How to load each exercise

6 reps, heavy. Use the strongest or most stable variation first. Pick a load that makes six reps hard while you can still hold the intended range and execution.

12 reps, moderate. Reduce the load for the second exercise. The target muscle is already fatigued, so choose a weight you can control for all 12 reps.

25 reps, lighter. Finish with a variation that lets you keep continuous tension on the target muscle. If you have to swing the weight to finish, reduce the load for the next round.

Two 6–12–25 arm tri-sets

Biceps. EZ-bar curl × 6, incline dumbbell curl × 12, cable curl × 25.

Triceps. Close-grip bench press × 6, overhead dumbbell extension × 12, rope pressdown × 25.

Set up the equipment before you start. Take about 10 seconds to move from the sixes to the twelves, then another 10 seconds before the 25s. All three exercises make up one round.

Rest between rounds

One muscle group. Finish all three exercises, then rest three minutes before repeating the same tri-set. The infographic gives a general range of two to three minutes and three to five rounds. The arm example uses three to four rounds, with three minutes of rest as prescribed in the caption.

Antagonist pairing. Finish the whole biceps tri-set, rest 90 seconds, then do the whole triceps tri-set. Rest another 90 seconds before returning to biceps. The 90 seconds go between completed tri-sets. The short transitions still apply within each one.

Keep the rep standard across rounds

Watch the first and last exercises closely. If six reps are easy at the prescribed range, you’ve missed the purpose of putting the heavy exercise first. If the cable curl turns into a body swing late in the 25, the load is too high for the standard you set. Adjust the relevant load and keep the exercise order, joint position and execution consistent.