Sweet spot has become the default training zone for a huge number of cyclists, and I understand why. It feels productive. The numbers look good on TrainingPeaks. You finish the session tired but not wrecked. That 88-93% FTP range hits a psychological sweet spot as much as a physiological one.
But that is exactly where the problem starts.
The evidence for sweet spot training is solid — when it is used in the right context. During a base or early build phase, those sessions push your aerobic system without the massive glycogen drain and multi-day recovery cost of repeated threshold efforts. For time-crunched riders who can only train an hour, a well-placed sweet spot session gives more bang per minute than zone two alone.
Where it falls apart is when every session becomes sweet spot. I see this constantly. Riders skip their easy days because forty-five minutes at zone two feels like a waste. They replace VO2max intervals because sweet spot is less painful. Over weeks and months, everything converges into this middle band where you are always a bit tired, never fully recovered, and your actual ceiling — your VO2max — is not getting any stimulus at all.
The research on polarised training tells us something important: the riders who improve the most over years tend to keep their easy days properly easy and their hard days properly hard. Sweet spot lives in neither camp. It is useful as a specific block or a once-a-week session, but it should not be the backbone of your plan.
If you have been doing sweet spot three or four times a week and your FTP has flatlined, that is not a coincidence. Pull back, restore the polarisation, and watch what happens.
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