Heart Rate Zones and Zone 2 Training

Walk into any gym and you’re almost guaranteed to find people wearing fitness wearables. Whether it’s a Fitbit, Whoop, Apple Watch, Garmin, etc, these wearables are able to tell us our heart rate while training. This article will help you better understand the information you’re presented with and use it to improve your training and fitness. 

Background Science Information

First, let’s briefly talk about the science behind this. Aerobic metabolism is when your body is able to produce energy using the oxygen you breathe in.  This occurs at lower intensity levels which we can monitor via heart rate.  These activities can be performed for an extended duration. (If you don’t have a heart rate monitor, a simple test you can use is the conversation test. Can you hold a conversation while performing the activity? If so, you’re likely using predominantly aerobic metabolism.)

Anaerobic metabolism is the ability to produce energy independent of the oxygen you breathe in.  This happens at higher heart rates and has the byproduct of lactic acid. Anaerobic metabolism is not able to be sustained nearly as long as aerobic metabolism. 

Heart Rate Zones

To focus on your training at a specific intensity, heart rates are often expressed as what “zone” you’re training in. Generally zones are split up into these categories. 

Zone 0 - <50% HR max, happens at rest 

Zone 1 - 50-60% HR max, very light activity

Zone 2 - 60-70% HR max, light activity, sustainable for long duration

Zone 3 - 70-80% HR max, moderate intensity

Zone 4 - 80-90% HR max, Hard

Zone 5 - 90-100% HR max, very hard, very brief durations

(Max heart rate can be estimated by taking 220-Age.)

Now that I’ve had my science lecture, how can this help me?

It’s important to train at varying intensities. High intensity training is common in CrossFit or other High Intensity Interval Training programs and has many health benefits and can get you in great shape. Let’s focus on CrossFit in particular.  CrossFit athletes are often reaching zones 4 and 5 during their workouts. This is important for seeing the benefits of working at intensity. 

Zone 2 Training

While reaching high heart rates and training extremely hard have their time and place, training at lower heart rates is also very important and often ignored. Long bouts (30-40 minutes) in zone 2 on a bike, rower, or with a light jog are great ways to build your aerobic baseline.  You’ll learn to get comfortable working for longer durations when your heart rate is elevated from its resting level.  Becoming comfortable at these heart rates help you when it comes to your next CrossFit metcon. 

Training in zone 2 is also a great way to focus on recovery.  This allows you to have the benefits of cardiovascular training without requiring excessive loads and stress on the body.  It serves as active recovery to help get you ready to push it in the gym in the following days. 

Not only is zone 2 great for recovery, it is also a great way to progress your training volume safely.  When CrossFitters are trying to get more fit, you often hear of athletes performing extra workouts after class.  While this works for some people who have put in a lot of time ramping up to this level, it can be a recipe for injury for others who don’t have that training baseline.  Zone two is a great option to add some more volume to your training without excessively stressing your body.