What's leg day [1] without some lunges [2]? You'll want to add this variation to your routine for two reasons. One, holding a dumbbell over your head will also target your core and your arm. Two, having the instability of holding one dumbbell overhead will make your legs and butt work harder. This means you'll only need to do a few reps to start feeling this, and you'll be feeling it for days!

• Stand with your feet hip-distance apart, holding a medium-sized dumbbell in your right hand.
• Press the dumbbell overhead, locking your elbow.
• Step your right foot forward into a lunge position so both knees are at 90-degree angles, and your left knee just taps the floor.
• Step the right foot back to complete the rep.
• Complete the same number of reps on each side.