How do you want to improve your times? What distance? sprint or 5k or longer?

If longer, I think you should concentrate on fartlek, tempo runs, running uphills. It's much better and more effective

Good luck

Cyndi,

Squats and lunges. They are compound exercises that when performed properly can build strength for speed or promote mitochondrial growth for endurance.

Studies have shown, runners that perform resistance exercise can have greater speed gains than those that do not.

Stay away from the leg extensions and leg curl machines, they can cause undo stress on the joints.