Setting Your Heart Rate Zones

Monitoring and controlling the intensity of your endurance training is important, especially if you are new to this type of exercise. By conducting these tests, you can quite accurately determine your body’s metabolic response to exercise at different intensities.

Endurance training is essentially training to affect your body’s metabolism. All endurance training should aim to increase your aerobic metabolic turnover or recycling rate of ATP. If this is a new concept to you, please read this article https://evokeendurance.com/endurance-its-evolution-psychology-meaning-physiology-and-how-to-improve-yours/ to give you an understanding of the basics of metabolism and why it is the driving force in endurance exercises.

The tests referenced in this article https://evokeendurance.com/our-latest-thinking-on-aerobic-assessment-for-the-mountain-athlete/ will establish two cornerstone metabolic breakpoints or thresholds that will help you anchor your individualized heart rate intensity zones.

We use and recommend a simple 4 Zone intensity scale. There are other systems with as many as 7 zones. These attempt to slice the metabolism into unrealistically small pieces that are not useful to the athlete. Trying to keep one’s heart rate within a range as small as 3-5 beats is nearly impossible. The 4-zone system instead uses the Aerobic and Anaerobic Thresholds you establish in the tests above. Below we’ll explain the addition of an optional fifth zone at the top of the scale.

Below is a breakdown of the most common endurance training zone system.

Recovery

Recovery exercise is conducted without much regard for heart rate but should instead leave you feeling better than when you started it. In some cases, that might creep up into Zone 1, but in most cases, it is done below a heart rate that is less than 20% below your aerobic threshold (Zone 2).

Zone 1

Zone 1 is an intensity used for exercise lasting from 1 to many hours for aerobic base conditioning. It helps improve your body’s ability to use fat as fuel. It can aid recovery between more taxing sessions, although it may be too intense for some athletes to use for recovery.  It is not defined so strictly as Zone 2, and the upper limit is set arbitrarily at 10% below the Aerobic Threshold (AeT or top of Zone 2).  Athletes with very high aerobic capacities will do a large portion of their aerobic base training in this zone because Zone 2 will be a very demanding pace.

Zone 2

Zone 2 is the intensity just below and up to one’s Aerobic Threshold (AeT).  The top of Zone 2 is the heart rate you will derive from your aerobic threshold test explained here. That value can be determined by any of the tests explained in that article.  For most people it will come from the heart rate drift test. The AeT is the intensity below which the aerobic metabolism is able to produce the majority of the ATP needed for movement.   This intensity will feel very easy for those with Aerobic Deficiency.  It will feel moderately challenging for the fittest endurance athletes.  Their pace will be quite fast and must be used with some caution by them.  This is the best zone to increase your aerobic capacity.  It is fueled primarily by fat metabolism fueling Slow Twitch muscle fibers. Duration of this sort of intensity can last around 2 hours continuously.

The aerobic base zones 1 and 2 should make up the vast majority (75-90%) of your training volume.

Zone 3

Zone 3 is the most overused intensity zone because it “feels like training.” It is thought that since this intensity challenges both the aerobic and anaerobic systems, it is the “one-stop shop” for all endurance training.  The top of Zone 3 is the heart rate you will derive from the the anaerobic threshold test explained here.  At this intensity, the glycolytic (anaerobic) metabolism begins to dominate the production of ATP.  The lower force Fast Twitch (FTa) muscle fibers are being used.  This intensity feels “fun fast”.  Most amateur endurance athletes can sustain this intensity for up to about 30min before local muscular fatigue begins to limit the pace and heart rate.  For the elite, this is a pace that can be sustained for about 1 hour.  The top of Zone 3 is the endurance limit for the mountain endurance athlete engaged in exercise lasting hours.  The upper end of Zone 3 is the Anaerobic Threshold (AnT) established in the previously referred to tests.  The temptation to use this zone for most of your endurance training should be avoided as that will lead to rapid gains in endurance performance, usually followed by a plateau and often a decline in that performance weeks later.

Zone 4

Zone 4 is the intensity where exercise becomes hard and impossible to sustain for more than a few minutes at a time.  This is the intensity above Zone 3.  This is where interval-style training is most often used:  intense bouts of exercise lasting from 30 seconds to several minutes, separated by rest intervals.  This intensity is usually done at heart rates of about 90-95% of maximum.  It is considered the most effective way to increase one’s max VO2.  Like Zone 3,  most athletes will be limited in both the length of the work bouts and the total volume of Zone 4 in a single workout by local muscular fatigue.  Especially when the work bouts get longer than 3-4 minutes, most athletes will see a drop in speed and, consequently, heart rate after just a few repetitions.  Even extending the rest interval will often not allow the session to be completed in Zone 4.  Most of the training effect is directed towards the anaerobic (glycolytic metabolism) by increasing several anaerobic enzymes (increasing the anaerobic capacity). These enzymatic changes occur quickly, which is why athletes see increases in performance within a few sessions from this kind of training.  Those enzymatic increases are quickly lost with the cessation of this kind of training or racing.  Increasing the anaerobic capacity will decrease the aerobic capacity, so a careful balancing of Zone 4 and 5 training with adequate aerobic capacity training in Zones 1 and 2 must be maintained.

Zone 5

There is another zone often called Zone 5 that is used very sparingly by mountain endurance athletes, making up less than 1% of the total annual training volume.  We think of this as power training to increase an athlete’s sport-specific power.  Like Zone 4, it is conducted using short work bouts (this time from 10 to 30 seconds), separated by very long rest intervals of several minutes to allow full recovery.  Heart rate is not a good measure of intensity for these short absolute maximal efforts so we’re not suggesting you set this zone into your watch.  A preferred Zone 5 workout of ours is hill sprints. Make a mark at the end of the first 1 or 2 sprints. The workout is over when you can no longer reach that mark despite increasing the rest interval.

And there you have it.  Careful use of this Zone system will allow you to get the most benefit from your training.