In part 1 and part 2 of this series, I described the three metabolic pathways, defined aerobic and anaerobic exercise, then laid out the advantages and disadvantages of each. Part 2 ended with the conclusion that anaerobic exercise is superior and thus, the staple of the CrossFit program. Today, I’ll briefly describe how anaerobic exercise can be used to condition all three metabolic pathways.
At the heart of it is something called “high intensity interval training” (HIIT, for short). HIIT means doing short bouts of exercise at unsustainable (anaerobic) levels of intensity with periods of rest interspersed. The work and rest intervals of HIIT can be manipulated to condition different metabolic pathways. Below is a table from the October 2002 issue of the CrossFit Journal (page 5, figure 3) that shows the details. A very similar table can be found in exercise science textbooks as well, such as the “Essentials of Personal Training” and “Essentials of Strength and Conditioning” from the National Strength and Conditioning Association.
CrossFit workouts implement these intervals in a number of ways. In workouts like “Tabata Something Else” or “Fight Gone Bad”, you are asked to exercise and rest for certain periods of time: 20 seconds on, then 10 seconds off for Tabata; for “Fight Gone Bad”, it’s five one-minute rounds, followed by a one-minute rest. In a workout like “Barbara”, you have to do a certain amount of work (20 pullups, 30 pushups, 40 situps, 50 squats) before you get to rest (three minutes). Similarly, we occasionally do rowing or running workouts in which you go a certain distance, then rest (see today’s workout, for instance). Finally, in many CrossFit workouts, the intervals are created by the rest you have to take to get through it. An example of this is “Angie” (100 pullups, 100 pushups, 100 situps, 100 squats). These self-enforced intervals are probably the most common form of intervals in CrossFit workouts.
To summarize, CrossFit uses anaerobic exercise through a variety of intervals to condition all three metabolic pathways. This has numerous benefits, with none of the muscle-wasting side effects of aerobic exercise.
December 1, 2008 WOD
5 rounds:
400m run for time
2 minute rest
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