What it works: hip flexors, glutes, ankles, core

How to: Place the arch of your foot on a rock with a rounded point that gives your foot and ankle full range of motion. Focus on a spot straight ahead, 20 feet away. Using your arms for balance, while keeping your foot on the rock, lift your leg that's on the ground and draw a half circle around your body -- forward, to the side, and behind. Reverse, then repeat with the other leg, 30 seconds to one minute per leg.

You could also use: curb or tree root

What it works: chest, upper back, core

How to: Place your hands a bit wider than your shoulders on a low table or bench. Step back so that your spine is long and straight. Inhale as you lower to mid-chest (make sure your sternum is centered over the bench). Engage your core and exhale as you push firmly through your hands back to the start position. Do 8 to 12 reps, working your way up to 20 over time.

You could also use: low wall, bench, boulder, or curb

What it works: triceps, deltoids, abs, quadriceps, hamstrings, glutes 

How to: Supporting yourself on the edge of a bench, kick one leg straight out in front of you. As you lower your body into a dip, curl your knee toward your chest and engage your abs. Press firmly with your palms and heel to work your triceps and glutes, and return to start with a straightened leg. Repeat 6 to 12 times per leg. 

You could also use: step or low wall

What it works: glutes, thighs, calves, abs 

How to: Place your right foot squarely on a bench and lead with your chest as you press into the bench with your heel (not the ball of your foot). Focus on engaging your core and getting your body over your leg. Bring your left leg up, then step back down and do it again. Repeat 8 to 15 times with each leg. 

You could also use: step or other raised, stable surface

What it works: lower abs, hip flexors

How to: Hang from a sturdy tree limb, feeling your spine lengthen. (This is great for stretching a tight back.) Exhale as you slowly lift your knees toward your chest. Inhale as you lower your knees. (Don't swing your legs.) Do 5 to 10 reps, working toward 20.

You could also use: jungle gym or other supportive structure

What it works: back muscles (traps, rhomboids, deltoids), biceps

How to: With fingers laced, hang from a strong branch. Exhale as you pull yourself up toward your right shoulder and your chin rises above the limb. Inhale as you lower down. Do as many as you can, alternating between shoulders. If one is too hard, don't feel bad! Recruit a friend to cradle your foot for leverage.

You could also use: monkey bars or any sturdy structure

What it works: glutes, hamstrings, inner thighs

How to: Face downhill on a slope with feet shoulder-width apart, toes angled outward. (A wider stance gives you more control over uneven terrain.) Inhale as you lower your hips for a count of three, pressing your tailbone back, knees directly over ankles. Try to create a 45-degree angle with your knees. Exhale as you press back to start. Do 8 to 12 reps, working up to 20 over time.

You could also use: any flat surface

What it works: glutes, calves, inner and outer thighs

How to: Facing uphill, take a long, diagonal step with your left leg, right elbow in line with left knee. Lean into the hill, distributing your body weight evenly between both feet. Slowly lower your hips, exhaling as you press off the ball of your back foot and bring your feet together. Then step forward with your right leg. Use your arms to give your stride more power. Do 8 to 12 reps per leg; work your way up to 20 reps.

You could also use: steps or a ramp

What it works: whole body

How to: Lean into the hill from your hips (rather than curving your back) and start running, pushing through your glutes and core. To increase your speed, pump your arms faster. If 1 is a stroll and 10 is an all-out sprint, push yourself to an 8 or 9. Take deep breaths to get enough oxygen and stay fueled. However long you run -- short spurts are better -- rest for twice as long (run one minute, rest two). Repeat 3 to 5 times.

You could also use: steps