When participating in an aerobic workout, an athlete will notice his or her heart rate increase. When the body exercises, the heart must work harder to circulate blood throughout the body, meaning the heart beats faster. The pace at which the heart beats is called heart rate. Heart rate zones are specific heart rates that are best for different fitness goals. Heart rate zones are calculated by first establishing an athlete's resting heart rate, then establishing his or her maximum heart rate. The zones in between the minimum and maximum heart rates are essentially targets the athlete must hit to achieve different fitness goals, such as fat burning or VO2 max training.
Different heart rate zones accomplish different goals. Working in heart rate zones that are within 60% to 70% of maximum heart rate will allow the athlete to accomplish fat burning and muscle recovery. This zone also helps build endurance if the athlete stays within the zone for an extended period of time. This is called the recovery area of heart rate zones, as muscles are able to recover from strenuous workouts by producing glycogen.
The opposite in terms of heart rate zones is the 90% to 100% output zone. Athletes cannot maintain performance in this zone for extended periods of time, as it is the most strenuous of the heart rate zones. The athlete is working at full capacity, and this zone is reached by running sprints or cycling as hard as possible. This zone helps the body develop fast twitch muscles that are useful in quick, explosive movements. Training in this zone is extremely difficult and it is common to reach this heart rate zone during interval training.
In between the maximum output and the moderate output are several zones that can help burn fat, build endurance, and develop a healthy heart and cardiovascular system. The 80% to 90% output zone will help muscles develop a higher lactic acid threshold. As the body burns glycogen for energy, lactic acid builds up in the muscles. The rate at which the body can remove the lactic acid is the lactic acid threshold, and training in this zone can help the body learn to remove more lactic acid quickly.
Heart rate zones differ significantly from person to person, as everyone's maximum and minimum heart rates change depending on size, overall health, age, and other factors. Minimum and maximum heart rates can be determined rather easily in one or more workouts, and target zones can be determined from there. Beginners should remember to stay in their target zones as much as possible to build up to more intense workouts, and people with medical conditions should consult a doctor before any type of workout.