Everyone claims to have some secret sauce to endurance training. Really it isn’t that complicated. At the risk of giving away the farm I think it is important to help dispel some myths, help athletes have some basis of determining good versus bad advice, and give athletes have a basic level of knowledge when it comes to endurance training. This is a pretty quick over view and things do get a lot more nuanced, complicated and precise, but just having this basic knowledge will allow you to refine your own training and quickly assess if that advice you are hearing from that master’s racer on the group ride makes any sense.
First off, I think it is helpful to go over some basic exercise physiology. We don’t need to go very in-depth here, but having basic knowledge of the three main energy systems in the body is important in understanding basic training concepts. First off there is the aerobic system that requires oxygen and predominantly burns fat. This is by far the biggest energy contributor for any endurance activity lasting more than a few minutes. Next we have the anaerobic system which is doesn’t require oxygen, burns glucose (carbohydrates), can give us a lot of energy but fatigues very quickly (15 – 180 seconds). Lastly there is the phosphate creatine system which gives us a lot of energy, but only lasts a few seconds. This is where the majority of your sprint power comes from. These basic energy systems are the foundation of athletic performance. It is important to note that these energy systems don’t flip on and off as intensity changes and recover at different rates. All of them are active across all exercise intensities. The dominant energy system will change as intensity changes, but all are active at all intensities. Even as you sit there reading this your body is creating some energy anaerobically. The point where we shift from supplying the majority of our energy aerobically to supplying the majority of our energy anaerobically is often referred to as threshold, whether that be lactate threshold or functional threshold. Functional threshold, not really a reference to any underlying physiology (although it does correlate with most) is the most amount of work you can do for an hour, is often described as upper level 4.
These systems are a bit abstract and it can be helpful to put them into something we can better understand, like heart rate or power zones. There are varying percentages given for the specific training levels but the most effective ones are based off of an athlete’s functional threshold as defined by lab testing or field testing (I typically will use a 5 minute all-out effort, followed by a 20 minute all-out effort and take 95% of the 20 minute effort to determine threshold and then verify it through further data analysis of other hard rides). Two of the most popular are the levels determined by Joe Friel and Dr. Andy Coggan. Through the work of Dr. Coggan we also have this awesome chart (courtesy of training peaks) showing what is happening physiologically at different riding intensities (the more check marks the more adaptation):
Recently, these have been further refined into Coggan’s iLevels. These are 9 levels based on the power:duration curve (which is one of the best tools available in understanding an athletes abilities). As you can see from the chart below, the bottom 5 are set from percentages of threshold while the upper 4 are based off the determined strengths of an athlete from their unique power:duration curve. This gets a bit more complex and for the sake of this article we won’t go too deep on this but the general concepts are the same. iLevels are just a bit more customized to an athlete’s strength and weaknesses. One last important note on the adaptations noted for different training levels is that they act on a continuum, just like the energy systems.
So now that you know what systems you are working on when riding at different intensities, how do you decide what systems you should be working on? This can get a bit complicated but since all endurance sports are predominantly aerobic, most of your time should be spent building a robust aerobic system that can maintain energy production for the length of time of your goals. This can be defined as stamina (being able to ride the distance), or functional threshold development (being able to produce as much energy aerobically as possible). This is commonly referred to as base training and really does create the foundation of training for most athletes. If you’re an Ironman triathlete, this may be where you live throughout the entire year. If you are a road racer you probably won’t be able to win races by staying at or below threshold (if you can than you need to upgrade!) so at some point you have to spend some time above threshold. How much and at what levels is determined by your goals and strengths, as well as your overall training level. If you want to race criteriums than you better have a good anaerobic system to respond to attacks, accelerate out of corners, and a good phosphate creatine system to sprint at the end. Those aren’t going to be developed by riding at level 2 all day. If you are a road racer that has good stamina and a pretty well-developed aerobic threshold but not much anaerobic ability, it may good to spend a bit more time working on those abilities to match accelerations, power over short climbs, and finish strong in field sprints. Finishing positions in a 4-hour road race are often determined by relatively short time periods of riding above threshold. We definitely want threshold as high as possible, but if you never work above that than you won’t be ready for those times when the group accelerates up that 5-minute climb or the skinny climber accelerates through the steeper section on a longer climb. Times above threshold often determine success.
Define the demands of your goals, see how that matches your strengths, and start training your weakness.
Now that you know what you need to work on, you have to define how much you should do. This is as much science as experience, intuition, and the mindfulness of the athlete. In basic terms you need to be able to produce the required energy to do your goal event. If you are using power you can figure this in kilojoules and watch the power:heart rate ratio to know your overall efficiency. Ideally, we don’t want to see heart rate come up at a sub-threshold steady state power output over a long duration. In the chronic sense, it is typically safe to increase training volume around 10% a week as well as your long ride. This is also the same for your time spent at the higher intensities. There is a point of diminishing returns for both chronic training and higher intensity interval work. This where that mindfulness component comes in. If you are self-coaching, take account of how you are feeling after workouts and look for patterns in your training. Waking up feeling wrecked on a consistent basis, changes in mood, or not sleeping are all warning signs you are doing too much. If you are coached you should be talking to your coach about how you are feeling on a regular basis as well. Data only tells us so much and having that context is invaluable. If you want to go the more scientific route (and honestly you should!), using a chart like the performance manager chart can be useful in regulating training progressions and determining when doing more isn’t really increasing performance.
You have probably noticed I am referring a lot to power in this. That is because power makes a lot of this more precise and simpler to describe. All of this can be done with heart rate (HR) as well but it does get a bit subjective as a lot can affect HR. HR is also not reflective of higher intensity efforts since it responds relatively slowly to changes in effort. Doing a hard 30 second effort followed by 90 seconds of recovery is a workout we may do to increase anaerobic work capacity (or functional reserve capacity or W’), but if you are just using heart rate you might think you are just doing a level 2 or level 3 ride. This isn’t necessarily wrong but isn’t reflective of the stress of the workout.
Monitoring training progression through a tool like the performance manager chart can also help us be optimally prepared for our goals. We can better structure tapers to events to ensure we are rested and not losing too much fitness in the process. But even without a tool like this we can follow the work of Inigo Mujika to design an effective taper to a goal event. In basic terms, research has shown an exponential taper decreasing volume up to 75% while maintaining intensity will produce a well-rested athlete while minimizing fitness loss. Most athletes have a real mental challenge with cutting training this much so we often find a compromise that maintains confidence.
Obviously there is a lot more to all of this and the number of data analysis tools and advanced concepts continue to grow. It is a pretty cool time to be an endurance athlete but at the same time it can get a bit over whelming. It is important to remember that everything still comes back to basic physiology and increasing maximal work rates over time. Of course there are a lot of great coaches out there that can help you on this journey as well, but if you decide to go it alone you should have a better idea of what you should be doing, what is good advice, and what is some crazy geezer telling you some crazy BS about training. This should also help you determine the good coaches that create a customized training program around an athlete’s unique abilities, or a canned program from someone who just has you do what they did to get fast. If a coach, teammate, or riding buddy is telling you what you should be doing without asking about your training, looking at some ride files, and having some understanding of your physiology than it is probably best to just walk away.
Most importantly, none of this replaces riding your bike! Keep it fun!