Two minutes of one groove. No fills. No variations. No kick changes. No accelerando. No "let me try a small thing here." Just the same bar, repeated, for one hundred and twenty seconds.
If that sounds easy, you haven't done it yet. The two-minute loop is the most boring exercise in this curriculum — and one of the most useful. It builds three things at once: endurance (the small muscles in your hands and feet getting tired and recovering inside the same groove), time (every micro-drift becomes audible against a click), and discipline (the active resistance to making things "more interesting").
Around the 30-second mark, your brain will offer up suggestions. Why don't I add a fill? What if I change the kick? Could I open the hi-hat on this one? All of these voices are wrong; the exercise is to ignore them. The discipline of holding one groove without variation is the same skill that lets a working drummer sit in a 5-minute verse without varying the part.
The other temptation is to drift into a different feel without noticing. A straight 8th-note groove can imperceptibly become slightly swung; a quarter-note hi-hat can start ghosting in extra hits. These drifts are subtle and often unconscious — the recording reveals them, the playing doesn't. If you find yourself in a different feel from the one you started in, reset and start again.
A brain that's bored speeds up. A click is the only defense — and even with a click, you'll notice yourself wanting to lean ahead of the click in the second minute. Don't. Behind the click is also wrong but at least it's not the panic-direction. Stay in the click; let the boredom be boring.
The three exercises below are three different grooves — same tempo, different patterns. The point of having three is so that across a single practice session you have variety, while within each two-minute loop you have none. Pick one. Set the click. Play the same bar 60 times in a row.