Before you begin: You need dumbbells and a bench.
1. Down-down, up-up
Start in plank position, with your hands directly below your shoulders. Lower your right forearm, then your left one, to the ground. Hold for two seconds, then straighten one arm at a time to return to your starting position. Do eight reps, alternating starting arms.
Perfect your form: Keep your body in a straight line throughout the exercise.
Dial it down: Perform the exercise from your knees.
Amp it up: Increase your reps to 12 in total, or lift one leg off the ground.
2. Scissor kicks
Lie on your back, with arms by your sides and legs in the air. Keeping core tight, lower your left leg to the ground and raise back up while lowering your right leg, in a scissor action. Repeat 20 times.
Perfect your form: Do not arch or round your lower back as you move your legs up and down. Keep your shoulders and neck relaxed.
Dial it down: Start with your knees bent at 90 degrees, and straighten legs to the ceiling.
Amp it up: Hold each leg at the bottom for five counts before switching legs.
3. Lunging wood chop
Start in a lunge position with your left leg forward, holding a single weight in both hands. Bring the weight toward your right hip. Then, maintaining the lunge, diagonally raise the weight over your left shoulder. Do 10 reps on each leg.
Perfect your form: Do not let your front knee bend farther forward than your shoelaces.
Dial it down: Do the exercise without the weight.
Amp it up: Slow it down. Take four counts to lower and four counts to return to your starting position.
4. Bench plank twists
Begin in plank position, with your hands on a bench. Lift your right foot off the ground and bring your right knee diagonally across your body toward your left shoulder. Return to the starting position and repeat on the other side. Do 12 reps.
Perfect your form: Keep your body in a straight line from your feet to your shoulders.
Dial it down: Skip the twist and simply lift each foot off the floor.
Amp it up: Do two alternating reps, holding the knee in for two counts. On the third rep, hold for six counts. Repeat cycle.
Calorie-burning bonus: Do one minute of jumping jacks between core exercises.