Weighted Bird Dog

On hands and knees, hands under shoulders, knees under hips. Hold a dumbbell in one hand and reach that arm straight forward while extending the opposite leg straight back, both finishing level with your torso. Your hips and shoulders stay square to the floor the entire time, if one hip lifts to compensate for the weight, you have gone too heavy or too far. Brace your core before you move, not after, and hold the extended position steady rather than pulsing it. The dumbbell adds an anti-rotation demand: your job is to resist the twist it creates, not to swing it. Switch sides with the same control you started with.