Training with Northwoods Endurance: Zone Training

This installment of the BTK training article builds on the last, which outlined the reasons and methods for measuring intensity during training rides. In this article I'll talk about why workouts of different intensity should be incorporated into your training plan and how often you should ride at different intensity levels. The goal here is to develop fitness that allows you to deal with the variety of physical demands that are placed on your body during an actual bike race. An athlete who only trains at a "moderate" pace will not be able to keep up with fast starts, initiate or challenge breakaways, tackle challenging climbs, and hold on for sprint finishes. Conversely, an athlete who only trains for sprints or climbs will not be able to keep up during longer distance events. Assuming that most racers looking at this website are not track cyclists, or ultra‐distance athletes, but fall somewhere in between, you are going to want to have the ability to go hard when circumstances call for it, and go long when circumstances call for that.

Remember that intensity can be measured several different ways; RPE (Rate of Perceived Exertion), heart rate (beats per minute), and power output (watts). Please see the previous article for more details on each measurement method. For the sake of simplicity, in this article I will talk about intensity in terms of heart rate only.

The human heart is capable of beating between about 60 and 200 times each minute, 60 being the rate experienced during rest, and higher rates occurring at increasing levels of exercise intensity. This is represented graphically in Figure 1. The range of heart rates between 60 and 200 beats per minute (bpm) is called the heart rate (HR) reserve, and can be divided into separate zones that an athlete can target during a workout to induce a specific physiological response. There are a variety of methods for dividing the HR reserve into training zones, as shown in Figure 2. Some are simpler than others, and they may use different language or numbering systems, but they all are meant to do the same thing; focus your training to give purpose to every workout.



Figure 1: Graphical representation of heart rates experienced by most athletes. The operating range from 60 to 200 bpm can be divided into different intensity zones.



Figure 2: Three methods for dividing heart rate reserve into training zones.


Table 1 breaks down the physiological response associated with training in the different HR zones proposed by the Karvonen method. Zone 1 and zone 2 workouts are better for training your body to utilize fat as a fuel source (important for all athletes, not just folks who are overweight), promoting proliferation of capillaries in active muscles (think better delivery of oxygen to muscles), and producing mitochondria, which convert glucose into usable chemical energy. Zone 3 and zone 4 workouts are better for teaching your body to recruit fast twitch muscle fibers, utilize anaerobic energy systems, and deal with the lactic acid build‐up that is associated with the "pain" of going hard.



Table 1: Physiological response associated with training in specific heart rate zones.

So now that you know a little about the different HR zones, how can you implement zone training into your exercise plan? Let's take a look at the steps involved.

Step 1 – Acquire a heart rate monitor
The only way to know if you are exercising in the correct HR zone is to use a HR monitor, and consciously regulate your exercise intensity to force your HR into a specific zone.

Step 2 – Determine your HR zones
The actual heart rates associated with each zone are unique to every person. For example, Joe's Zone 2 may be 145 to 155 bpm, while Jane's Zone 2 may be 140 to 150 bpm. The easiest and least invasive way to determine your zones is using the Karvonen method. Click here for a worksheet you can use to calculate your zones according to the Karvonen method. An alternative, more complex method can be found in The Cyclists Training Bible, by Joe Friel.

Step 3 – Figure out how often you should exercise in each zone
Each workout you do should focus on one of your HR zones. Too much mixing of intensities within a single workout defeats the purpose of the zone training, which is to promote a specific physiological response in your body that only comes from spending the appropriate amount of time in a specific zone (note that some mixing of intensity is required to get rest during interval training in zone 4). So, some of your weekly workouts should be in zone 1, some should be in zone 2, some in zone 3, and some in zone 4. The exact mix will depend somewhat on your race goals and where you are in your training season, but a good starting point would be 60% of your total volume (workout time) in zones 1 and 2, 30% in zone 3, and 10% in zone 4. Choose zone 1 over zone 2 if you completed a particularly hard or long workout the previous day. Note that the bulk of your time should be spent at the lower intensities, partially because the proliferation of capillaries and mitochondria is so important, and partially because it is more difficult to recover from the higher intensity workouts. This is counterintuitive to some people who assume you need to go hard every day to get the most from your training, but the experience and practice of every elite endurance athlete shows us that most time needs to be spent at the lower intensities. That said, when you do go out for a zone 3 or zone 4 workout, you should put in your best effort and take advantage of the rested feeling that the slower workouts have provided. It is harder to have a quality zone 3 or zone 4 workout if you are doing them every day, and never recovering with some zone 1 or zone 2 time.

Step 4 – Do it
Once you figure out which zone you will target during a particular training day, strap on your HR monitor and get to work. It will take time to figure out how increasing and decreasing your pace influences your heart rate, and how you can force your heart rate into a specific zone. If you are new to zone training I recommend that you look at your HR monitor frequently during workouts and observe the fact climbing a hill increases your heart rate, coasting down a hill decreases your heart rate, sprinting increases your heart rate, etc. For most people it only requires a very slight change of pace to boost or lower the heart rate by 5 beats per minute, so it will take practice to induce very subtle changes in heart rate.

For more detailed information on zone training I recommend looking at The Cyclists Training Bible by Joe Friel and/or Serious Training for Endurance Athletes by Rob Sleamaker and Ray Browning.