If an athlete tells me they have six hours a week and want to get faster on the bike, I do not give them polarised training and I do not give them long slow distance.
I give them sweet spot, and it is the least glamorous answer available.
Sweet spot is what you do when you do not have enough hours for the theoretically optimal thing.
Where It Sits
Roughly eighty eight to ninety four percent of FTP. Just underneath threshold, in the zone that feels firm but controlled. You could talk in short sentences and would rather not.
The name comes from the trade it makes. It is close enough to threshold to produce a substantial aerobic stimulus, and far enough below it that the fatigue cost is modest. That combination is the point.
Threshold work at ninety five to a hundred and five percent produces slightly more stimulus and considerably more fatigue. You can do it twice a week at most, and it eats your other sessions. Sweet spot you can do three or four times a week and still run properly on Thursday.
Why It Suits Triathletes Specifically
Because triathletes do not only ride bikes.
A cyclist can afford to be wrecked by Tuesday's session because Wednesday is a recovery spin. A triathlete has a swim on Wednesday morning and a run on Wednesday evening, and a bike session that costs three days has just taken out two other disciplines.
Sweet spot is the highest stimulus you can apply to the bike without damaging the rest of the week. That is the actual constraint most amateurs are training under, and it is why the answer differs from what a pure cyclist would be told.
It also sits very close to the intensity you will actually ride a middle distance race at, which means the sessions double as race rehearsal.
What the Sessions Look Like
Start with three lots of ten minutes at ninety percent, five minutes easy between. That is a genuine session for somebody new to structure and it takes an hour with warm up.
Progress to three lots of fifteen, then three of twenty, then two of thirty. The progression is duration of interval rather than intensity, because the intensity is already correct.
Two of those a week, plus a longer easy ride at the weekend, will move most time-poor athletes' FTP more in eight weeks than anything else they could do with the same hours.
And it works indoors, which matters in a British winter. Sweet spot is one of the few sessions that is arguably better on a turbo, because there are no junctions, descents or traffic lights breaking up the effort.
The Honest Limitation
It is not optimal in an absolute sense, and I want to be straight about that.
If you have fifteen or twenty hours a week, a polarised approach with a large volume of genuinely easy riding and a small amount of very hard work will take you further. The evidence for that in trained endurance athletes is good.
Sweet spot is what you do when you cannot accumulate that volume. It buys aerobic development at an accelerated rate in exchange for accumulating more fatigue per hour, and at six to eight hours a week that is a trade worth making. At fifteen it is not.
The failure mode is doing it forever. Athletes who ride sweet spot every session for a year plateau, get stale, and lose their top end entirely. It is a block, eight to twelve weeks, and then something else.
The Mistake I See Most
Riding it too hard.
Ninety percent feels achievable, so people drift to ninety five, then ninety eight, and now they are doing threshold work while calling it sweet spot and wondering why they are exhausted and why the third interval collapses.
If you cannot complete the last interval at the same power as the first, you started too high. The discipline of holding back on the opening effort is most of the skill.
The Bottom Line
Two sessions a week at eighty eight to ninety four percent of FTP, intervals of ten to thirty minutes, progressing duration rather than intensity, for eight to twelve weeks.
Hold the power down on the first interval. Then move on to something else before it goes stale, and come back to it next winter.
