Just because summer isn't for several more months, it doesn't mean that it's time to let our exercise programs go. People tend to put on more weight during the colder months for a few reasons: 1) Because they probably won't be donning their bathing suits at the beach for quite some time, and 2) Because our bodies are designed to slow our metabolism down -- a carry-over from our more primitive days when food sources became more scarce during the cold season.

For these reasons, and probably about eight thousand others, it's a smart idea to keep stoking the flames of your metabolism right through these frosty months. So, to help you do just that, here's an exercise that that will help you burn some serious calories while toning up your legs.

Called the Step-Up, this cardiovascular movement will help you speed up your metabolism as you strengthen and tone your quadriceps, glutes, hamstrings, and even your calves. To perform this exercise, start by standing in front of a weight bench or any safe substitute for one (tip: take two milk crates, spread them apart, and place a firm, wooden board over them -- a great, makeshift bench). Next, take your right foot and place it on the surface of the bench. From there, step-up onto the bench, using your right leg to power the rest of your body up.

Once you are standing firmly on top of the bench with both feet, step back down with one leg and follow with the other. Then, step up onto the bench with your left leg, following with your right. Repeat this movement for several repetitions, increasing speed and perhaps even adding small weights (dumbbells in hand work well, as does holding a medicine ball) as you get stronger and more familiar with the movement.