Is your bottom half in shape for short skirts and strappy summer sandals? Besides more revealing (and less supportive) fashions, warmer weather also means more time spent outdoors and more physical activity -- which, if you're not prepared, can lead to stress, stiffness, and injury. 

Practice these key exercises two to three times a week and you'll not only improve strength and balance, but also make strides toward preventing pain and injury in your knees, ankles, feet, and hips.

What it does: Strengthens and sculpts calves; enhances balance.

How to do it: Stand with the balls of your feet on a step or curb and your heels hanging over the edge. Hold a wall or railing for balance. Slowly lift up on your tiptoes as high as you can go, and then slowly lower your heels until they've dropped lower than the step. Repeat 10 times.

What it does: Strengthens and tones quadriceps, hamstrings, and gluteal muscles.

How to do it: Start with your feet hip-width apart. Then shift your hips back and down, as if you were lowering yourself into a chair. As you do this, engage your abdominal muscles and raise your arms to shoulder height, either straight in front or folded, as shown. Stop just before your knees reach a 90-degree angle; don't let your knees move past your toes. Rest your weight back on your heels. Pause, then slowly return to the starting position and repeat 10 times.

What it does: Works and shapes your entire leg; enhances balance and coordination.

How to do it: Stand with your feet hip-width apart and a weight in each hand (or skip the weights altogether). Take a giant step forward with your left foot, lifting your right heel off the ground. Moving very slowly and breathing naturally, lower your torso straight down, keeping your upper body perpendicular to the ground. Stop when your back knee is 1 to 2 inches from the ground and your front knee reaches a 90-degree angle. Keep your left knee in line with your ankle (don't push past your toes). Pause, and then slowly come back up. Do this 9 more times, and then step your feet back together. Repeat 10 times on the other side.

What it does: The foot has four layers of muscles; this balancing pose challenges all of them to engage and work together to find stability. 

How to do it: Stand tall with bare feet about a fist-distance apart, arms by your sides. Shift your weight to the left foot and place the sole of your right foot, toes pointing to the floor, as high up on the inside of your left leg as you can -- it could be on your ankle, your calf, or your inner thigh (avoid the knee joint). Bring your palms together in front of your heart. To help you balance, find a point at eye level to gaze at. Inhale for a count of 5, then exhale for the same. Stay for 5 breaths, then repeat on the other side.

What it does: Releases the connective tissues (also known as fascia) that support the muscles on the soles of your feet, making the foot more supple and better able to support you when walking on uneven surfaces, such as grass and sand.

How to do it: Sitting tall on the edge of a chair, place a tennis ball under the sole of your bare right foot. Using steady but not painful pressure, roll your foot slowly back and forth across the tennis ball from toe to heel. Continue for 2 to 3 minutes, massaging the entire sole. Repeat on the other foot.

What it does: Stretches the tops and bottoms of the feet evenly and restores flexibility.

How to do it: Sit with your shins on the floor and your buttocks resting on your feet. Point your toes so the entire top of the foot rests on the floor. Lengthen the spine and rest your hands on your thighs. Inhale for a count of 5, then exhale for 5. Stay for 5 breaths, then tuck your toes under and stay for another 5 breaths. If you find this stretch too intense, stay for as many breaths as possible, gradually increasing the number over time as your flexibility improves.

What it does: Opens the front of the hip while strengthening the opposite leg, helping you to stabilize the muscles around the bone and engage the core muscles.

How to do it: With your feet hip-width apart, step the right leg back into a deep lunge, bending your front leg to about 90 degrees. Stay on the ball of your right foot and keep your hips squared. Extend the arms straight overhead, using the abdominal muscles to keep your upper body erect and stable. Take 3 to 5 deep breaths, imagining that you're breathing into your right hip and releasing tension there. Repeat on the other side.

What it does: Releases tension in the hip socket and loosens the glutes.

How to do it: Lie on your back with legs bent and feet flat on the floor. Lift the right leg and rest your right ankle on your left knee, rotating the right hip out. Reach your arms around your left leg, gently hugging the leg toward you. For a deeper stretch, press the right knee outward. Take a few deep breaths, keeping your spine long and letting your lower back release into the floor. Switch legs and repeat.

What it does: Stretches the glute muscles, hip flexor, and lower-abdominal muscles.

How to do it: Starting in a push-up position, draw your left knee in and sit up, resting with your left leg bent in front of you and the other leg straight behind you. Keep your hips squared and your weight balanced between them. You can also bend forward, stretching your arms out in front of you and resting your forehead on your mat. Take 5 to 10 deep, relaxed breaths, letting gravity draw you down deeper into the stretch.