The acidosis threshold (AT) demarcates the transition between running that is almost purely aerobic and running that includes significant oxygen-independent (anaerobic) metabolism. (All running speeds have an anaerobic contribution, although when running slower than acidosis-threshold pace, that contribution is negligible.) Therefore, the AT represents the fastest speed that can be sustained aerobically. Research has shown that the AT is the best physiological predictor of distance running performance.
Training the AT increases the speed at which acidosis occurs, enabling athletes to run at a higher percentage of VO2max for a longer time. Increasing the AT pace allows runners to run faster before they fatigue because it allows them to run faster before oxygen-independent metabolism begins to playa significant role. What was once an anaerobic pace becomes high aerobic. Imagine two runners who have similar VO2max values but differ in their AT paces. If Runner A and Runner B both have a VO2max of 60 milliliters of oxygen per kilogram per minute (ml/kg/min), but Runner A's AT is 70 percent and Runner B's AT is 80 percent of VO2max, Runner B can sustain a higher intensity and will beat Runner A. Also, a runner with a lower VO2max can perform
similarly to a runner with a higher VO2max if she has a higher AT. If Runner X has a VO2max of 50 ml/kg/min and an AT that is 80 percent of her VO2max and Runner Y has a VO2max of 60 ml/kg/min and an AT that is 67 percent of her VO2max, Runner X will be able to sustain a similar intensity as Runner Y, despite having a lower VO2max (80 percent of 50 = 40 ml/kg/min vs. 67 percent of 60 = 40 ml/kg/min).
AT workouts are not all-out. They are high-end aerobic. The pace should feel comfortably hard. AT workouts are the most difficult type for athletes to run at the correct speed, especially those runners who are young or inexperienced with these workouts, since these workouts require holding back and not pushing the pace. There's a comfortably hard feeling to the pace that requires practice.
For competitive runners, AT pace is about 25 to 30 seconds per mile slower than 5K race pace (about 15 seconds per mile slower than 10K race pace) and corresponds to about 85 to 90 percent of maximum heart rate.
Workout #5: AT Run
Objective: To increase the athlete's acidosis threshold.
Description: On a measured and preferably flat cross country course or grass field, athletes run 3 to 6 miles (20 to 40 minutes) at AT pace. This is the most basic of AT workouts, but it is very effective for raising the athlete's acidosis threshold.
Coaching Points:
● It's important to keep the AT pace as steady as possible during these workouts, with little to no fluctuation in pace. The point is to raise the athlete's blood lactate level to it's threshold value (which indicates the onset of acidosis), and then hold it there for the duration of the workout.
● Since it's tempting for athletes to push the pace during these AT workouts, emphasize the purpose of the workout and the importance to remain aerobic.
● To practice the final push to the finish line during races, athletes may pick up the pace (albeit slightly) during the last quarter-mile of the AT run.
Workout #6: Long AT Run
Objective: To increase the acidosis threshold while running farther to prepare for longer races.
Description: Sometimes, it's beneficial to run a bit slower than AT pace to accommodate a longer distance, which comes with it the psychological demand of holding a comfortably hard pace for an extended time. Athletes run 6 to 10 miles (40 to 60 minutes) at 10 to 20 seconds per mile slower than AT pace.
Coaching Point: Athletes should view this workout as a way to increase the length of their runs at near AT pace. Therefore, they should be close to their AT pace for the entire run.
Workout #7: Handicap AT Run
Objective: To increase acidosis-threshold pace during a fun workout in which everyone finishes at the same time.
Description: Athletes run 3 miles at AT pace, with the slowest runner starting first and the fastest runner starting last. After the first runner begins, each subsequent runner begins after the amount of time has elapsed that equals the difference in AT paces over the entire run. For example, if Runners A, B, and C have AT paces of 5:30, 5:45, and 6:10, respectively, Runner C starts first, followed 1 minute and 15 seconds later (25 seconds times 3 miles) by Runner B, and 2 minutes later (40 seconds times 3 miles) by Runner A. If all runners run at their correct AT paces, everyone should cross the finish line together. This workout puts both the faster and slower runners in a unique position---the faster runners get the opportunity to catch the slower runners, and the slower runners get the opportunity to know what it's like to lead and be chased. This workout can be made longer by calculating the correct handicapped time for each runner.
Coaching Point: Don't let the faster runners "chase" the slower runners by running faster than their correct AT paces.
Workout #8: AT Serial Runs
Objective: To make the AT run both physically and psychologically easier while still obtaining the same benefit of continuous running at AT pace.
Description: This workout breaks the continuous AT run into shorter runs with recovery periods. Athletes run 2 to 4 x 10 to 15 minutes (about 2 miles) at AT pace with 3 to 5 minutes rest.
Coaching Point: If athletes have heart rate monitors, AT runs should be run at 85 to 90 percent of maximum heart rate.
Workout #9: AT Intervals
Objective: To make the AT workout both physically and psychologically easier and to increase the distance athletes can run at AT pace, you can design the workout in an interval format.
Description: Athletes run 3 to 6 x 1 mile at AT pace with a one-minute rest or 6 to 8 X 1,000 meters at AT pace with a one-minute rest.
Coaching Points:
● While it is tempting for athletes to run faster when the work periods are shorter, the purpose of this workout is the same as it is with continuous AT runs---to increase the acidosis threshold. Therefore, make sure athletes do not run any faster when doing AT intervals as when they do AT runs. They should still run' at AT pace.
● Each repetition should be run at exactly the same pace, completing all reps within 1 to 2 seconds of each other, assuming you're using the same part of the cross country course for each rep.
● AT intervals are "rhythm" workouts. Encourage athletes to try to find the rhythm within each repetition .
● Athletes should focus on having their feet land directly beneath their center of gravity and "roll" through each step to maintain a solid rhythm.
Workout # 10: AT + Intervals
Objective: To add slightly more stress to the AT intervals as a way to further stimulate changes in AT pace to reach a faster speed.
Description: This version of AT intervals is run slightly faster than AT pace (hence the plus). Athletes run 2 sets of 4 x 1,000 meters (or 800 meters for less talented runners) at 5 to 10 seconds per mile faster than AT pace with 45 seconds rest and 2 minutes rest between sets.
Coaching Point: Make sure athletes don't get carried away with this workout. The pace must be only slightly faster than AT pace. If AT runs and AT intervals feel "comfortably hard," AT + intervals should feel "hard but comfortable"
Workout #11: AT/LSD Combo Run
Objective: To increase the acidosis threshold while learning to combat fatigue in long cross country races.
Description: A twist on the 1970s term, "long slow distance," athletes run medium-long runs with a portion run at AT pace: 10 to 12 miles easy + 2 to 4 miles at AT pace. You can also mix the AT-paced running throughout the workout, such as 3 miles easy + 3 miles at AT pace + 5 miles easy + 3 miles at AT pace.
Coaching Points:
● These workouts are demanding, so it is necessary that athletes run the easy portions easy.
● When running the AT portion at the end of the run, the athletes' heart rates may exceed their normal AT heart rates (85 to 90 percent maximum heart rate) due to the cardiac drift associated with longer runs, especially on hot and humid days. However, athletes should not slow down their AT pace in an attempt to bring the higher heart rate down. Rather, they should focus on maintaining their correct AT paces.
Training the AT increases the speed at which acidosis occurs, enabling athletes to run at a higher percentage of VO2max for a longer time. Increasing the AT pace allows runners to run faster before they fatigue because it allows them to run faster before oxygen-independent metabolism begins to playa significant role. What was once an anaerobic pace becomes high aerobic. Imagine two runners who have similar VO2max values but differ in their AT paces. If Runner A and Runner B both have a VO2max of 60 milliliters of oxygen per kilogram per minute (ml/kg/min), but Runner A's AT is 70 percent and Runner B's AT is 80 percent of VO2max, Runner B can sustain a higher intensity and will beat Runner A. Also, a runner with a lower VO2max can perform
similarly to a runner with a higher VO2max if she has a higher AT. If Runner X has a VO2max of 50 ml/kg/min and an AT that is 80 percent of her VO2max and Runner Y has a VO2max of 60 ml/kg/min and an AT that is 67 percent of her VO2max, Runner X will be able to sustain a similar intensity as Runner Y, despite having a lower VO2max (80 percent of 50 = 40 ml/kg/min vs. 67 percent of 60 = 40 ml/kg/min).
AT workouts are not all-out. They are high-end aerobic. The pace should feel comfortably hard. AT workouts are the most difficult type for athletes to run at the correct speed, especially those runners who are young or inexperienced with these workouts, since these workouts require holding back and not pushing the pace. There's a comfortably hard feeling to the pace that requires practice.
For competitive runners, AT pace is about 25 to 30 seconds per mile slower than 5K race pace (about 15 seconds per mile slower than 10K race pace) and corresponds to about 85 to 90 percent of maximum heart rate.
Workout #5: AT Run
Objective: To increase the athlete's acidosis threshold.
Description: On a measured and preferably flat cross country course or grass field, athletes run 3 to 6 miles (20 to 40 minutes) at AT pace. This is the most basic of AT workouts, but it is very effective for raising the athlete's acidosis threshold.
Coaching Points:
● It's important to keep the AT pace as steady as possible during these workouts, with little to no fluctuation in pace. The point is to raise the athlete's blood lactate level to it's threshold value (which indicates the onset of acidosis), and then hold it there for the duration of the workout.
● Since it's tempting for athletes to push the pace during these AT workouts, emphasize the purpose of the workout and the importance to remain aerobic.
● To practice the final push to the finish line during races, athletes may pick up the pace (albeit slightly) during the last quarter-mile of the AT run.
Workout #6: Long AT Run
Objective: To increase the acidosis threshold while running farther to prepare for longer races.
Description: Sometimes, it's beneficial to run a bit slower than AT pace to accommodate a longer distance, which comes with it the psychological demand of holding a comfortably hard pace for an extended time. Athletes run 6 to 10 miles (40 to 60 minutes) at 10 to 20 seconds per mile slower than AT pace.
Coaching Point: Athletes should view this workout as a way to increase the length of their runs at near AT pace. Therefore, they should be close to their AT pace for the entire run.
Workout #7: Handicap AT Run
Objective: To increase acidosis-threshold pace during a fun workout in which everyone finishes at the same time.
Description: Athletes run 3 miles at AT pace, with the slowest runner starting first and the fastest runner starting last. After the first runner begins, each subsequent runner begins after the amount of time has elapsed that equals the difference in AT paces over the entire run. For example, if Runners A, B, and C have AT paces of 5:30, 5:45, and 6:10, respectively, Runner C starts first, followed 1 minute and 15 seconds later (25 seconds times 3 miles) by Runner B, and 2 minutes later (40 seconds times 3 miles) by Runner A. If all runners run at their correct AT paces, everyone should cross the finish line together. This workout puts both the faster and slower runners in a unique position---the faster runners get the opportunity to catch the slower runners, and the slower runners get the opportunity to know what it's like to lead and be chased. This workout can be made longer by calculating the correct handicapped time for each runner.
Coaching Point: Don't let the faster runners "chase" the slower runners by running faster than their correct AT paces.
Workout #8: AT Serial Runs
Objective: To make the AT run both physically and psychologically easier while still obtaining the same benefit of continuous running at AT pace.
Description: This workout breaks the continuous AT run into shorter runs with recovery periods. Athletes run 2 to 4 x 10 to 15 minutes (about 2 miles) at AT pace with 3 to 5 minutes rest.
Coaching Point: If athletes have heart rate monitors, AT runs should be run at 85 to 90 percent of maximum heart rate.
Workout #9: AT Intervals
Objective: To make the AT workout both physically and psychologically easier and to increase the distance athletes can run at AT pace, you can design the workout in an interval format.
Description: Athletes run 3 to 6 x 1 mile at AT pace with a one-minute rest or 6 to 8 X 1,000 meters at AT pace with a one-minute rest.
Coaching Points:
● While it is tempting for athletes to run faster when the work periods are shorter, the purpose of this workout is the same as it is with continuous AT runs---to increase the acidosis threshold. Therefore, make sure athletes do not run any faster when doing AT intervals as when they do AT runs. They should still run' at AT pace.
● Each repetition should be run at exactly the same pace, completing all reps within 1 to 2 seconds of each other, assuming you're using the same part of the cross country course for each rep.
● AT intervals are "rhythm" workouts. Encourage athletes to try to find the rhythm within each repetition .
● Athletes should focus on having their feet land directly beneath their center of gravity and "roll" through each step to maintain a solid rhythm.
Workout # 10: AT + Intervals
Objective: To add slightly more stress to the AT intervals as a way to further stimulate changes in AT pace to reach a faster speed.
Description: This version of AT intervals is run slightly faster than AT pace (hence the plus). Athletes run 2 sets of 4 x 1,000 meters (or 800 meters for less talented runners) at 5 to 10 seconds per mile faster than AT pace with 45 seconds rest and 2 minutes rest between sets.
Coaching Point: Make sure athletes don't get carried away with this workout. The pace must be only slightly faster than AT pace. If AT runs and AT intervals feel "comfortably hard," AT + intervals should feel "hard but comfortable"
Workout #11: AT/LSD Combo Run
Objective: To increase the acidosis threshold while learning to combat fatigue in long cross country races.
Description: A twist on the 1970s term, "long slow distance," athletes run medium-long runs with a portion run at AT pace: 10 to 12 miles easy + 2 to 4 miles at AT pace. You can also mix the AT-paced running throughout the workout, such as 3 miles easy + 3 miles at AT pace + 5 miles easy + 3 miles at AT pace.
Coaching Points:
● These workouts are demanding, so it is necessary that athletes run the easy portions easy.
● When running the AT portion at the end of the run, the athletes' heart rates may exceed their normal AT heart rates (85 to 90 percent maximum heart rate) due to the cardiac drift associated with longer runs, especially on hot and humid days. However, athletes should not slow down their AT pace in an attempt to bring the higher heart rate down. Rather, they should focus on maintaining their correct AT paces.
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