The double-leg straddle is a beginner-level plyometric, i.e., lower-body explosive exercise.
Begin by standing on a flat bench, standing erect and facing forward.
Move your feet outward just enough to clear each side of the bench as you squat down and your buttocks touch the top of the bench.
You will note that you are essentially in a squat position atop the bench with your thighs horizontal with floor and bench. Your hands are cocked, open, and touching either side of your waist.
Without hesitation, push with both legs as hard as you can while at the same time thrusting both arms upward into the air to help with your momentum.
You will land back atop the bench in the same standing position from which you started. Repeat movement for each subsequent rep. Rest only 30-45 seconds between sets.