Instantly Feel the Burn With This 4-Minute Arm and Ab Workout

We love the woodchop, and this variation is one of celeb trainer Gunnar Peterson's favorites.

• Holding an eight- to 10-pound dumbbell overhead, twist to the left, pivoting your right foot as needed.
• Exhale, and slice the dumbbell across your body to the right as you raise your right knee, bringing the weight to the outside of your right hip.
• Raise the weight back to starting position, and lightly tap your right toes to the floor. This completes one rep.
• Repeat as many reps as you can on one side for 30 seconds, then repeat on the other side for another 30.