People.com Lifestyle Food Celebrity Trainer Harley Pasternak: The Key to Sexy Summer Abs The celeb trainer has four easy moves that'll get you from slouchy to six-pack in no time By Staff Author Published on July 9, 2015 12:20 PM Share Tweet Pin Email Harley Pasternak is a celebrity trainer and nutrition expert who has worked with stars from Halle Berry and Lady Gaga to Robert Pattinson and Robert Downey Jr. He’s also aNew York Times best-selling author, with titles including The Body Reset Diet and The 5-Factor Diet. His new book 5 Pounds is out now. Tweet him @harleypasternak. It’s that time of year that we’re looking for ways to look our best poolside, and one of the most common problematic areas is the midsection.When thinking of ‘great abs,’ many people make the mistake of only considering the front of their midsection (where the ‘six pack’ would be), but really that’s only a fraction of what makes for a flat, toned tummy. So what’s the secret to a sexy, toned trunk? Other than overall fat reduction, the most important thing is to train your whole core. Crunches, for example, really only work one-quarter of our core. For a toned, beach-ready tummy, make sure you hit all these groups: Rectus Abdominis (front of abs)The plank is a classic for a reason: it’s simple and effective. The PlankRest your forearms on the floor and extend your legs back so your toes are on the ground and there’s a straight line from your heels to your shoulders. Contract your midsection, forming a rigid plank with your body, and hold as long as you can, breathing normally throughout. Transverse Abs (‘corset’ muscles)I like to think of the transverse abs as our body’s own Spanx. It pulls in our trunk, whittling our waistlines. Lying Trunk TwistLie on your back with your legs in the air, knees bent at 90 degrees. Keeping your shoulders flat on the floor and arms straight out to the sides, with your palms facing up, rotate your lower body to the left side until your left leg touches the floor on your left side. Hold for five seconds, then return to center, maintaining the same leg position throughout. Repeat on other side. Courtesy Harley Pasternak Internal and External Obliques (‘love handles’)Avoid the dreaded muffin top by toning your obliques and carving the inguinal crease (the sexy lines from your hip to your groin). Side BendsStand straight with your feet shoulder-width apart, holding a dumbbell in your left hand. Gently tilt your upper body to the right as you stretch your left ‘love handles.’ Return to starting position and repeat. Then reverse direction as you slide the dumbbell down your left thigh and stretch out your right side. Spinal Erectors (lower back)Why did I include a lower back exercise in an ab routine? Because strengthening the lower back helps lengthen your midsection and provides support for a strong core. Hip ThrustLay down on the ground or a mat with your head and back flat and your knees bent so that your feet are also flat on the ground, shoulder-width apart and parallel. Using your abs and glutes, push your butt off the floor so that your head, hips and knees are in line. Hold for one beat and lower with control back to start. Courtesy Harley Pasternak RELATED: All of Harley’s Blogs and Training Advice Celeb Trainer Harley Pasternak Shares a Go-To Move to Get Buns like Beyoncé