3 Best Outdoor Summer Workouts

As anyone who's ever stepped onto a treadmill can tell you, a cardio routine is like a razor: After a few weeks of constant use, it becomes dull and ineffective. There's no better time than the summer, when the world can be your gym, to infuse it with new energy—and burn fat and boost endurance at the same time.

Ready for a new challenge? Here are three outdoor workouts for wherever your summer takes you. And don't forget: You can get more cool exercises, innovative workouts, and fast fitness fixes by signing up for our free Exercise of the Week newsletter.

ON THE BEACH
Draw a line in the sand near the water, but not where it will wash away. Draw another one 75 yards down the beach. (One long stride is roughly equal to a yard.) Run from one line to the other 16 times at 70 percent of your maximum effort—in other words, slightly faster than a conversational pace. Each time you reach a line, do one of the following exercises and then rest for 30 seconds: plank (hold 20 seconds), lunge (10 reps), or pushup (10 reps). Pick a different exercise each time. "It will become harder as you progress," says Patrick Ward, C.S.C.S., founder of Optimum Sports Performance in Tempe, Arizona, "so pace yourself."

Why it works: "All of your force dissipates into the sand, requiring you to work harder to cover the same distance," says Ward. The result: You'll burn more calories than you would pounding the pavement.

And for the ultimate beach workout, don't miss the first-of-its-kind Men's Health & Women's Health Beach Boot Camp, coming this August.

IN THE POOL
In a 25-yard pool, swim two laps (100 yards) using a freestyle stroke. Rest for 20 seconds. Next, do two laps using a backstroke. Rest 20 seconds. That's one round. Do four more rounds, for a total of 1,000 yards.

Why it works: Swimming provides all the heart-healthy benefits of running without the joint-jarring impact. A recent French study of triathletes found that swimming accounted for just 7 percent of training injuries while running accounted for 73 percent. "The pool is ideal for cross-training," says Ted Knapp, an associate head coach of the NCAA's third-ranked Stanford University men's swim team. "You can rest the muscles you typically hit on long runs or bike rides without sacrificing your cardio burn."

IN THE BACKYARD
Do the two exercises described below as a superset (back-to-back), performing as many reps of each as you can in 30 seconds; rest for 30 seconds between them. Continue alternating back and forth until you complete 6 sets of both. "You want to move as much as possible during each of those active 30 seconds," says Craig Ballantyne, C.T.T., the author of Turbulence Training. "So crank up the intensity level as high as you can, and keep it that way for the duration of the workout."

Double Burpee
Stand with your feet shoulder-width apart and your arms at your sides. Push your hips back, bend your knees, and lower your body as deep as you can into a squat. Place your hands on the ground in front of you and kick back into a pushup position. Do two pushups and then quickly bring your legs back into a squat. Now jump up. When you land, go immediately into your next rep.

Prisoner Lunge
Stand with your feet shoulder-width apart and put your hands behind your head, elbows back. Keeping your back straight, step forward with your right foot and slowly lower your body until your right knee is bent at least 90 degrees. Pause, and then push yourself back up to the starting position as quickly as you can. Repeat the movement, this time stepping forward with your left foot. That's 1 rep. Keep alternating back and forth.

Why it works: These exercises target different muscle groups. "While one muscle group is active, the other rests," says Ballantyne. "That allows you to do more work with less fatigue in less time." In this case, you'll complete a total-body, metabolism-revving workout in just 10 minutes. And, perhaps, build the best backyard body in your neighborhood.