Use a bench or a partner's back while they hold a plank position. Extend one leg out roughly 24 inches, with the other leg placed on the bench or your partner’s back. Squat down until your knee is nearly touching the ground, then return to the starting position. Perform the movement on the ‘down’ command, typically in sets of 15-20 reps per leg. To modify, add weight using a coupon, ruck, or sandbag.