Earlier this week, I posted on reasons why runners may have stagnated in their running and why they might even be seeing some weight gain. As promised in that post, below is a workout perfect for upping your metabolism, increasing your caloric burn, and increasing your lower-body strength. The extra testosterone (men) and human growth hormone (women) produced from these lower-body exercises will also help offset the cortisol release from your long slow runs which will help preserve your muscle mass and keep your metabolism going strong.
Remember that adding this workout along with a speed workout once a week (on separate days) into your running routine will help make you a lean, mean, running machine. Well, maybe not mean, but you get my drift. The lower-body workout is perfect to add to a day you're doing an easy short to mid-distance run.
If you're currently in training for a big race, I recommend holding off on adding the lower-body workout to your routine until after the race. With anything new, your body will go through a period of acclimation and you may even experience a short period of slower running as your body adapts to the workouts and speedwork. Once you do start, stick with it though and your body will recover and get stronger and faster.