ZONE 2 WORKOUTS may be the missing link in helping you reach your true performance potential.
Appropriately incorporating this level of zone training can make a profound difference for most cyclists. To understand the Zone 2 Workout, you need to understand the concept of zone training.
SO, WHAT IS ZONE TRAINING?
Zone training is simply following or managing various internal (e.g. heart rate) and external (e.g., power) intensity levels that represent specific metabolic domains when training. Metabolic domains define the way we use our energy systems to do the work.
Generally, lower zones involve metabolic pathways that rely more on fat and thereby limit carbohydrate need, while upper zones utilize pathways dependent on carbohydrates. Because we have a limited supply of stored carbohydrates, these upper zone exertions cannot be sustained. Theoretically, depending on the zone of emphasis for a given workout, time spent in specific zones can dictate an expected training effect and required recovery.
In a five zone training model, Zone 2 typically demonstrates the highest level of fat utilization for fuel. One of the benefits of training at this intensity is you can ride longer while at the same time limiting your carbohydrate depletion rate, limit the buildup of acidosis, and the need for more recovery time.
Physiologically Zone 2 training increases mitochondrial density as well as MCT-1 transporters (e.g., a protein that transports lactate, pyruvic and ketone bodies), which encourages the use of fat for energy and improves lactate clearance to delay fatigue. Both of these adaptations can help to increase your sustainable power and insure a speedy recovery from training.
In the lab we determine the Zone 2 range by identifying the aerobic threshold (AeT) using a VO2Max test on the bike. Fuel oxidation during a VO2Max test is depicted in the chart below. The red area demonstrates fat calories per minute throughout the test.
Notice that Zone 2 is defined at or near the aerobic threshold and corresponds with the highest levels of fat utilization (e.g., the fat bump).
You can also determine your Zone 2 from lactate testing in which the onset of 1 mmol of blood lactate would be at or near the aerobic threshold (AeT). If you don’t have access to a lab then you would typically estimate the zone as a percentage of your Functional Threshold Power (FTP) power output (56-75%) and/or a percentage of maximum heart rate (60-70% MHR).
Numerous studies among endurance athletes suggest that a “polarized” training approach may provide greater increases in performance while also preventing problems related to overtraining (e.g., injury and illness). Specialists in the field, such as Dr. Seiler, have consistently demonstrated that athletes who perform a significant amount (75-80% or more) of their training time in Zone 2 tend to adapt and perform at the highest levels.
One reason for this potential training enhancement may be because the athlete is able to avoid “over-doing-it” or compromising the adaptation effect due to lack of recovery time. It is therefore suggested athletes who spend a significant amount of time training above the aerobic threshold are not able to recover as well.
Even training in more moderate zone(s) like zone 3 has been shown to require longer recovery time compared to zone 2 training. Moreover, required recovery time in zone 3 was indistinguishable from that of zones 4 and 5. This suggests that even the moderately hard work can interfere with or prolong recovery time.
Adequate recovery brings about two key benefits for increased performance:
If you are an endurance athlete who wants the best bang for your buck from your training, then learn where your zone 2 range is and spend time training there. Heart rate or power measures can be used to keep yourself accountable, and the increased time in zone 2 will allow you to ride more frequently and longer with less rest.
In general, if you ride more than a few days a week you might consider following a more polarized approach. For best results you only need to work very hard during 15-20% of your training time. Then, to ensure you are recovering and adapting optimally, you should stay in zones 1 and 2 for the remaining 75-80% of your training time. Follow these guidelines and you’ll likely see noticeable improvements in performance in just a few weeks.