Training with power has revolutionised the way many people train in cycling, but whilst there are many advantages to training with power, there are some big mistakes to be avoided when following a cycling training plan. In this post, I’ll be explaining three of the biggest mistakes people make when using power based training zones and what we can do to avoid them.

In any given workout, power targets are usually created based on training zones, which are calculated as percentages of the cyclist’s Functional Threshold Power (FTP). You’ve probably heard the term “threshold” a lot, and with good reason, although it’s far from everything in endurance cycling, it represents an extremely important component of your fitness, it represents your tipping point. Your threshold is your “red line”, go beyond your threshold and try to stay there, and you’re going to fatigue very quickly. However, ride below your threshold and you can keep going for ages, providing you’re reasonably fit and are eating and drinking well before and during the ride. A good indicator of your threshold is the level of effort you can sustain for 40-60 minutes, this is widely termed your “Functional Threshold”.

Mistake 1: Fixing an exact power value to your Functional Threshold.

Functional Threshold is reached at a level of work, not a set level of power. A functional threshold power value (in watts) is only valid when you are at the same level of fitness and fatigue as when you completed the test you used to calculate it. Therefore, depending on levels of fitness and fatigue, the power produced whilst working at your threshold will vary massively, even from one day to the next.

In many cases we will measure our FTP when well rested, after all, it is during a period of rest that our bodies recover and adapt to the stresses of the training we have been doing, to come back fitter than we were before training. The limiting factor is that when an FTP value established when fully rested, is being used to calculate the power level for all our following training sessions, regardless of fatigue levels.

So, whether it be from training fatigue or life stresses, we may find that some days (probably quite often) we are unable to hit the same power numbers. For a 100% effort level over 1 hour when fresh, we may be able to perform at 100% of our calculated threshold power. However, when fatigued, for the same 100% effort level we may only be able to produce 85% of our calculated threshold power.

Regardless of what we have recorded as our FTP value, our true FTP (the power we could sustain for 1 hour), changes on a daily basis based on how fatigued or fresh we are. A rider’s threshold may be 300 watts on Day 1 of a training block, but by day 3, depending on the training type and the recovery speed of the individual, could be as low as 250 watts. When attempting to measure the training stress caused by a workout, it’s the actual metabolic cost of the effort that counts, not the number of watts produced.

How to Avoid: Give yourself some slippage room on your FTP value, don’t expect to be able to hit the same power numbers when tired as when you’re fresh. If you are completing longer threshold based intervals and you know you are partly fatigued, reduce the level of power and maintain the effort duration, rather than trying to ride at your set FTP value and fall apart after a few minutes. Remember, to be riding at threshold involves a certain level of work, a level of work which is sustainable. If it’s not sustainable then you are above threshold, regardless of the number displayed by your power meter.

Additionally, it’s also important to re-test regularly to ensure the numbers you are using reflect your current fitness. Every 3 months is usually often enough but it does vary from person to person depending on your starting point and the amount and type of training you are doing.


Mistake Two: Using the same FTP value across different cycling disciplines.

Just like US dollars can’t be directly spent in the UK, your FTP may not be directly exchangeable in a different discipline. We need to apply an exchange rate.

Many people ride more than one discipline in cycling, and most of these people will achieve different threshold power values in testing across different disciplines, and in some cases these values will be dramatically different. Most commonly the difference between riding a threshold test on a road bike vs riding a threshold test on a time trial (TT) bike.

For all but the most experienced Time Trial riders, when riding in TT position, people generally won’t be able to maintain the same levels of power which they achieve on their road bike. The position adopted on a TT bike places a large emphasis on aerodynamics, and this comes at a cost of lower power production, with a tighter hip angle restricting breathing and blood circulation. This however doesn’t matter (up to a point) if the gains in speed made from a more aerodynamic position are bigger than the reduction in speed caused by lower power. I say up to a point because there is a tipping point where if you restrict power production too much, you would actually get slower, but I don’t want to go off at a tangent, so let’s park that point for now.

For people who ride a mix of road and time trial, a power loss on the TT bike of 5-10% is typical. The most efficient TT riders will have a power loss less than this, and riders who have just started out in time trialling or riders whose position is too inefficient will experience power losses greater than this.

So, it’s really important that when training with power, you are working to a power level which is appropriate to the bike and position you are riding in. There’s no point in calculating power training zones based on an upright road position and then trying to ride TT specific efforts using those training zone numbers, because you won’t get anywhere near them (in most cases).  On the flip side, power values established by testing in a TT positon are going to be too low for the same level of work when up on the hoods of a road bike.

How to Avoid: Calculate your exchange rates: If you are going to be training using power for multiple cycling disciplines then you need to test your threshold in those different disciplines and train accordingly to the type of cycling you are doing. For example, if you test your TT power and your Road bike power and find your power is 10% lower on the TT bike, you need to factor in this “exchange rate” when completing a workout on the TT bike.


Mistake 3: Viewing yourself as “Average”.

The most widely used test to establish a cyclist’s Functional Threshold Power involves completing a 20-minute sustained effort, where the rider attempts to maintain the highest average power possible for the 20-minute period. FTP is then calculated as being 95% of the 20-minute power. This calculation was based on the analysis of a large number of cyclists, where on average, the percentage level of 20-minute power which was sustainable for 1 hour, was 95%. The issue here is that this is an average. Some people may be able to maintain 98% of their 20min power for 1 hour, whilst others may only be able to sustain 92%, the actual chance of you being bang on average is quite unlikely.

Example: The average of the below numbers is 95. However, none of the individual numbers are actually 95.

92, 93, 94, 96, 97, 97, 93, 98

In the same way that using an average can cause an error in establishing a cyclist’s FTP, the upper and lower limits of training zones are also susceptible to being incorrectly set. Depending on the specific strengths and weaknesses of the individual, the percentage of power sustainable above and below threshold is going to vary massively. These individual variations could come from either the miscalculation of FTP as just mentioned, or because the individual has a greater than average strength or weakness in relation to their calculated FTP value.

Real world example, I tested a former international level cyclo-cross rider and their FTP value was far lower than you would assume for the level of athlete. This is because the individual had spent years training and racing specifically in cyclo-cross, which by its very nature can produce a very stop-start style of riding. The athlete was therefore able to sustain very high-power values well above their calculated FTP for up to a minute or two, then after only a very short recovery period, reproduce the same level of effort, over and over again. When tasked with maintaining a consistent power output for 20 minutes, the results were much more ordinary than their extremely impressive stop-start work. With this rider’s FTP being relatively low compared to their VO2max and on the flip side, their VO2max being relatively high compared to their FTP, the standard VO2 max zone calculation based on a percentage of FTP just isn’t suitable for this rider. Note: VO2max represents the highest amount of oxygen an individual can consume and use to supply oxygenated blood to the working muscles.

This is not a criticism of power zone calculations methods, they are extremely useful for a huge number of people. Just bear in mind there are individual differences to consider, so if you feel you don’t quite fit the model, it’s quite likely that you don’t.

How to Avoid: With the ever-increasing amount of software available it is now possible to establish power training zones based on analysis of training data of the individual. With more accurate values being produced with greater levels of data recorded in the system and over a wide range of durations eg. 5 second power all the way up to multiple hour power. Individualized power training zones like the “i levels” established using the WKO4 software are an extremely valuable tool.

It’s also possible to use something called a Modelled FTP rather than a Set FTP, in this case software is used to constantly update a predicted FTP value for you, based on the training data you feed in to the programme. The biggest limitation of this however, is if you don’t feed a sufficient amount of data in to the system, using power data recorded over certain time durations, the Modelled FTP could end up being less accurate than your Set FTP.

Another thing to consider is riding a 40-60min effort to establish a more individualized threshold value, but this does take great mental strength, and it’s certainly not for everyone!

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Dan Small, Mountain Goat Coaching