Here's the situation. You have a lot going on today and time isn't on your side. You need to get in a good ab workout and get on with the rest of your day. If you can spare just 15 minutes, then this workout will help you get the job done.

This program is based on EMOM (Every Minute On the Minute) training. At the top of every minute, start your set. Once you finish, whatever is left of that minute is your rest time. The next minute is the start of your next set. You'll do five exercises and rotate through them for three complete sets of each within the quarter-hour.

Ab Roller

This exercise looks simple enough, but don't let that fool you—the ab roller is intense! And don't even think about trying to cheat. You won't get nearly the same ab-sculptingresults.

Holding the handles of the wheel, roll out as far as you can on each rep without touching the floor. Stretch out your arms in front of you and imagine you're going to touch your nose to the floor. Contract your abs and use your core to pull yourself back.

If you can't keep your back straight, or you're struggling to hold yourself up for the last few reps, take a few seconds of rest and try again, or just hold the plank. Once you get the hang of it, you'll begin to feel the results for yourself. One set should take 20-25 seconds to complete.

Lying Leg Raise

Perform leg raises on the floor or on a bench, and even add weight if you want to. Keep your hands under your butt and lift your legs straight up without bending them. If you have a weak or injured back, it's okay to bend your knees to reduce the intensity until you build more strength in your core.

For an extra-intense abdominal contraction, lift your hips up at the top of the movement and pull your abs in toward your spine. Control your legs as you lower them back down, using your abs and not your hip flexors. One set should take 30-40 seconds to complete.

Bicycle

Because you're maintaining an isometric contraction while twisting back and forth, your six-pack will feel this exercise from every angle.

Resist the temptation speed up this exercise during your timed interval. It's natural to want to get as many reps in as possible, but with only 15 minutes, we're looking for quality over quantity. Slow down and focus on the muscles working to reap better ab-building results.

You're locked into 30 seconds, so you know you get at least 30 seconds of rest before your next exercise. Dig deep. Make every rep count.

Crunch

Crunches are basic, but can be highly effective when done right. When you're doing your crunches, don't think of rolling up your shoulders. Instead, focus on contracting your abs and let that movement naturally lift your upper body. By the time you bring your shoulders off the ground, you should feel an intense contraction in your abs.

Remember to protect your neck by keeping it in as neutral a position as possible. Do not lock your fingers behind your head. Cross your arms across your chest or place your hands on the sides of your head, fingertips behind your ears. All 15 crunches should take 20-30 seconds to complete.

Side Plank

Regular planks are awesome, but side planks bring your ab game to a whole new level. They force you to work your transverse abdominis, the muscle that wraps around your waist like a girdle. Working this muscle can help tighten and define your midsection, so if you haven't been doing side planks, now is the time to start.

Lie on your side and position your bottom elbow under your shoulder. Exhale as you lift your hips off the ground until your body is in a plank position balanced on the one elbow and your feet. Keep breathing as you hold this position without letting your hips drop. Once 20 seconds pass, switch to the other side and repeat. By the time this is over, you'll have only 10-15 seconds to recover before the circuit starts again.