High plank position, hands directly beneath your shoulders, feet set fairly wide apart for stability. Shift your weight slightly to one side, pulling the elbow of the free hand backwards (simulating a rowing motion); lift your hand briefly off the floor, then lower it back down in a controlled manner. Switch sides after each repetition.
Attention:
Do not tilt or twist the hips too much (aim for stability, not weight transfer), do not raise the buttocks too high or let the back sag (hollow back), do not move too quickly (loss of control), do not shift your weight too much (unstable), do not let your shoulders slump inwards, do not have too little body tension, do not use too heavy a weight (movement becomes sloppy).
Lighten:
Hands slightly raised (e.g. on a bench): feet wider apart for greater stability.
Harden:
Narrower stance (more core engagement); added weight (hold two dumbbells in your hands); combine with push-ups; slower repetitions (more control); unstable surface (e.g. balance tools); one-legged variation (very challenging).
Variation:
Raise your hand and tap the opposite shoulder (shoulder tap).
