Aerobic Endurance

Depending on the time of year and goals, aerobic endurance training will be used to either build or maintain general fitness. In this article, we’ll explore why aerobic endurance training is beneficial, how much volume is required to build/maintain fitness, and how to structure this type of training into a training plan. 

What is the Goal of Aerobic Endurance Training?

Training at aerobic endurance (Zone 2 / Aerobic Capacity) intensities will help build and maintain general adaptations to the aerobic energy system. 

While shorter maximal efforts  (<30 seconds) are primarily fueled by the anaerobic energy system, longer efforts of even 60+ seconds will see nearly a 50/50 contribution between aerobic and anaerobic systems. This means improvements in aerobic capacity have the potential to benefit nearly all types of efforts ranging from sprinting the final 200 meters in a criterium to the more obvious example of ultra-endurance gravel events.

Increase Aerobic Efficiency 

Improvements in heart stroke volume, muscle capillarization, and greater mitochondrial density will lead to more efficiency. Put another way, the heart will get better at sending oxygenating blood where it needs to go, and the muscle/mitochondria will become better at utilizing that oxygenated blood.

Improve Fuel Storage / Utilization

Consistent endurance training will lead to improved glycogen storage capacity in the muscles. Glycogen is the stored form of carbohydrate and having more readily available energy is very beneficial to avoiding fatigue during training and racing. Athletes with higher relative aerobic fitness will also see improvements in fat utilization, which in turn spares finite glycogen stores and can help stave off fatigue for longer.

Train The Mind

Long endurance sessions that push beyond an athlete’s comfort zone are beneficial for learning how to “endure” the challenges that come with certain events. Learning how to manage mental/physical fatigue is a skill that seasoned athletes understand to be as much about being prepared as it is being tough.

Train The Gut

Fueling for extensive training sessions and races requires higher intakes of fuel (most commonly in the form of carbohydrates) to maintain performance levels. Many athletes find themselves struggling with stomach distress during initial attempts to increase the amount of fuel they take in during longer efforts. With a well-developed nutrition plan and some trial and error, it’s possible to 1) learn which foods/products work best for an athlete, and 2) increase the guts tolerance to higher intakes of fuel during exercise. 

Aerobic Endurance Duration/Volume

The ideal duration for aerobic endurance training rides can range from 60 minutes to many hours. Factors to consider when deciding the ideal session length are an athlete’s goals, training experience, annual/monthly/weekly training load, time constraints, and what phase of the training plan they are in. Because so many factors must be considered when determining training volume it’s difficult to provide strict guidelines.

• When appropriate, increasing the volume of aerobic endurance training is beneficial for most athletes during the general preparation (aka base training) phase. 
• The ideal session length and the weekly volume of endurance training should always be viewed in the context of the larger picture. Avoid drastic jumps in both single session duration and weekly volume. 
• Time-crunched athletes can still benefit from shorter aerobic endurance training rides. While a 60-minute endurance ride may not provide enough stimulus to drive improvements, it will still help maintain general fitness and provide a mental break from the more difficult training required to improve as a time-crunched athlete. 

Aerobic Endurance Intensity / Technique

Aerobic endurance training should be thought of as aiming for a general range rather than a specific on/off intensity. This intensity range should feel relatively easy but can become challenging to sustain when fatigue sets in. 

Power and heart rate guidelines are very useful, but athletes are encouraged to focus first on technique and perceived exertion and adjust their effort accordingly. It’s usually best to perform aerobic endurance rides solo or with a small group of athletes with a similar goal.

Technique Guidelines

Focus on maintaining steady pressure on the pedals throughout the entire effort. It’s important to avoid pushing significantly harder while ascending in an effort to maintain speed. It’s also important to avoid coasting; maintain pressure on the pedals while descending, provided it’s safe to do so. Maintaining steady pressure on the pedals is a skill that will take time to master.

Rate of Perceived Exertion Guidelines

Rate of perceived exertion is the best guideline when a power meter or heart rate monitor cannot be used. Using a 1-10 Borg Scale, the aerobic endurance range is 2-3. The ability to complete full sentences before needing to pause for a breath is a great guideline. If an athlete can only speak in short phrases then the intensity is too high. If the athlete can sing a Whitney Houston power ballad then the intensity is too low.

Power Guidelines

The aerobic endurance power range is 56-75% of functional threshold power (FTP) or Zone 2 in Coggan’s Classic Power Zones. 

Heart Rate Guidelines

The aerobic endurance heart rate range is 69-83% of threshold heart rate (THR) or Zone 2. 

Monitoring Improvement in Aerobic Endurance

Power to Heart Rate Ratio (Pw:Hr) 

This metric looks at the relationship between power and heart rate over the course of a ride. A constant relationship between heart rate and power during the entire length of a steady-state endurance ride indicates an athlete is adequately fit for that duration. If heart rate begins to rise while power remains steady or power drops while heart rate remains steady this is called aerobic decoupling or cardiac drift. This change in the heart rate/power relationship can indicate the athlete has pushed beyond their current fitness level. 

Many factors contribute to the power/heart rate ratio and it’s important to not over-rely on this metric as a means to determine fitness. Training load, life stress, temperature, nutrition, hydration, etc.. are all variables that can impact this data. It’s important to always review data as part of the larger picture and monitor trends versus single rides to make training decisions.   

Example 1: Experienced athletes knocks out a 4-hour ride

• This athlete finished the ride with a Pw:Hr of 3.34%. This is below the 5% threshold and is considered very good, especially for a ride of this duration and intensity. 
• Note average power (220) and normalized power (225). This indicates the athlete rode at a very steady effort. The VI (variability index) metric shows this relationship. A perfectly steady effort will have a VI of 1.0. Anything below 1.02 is great for a steady-state endurance effort. You can read more about the variability index here.

Example 2: Athlete in the first year of structured training performs a 4 hour ride in the summer 

• This athlete finished the ride with a Pw:Hr of 10.73%. This is above the 5% threshold and indicates there is room for improvement. After discussion with the athlete, a couple of areas for improvement are identified. 1) Carbohydrate intake was only 20-30g/hour in the form of gels. Glycogen depletion likely played a role in fatigue. 2) The athlete only consumed 16 ounces of plain water per hour on a relatively hot/humid day. More water with an electrolyte/carbohydrate mix will likely help.
• The pacing could have been better on this ride. A VI of 1.14 indicates the athlete was likely pushing too hard on hills and soft-pedaling/coasting too frequently on descents. This can be improved with better pacing and potentially better route selection.

Additional Considerations for Aerobic Endurance Training

Time

Many athletes will benefit by adding additional aerobic endurance training volume when possible. There are a couple of general rules we give to athletes who may find themselves with extra time to train:

1. Always focus on completing your scheduled interval work first and foremost. If adding additional Zone 2 riding interferes with training quality then it should be reduced/eliminated. An extra 30 minutes here and there shouldn’t cause any issues, but an extra 1 to 2 hours multiple times per week likely will. This is especially true if the extra training is not supported with enough rest and adequate nutrition.
2. During periods of intense training (usually the 4-8 weeks before a target event) it’s best to avoid extra Zone 2 riding. The goal for training should be to crush the scheduled workout and get home to start recovering for the next.

Weather

These are our general recommendations for adjusting aerobic endurance to the weather:

• Heat – Plan your route to ensure frequent water stops are available. Consider using larger insulated bottles filled with ice to start. Sports drinks are recommended, but many athletes will find having plain water available is a must.
• Cold – Dress in layers so that adjusting body temperature is possible. It’s important to stay warm while avoiding becoming excessively sweaty. This is especially important on longer Zone 2 rides during winter when temperatures can fluctuate drastically during a 3-4 hour period.

Indoor Training

Not all athletes loathe the trainer, but for those of you that do, we recommend adjusting the training plan when it comes to extensive aerobic endurance training. It’s important to maintain motivation and enjoy the process throughout the winter to avoid burnout.

• If there is a window of nice weather to ride outside then move your most important training session to that day. For example, if you have a 4-hour Zone 2 ride scheduled for Sunday and the weather forecast predicts great weather Saturday and snow Sunday then switch days.
• If you have an aerobic endurance session longer than 2 hours scheduled and have no choice but to ride indoors then shorten the ride duration to 1.5-2 hours. We find 1.5-2 hours is tolerable for most athletes accustomed to following a structured training plan.

Conclusion

Aerobic endurance training is the bread and butter of every endurance cyclist’s training plan (yes, this includes you criterium and cyclocross racers). A shorter aerobic endurance ride can help promote recovery, reduce stress, and maintain general fitness. Longer sessions can help improve general aerobic fitness and teach important skills for surviving challenging endurance events.