What is Durability
Durability is the newest buzzword in the cycling training space. Unfortunately I cannot be contrarian and deny the importance of durability. A durable rider is one who is strong at both the start and end of a hard ride/race. This is of great importance as races finish at the end of the race, therefore being strong at the end of the race is essential.
How to increase Durability
There are specific and key workout types you should be focusing on if increasing durability is your main objective. A brief note on objectives first though, durability isn’t always the most important or limiting factor to a riders performance. Is your fresh or absolute power good enough? For example are you getting dropped earlier in the fastest sections of races, are you missing the punch to win or stay in races? Are your races super short? Is your bike handling and tactics up to par? The reason I mention this is to make it clear that durability isn’t a catch all or the answer for every athlete. That being said if you find yourself falling short at the end of long hard road or gravel races, your durability may need attention.
Long Ride
Durability can be focused on by riding harder for longer. Very groundbreaking stuff. In specific, there are a few key workouts that focus around durability. The most simplest being a long hardish ride. By this I mean a session ridden around high zone 2, around 65 to 70% of FTP/CP, for 3 to 7 hours. The rider’s intention of these rides should be pushing on the pedals all day, breaks or coasting should ideally be kept to a minimum. I cue I think of is keeping the chain tight all day. Average and normalized power should be quite close at the end of the ride. These type of sessions can be very boring as they favor long flat rides by yourself. One piece of suggestion I would give is to ride with likeminded people on gravel, as it is less mentally draining and gives nearly the same result.
Intervals at the End
The second type of workout I suggest would be backloading your intervals. This is a fairly simple change to your workout session. Instead of warming up and doing your workout immediately then doing your zone 2 afterwards; do your warmup and zone 2 first, then your sets of interval work, then cool down and finish. A warning however: your power will likely be slightly lower and perceived exertion higher. This is a simple way to shift the intention of a workout from gaining absolute power to gaining strength at the end of a ride. As always the intervals should be focused around your goals, e.g. sprints and VO2 for crits and short races, and threshold or sweet spot for gravel and longer races, or focusing on whatever you lack. Sprints for people who lose in sprints, threshold climbing for people who get dropped on climbs.
Now to what I would consider specialized workouts intended to increase durability. In this category I would lump workouts such as low cadence or LT1/Fatmax rides. In my view these style of workouts fall into two main pools, ones that intends to increase muscular endurance, and other workouts that intends to create energy synthesizing pathways.
Muscular Endurance
The prior focuses around creating resistance to muscular fatigue, usually by muscle type conversions. Typically hoping to turn fast twitch fibers into more efficient slow twitch fibers. The most common method is by low cadence intervals, around zone 2 to zone 3 at lower than comfortable cadence, 60 to 70rpms. Length and recovery time don’t seem to have drastic effects on results. I would recommend longer than 10 minutes and shorter than an hour for working sets. One way I like to do these is choose a ride with decent climbs, headwind, or gravel segments to ride within the grey area intensity with a low cadence. This is unstructured which I prefer as it is more mentally stimulating, however I would stress to not forget about progressive overload. If you choose the unstructured route just don’t forget to make the next ride harder in some way, usually by creating or finding longer low cadence segments.
Energy Utilization
The other type of workout has the intention of rerouting energy pathways. I’m gonna admit that I don’t fully understand or believe in the intricate differences between LT1 training and Fatmax training, but I do think the rough idea falls into this category. Both fall close enough to the grey zone between z2 and z3 of FTP/CP, but the feeling is the same, not quite unsustainable but definitely not easy. To accurately determine either requires specialized equipment, but I think one can get close enough without. The main idea is to ride at the nebulous zone of hard but all-day sustainable. Whether this primarily focuses on getting better at burning fat to hold carbs for late harder efforts, or to stay aerobic and save the production of lactate for later stages, or maybe a bit of both, the effect is the same. You are building pathways to use energy that is easily expendable or replaceable, so you have more of the high intensity energy saved for the end of the race.
To sum up, a lot of durability training revolves around the same training zones and ideology. If you are consistently close, you will definitely get better at being stronger in the late game. A few tips. Properly fueling will always make you stronger and more durable. You should focus on this. Strength training is also a very good way to get more durable. For the most part cyclists should always be lifting more. There are big gains to be had in all facets of cycling with lifting heavy.
How to Track Durability
As always, tracking progression is one of the fundamentals of effective training. Unlike fresh power, durability is more situational dependent and prone to underlying factors. I will suggest two methods to track durability.
Work: The Gold Standard
The most logical way to test durability would be to set your fresh power, fatigue yourself, then test your tired power. The method recommended by High North Performance is to warm up, ride a 5 minute maximal test, then straight into 60 minutes at 90% FTP, then immediately send another 5 minute test(shown below). The idea would then be to compare the results of both tests and look at the drop off from the first to second. I am sure this is an effective way to track durability, however I personally do not want to do this. Not only is this an extremely taxing ride that I don’t want to do(much like a 20 minute max), I argue that it is not particularly a good representation of real life scenarios. I don’t particularly see the application or similarity to typical races. Perhaps a criterium race, however I would want to test a higher intensity power, like a 1 minute(or less) max effort. Nearly every other style of racing will have a different protocol, which should be reflected in the training/testing of fitness.
I have begun to settle on a method similar, but one that allows for flexibility to account for different goals. I am of course talking about work. Work on the bike is measured in Kilojoules, and is the total energetic output of a rider over the course of the ride. This is closely related to power, as power is work divided by time. Power is simply how fast you are doing work. Work is a good metric to use for durability testing as you are directly measuring the amount of energy you put into the bike, before doing your max test. I would add one stipulation into this, being the rate of which work is done.
The metric to measure this is kJ/hr(or kJ/hr*kg for small people to feel better about themselves). This takes into account how quickly you are doing work, for the relative difficulty. For example it would be a lot easier to do 800 kJ in an hour vs two hours. I believe this should be accounted for, as it would effect your final test power. This is sounding a lot like I am transferring to an average power, the whole work over time part. I would argue this is different than holding an average power, as it allows for more realistic conditions. I personally don’t want to ride purely at 220 watts for 2 hours and I don’t see that as a race condition. kJ/hr allow for some variance in power, whilst still completing the work needed. Personally this makes the ride more enjoyable so I can ride with friends or ride to terrain. To add, this is also the metric that cycling twitter uses to analyze the difficulty of a stage before a climbing performance, so it surly can be a trusted metric.
With this metric, you use a similar protocol as the High North test, just with the flexibility to add specificity. By this I mean you can tailor to your goals and intended races. For example if you want to train for a crit, perhaps you center around 1 minute tests and try for 1000kj in one hour on a route that favors punching out of corners or up hills. Maybe if you want to race long road races you do 20 minute tests that sandwich 3000 kJ in 4 hours. Specify the test to your needs.
The most important part of this is to ensure you are keeping as many factors constant as you can. Heat, hydration, fueling, they all can affect durability greatly and can confound results if not taken into account. I figure as long as you apply the main structure of test-fatigue-test, specify for your needs, and keep the same test to test progression, you are plenty close enough.
Aerobic Decoupling: the Grey Standard?
Aerobic decoupling is a measure of how your body’s effort and output relate. Simply put aerobic decoupling shows how your heart rate changes over the course of a ride when power is held steady. It is mainly used to track cardiac drift, or when your heart rate slowly raises through an interval, despite power remaining the same. This is typically understood as fitness metric, e.g. can your heart rate stay steady at the same output. A large cardiac drift is shown below.
This particular day was not a good day on the bike for me. I could feel so during the ride, but it can also be seen in the data. For part of the ride I paced back home on a long headwind uphill. The screenshot of this period shows a very consistent power, however my heart rate climbs throughout. This is generally understood as a lack of fitness, which was certainly confirmed by my sensations that day. This data can be understood as an aerobic decoupling. To specify further, cardiac drift is a qualitative measure of seeing heart rate increase despite consistent power. Aerobic decoupling is measured quantitatively. To determine aerobic decoupling, one would take the derivative of power/heart rate. This means that aerobic decoupling tracks the change in the ratio of power to heart rate. Usually aerobic decoupling is measured in percentage change. The difference of the end of the ride’s power to heart rate ratio to the beginning shown as percentage change. A positive percentage shows a decoupling, or a smaller power/hr ratio.
This by itself can already be hacked or invalidated, as power and heart rate don’t increase at the same rate. For example I would expect my power to be around 240 at a heart rate of 160. At a heart rate of 170 I would expect to have a heart rate around 270-280 watts. These ratios solve to 1.5 and 1.6. If I were to do this in a ride, start at 160 bpm then raise to 170 bpm, aerobic decoupling would be negative. This does not make logical sense, heart rate decreases as power stays the same. For this reason one can only use aerobic decoupling at power values that are relatively similar.
How to apply Aerobic Decoupling
The main use of aerobic decoupling has been to tell a rider when they are done with the base season. The idea being that after the offseason, a rider is unfit, but likely to hold the zone two power they need to in a zone 2 ride as they start their base season. Heart rate is then examined to see how the body reacts to steady zone 2 power. In an unfit/undertrained rider, heart rate will raise as power stays the same across the zone 2 ride. This is the exact situation from the chart above that I used to show cardiac drift. Aerobic decoupling is used to track the fitness of a rider as they progress through the base season. It is typically understood that once the rider can consistently do rides of sufficient length(which varies based on goal races) without aerobic decoupling, they are ready to progress to intervals and building to race fitness.
There is one more application of aerobic decoupling that I believe has potential as being very useful. I have been applying aerobic decoupling as a measure of stress from a workout recently. For this, I sufficiently warm up, ride at zone 2 for at least 20 minutes, do my workout, then zone 2 home. What I then do after the ride is analyze the decoupling between the zone 2 before the workout vs after the workout. This gives me a sense of how hard the workout was on my body. This can be used as progression tracking or as a sign to up the difficulty of a workout. I think this is a sneaker application of heart rate that can be very valuable. The graphics lower show how I take a ride and find the data from it. The first graphic shows the preset that Intervals.icu apply to the data. This splits the ride into the first half vs the second half, and compares the power/HR ratio between them to find aerobic decoupling. This is useful for the standard application of aerobic decoupling, a steady zone 2 ride(where power is kept constant), but for this particular application we are only looking at the averaged power/HR ratio.
The next two screenshots show the two zone 2 blocks, before and after the workout, in isolation. You can see that the zone 2 block before the workout shows an average Power/HR ratio of 1.38. The next screenshot shows the zone 2 block after the workout to have a ratio of 1.28. This is an aerobic decoupling of 7.8%. I can then use this percentage for tracking progress, as in if I repeat this workout and my aerobic decoupling decreases, I am properly adapting. I can also use this as I apply progressive overload, making each workout harder as the weeks go by, I can track my relative effort to the workout to make sure I am adapting and not just going harder and harder each week. It should also be noted the overall shape of the data, showing the ratio changing as power changes(particularly during the 3 threshold intervals), further cementing the fact that for standard aerobic decoupling analyzation to be used, the power must stay constant.
Another quick word on aerobic decoupling. There are weird quirks and confounding data to be noted. As mentioned before, power consistency is essential. There are also other factors that effect the power: heart rate balance, like heat, dehydration, fueling, caffeine, and even sleep. These should all be taken into consideration. Besides this, I have noticed within myself when my aerobic base is decent, I will have long zone 2 rides that have a negative decoupling. This means as I continue my ride my power stays steady and my heart rate drops. I went to online forms, reddit and Intervals.icu, to try to look for answers. Not only is this apparently a somewhat common occurrence, there seems to be an array of likely answers. Some people noted fatigue, cadence, temperature decrease, caffeine synthetization over the course of a ride, as well as food synthetization, and even simply mentally settling into the ride. For myself I think food synthetization is a likely culprit, as I usually eat a decent portion before I ride, which would take energy/increased heart rate to digest until it is gone partway through my ride. I would also figure that simply settling into my ride, lowering my pre-ride excitement and calming down would play a big part in lowering my heart rate. I simply mention this to think about other factors when analyzing heart rate.
Conclusion
In sum, to perform in the current cycling era, particularly in gravel, durability and endurance on the bike is a very important metric. This can be targeted by specific workouts with specific intentions, and can be tracked via two methods. As always, pedal intentionally.