A. Start in plank position, feet about hip-width apart, hands directly under shoulders, neck in line with spine, abdominals engaged.
 


B. Slowly lower body to floor, then push quickly back to start. Do 8 reps.

A. Start in forearm plank, elbows directly under shoulders, abs engaged, neck in line with spine. 
&nbsp;
B. Keeping hips square, tap right shoulder with left hand, then return to start. Repeat on opposite side for one rep. Do 8 reps.

A. Stand with feet slightly wider than hip-width apart, holding kettlebell handle with both hands in front of you. 
&nbsp;
B. Lower kettlebell to floor, pushing hips back and bending knees while keeping back flat, then quickly return to start, driving hips slightly forward for one rep. Do 8 reps.

A. Stand with feet slightly wider than hip-width apart, knees slightly bent, a kettlebell in each hand, palms facing body. Hinge forward from hips, back flat, arms extended in front of you (as shown). 
&nbsp;
B. Row, driving elbows back and squeezing shoulder blades together, keeping back flat. Do 8 reps.

A. Stand with left leg about 3 feet in front of right, toes facing forward holding a kettlebell upside down with both hands at chest, elbows bent, palms facing body, then sink into lunge (as shown). 
&nbsp;
B. Rotate torso to left, keeping hips forward, then raise kettlebell overhead; elbows soft (as shown). Lower kettlebell back to chest, rotate torso forward and return to start for one rep. Do 8 reps. Switch sides; repeat.

A. Kneel on floor with forearms on stability ball, elbows bent, palms pressed together (as shown). 
&nbsp;
B. Engage abs and press arms forward until straight, roll ball towards body, keeping back flat (as shown). Bend elbows to roll ball back to start for one rep. Do 8 reps.

A. Stand with right foot about 2 feet in front of left, right foot flat, left heel raised, toes pointing forward, cradling ViPR at chest level (as shown). 
B. Lower into lunge, without moving torso (as shown), then return to start for one rep. Do 8 reps. Switch sides; repeat.

A. Lie on back with knees bent, feet flat on floor about hips-width apart, with arms extended overhead holding kettlebell with both hands, palms facing; kettlebell resting on floor (as shown). 
&nbsp;
B. Keeping lower back flat on floor, engage abs and use chest to pull kettlebell forward until arms are extended over chest (as shown), then lower kettlebell back overhead to floor to return to start for one rep. Do 8 reps.

The Equipment:A kettlebell, ViPR and a stability ball The Circuit:Click through the slideshow above or download the pdf for this week's moves. Do 8 reps of each exercise and complete the circuit three times, resting for 90 seconds between each circuit. The Philosophy: The targeted strength training circuit is the core of Stolz’s program. He uses a progression model — building on the moves each week by tweaking them slightly and playing with the sets and reps. "I always hear people saying you need to 'change things up' in order to see results, and that’s true to a certain extent, but there’s much more to it," Stolz says, "The key is changing things up without changing it too much. If I throw something completely different into the mix without your body adjusting to that first movement, it doesn’t do you any good. You have to have some efficiency in order for the movement to take real effect." Another key element: speed of movement. Use slower movements eccentrically — loading toward the body — and faster movements going concentrically — when you push away from your body. "In general, the more time muscles spend under tension, the more muscle fibers you'll activate," he says, "so muscles will grow more quickly, and you'll see better results."Bring the moves with you.Download pdf instructions. Done with week one? Move on to <a href=/articles/2012/02/change-the-shape-of-your-body-week2>week two</a>.

Trainer Josh Stolz is the secret to the fit physiques of A-list celebrities and power players at Equinox in New York City. But his own body is his ultimate billboard (yes, those are his actual abdominals). Stolz's carefully carved cuts are no accident: they're the result of serious physiological knowledge put into practice (he recently added a Master's Degree from Columbia University in motor learning to his long list of certifications and accolades). We asked him to create an exclusive 4-week plan designed to measurably change the shape of your body. The Details: Follow the 7-day protocol strictly — there is a method to the madness — then move on to weeks <a href=/articles/2012/02/change-the-shape-of-your-body-week2>two</a>, <a href=/articles/2012/02/change-the-shape-of-your-body-week3>three</a> and <a href=/articles/2012/02/change-the-shape-of-your-body-week4>four</a>. (Be prepared: The moves will get harder each week.) The Plan: <div style="margin:0 auto;width:650px"><h3 style=font-size:24px;color:#00c09e></h3></div>