Shake Up Your Cardio

When you're bored with working out, it's tempting to just bail. These three-pronged routines will keep you amped.

There's a reason triathletes look so fabulous: by combining three events, they get the results of each - a swimmer's cut shoulders, a cyclist's toned legs, and a runner's lean physique. But you don't have to go hardcore for those perks. These four cardio plans will freshen up your workout, and you can finish each in 30 minutes or less. Do one three times a week on nonconsecutive days, says Karl Scott, a private trainer at The Sports Club/LA in New York City.

THE TRIATHON TRAINER
A triple play that gets fast results: Do It: Pedal a bike at a moderate pace-an effort level of 5 0r 6 (you're working hard but can still carry on a conversation)-for 10 minutes. Next, run either outside or on a treadmill for 10 minutes, again at an effort level of 5 or 6. Last, head to the pool or a rowing machine and put in 10 minutes at the same effort.

THE FULL-BODY TONER
Combines strength moves and cardio for maximum fat-balsting: Do It: Jump rope for 30 seconds and rest for 30 seconds; do 5 sets. Then perform 2 sets of this 5 minute body weight circuit; squats, pushups, step-ups, dips, and crunches. Do as many reps of each exercise as you can in 1 minute, moving to the next without rest. Finish with a 10 minute jog at a medium pace.

THE POWER BOOSTER
This interval workout builds speed, power and lower-body tone: Do It: Pick three cardio machines with adjustable resisteance and do the following on each: warm up for 2 minutes at a medium pace. For the first interval, raise to max effort by upping the resistance and/or incline, keeping the pace steady; go for 30 seconds, then recover at wormup pace for 2 minutes. Do 2 intervals per machine. Finish on one machine before moving to the next.

THE CALORIE SCORCHER
Challenges your cardiovascular system and strengthens your body: Do It: Choose any three cardio machines. One the first one, go for 10 minutes at an effort level of 5 0r 6. Move immediately to the next machine and go hard, at an effort level of 9 or 10-you should just barely be able to huff out words, for another 10 minutes. Finally, switch to the last machine and do 10 minutes at a 5 or 6 effort.