Tempo intervals were popularized by the late Charlie Francis, who used this method with his sprinters to improve their speed on low-intensity training days. These intervals improve the body’s ability to recover from high-intensity exercises, increase work capacity, and promote regeneration without accumulating fatigue. The key to this method is to select an intensity that’s about 70% of the athlete’s maximum intensity. The work period is 10 seconds with a 60 second active rest period between intervals. Working at 70% of the maximum intensity sends extra blood flow to medium-threshold muscle fibers, which stimulates their recovery. Avoid using higher intensities to minimize fatigue. If you’re doing this method indoors, start out on a machine that measures distance covered over time. This allows you to take an initial measure of distance covered at maximum intensity for 10 seconds. From this measure, you can determine your 70% maximum intensity for the tempo interval work period. Use dynamic energy control between work periods to bring the heart rate back down as quickly as possible.