A more advanced variation is the split squat, which begins with one foot slightly ahead of the other. Keeping your back straight, bend your back knee until it's almost touching the floor and your front leg is forming a 90-degree angle. Make sure the front knee does not pass over your toes. You can also perform a split squat with your back foot resting upside down on a bench.
Lunges
Works quads, hip stabilizers, glutes and calves
Holding dumbbells or a barbell on your shoulders, stand with your feet shoulder-width apart. Keeping your head up and back straight, bring one leg forward and bend at the knee until your front leg forms a 90-degree angle and the knee of your back leg almost touches the floor. Return to the upright position and alternate legs. Again, keep proper form and don't allow the front knee to pass in front of the toes. The longer the stride, the better the results.
Other variations: lateral lunge, in which you lunge to the side; reverse lunge, in which you begin the lunge with the back leg; and walking lunge, in which you alternate legs while moving forward. Lunges are great balance exercises, which can improve your performance in sports like trail running or hiking.
Straight-leg deadlifts
Works hamstrings, glutes, lower back
Stand with your feet shoulder-width apart holding either dumbbells or a barbell. Keeping your back straight and flat, your knees slightly bent, and the weights or barbell brushing against your thighs, bend at the hips until the weight drops to about the middle of your shins. Then, maintaining the same posture, straighten up by bringing your hips forward. This exercise helps offset hamstring-to-quad muscle strength imbalances.
Step-ups
Works quads, glutes and hamstrings
Holding dumbbells or a barbell across your shoulders, stand facing a 12- to 18-inch-high platform. Place one foot up on the center of the platform, making sure the entire foot is making contact with the surface. With your head up, back straight and shoulders back, push with that lead leg until you're standing on top of the platform. Then step off it with the other leg. Alternate legs.
Side-lying leg lifts
Works hip abductors and adductors
To work your outer thigh, lie on your side with an ankle weight on your upper leg. Lift it as high as you can, hold for two seconds, then bring it down slowly. For your inner thigh, put the ankle weight on your lower leg. Then bend your upper leg and bring your foot forward so that your foot is in front of the lower knee forming a bridge. Lift the lower leg, hold and return. This exercise helps stabilize your hips for better running performance.
Standing calf raises
Works calf muscles
Stand with the balls of your feet on a platform and your heels hanging off. At first, do this exercise without weight. As you get stronger, hold dumbbells that allow you to stay in the 15 to 20-rep range comfortably. Raise your heels upward until you're on your toes. Using too much weight and straining for that last rep can damage the Achilles tendon, which connects this muscle group to your foot.