April 6, 2021
This winter I hosted a series of Zwift Bike Rides. Every other Sunday I would take athletes through a one-hour workout. I had several riders that were new to paying attention to their power numbers and riding in specific zones. And what I learned was that many of the athletes didn’t quite understand the different zones, and when to use them. So let’s break it down and see if we can shed some light on something that as a runner-turned-triathlete I also found confusing.
This 7 Zone System is based on the research of Dr. Andrew Coogan. They are defined as a percentage of your Functional Threshold Power. You can use a ramp rest on an indoor trainer to determine your FTP, which is the level of intensity you could theoretically hold for one hour. It is the point where your body starts to accumulate lactic acid faster than it can shed it. Any efforts below FTP can be held for a relatively long time. Once you go over FTP, your ability to sustain harder efforts diminishes quickly!
Zone 1: Active Recovery
This is an effort you could literally ride all day. Active recovery is mostly used in rest intervals between hard efforts, allowing you an opportunity to catch your breath, lower your heart rate, and clear lactate acid from your muscles. Longer Zone 1 Rides can be used to add time in the saddle without adding stress to your body while focusing on form.
Zone 2: Endurance
While it will produce a little more fatigue than Zone 1, this is mostly aerobic; it is still an effort that can be sustained for a very long time. Your body is able to use fat as fuel. The majority of your long rides will be at this effort, and this is the best zone to work on base fitness.
Zone 3: Tempo
Tempo work is best described as riding hard but comfortable. While still mostly aerobic, this zone is the first one that will shart to feel challenging as it adds more muscular demands on the body over long efforts.
Zone 4: Sweet Spot
This is a grey transitional area between Tempo and Threshold work, as it combines the benefits of both. It is challenging to maintain for longer periods of time, while not as exhausting as riding at Threshold.
Zone 5: Threshold
This zone shifts your body’s fuel demands from fat to sugar, producing a great deal of lactic acid. Training at this effort increases your ability to maintain high levels of intensity for longer periods of time. Theoretically, this is pace you could sustain for an hour. However, most athletes find Threshold work uncomfortable for anything longer than 20 to 30 minutes. This is the effort you ride most of your intervals at, with rest periods (Zone 1) between efforts.
Zone 6: VO2 Max
These efforts are generally an intensity you can hold for 3 to 8 minutes. These are leg-burning efforts! In shorter intervals, your heart rate may not even have time to respond until after you have completed the effort. VO2 Max refers to the maximum amount of oxygen your body is able to use during exercise. This zone requires a high level of intensity. A good example of this would be how it would feel to climb a short hill when riding as hard as possible!
Zone 7: Anaerobic Capacity
Max effort going as hard as possible! At the highest level of intensity, these efforts are higher-force and for shorter durations. Again, heart rate will not be a good measure of this effort as it won’t have time to respond to the effort. This type of energy can only be held for a few minutes at a time.
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