Sandbag Press

Clean or hug a sandbag up to your chest, then press it overhead the same way you would a barbell or dumbbells, driving straight up until your arms lock out above your ears. The sand inside shifts and settles as you move, so the bag never presses the same way twice -- you'll feel it slosh and pull you off your intended path mid-rep, which forces your shoulders, core, and grip to constantly adjust rather than grooving one fixed motion. Brace your core hard before you press rather than after you feel the shift start, and keep your ribs down so the moving weight doesn't pull your lower back into an arch as it settles overhead.