Jumping rope is a GREAT cross-training exercise, is terrific for increasing cardiovascular fitness and increases the performance of fast-twitch muscles (for speed in running). It's best to jump with a light "speed rope" at a pretty fast cadence - about 60-200 jumps per minute. To get started, do a a short run (2 miles), then jump rope for 5 minutes, alternating 30 seconds of jumping with 30 seconds of rest (like intervals.) Gradually increase the workout to 20 minutes of continuous jumping. You can also use a weighted rope, which will build more upper-body strength. For more information on this fun and effective cross-training exercise, visit the the Jump Rope Institute at www.jumpropeinstitute.com.