The Red Zone: Common Questions

April 6, 2016

Most of us are trying to find the magic recipe for the workout routine that will help us reach our fitness goals. Because we all have different fitness goals and timelines, our training routines should be uniquely individualized.  

One of the advantages to training using the MYZONE heart rate monitoring system is getting real-time feedback of relative exercise intensity (as percentage of our maximum heart rate, MHR).  This objective feedback helps us find the right combinations of exercise frequency (how often), intensity (how hard), and duration (how long) to hit our goals.

This blog will focus on some of the most commonly asked questions about the red zone, a high intensity zone of 90-100% of MHR. General recommendations for frequency, intensity, and duration are provided.

First, it’s important to have a foundational understanding of the general purposes and benefits of training in each of the MYZONE heart rate zones. As provided in previous blogs and on our weekly Fitness Friday Periscope broadcast, here are some general purposes and benefits of training in each zone:


Gray: 50-59% MHR (1 MEP per minute) and Blue: 60-69% MHR (2 MEPs per minute)

Purpose: Moderate intensity zones, warm-up, build aerobic base (beginners), recovery workout, long duration workout

Benefit:  Build vascularity (capillary beds supplying blood, oxygen, and nutrients to working muscles), increase mitochondrial density (fuel production capability), improve ability to use fat as a fuel source


Green: 70-79% MHR (3 MEPs per minute)

Purpose: Moderate (70-74%) to high (75-79%) intensity zone, steady state aerobic training, recovery zone for tempo/pace training and high intensity interval training

Benefits: Build aerobic base, work closer to aerobic capacity (maximal ability to efficiently take in and process oxygen), efficient recovery


Yellow: 80-89% MHR (4 MEPs per minute)

Purpose: High intensity zone, threshold training (maximal steady state training), work phase of tempo/pace training, work phase of high intensity interval training

Benefits: Expand aerobic capacity, build lactate threshold, increase endurance and stamina, improve speed/power, improve recovery, increase ability to sustain higher intensities for longer duration, crush calories


Red: 90-100% MHR (4 MEPs per minute)

Purpose: High intensity zone, work phase of high intensity interval training

Benefits: Same as yellow zone

Now that we have a foundational understanding of the purposes and benefits of training in each zone, we will move into addressing three of the most commonly asked questions about training in the red zone.

  1. Is it safe to get into the red?
  2. How long should I stay in the red?
  3. Should I get into the red during every workout?

The short answer to all three of these questions is, it depends.  There are many individual factors that will influence the answer to each of these questions, but we will provide some general answers to each question.  Please be sure to consult your trainer and/or your physician for specific recommendations.


Question 1: Is it safe to get into the Red Zone?

In general, if you have built an aerobic base (training for a month or two using the blue, green, and yellow zones), you should be able to safely take your intensity into the red zone.  You may even touch red a few times as you are beginning an exercise routine, but it will probably be very hard to sustain for any length of time.

If you have any cardiac or pulmonary ailments (for example, high blood pressure or asthma), it is recommended you consult your physician (and other allied health professionals supporting your health) prior to exercising in the higher intensity zones (yellow and red).

Another key factor to check on is the accuracy of your estimated MHR.  The MYZONE system uses an equation to estimate your MHR, and although this will be accurate for many individuals, it may require some adjustment for others.  The MYZONE system will automatically update your MHR if you reach a heart rate higher than your estimated MHR.  Work with your personal trainer or another fitness professional at your facility to determine if your estimated MHR seems accurate.


Question 2: How long should I stay in the red?

The length of time that you spend in red should depend on your overall fitness goals and the goals of the particular session you are engaging in.  As stated above, the red zone can be used for maximal steady state training (threshold training) and high intensity interval training (HIIT).  These types of training should only be performed once you first have a solid aerobic base.

During threshold training, you might expect to see several minutes of red toward the end of the session.  For example, if you are performing a threshold run for 30 minutes, you might hit red for 3 to 5 minutes at the end if you are finishing hard.

During HIIT, you may hit red during the work phase of the interval, and the work phase could be anywhere from 15 seconds up to 120 seconds.  Each work phase should be followed by a recovery phase.  The length of the recovery phase will depend on your fitness level.  You may be able to progress up to a work-to-recovery ratio of 3 or 4-to-1.  For example, if your work phase lasts 60 seconds, your recovery phase would be 15 to 20 seconds.  Play around with different work-to-recovery ratios to see how your heart rate responds.

Research does not offer a prescriptive length of time that an individual should stay in the red to experience additional health or fitness benefits beyond training in the yellow zone.  Therefore, as with most exercise, the best advice is probably to listen to your body and honor your limits.


Question 3: Should I get into the red during every workout?

Whether or not you get into red during every workout will depend heavily on the frequency and duration of your workouts.  In order to maximize the benefits of your workout routine, you should plan to offer your body at least 24 hours between high intensity sessions.  If you performed HIIT on Monday and your activity profile consisted of a lot of red and yellow, you would be well-served to stay in blue and green on Tuesday.  

Finding the right rhythm of volume (frequency and duration) and intensity is often a trial and error process for most individuals.  This is why the MYZONE heart rate monitoring system is such a valuable tool – you can look back at your activity calendar over time and determine which rhythms best served your fitness goals.

In general, if you are exercising more frequently (more than 4 to 5 times in the week), you would not want to perform high intensity exercise for every session (getting into the red).  Your musculoskeletal and nervous system need time to rest and replenish in order to adapt and improve.  Research has demonstrated that two to three high intensity sessions a week are plenty to glean health and fitness benefits.

In general, the longer you are exercising during each session, the less time you should spend in the higher intensity zones (yellow and red).  For example, if you are exercising for longer than 30 to 60 minutes, you would want your profile to consist of more green and blue than yellow and red (unless you are very well conditioned and performing a threshold workout).

In closing, research has indicated that training programs that have a variety of high volume (low to moderate intensity), maximal steady-state (threshold training), and interval training (work phase followed by recovery phase) have the strongest effect on improving endurance fitness. So embrace the red zone as part of a balanced training program!

Let us know how your experiments with the red zone are going!  As you post your progress on Twitter, Facebook, and Instagram, use the hashtags: #myzone, #myzonemoves, and #effortrewarded.  Keep moving forward!

Get MYZONE Previous Next