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If I Want to Ride Fast, Why Do I Have to Do So Much Zone 2 Endurance Training?

If there is one thing I repeat more than anything to my athletes and endurance sports friends, it’s this: slow down!

Here’s what I mean: The majority of your training should be at a slow endurance pace where you are able to have a conversation with a friend and be able to breathe through your nose.

These are not recovery rides to the coffee shops, but intentional rides where you’re riding at a moderate intensity for long periods of time. 

This also goes for runners and other endurance athletes. 

If you do this Zone 2 endurance training, you get a ton of adaptation without all the fatigue that comes from training harder. 

Plus, you get a critical adaptation - learning to burn fat as a fuel - ONLY when you ride slow!

In fact, when you start to increase your intensity just a little, your body starts burning more carbohydrates.

Zone 2 endurance training is a staple of any good endurance running program. Learn how to train in this zone, and you'll be set up for success.

You get the most adaptation from Zone 2 endurance training

Here’s the general thinking:

  • Really hard training sessions get the most bang for your buck in terms of adaptations and benefits.
  • To be able to do these at the intensity we need to get the benefits, we need to be rested. If we do them when we’re not rested, we simply can’t get the full benefit of the work. We’re sort of wasting our time. 
  • However, these high-intensity sessions build a LOT of fatigue, so we can’t do more than about 2 of them per week. Otherwise, we won’t be rested enough to go hard enough!
  • But what do we do with the rest of the week? We still need to train. 

Doing Zone 2 endurance training allows us to still get adaptations and benefits from the training WITHOUT building all the fatigue.

What are the adaptations and benefits of Zone 2 endurance training

We’ll get into the research about why Zone 2 endurance training works, and then talk about how to do endurance training.

Essentially, here are the key adaptations:

  • Better fat utilization: Your body uses fat and carbohydrates as fuel. But if you can train your body to use the virtually unlimited fat stores as fuel, you’ll be far more efficient.
  • Increased mitochondria development: The more mitochondria in your cells, the more efficient you’ll become.
  • Increase capillarization: You create more and larger webs of capillaries in the muscles which allows for more blood flow.
  • Increased VO2max and lactate threshold. You’ll be able to ride harder and for longer periods. 
  • Improved lactate buffering: When you exercise, you produce lactate, which serves as fuel. The more you’re able to turn the lactate into fuel, the more efficient you become.

Zone 2 endurance training brings speed, power improvement

Lucia et al., in a 2000 study by called "Effect of aerobic base training on endurance performance in cyclists" found that cyclists who incorporated zone 2 endurance training into their training regimen showed significant improvements in endurance performance, including increased speed and power output. 

The adaptations observed in the cyclists who did Zone 2 endurance training were primarily related to improvements in endurance performance. 

Lucia observed some specific adaptations:

  1. Increased VO2max: VO2max is the maximum amount of oxygen that an individual can utilize during intense exercise. The study found that the cyclists who incorporated aerobic base training saw significant increases in their VO2max. This suggests that their cardiovascular systems became more efficient at delivering oxygen to the working muscles, enabling them to sustain higher levels of effort for longer durations.
  2. Enhanced lactate threshold: Lactate threshold refers to the exercise intensity at which lactate begins to accumulate in the bloodstream. The cyclists in the study showed improvements in their lactate threshold, which means they were able to sustain higher exercise intensities before experiencing a significant increase in blood lactate levels. This adaptation is indicative of improved aerobic capacity and better utilization of lactate as a fuel source.
  3. Improved economy of movement: Economy of movement refers to the energy efficiency of an athlete's movements during exercise. The study found that the cyclists who underwent aerobic base training demonstrated improvements in their cycling economy. This means they became more efficient at converting energy into forward motion, requiring less energy to maintain a given speed or power output. Improved economy translates to greater speed and endurance during cycling activities.
  4. Increased power output: The cyclists who incorporated Zone 2 endurance training also experienced increases in their power output. Power output is a measure of the work performed per unit of time and is a crucial factor in cycling performance. The observed increase in power output indicates that the cyclists became stronger and more capable of generating greater force on the pedals, resulting in improved speed and performance.

Seiler study shows essential adaptations through regular aerobic training

Seiler et al. (2013), "Aerobic Base Training for Endurance Athletes: A Systematic Review and Meta-analysis" conducted a systematic review and meta-analysis on aerobic base training for endurance athletes, and found several physiological and cellular adaptations as a result of incorporating zone 2 endurance training. 

Here are some of the key adaptations:

  1. Increased mitochondrial density and function: Mitochondria are the energy-producing organelles within cells, responsible for aerobic energy production. The research indicated that aerobic base training, including zone 2 work, led to an increase in mitochondrial density (the number of mitochondria) and improved mitochondrial function. This allows for more efficient energy production through aerobic metabolism, enhancing endurance capacity.
  2. Improved fat burning: Zone 2 endurance training promotes the utilization of fat as a fuel source during exercise. The meta-analysis found that this type of training induces adaptations that enhance the body's ability to mobilize and utilize fatty acids for energy. By optimizing fat metabolism, athletes can preserve their glycogen stores, which are crucial for sustaining high-intensity efforts.
  3. Enhanced capillarization: Capillaries are the smallest blood vessels that supply oxygen and nutrients to muscles. The findings indicated that zone 2 endurance training promoted an increase in capillary density within trained muscles. This increased capillarization improves blood flow and oxygen delivery to the working muscles, facilitating better endurance performance.
  4. Improved lactate clearance: Lactate, often associated with fatigue, is produced during intense exercise. The research showed that zone 2 endurance training enhances the body's ability to clear lactate more efficiently. This adaptation helps delay the onset of muscle fatigue by preventing the buildup of lactate and promoting its utilization as a fuel source.
  5. Altered gene expression: At a cellular level, aerobic base training was found to induce changes in gene expression related to aerobic metabolism and endurance performance. This includes the upregulation of genes involved in mitochondrial biogenesis, fatty acid oxidation, and oxidative phosphorylation. These alterations optimize cellular processes to improve endurance capacity.

Another study on Zone 2 endurance training shows improved economy

The study "The Effect of Low-Intensity Training on Speed and Power in Competitive Cyclists" by Jürimäe et al. (2014) focuses on the impact of Zone 2 endurance training on various performance parameters in competitive cyclists, particularly cycling economy, speed, and power output.

The cycling economy refers to the energy cost of maintaining a given cycling speed, and it is influenced by factors such as oxygen consumption, oxygen delivery, muscle fiber type distribution, and neuromuscular coordination. 

We can often see economy in the Efficiency Factor and Heart Rate to Power ratios on Training Peaks. 

The study found that Zone 2 endurance training improved the cycling economy by promoting several physiological adaptations, including, as we mentioned earlier, increased mitochondrial density, increased capillary biogenesis (new and more capillaries to carry more blood), and the development of more slow-twitch muscle fibers. 

Additionally, the study found that low-intensity training positively impacted speed and power output in competitive cyclists. 

While low-intensity training primarily targets aerobic capacity, it indirectly enhances anaerobic performance through its positive effects on overall fitness levels.

By improving maximal oxygen uptake (VO2max), lactate threshold, and muscle glycogen storage capacity, low-intensity training allows cyclists to generate more power and maintain higher speeds for longer durations. 

That means an improvement in anaerobic capacity that contributes to enhanced performance during short bursts of intense effort, such as sprinting or climbing steep inclines.

In summary, the study by Jürimäe et al. (2014) demonstrates that low-intensity training indirectly enhances speed and power output by improving aerobic and anaerobic capacity, VO2max, lactate threshold, and muscle glycogen storage capacity.

Zone 2 endurance training builds a strong aerobic base

Zone 2 endurance training is effective for cyclists because it primarily targets the aerobic energy system, helping to develop a strong aerobic base. 

This type of training improves the body's ability to efficiently utilize oxygen and convert fat sources into energy, leading to enhanced endurance capacity.

Zone 2 training also promotes muscular endurance and helps clear metabolic waste products, delaying fatigue during longer or more intense efforts.

Additionally, doing a lot of zone 2 endurance work helps cyclists perform hard intervals at different times by providing a solid foundation of aerobic fitness. 

The aerobic base developed through zone 2 training allows cyclists to recover more quickly between intense efforts, maintain higher power outputs for longer durations, and improve their ability to tolerate and clear lactate during high-intensity intervals.

Talk Test and nose breathing are two ways to determine endurance zone

Zone 2 refers to a five-zone model of training intensities, with Zone 1 being recovery, Zone 3 tempo, Zone 4 threshold, and Zone 5 VO2max. 

Zone 2 refers to intensities at or below your first threshold. 

This first threshold is where your blood lactate starts to increase and your breathing gets a little harder. 

Generally, I tell clients to do their Zone 2 rides using the Talk Test or to ride with their mouths closed, kind of the opposite, although you could do both!

The Talk Test is when you’re able to have a decent conversation with a friend, but not about politics or religion! 

Your breathing is slightly labored, but you’re still able to talk. 

The other method is to work on nose-breathing, where you keep your mouth closed and work on breathing through your nose into your belly.

Besides being a good way to monitor your intensity, nose-breathing is also a great way to make sure you’re getting all the oxygen possible into your bloodstream!

Heart rate is probably the best way to determine endurance intensity for Zone 2 endurance training

Monitoring your heart rate is a good way to make sure you’re still doing Zone 2 endurance training. 

For most of us as masters’ athletes, staying under 130 to 135 bpm keeps us in the right zone. 

Some of the kids I coach have aerobic thresholds of 145 bpm. 

The key to using heart rate is that your heart rate will INCREASE the longer you ride simply because you’re getting tired. 

So if you want to ride at a consistent 200 watts for four hours, your heart rate will actually increase and may put you out of the fat-burning zone. 

That’s why it’s better to use heart rate as a guide for these rides.

What are three ways you should use slow endurance training in your own program?

  1. The majority of your week should be Zone 2 endurance training done at your first threshold or in the Talk Test conversation zone. 
  2. Use your heart rate as a guide to make sure you stay in the fat-burning zone. 
  3. When it’s time to go hard, go hard.

Need to learn more about Zone 2 endurance training? 

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Paul Warloski is a:

  • USA Cycling Level 3 Coach
  • RRCA Running Coach
  • Training Peaks Level 2 Coach
  • RYT-200 Yoga Instructor
  • Certified Personal Trainer
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