complement.
Do you need a smart trainer for sweet spot?
No, but it helps a lot. The honest answer depends on your kit.
- Smart trainer with ERG mode (best): Set the watts, hold cadence, done. This is the easiest way to nail sustained sweet spot blocks, and it is why I recommend a direct-drive smart unit to anyone serious about structured indoor training. If you are weighing types, my direct drive vs wheel-on comparison lays out the trade-offs.
- Dumb trainer plus power meter: Totally workable. You hold the effort manually in a fixed gear and watch your power. It demands more focus, but the training is identical.
- Dumb trainer, no power: Use heart rate as a proxy. Sweet spot roughly corresponds to 84 to 90 percent of your maximum heart rate once you have settled into an interval, though heart rate lags the effort by a minute or two, so pace by feel first and let HR confirm.
How accurate does the power reading need to be?
Accurate enough to be consistent, which is more important than being absolutely correct. A decent smart trainer reads within a couple of percent, which is more than good enough for sweet spot work. What matters is that the number is stable day to day, because you are training off your own FTP measured on the same device. If you want to understand what the figures on your screen actually mean, read understanding power readings on your turbo trainer.
Common sweet spot mistakes I see
- Living in the zone. Sweet spot is so doable that riders pile on session after session and never go truly easy or truly hard. You stagnate. Cap it at 2-3 sessions a week and protect your easy rides.
- Riding it as threshold. Letting every block creep up to 95 percent plus turns a sustainable session into a fatiguing one. Watch the discipline on the top end.
- Stale FTP. Training off a number from three months ago means your “sweet spot” is no longer your sweet spot. Re-test regularly.
- Skipping the warm-up. Ten minutes of progressive warm-up makes the first interval land properly instead of feeling like a wall.
The bottom line
Sweet spot training at 88 to 94 percent of FTP is, for most time-limited riders, the highest return on investment you can get on a turbo trainer. It builds the sustainable power that makes you faster on real roads, it is repeatable enough to do several times a week, and the controlled environment of indoor training is tailor-made for it. Get your FTP right, start with 3 x 10 minutes at 90 percent, progress the duration before the intensity, and keep it to a few sessions a week. Do that consistently through a block and you will feel the difference within a month.