Tight calves and hamstrings can put a cramp in your cardio workout -- literally. And while the quads don't tend to cramp as much, if any of these muscles are tighter than the others, the condition could lead to knee pain or injury and even back aches. While some problems may require professional attention, generally, you can treat tight leg muscles with simple stretches.
Stretching after a workout is always recommended. However, the benefit of pre-workout stretching for the average person, or even an athlete, is somewhat controversial, as is the question of dynamic versus static stretching. However, if your leg muscles feel tight before your cardio workout, then you'll want to stretch them first, and since you shouldn't stretch a cold muscle, you'll need to do a short warm up. This means walking around the gym or starting with a slow walk on the treadmill before beginning your brisk walk, run or elliptical workout. You won't need to warm up for more than three to five minutes, after which you'll stop to do some simple stretches.
A static stretch is one where you hold the stretch for several seconds. A common static calf stretch involves pressing your heels off the edge of a step. To stretch your quads, you can bend your knee and grab your foot to pull your heel toward your buttocks. You can do this while standing or lying face down or on your side. Hamstring stretches involve resting your heel on an elevated surface, like a bench, and bending forward from your hips while keeping your leg extended but your knee soft. Flexing your foot back will make it more effective. You can also stretch both legs while sitting on the floor with your legs extended directly in front of you. In this case, you'll reach toward your toes, while again, keeping your knees soft.
Some trainers believe that dynamic stretching, which involves movement, is preferable to static stretching, especially when the movement mimics what you'll do during your workout. You can do dynamic stretches for your calves by leaning against a wall with your forearms so that your body forms an inclined plane, and your heels rest on the ground. Alternate bending one knee and lifting the heel of the same leg to get a stretch in the opposite leg. A good dynamic whole-leg stretch involves lunging forward so that your front thigh is parallel to the ground and your back leg is also bent to about 90 degrees. You'll lean your torso over your front leg so that you can support yourself on your hands. At this point, you're stretching the quads on your back leg. Alternate this with straightening both legs and, if possible, flexing your front foot back to do a combined hamstring and calf stretch.
You should repeat each stretch at least three times. Do more reps for muscles that are chronically tight. Hold static stretches for about 15 seconds, or the time it takes to finish four slow breaths. Dynamic stretches should be done in a slow and controlled motion, and whether you are doing static or dynamic stretches, avoid bouncing as this can lead to injury.