What is an appropriate heart rate recovery time from a high intensity interval (i.e., doing work at 85 to 90 percent of max HR and recovering to 75 percent)? Also, what is happening from a physiological standpoint when a person trains aerobicly and anaerobicly? At what heart rate zone does VO2 max start improving?
We’ll tackle these one at a time: "What is an appropriate heart rate recovery time from a high intensity interval?" Unfortunately, there is no simple number or formula that can answer this question. You need to do self comparisons with a given client as opposed to comparing different clients to each other or to some "norm." The goal is to make sure that any given client's recovery time trends downward over the course of a few weeks. That's one of the markers of conditioning. You can also track recovery times to indicate overtraining. If the recovery time is greater than usual, you need to reduce the training load that day or even for several days.
"What is happening from a physiological standpoint when a person trains aerobicly and anaerobicly?" Obviously, we don't have the space here for the equivalent of a semester of Exercise Physiology 101, so I'll just stick to the absolute basics. The salient physiological changes with aerobic training include increases in the following:
- Number and size of mitochondria
- Capillary density
- Activity of aerobic enzymes in the mitochondria
- Myoglobin content
- Ability to oxidize fat
- Maximum ventilation
- Maximal cardiac output
- Blood flow to the working muscles
- Extraction of oxygen (a-v O2 difference)
The salient physiological changes with anaerobic training include increases in the following:
- The ability to metabolize lactic acid
- The ability to produce ATP without oxygen (glycolysis)
- Ability to store and use glycogen
- ATP and CP stores
VO2max is a combination of cardiac output and oxygen extraction (a-v O2 diff) from the blood at the capillaries to be used by the mitochondria. Therefore, any training modality that improves either of these factors whether directly or indirectly will improve VO2max. Looking at the bullet points above, it's obvious that aerobic and anaerobic workouts both help improve VO2max. This is why interval training (anaerobic work with an aerobic recovery) has been shown to be especially effective for increasing VO2max in a relatively short period of time.