Losing your balance, or rather, fighting to keep it, forces your core to brace your spine. One simple way to train core stability is with weight in one hand while the other is free, as in the off-set loaded lunge.
Use the off-set loaded lunge for 6–12 reps after a squat or deadlift variation.
HOW TO DO IT: OFF-SET LOADED LUNGE
1. Hold a dumbbell in your left hand at shoulder level and stand with feet hip- width apart.
2. Step forward with your right leg and bend both knees until the rear knee nearly touches the floor and the front thigh is parallel to the floor. Keep your torso upright. Perform all your reps and then switch arms and legs.
The side holding the weight will want to bend, but your core has to work to keep your torso straight—especially while it’s moving during the lunge. Maintaining stability strengthens your abs, while the lunge trains your legs, making this move multifunctional.