The signs of spring are everywhere. Meadows festooned with wildflowers. The lazy thwack of exhibition baseball. Girls Gone Wild at spring break, and willing to be filmed in the process by Snoop Dogg. The gentle passing of winter… which means shedding your clothes… which means revealing your body… which means… Yikes.

Unless you want to be approached at the beach by the film crew of Guys Gone Fat, you probably have some major work to do right about now, and one month in which to do it. The good news is, if you follow this admittedly demanding program to a T, there’’s time left for you to hit the beach with a V-taper, perhaps even a six-pack.

This four-week training program, designed by m&f resident science expert Jim Stoppani, PhD, combines fast-moving weight workouts with high-intensity cardio sessions to help you burn off fat while main-taining the muscle hibernating beneath.

Meanwhile, a conventional diet won’’t do for this tight timeframe. Instead, you need the sort of crash course bodybuilders take before contests to achieve the results they display onstage, modified for a noncompetitor who wants to lose a dramatic amount of bodyfat posthaste, and safely. For this, we recruited Todd Swinney, a bodybuilding contest-prep guru who has helped everyone from pro bodybuilder Kevin Levrone to fitness competitor Stacy Simons for shows.

Follow this muscle-pumping, fat-burning formula to the letter, and you’’ll be looking for any excuse to shed your shirt this summer.

NEXT: Weeks 1 & 2 >>

Weeks 1 and 2

Muscle Buildup

These resistance workouts, in which the entire body is split over two days, should take no longer than 30-40 minutes tops. You’’ll do each workout twice per week. ““This is a building and prepping phase”” Stoppani explains. ““The reps are low enough so that you aren’t too fatigued, but you should still use enough resistance to make it challenging”.”

Take no more than 30-–60 seconds to rest between sets, and if you’’re feeling fatigued, back off a little on the poundage. Once your body gets used to this faster training pace, you’’ll be able to move up again in weight in the weeks to come.

While Week 1 has you working in straight sets, Week 2 pumps up the intensity: You’’ll do two straight sets, then make the third set of each exercise a drop set. In a drop set, you do one complete set of an exercise with a challenging weight, then immediately pick up a slightly lighter weight and continue reps to failure.

Cardio

The basis of the cardio program is interval training, which has been shown to be more effective for burning bodyfat than steady-state cardio. Says Stoppani, “It encourages an ‘afterburn’ effect, meaning that the rest of the day after your cardio session, your metabolism remains elevated, burning more calories than you would otherwise.”

Your cardio choices are limitless, and you can work indoors or out. Inline skating, running, biking, stair-steppers, rowing machines, ellipticals — all of these are viable options. Each session begins with a five-minute warm-up at an easy pace. Then, for Week 1, a one-minute, highly intense interval is followed by two minutes of ‘working rest,’a period of moderately intense activity in which you’re still working harder than your warm-up but aren’t going all out, enabling you to recover in time for your next interval. Repeat this format several times, as directed, and round out each session with a five-minute cool-down. Week 2 of the program tacks on two additional intervals, and flip-flops your interval- and working-rest times.

NOTE: This cardio program is designed for individuals with a moderate level of cardiovascular fitness. If this program is too difficult for you, perform as many intervals as you can, and try to increase it by one or two each subsequent session. If you are over 40 or have a health condition, check with your doctor before beginning an exercise program.

NEXT: Weeks 3 & 4 >>

Weeks 3 and 4

Ultimate Fat Burning

This is a three-day body split; each workout should be completed twice per week. “The intensity and work load go up, but the rest interval between sets stays the same at 30-–60 seconds at most”” says Stoppani. “Your total weight-training time will be longer now, maybe 40-–50 minutes each day”.

Weeks 3 and 4 are do or die — you increase intensity by using compound, drop and tri-sets. (A compound set is performing two exercises for the same muscle group back to back with no rest. A tri-set is performing three for the same bodypart consecutively without rest.)

Cardio

Your interval training continues to increase in frequency, duration and intensity. During Week 3, you should be doing 5-6 days a week of 52-minute sessions, while Week 4 puts your cardio system to the test, increasing the frequency to 6 days a week and the duration to 60 minutes.