Why Zone 2 Hype is Bad For You

Easy is in. If you are an athlete and paying even a little attention to endurance sport media, you have likely been inundated with content hyping easy training intensities. ‘Go slow to go fast’ is trending, with loads of content creators going all in on Zone 1, Zone 2, more rest days, fewer intervals, and avoiding Zone 3 at all costs. They’re not wrong but they’re encouraging the overuse of a blunt instrument where a nuanced approach is more appropriate. Zone 2 is good for you, but here’s why overhyping Zone 2 isn’t.

The Strength of Simple

I’m not above the fray when it comes to commercializing training content. I’ve made a career of packaging training and nutrition ideas in ways that resonate with athletes. I co-authored “The Time-Crunched Cyclist”, which promoted the idea of using high-intensity interval work to address athletes’ common pain point: limited time available for training. The boundary, for me and for the coaches I’ve worked with, is saying that any method of training is the only one that works.

Human physiology and the factors that influence human performance are incredibly complex. The interventions that improve physiology and performance can be remarkably simple. More importantly, because of the complexity of the body and mind, multiple interventions can lead to similar adaptations and improvements in real-world performance.

Anyone trying to sell you a training method, workout product, diet, or supplement by excluding and dismissing everything else is more interested in commerce than performance.

Why the hype around Zone 2?

Zone 2 and an emphasis on easy to moderate intensities for aerobic development are easy to hype because they work. A high volume of easy aerobic training has always worked.

Zone 2 is a low intensity training zone that is almost entirely powered by aerobic metabolism. This means most of the energy expended while riding in Zone 2 comes from the breakdown of fat. It also means the contribution from carbohydrate is low, and there is very little energy coming from anaerobic glycolysis. Because you have essentially unlimited fat stores and only limited carbohydrate stores, this intensity is sustainable for very long periods of time.

If you have the available time for it, a large volume (10-20 hours per week) of predominantly Zone 1 and Zone 2 training will:

• Increase mitochondrial density: accelerates the rate at which you can break down fat and carbohydrate to usable energy within muscle cells.
• Increase capillary density: improves blood flow to and from working muscle cells.
• Increased fat oxidation at greater power outputs (i.e. you rely on fat for fuel a bit more, which spares carbohydrate for more intense efforts).
• Read more about the benefits of Zone 2 training

The adaptations from low to moderate-intensity aerobic training are phenomenal. They create the foundation necessary to support higher intensity workouts as well as the high power, high speed efforts that win races.

Zone 2 is also easy for coaches to explain and prescribe; you just go ride at a conversational pace. It’s more appealing to a lot of athletes than hard intervals, and it’s simple for athletes to execute. However, that doesn’t mean athletes are good at completing hours of easy training. Many athletes overshoot Zone 2, which is the problem or mistake the current Zone 2 hype capitalizes on.

What Zone 2 Hype Overlooks

Helping athletes recognize they’re likely riding too hard during long aerobic endurance rides is a good thing. However, the benefits of ‘train slow to race fast’ are being oversold and overhyped. This is particularly true for amateur cyclists with limited training time.

Time x Intensity = Workload

Your training workload must create enough training stress – during individual workouts and across weeks and months – to stimulate adaptation. Moderately trained amateur cyclists often run out of available hours before accumulating sufficient workload to continue making progress. Adding intensity provides the opportunity to create the necessary stimulus.

Proponents of low-intensity training often suggest the benefit comes from reducing training stress rather than seeking to increase it. And for athletes who have been overshooting Zone 2 during endurance rides and maintaining a high level of training and lifestyle stress for a long time, they’re right. Buying into the Zone 2 hype for a few months or a whole season can create a period of deloading. This may rebalance stress and recovery, give the body the opportunity to reap benefits from long-term training, and help athletes recover mentally from highly-regimented training plans.

There’s more to training than sports science

The current Zone 2 hype overlooks many of the non-sports science components of performance. All athletes have affinities for certain aspects of training and are willing to endure the aspects they don’t enjoy much. If you love long easy rides, the hype around Zone 2 probably resonates very well! For athletes who enjoy structured or spontaneous hard efforts, it may be difficult to maintain interest in long periods of easy training. If you were a pro you’d do whatever was necessary, but to stay engaged as an amateur it is important to incorporate training you like to do that is also effective.

Training must address all your goals, even if that means aspects of your training aren’t optimal for sports science. The degree to which you utilize training for social connection, stress relief, an anchor for daily routines, transportation, and – of course – fun, affects the composition of your actvities and the distribution of your exercise intensities.

What works for pros doesn’t always work for you

Polarized training, which features a large amount of easy to moderate intensity training (80-90% below Zone 3) and a small amount (10-20%)of highly focused interval work at Zone 4 and above, is another training paradigm that can work very well for cyclists. The proof of concept came from ranks of elite endurance athletes. That’s what the annual training intensity distribution looks like for many of the world’s best cyclists, runners, triathletes, and cross-country skiers. That doesn’t necessarily mean it’s the best intensity distribution for you.

Here’s why. Gradually increasing training volume was another important factor in athletes’ progression from amateur to elite. Training became more polarized as their progression continued. In context, this makes sense. As you increase training time, overall intensity must decrease to control the rate at which total workload increases. Athletes don’t have infinite energy nor infinite time for recovery. So, if you’re going to increase annual training volume and incorporate the intensity required to meet sport-specific demands for elite competition, the vast majority of that volume needs to be easy and moderate.

For Time-Crunched Cyclists, the more applicable lesson from the pros is to be deliberate with intensity. Whether the distribution works out to 80/20 or 70/30, the more important aspect is to separate hard from easy.

What Amateur Cyclists Should Do

A big part of the reason Zone 2 got so hyped is that lots of cyclists gravitate to Zone 3 – a moderately challenging aerobic intensity – and end up spending too much time there. But if you’re being purposeful about it, Zone 3 can be used effectively to increase training workload and stress on the aerobic system. And if your goals require high-power and high-speed efforts, you eventually need to incorporate similar efforts in training!

If you’ve been diligently (or unwittingly) following a predominantly Zone 2 training paradigm, consider the following as potential next steps:

• Separate Zones 2 and 3:

  In TrainingPeaks or your preferred training software, look at the power and/or heart rate zone distribution of your individual workouts and weekly training. You may find you’re spending the same or more time in Zone 3 compared to Zone 2. If so, work on creating greater separation between Zone 2 and Zone 3. You’re most likely just going too hard on endurance rides rather than executing endurance rides in Zone 2 and performing intervals (Tempo and Sweetspot) in Zone 3.

• Examine your performance goals for the season:

  If your distribution is almost all Zone 1 and 2, consider your goals for the season. A base of aerobic endurance (from that Zone 1 and 2) is the springboard for performance at higher intensities. But, power for high-intensity efforts doesn’t appear through magic. You still need to do the high intensity training. When you incorporate intensity, keep it to one or maybe two interval workouts per week. Advanced athletes may be able to add a third. Don’t tip the scales too far in the intensity direction you’ll ramp up workload too quickly and eventually erode your aerobic foundation.

Once you layer higher intensity atop the aerobic base from Zone 2 work, you’ll have a well-balanced engine for speed and endurance. Focusing too much on Zone 2, to the exclusion of other areas on the intensity spectrum, will make you a wonderfully economical cyclist who can ride all day. However, it won’t provide the physiological flexibility for high-speed, high-power efforts during group rides, races, and personal challenges. To be a complete cyclist, your training needs to incorporate efforts from the full spectrum of intensities.

By Jim Rutberg,
CTS Pro Coach, co-author of “Ride Inside“, “The Time-Crunched Cyclist”, and “Training Essentials for Ultrarunning”