«This move really challenges the core without hurting the spine, and also works the hips, glutes and upper body, giving you a lot of bang for your buck,» says Matthews.

1. Start in a high plank position, with palms on the ground underneath the shoulders (not slightly out to the side, as in a push-up position), arms straight, toes tucked under, quads and abs engaged and head aligned with your spine. Bend your left knee and bring your left foot up toward the outside of your left hand. (Don’t worry if you can only get it halfway up there.)
2. Step the left foot back to meet the right foot. You should be in plank position again.
3. Repeat the move with your right foot.

After mastering this cardio-and-strength combo, you’ll feel as body-confident in your shorts as professional sprinters are in their racing briefs.

1. Begin in a half-kneeling position with your right foot forward and left leg back, and bend both elbows.
2. Keeping your abs engaged, draw your left arm forward and your right arm back, like you’re about to take off in a race.
3. Exhale as you drive your left knee and right arm forward and up.
4. Hold this position briefly before returning to your starting position.
5. Repeat on the same side for 15 seconds, then switch to the other arm and leg.
6. Not hard enough for you? Matthews suggests kicking up the intensity by rising up onto the toes of the standing leg.

Like classic push-ups, these work the chest, shoulders and core, but they also strengthen the triceps (and firm up jiggly under-arms) more effectively than almost any other exercise, found an ACE-funded research study.

1. Begin in a kneeling position. Place your thumbs and forefingers together in a triangle shape directly underneath your chest.
2. Now straighten your legs (or keep your legs bent with knees on the ground) so that you’re in a push-up position. Engage your abdominals and slowly bend your elbows, allowing them to flare slightly outward. Lower your chest toward the floor.
3. To come up, push through the outside surface and heel of your palms until your arms are fully extended.

This fitness-inspired twist on a yoga boat pose, or navasana, works the entire core as well as the hard-to-target hip flexors, says Matthews, who also teaches yoga.

1. Begin in a seated position with knees bent and feet flat on the floor. Cross your arms in front of your chest.
2. Slowly pick both feet up, keeping knees bent at 90 degrees. Recline the torso back slightly as you keep the core engaged and the spine long. This is the high-boat pose.
3. As you inhale, lower back with control. Extend the legs out in front of you and recline your torso closer to the floor. This is the low-boat pose.
4. As you exhale, rise back up with control into high-boat pose.