Sandbag Lunges

Hug the sandbag against your chest or rest it across the front of your shoulders, whichever it sits still in. Unlike a fixed dumbbell, the load shifts and settles unevenly as you move, so your core has to work constantly just to keep the bag from pulling you off balance. Step forward into a lunge, front knee tracking over your foot, back knee dropping toward the floor, then drive back up and step through to alternate legs. Keep your torso tall rather than hunching around the bag — that shifting weight is exactly what makes this harder than the same lunge with a fixed load.