Heart Rate Zones - The Fundamentals
Updated: Apr 22, 2022
Your training goals and your body’s capacity to receive training load are not the same as that of another athlete or fitness enthusiast. If you do not listen to your body’s needs, you could even land up in injuries and infections. Therefore, monitoring the frequency, intensity, type, and time of training is crucial to optimising your training.
Any training intensity is reflected immediately in the heart rate (heartbeats per minute) as the heart adjusts it's pumping to match up to the body’s requirements.
Thus monitoring the heart rate before, during, and after training is an effective way to check the quality of a workout and to strategically optimise your training for peak performance.
Why should one go for HR based training?
Heart rate based training aims at keeping the heart rate in a predetermined range during training. Heart rate based training gives an objective direction towards training details, i.e., if you are under training (need to push more), on correct track (maintaining), or getting overtrained (need recovery).
According to the principles of training, progressive overload is required to improve an athlete’s performance. This load must be progressively increased after giving sufficient time for the body to adapt to the current training load.
However, if this is not strictly adhered to, training may become excessive. Pushing the body beyond its ability to adapt will not give any additional improvement in performance. On the other hand, it leads to performance decrement and overreaching (a brief period of heavy overload without adequate recovery) or overtraining (physiological maladaptation and chronic performance decrement).
Alternatively, training below the body’s capacity will not do the intended benefits of improved performance or a targeted weight loss.
What are HR Zones?
To get a sense of heart rate numbers, the range in which your heart rate varies can be divided into heart rate (HR) zones. In general, five heart rate zones are considered during training, ranging from a low heart rate to one’s maximum heart rate. The heart rate zones will vary from person to person, based on his/her maximum heart rate.
Now, what is max HR? How do you calculate it? It is the theoretical maximum that your heart rate can reach. Any training beyond this heart rate is not advised. Universally, the formula used for calculating your max HR is
Max HR = 220 – Age
Once you know your max HR, you can calculate the limits of your HR Zones based on the above table. Now let’s have a closer look at the various HR Zones and its effects.
ZONE 1 (Target Heart Rate: — 50–60% of max HR) - Warm up/ Recovery
Intensity in this zone is very less. This zone is used for easy, recovery-day workouts, warm-ups, and cool-downs. Zone 1 workouts have the potential to give recovery from an earlier heavy workout.
Zone 1 training places only a little stress on the muscles and therefore a little to no pain is experienced. The low intensity training increases blood flow to muscles, providing nutrients and oxygen while removing the waste products and improving recovery between hard training sessions.
ZONE 2 (Target Heart Rate: — 60–70% of max HR) - Aerobic Capacity
The intensity of training in this zone is limited to the aerobic level, and the intensity of the workout should be in such a way that the athlete can breathe and talk during workouts. Training in this zone improves and maintains basic endurance ability.
Working in Zone 2 uses more of the body’s fat as fuel. Aerobic cycle happens here where the body converts more of your fats (and less of your carbohydrates) into energy in the presence of oxygen.
ZONE 3 (Target Heart Rate: — 70–80% of max HR) - Aerobic Threshold
Intensity of training in this zone reaches the aerobic level threshold and therefore, challenges the athlete to work somewhat hard with the first indication of heavy breathing. In this zone, fatigue starts with difficulty in breathing and completing sentences, as well as the athlete/ person requires greater time to recover compared to a training load in Zone 1 and 2.
Certain muscle fibers in the body are maximally challenged in Zone 3, producing a positive change in their aerobic functioning. It also improves oxygen carrying capacity towards the muscles. Your body still coverts more of fats into energy in the presence of oxygen. However, towards the end of this zone, the body slowly shifts to Anaerobic cycle for production of energy.
ZONE 4 (Target Heart Rate: — 80–90% of max HR) - Anaerobic Threshold
Intensity of training in this zone improves muscular endurance. It significantly improves performance for events that are about 1 to 3 hours in duration. This zone is where most of the overreaching and overtraining happen. Therefore, training should be done cautiously. Training in this zone should be incorporated only for a well-trained athlete. Novel players should not push limits to this zone unless they are trained under and are comfortable with previous zones.
Training in Zone 4 happens in the anaerobic zone (energy production without oxygen). Here, more of carbohydrates is converted into energy. During the anaerobic cycle, glycogen from the muscles is used for energy production, and the byproduct lactate is accumulated in the muscles which causes pain. Spending more time in this zone progressively produces changes in the muscles that increase the lactate threshold, power, and pace. This means that over time, the muscles will take a longer time to experience pain.
ZONE 5 (Target Heart Rate: — 90–100% of max HR) - VO2 max
Intensity of training in this zone is the maximum what the athlete can put. This trains him/ her for those few seconds in the game where a short bout of maximum effort is required. Athletes can’t talk even a single complete word during this zone.
Massive amount of lactic acid is produced at this Zone. The body cannot remove it immediately, resulting in severe muscle pain. The athlete can’t work further without adequate recovery. By analysing the time spent in each zone during training, one can understand if the warm-up/cool-down was adequate enough, whether the training load was easy, moderate, or high, etc.
If your training keeps you within the Aerobic threshold, you could perform for hours. Training under aerobic threshold includes low intensity long duration steady-state workouts like long runs, cycling, and swimming. On the other hand, if your training pushes you to Anaerobic zones, the lactate production rate in the body exceeds its clearance rate and therefore it accumulates in muscles, causing muscle pain. Here, the training duration cannot sustain more than a few minutes. This works well for sprinters.
So do make sure that your training aligns with your performance goals and that you don’t end up in an injury. How do you keep it on track? Use heart rate zones!