The Recovery Zone - 60% to 70%
Training within this zone develops basic endurance and aerobic capacity. All easy recovery exercising should be completed at a maximum of 70% effort. Another advantage to exercising in this zone is that you are still burning fat and allowing your muscles to re-energize with glycogen (glycogen is a derivative of carbohydrates, which feed your muscles giving you energy to workout). Glycogen is depleted during faster paced workouts.
The Aerobic Zone - 70% to 80%
Training in this zone will develop your cardiovascular system. The body's ability to transport oxygen to and carbon dioxide from the working muscles can be developed and improved. As you become fitter and stronger from training in this zone it will be possible to do some of your recovery workouts at up to 75% effort, getting the benefits of some fat burning and an improved aerobic capacity.
The Anaerobic Zone - 80% to 90%
Training in this zone will develop your lactic acid system. Lactic acid is usually the burning sensation you feel in your muscles during your workouts. In this zone, your individual anaerobic threshold (AT) is found. When in this zone, the amount of fat being utilized as the main source of energy is greatly reduced and glycogen stored in the muscle is predominantly used. One of the by-products of burning glycogen is lactic acid. There is a point at which the body can no longer remove the lactic acid from the working muscles quickly enough. This is your anaerobic threshold (AT). Through proper training, it is possible to delay the AT by increasing your body's ability to tolerate lactic acid for a longer period of time or by pushing your AT higher.
The Red Line Zone 90% to 100%
Training in this zone will be possible only for short periods. It effectively trains your fast twitch muscle fibres and helps to develop speed as you are pushing yourself as hard as you can. This zone is reserved for short and intense workouts. Examples of this type of training are short intervals on the track, wind sprints on the football/soccer field or speed drills on the hockey rink.