Strength to Run

Really, this title could be "Strength to do Anything" because I'm about to give you some exercises to strengthen the muscles of your legs - feet, hamstrings, hips, etc - that will help prepare your body to exercise with more intensity and not get injured. So let's get to it! 
(these ideas come from Runners World)

Single-Leg Directional Hops
Standing on your left leg, with the right knee raised to hip height, hop forward, landing softly. Hop back to start, then hop diagonally (to the left) and back to center, hop to the left and return to start. Do 12 reps; switch legs.

Forward Lunge
Stand with shoulders relaxed and back. Step forward onto one heel, then your whole foot. Do not lean sideways. End with the knee above the midfoot and the thigh parallel to the ground. Return to start; repeat 10 times on both legs.

Squat Jacks
Standing in the bottom of a squat position with feet hip-width apart and shoulders stacked over hips, shoot your legs out to the sides and your arms out to shoulder height (like a regular jumping jack) without moving your upper body. Do 16 to 24 reps.

Single-Leg Bridge
Lie on your back with knees bent. Squeeze your glutes while lifting your hips. Once you have your balance, rest one ankle on top of the other knee. Hold for five or more seconds; repeat five times on both legs.

Reverse Step-Up
Stand, facing forward, in front of an eight-inch step. Step backward onto the step, setting only one foot down. Don't let the knee turn in. Balance, then return to start. Repeat 10 times on both legs.

Reverse Hip Raise
Lie face-down on a Swiss ball with your hands flat on the floor. Keeping your legs straight, lift them until your thighs are in line with your torso. Squeeze your glutes as you lift your hips. Pause, then lower to the floor. Do 10 reps, rest, and repeat.

Far too often injury occurs because of tight hips and weak muscles in our legs. And once one muscle is too weak, our body then compensates and puts too much pressure on another. So be sure to take time to build strength in those legs that carry you throughout the day!