Tabata is the ultimate fitness trifecta. It's fast. It's fun. It's effective. We've tweaked the standard structure a bit for our Better-Body Challenge , turning each Tabata into a superset. Rather than doing one exercise for four minutes, you alternate between two complementary moves for a total of eight minutes. This modification gives your working muscles a bit more rest time between sets, which translates into better form for all your reps during each Tabata.
Get set to burn major calories. Print out this workout  and get your timer ready (we like the free programmable app SIT  — simple interval timer). Hope you dig this workout as much as we do.
Jumping jacks: This classic calisthenic move gets the heart rate going; add in some cross jacks  for variety.
Walkouts : This full-body move takes you slowly from standing, through plank, to a deep lunge stretch, and back to standing.
One-Minute Rest: Standing leg cradle 
Squats with reach : Take your basic squat, lift your arms overhead, and you've increased the core strength needed for each rep.
Up-down planks : Move steadily and smoothly between plank and elbow plank, which works your arms and your core.
One-Minute Rest: Standing quad stretch  (30 seconds each leg)
Alternating backward lunges : Step backward into a lunge and alternate legs with each rep.
Mountain climbers : Holding a plank position, move your legs like you're running in place to work your arms and abs.
One-Minute Rest: Deep hip flexor stretch  (30 seconds each side)
Alternating side lunges : Keep your chest high as you step wide to the side. Return to standing and repeat the lunge on the other side.
Bicycle crunches : Don't blast through your reps of this classic ab exercise. Keep your shoulder blades off the ground and twist through your ribs to bring your elbow to your opposite knee.