Sweet spot is the intensity just below threshold, often defined as roughly 88-94% of FTP. It became popular among time-limited cyclists because it combines a solid stimulus with manageable fatigue.
Typical sessions: 2×20 minutes, 3×15 minutes or longer blocks at sweet spot with short recoveries
It can raise threshold power, especially in riders coming from low training volumes
Doing sweet spot too often can push training into a “moderate” zone that leaves you tired without the benefits of truly easy or truly hard work
Many coaches use it in specific phases rather than all year
For a rider with 6 hours a week, one sweet spot session (for example 3×15 minutes at 88-92% FTP) and one VO2max session, with the rest easy, is a balanced week. Two sweet spot sessions plus intervals plus a hard group ride is where problems often start.