Every workout carries one of four type chips: EN AT HI SP. The chip names the job the workout does. You see it on every workout card in Today and the Library.
EN Endurance. Steady rowing at a moderate effort, usually thirty minutes or more. You can hold a conversation. It builds the aerobic base every other type relies on. Most of your metres belong here.
AT Anaerobic threshold. Moderate intervals with about as much rest as work, for example four 4-minute pieces with four minutes of easy rowing between. You could speak, but would rather not. It trains the point where your body stops keeping up with the effort: row just under it, for longer each time.
HI Hard intervals. Short, high-intensity pieces with rest about three times the work, for example 1-minute efforts with three minutes between. They take you past threshold on purpose, so your body gets better at clearing the build-up and you learn to keep rowing through it.
SP Speed.Bursts of half a minute to a minute and a half, with rest four or five times the work. It trains power and top speed, not endurance.
The pyramid
Stack the types by how much of your training each should get: a wide EN base, a band of AT, a thinner band of HI, and a small SP tip.
Intensity only pays off with an aerobic base under it; adding intensity without the base is how plateaus and injuries happen. A gentle-looking week of suggestions is the pyramid at work, not the app going easy on you.
Types overlap
A hard-interval session for a fit rower can be a threshold piece for a newer one. The type names the job; a workout's length and expected effort say how big it is. Choosing a workout covers both.