Reebok master trainer Sara Haley ratcheted up last week's series of moves to burn even more fat and increase lower-body toning. Pair these moves with either your upper body or cardio upgrades (or both!), depending on your Week 4 daily schedule. And if you feel sore the next day, take it easy, not off. "Consistency is key," Haley says.

For this first move, start again in squat position, but this week start on the balls of your feet. Hold for 2 counts. Straighten legs, staying on the balls of your feet throughout, and reaching for the ceiling (next image). Press shoulders away from ears; squeeze abs and butt, holding body in one long line. Do 20 reps.

With feet wide, legs turned out, and hands behind head, lower into a plie squat. As you return to standing, lift one knee and reach for it with the opposite elbow (next image). From the twist position, extend the lifted leg out to the side and then back in to the twist. Do 20 reps total, alternating sides.

Standing on a wood or tiled floor, put a towel underneath ball of one foot. With feet together and knees soft, slowly slide towel straight out to side as supporting leg bends into a deep, one-legged squat (next slide). Keep heel of supporting leg on floor. Hold at lowest part of lunge for a count of 4, then return to start. Alternate legs. Repeat 8 times per leg.

Kick one foot up to your glute, flexing foot to contract back of leg. Alternate legs, pumping arms. This week, turn the move into an exaggerated run by pushing off one foot at a time and picking up the pace. Continue for 45 seconds.

With arms raised out to sides, lunge your right leg forward, back leg straight. Engaging your core for balance, rotate upper torso toward front leg (next image). Squeeze glutes to keep hips facing front. After twisting to side, deepen the lunge and lean down to touch the floor (third image). Hold for 4 counts. Slowly reverse movements back to center. Do 6 times on this side, then switch legs and repeat series on the other side.

Lay on your side with legs extended straight and feet stacked. Press into your forearm, lifting hips off floor. Place free hand behind head to open up chest. Once in raised position, slowly lift top knee into chest and bring upper body toward chest, making elbow and knee meet (next image). Hold for a count of 2. Open up to starting position. Repeat 6 times, keeping hips off the floor and spine straight.

Place a towel under both feet. Begin in plank position with glutes and core engaged, and shoulders in line with hands. Using core, slide towel into chest to bring knees in, keeping upper body stationary (next image). Extend legs back out to plank. This week, do this move 15 times. Finish by holding plank as long as you can, working toward 60 seconds.

With arms raised out to sides, lunge your right leg forward, back leg straight. Engaging your core for balance, rotate upper torso toward front leg (next image). Squeeze glutes to keep hips facing front. After twisting to side, deepen the lunge and lean down to touch the floor (third image). Hold for 4 counts. Slowly reverse movements back to center. Do 6 times on this side, then switch legs and repeat series on the other side.

Lay on your side with legs extended straight and feet stacked. Press into your forearm, lifting hips off floor. Place free hand behind head to open up chest. Once in raised position, slowly lift top knee into chest and bring upper body toward chest, making elbow and knee meet (next image). Hold for a count of 2. Open up to starting position. Repeat 6 times, keeping hips off the floor and spine straight.