This interval method uses high resistance to improve the endurance and recovery of fast- twitch muscle fibers. One of the easiest ways to accomplish this is through inclined

running. General guidelines for High Resistance Intervals (HRI) are: • Set around a 15% incline • Cover as much distance as possible over a 5 second work period while maintaining proper technique • Actively recover until HR returns to 130-140bpm, depending on the athlete’s fitness level • If the HR does not go above 130-140bpm in the first few reps, actively recover for 60 seconds between work periods • Set the total time to 10-20 minutes, depending on the athlete’s fitness level • Count the number of reps completed over the total time Focus on HR recovery using dynamic energy control in between work periods. Gauge improvements in fast-twitch muscle fiber endurance by monitoring the number of work periods the athlete can complete it a given time frame. If this number increases, the athlete has increased his/her fast-twitch fiber endurance—make sure to point out this improvement!