The Best Abs Exercises: Side Plank

Why it works: This abs exercise is more challenging than a traditional plank because you're supporting your entire body weight on two points of contact instead of four. As a result, you must work your core harder to stay stabilized.

How to do it:
A. Lie on your left side with your elbow directly beneath your shoulder and legs stacked. Place your right hand on your left shoulder or on your right hip.

B. Brace your abs and lift your hips off the floor until you're balancing on your forearm and feet so that your body forms a diagonal line. Hold for 30 to 45 seconds. If you can’t hold that long, stay up as long as you can and then repeat until you’ve held for 30 seconds total. Switch sides and repeat.

More great stabilization moves: The standard plank and the anti-rotation hold.

The term "lower abs" is actually a misnomer—your rectus abdominis muscle, or abdominal wall, actually covers your entire midsection and connects at your pelvis. Still, women (and men!) are constantly searching for exercises that will help eliminate that dreaded lower-belly pooch. (We got your attention, right?) And now the search is over! Most of these effective exercises target multiple abdominal muscles, so you'll maximize your belly-burn with every rep.

Workout details: Do the prescribed number of sets and reps for each exercise consecutively, taking a short 45-60 second rest in between sets. Perform the full workout on 3-4 non-consecutive days per week. Another option is to pick a few of your favorite moves and do them after a cardio session or add them into your regular strength training routine.

You'll need: A mat or towel. That's it!

RELATED: For more secrets for flat belly and toned bikini body, check out Shape's exclusive weight loss plan, The Bikini Body Diet.

Workout details: Do a quick dynamic warm-up (1-2 minutes of jumping rope, jacks, or high-knee marches), and then do 1 set of the prescribed number of reps (or time) for each exercise. Move quickly from one move to the next with little rest in between. After you've finished the last exercise, rest 1-2 minutes, and then repeat the entire circuit 1 more time for a 15-minute, fat-blasting workout. If you're up for a challenge, complete 4 circuits total for a full 30-minute session.

You’ll need: A kettlebell (5-15 lbs, depending on your level)

(Never worked with a kettlebell before? Read these helpful tips before getting started.)

VIDEO: Gym's Crowded Workout

A six-pack may look strong, but looks can be deceiving. If you’re focusing only on the muscles you can see in the mirror, like the rectus abdominus and the obliques, you may be setting yourself up for bad posture and lower back pain. For a strong, functional, and attractive core, you also need to include exercises that strengthen deeper muscles, like the transverse abdominis, or back muscles, like the erector spinae group and the latissimus dorsi.

Stop ignoring these crucial parts of your core with a more balanced approach today. To keep your lower back feeling as good as your abs look, add in exercises that focus on stability and mobility.