Celebrity trainer Harley Pasternak is known for whipping famous bodies (like Katy Perry , Jessica Simpson , and Rihanna ) into shape, fast. And while the trainer is a spokesperson for gym equipment manufacturer Cybex , we asked him to share a workout that anyone can do, even if they don't have a gym membership (or personal gym!). Get the five-move workout, perfect for almost any small space, below. Repeat two to three times for an effective workout in under 30 minutes.
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The reverse lunge works your lower body but is a little easier on the knees than the classic lunge.
- To begin, stand tall, and take a controlled lunge (or large step) backward with your left foot.
- Lower your hips so that your right thigh (front leg) becomes parallel to the floor and your right knee is positioned directly over your ankle. Keep your left knee bent at a 90-degree angle and pointing toward the floor. Your left heel should be lifted.
- When your left knee is almost touching the floor, hold. Then, slowly push with your left foot to raise your pelvis up a bit; then straighten your knees, and return your left leg back to starting position next to your right leg.
- This completes one rep. Complete 10 reps before repeating the movement and the repetitions on your right side.
The Superman  is a simple, no-equipment-needed exercise that helps keep your back strong and butt toned. Here's how to do it:
- Start by lying down on the mat, belly down. Extend your arms above your head.
- Lift your upper back and legs, and hold for five seconds, squeezing your glutes. Lower back down.
- Repeat for 10 reps; then stretch your back out in Child's Pose  between sets.
Ball Pike to Plank
Make sure the ball is sized to your body; you should be able to sit on the ball with 90-degree angles at your hips and knees. If you don't have an exercise ball, use two sliders or paper plates on carpet to slide up to pike position.
- Start in a plank position with your hands directly under your shoulders and your shins on the ball.
- Do not allow your lower back to arch. Keep your feet, pelvis, and shoulders in one long line.
- On an exhale, pull your abs deeply to your spine, and use your abs to fold your body in half, pulling the ball forward toward your hands as your pelvis moves up in the air.
- Your toes will move onto the top of the ball, and your back will become perpendicular to the floor like a handstand. Allow your head to fall between your arms, keeping your neck long and in line with your spine.
- Lower yourself back into a plank position, and do not allow your pelvis to sag below your shoulders.
- Do 10 reps for two to three sets.
This push-up variation targets the triceps.
- Start in plank position with your hands under your shoulders and your body in one straight line.
- If your knees aren't on the floor, separate your feet so they're about shoulder-width apart to help you stay balanced throughout the exercise.
- Place your hands together, directly under your sternum, with the tips of your index fingers and thumbs touching. Your fingers and thumbs should form a diamond or triangle shape.
- Bend your elbows out to the sides, and lower your chest toward the floor. Then exhale to straighten your arms. This counts as one rep.
Lying Hamstring Curl
This move tones your butt and backs of the thighs. Harley recommends doing this move with one leg raised; to do so, plant one foot on the ball, and lift your other leg up, keeping it straight the whole time. Here's how to do it with both feet:
- Start by lying flat on your back with an exercise ball under your heels. Bridge your hips up, and hold that position through the entire exercise.
- Flex your feet, and dig your heels into the ball. Place your arms straight out to your side for support — don't use them, though; they are just for support.
- Slowly roll the ball toward your body as you curl your heels. Keep your hips in the bridge position; don't thrust them toward the ceiling as you do the move.
- Then slowly return to the start position (straight legs, hips bridged) to complete one repetition.
- Do three sets of 12 to 15 reps.