We regularly get practical questions from runners who run with the Stryd running power meter. Last week we answered the question about improving your critical power when training with Stryd training plans.

Actually, that explanation is valid for most training plans. Typically, you run many miles at a slow pace. The purpose of such workouts is to train you to run for a longer period of time.

With intervals and running in blocks at a higher pace you accustom your body to a high speed. With clever combinations of speed, rest, and repetitions, your coach ensures that your running economy improves. For middle and long distance runners, the energy sources are mainly aerobic glycogen and fatty acid burning.

Therefore the power requirements for the intervals in this article are not intended as a complete workout. They are building blocks for a workout.

Interval training makes you a better runner

Many serious runners train at least once a week with their athletics club on the track. On another day of the week, they train for themselves, or with a group, and do a bit longer intervals, speed work or hills according to the design of their training plan.

The added value is that you can train at higher intensity with intervals. It improves your speed, VO₂ max and anaerobic threshold. The goal can also be to train your different energy systems (you have four!). Or to get your body used to lactic acid. Because in between the intervals you are allowed some recovery, this type of training is not as stressful as a race.

Depending on the goal, the coach varies the length of the intervals and the intermediate rest in the training scheme. The coach also varies the pace during the intervals. Usually, coaches define a base intensity as 100%. In a rest week this can be reduced to 95% or even 90%. In the race period, the intensity can be 105%, or even 110%.

The coach divides the group based on the 10 K-times of the runners. You run in a group that is about as fast as you are. The number of seconds per 100 meters is different depending on your level, the interval distance and the intensity. This all seems to be the coach’s secret. If you train with a power meter, it needs no longer to be a secret to you.

Power-based interval training

In this article we explain how you can calculate the required power of your intervals. First you need to know your Functional Threshold Power (FTP), which is the power (wattage) that you can sustain for 60 minutes. In practice, for an average balanced runner the FTP is generally about the same as your Stryd Critical Power (CP), as determined as auto CP in the Stryd app. You can also read your FTP in the power duration curve in PowerCenter from Stryd at 1 hour.

It can be even simpler as you can also have your FTP determined with the calculator on our website www.theSecretofRunning.com. You enter the distance and time of a fast race and find on the second to last tab your calculated FTP in Watts/kg. This number you still need to multiply by your body weight. For Ron this is currently 3.25 Watt/kg at 80 kg, so 260 Watt.

In the table below you can see the percentage of your FTP that you should use as Target Power for different interval distances.

The percentages increase for short interval distances because your anaerobic energy systems kick in to supply extra energy. However, your anaerobic fuel supply is limited. For this reason high powers and fast speeds can only maintained for short periods. In an earlier article at Stryd.com you can read more about this. We fully explain this in our book The Secret of Running.

The figure below also gives these percentages. In the graph we have drawn a line that indicates the maximum theoretical power supplied by the energy systems of the human engine. That is the limit of your human power. In an interval work-out it is of course not intended to run that fast. It’s no race. If you do, you will miss your training goal and may get injured.

Practical examples Hans and Ron

As practical examples, we use the interval data of authors Hans and Ron. Hans runs 10 K in 38 minutes. Ron currently needs about 51 minutes. Their coach specifies the required pace in terms of a number of seconds per 100 meter for the various intervals. The table also shows their corresponding power targets for the intervals, which we have calculated with the same method as we explained in another article.

For the average runner this can be easily done with the formula:

P = 100/t*1.04*m

In the formula you enter for t the number of seconds per 100 meter and for m your body weight (in kg) to get the power P (in Watts).

The table clearly shows that Hans needs less power than Ron and still runs faster. Obviously, this is related to Hans’ lower body weight.

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Our book ‘The Secret of Running’ is for sale in our webshop. Also available in German as ‘Das Geheimnis des Laufens’, and in Italian as ‘Manuale completo della corsa’

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Running with power doesn’t mean you’re stuck with Stryd training plans if you want to train for a marathon or other race. It is obvious that many runners try out such a plan if they have purchased this running power meter.

Stryd offers, as they call it, a complete ecosystem with this footpod. An ecosystem that has more and more to offer and makes the qualification ‘the trainer is on your shoe’ true. For the most advanced options, you can’t escape a paid subscription after a free six-month introductory period.

On the Stryd.com website, everything is well documented without exception. This does not mean that every new owner of the Stryd footpod has read everything and has been able to let it sink in. We notice this in the questions we receive. In this article we answer a frequently asked question about the Stryd training plans, Critical Power (CP) and power duration curve.

Philosophy

More experienced runners know that not all training plans are structured in the same way. That’s not necessarily wrong. Not everyone is the same. And the insights into what a good training approach is are evolving. Older runners will tell you that they made a lot more kilometers than is common nowadays. Preferably they turned every training into a race.

Stryd’s plans are based on a modern basis. Their website opens in large letters with Stryd’s training philosophy:

“Most runners train at the wrong intensity.
It is a simple mistake that silently hinders runners at all levels.
It doesn’t have to be this way.”

Your own level

Stryd offers training plans for several distances. You can choose a plan that fits the number of days in the week you are able to train.

The building blocks (workouts) of such a plan are linked to your personal Critical Power (CP) in Watts. The CP says something about your condition. In that sense, it is similar to the VO₂ max, the best-known and traditionally most used indicator for determining your fitness.

Because of this link to your personal CP, Stryd offers you training plans that fit your level. If your condition improves, a higher CP is shown and the workouts adapt to your better fitness. The other way around is also the case. As a result, you do not train below or above your level.

Building blocks

If you have chosen a certain training plan, you can indicate when the race is. You also indicate on which day you usually have time for a long training. The calendar in Stryd PowerCenter (and the Stryd app) then fills with workouts. If you can’t train one day, you can easily swipe that workout to another day.

Long workouts are a lot slower than many runners are used to. Now and then there is a time trial in the plan, where you go all out for a longer period of time. Most workouts consist of strides, intervals and blocks in which you have to give a lot of throttle for the “prescribed” wattages. These are the workouts to improve your base speed. That is not the purpose of the long training sessions. If you did, you would have to recover longer and on balance you would benefit less from your workout.

Furthermore, it is striking that the schedule indicates the time that a workout lasts. The number of kilometers or miles you run are not a goal in itself. This also has to do with load and recovery.

Each training has a specific purpose. The explanation is always neatly in the box. We give three examples of a workout from a Stryd plan.

Example 1: Fartlek
Your workout today calls for four repeats of 5:00 at 95-102% of your Stryd Auto-Calculated Critical Power. Your goal for this 4 x 5:00 session is to start conservatively the first 5:00 repeat around 95% of your CP and progress the second and third repeat from 95-102% of your CP. After your last repeat run an easy cool down.

Example 2: Easy + Strides
“Strides” are defined as short bursts of faster running to get your body used to running at a higher intensity. Your goal for strides should be to start a bit above your CP and practice running at a fast speed without straining. After a brief warm up, you will run 30 seconds repeats with an easy 1 minute recovery. After you have completed the number of repetitions, cool down with an easy segment of running.

Example 3: Long Run
The long run is a main staple in training and is your longest continuous effort in the training week. The goal for this run is to practice extending duration and increasing your time spent running. Over the course of the training plan this run will build in duration and slightly vary in intensity.

My CP is barely getting better?

Runners who train with a Stryd plan often come up with this question, as we wrote in the introduction to this article. For the answer, you need to realize that these trainings are based on your personal Critical Power. Stryd calculates this from your power duration curve. This curve is built with the powers that you have actually ran in the past 90 days.

If you haven’t done any races or hard workouts with a longer duration during that period of 90 days, your power duration curve won’t improve. After all, a Stryd training plan mainly consists of long easy endurance runs (low power) and shorter repetitions with high intensity (high power). The time trials are useful but are scarce in number and have a relatively short duration.

Just like in any other training plans, you will have to build a number of hard workouts into your program. Due to the Corona pandemic, there are fewer options, but you will probably find a solution.

For example, the blue line in Ron’s power curve below is the result of a recent run. The white line is what Stryd expects Ron to be on the x-axis for the corresponding duration. Our free ebook ‘Your easiest way to a PR: Running on Power‘ gives the tip to occasionally build in a jack-up workout. The goal is then to run the power according to the white line in a workout. The blue line then shifts locally to the white line. A hard jack-up workout in the range of 20 to 50 minutes contributes the most to the improvement of your CP. If you “beat” the modeled ability, your CP goes up.
This improves your power duration curve. Your CP will adapt if it also shows a better fitness. In that case, Stryd adjusts the powers with which you have to run the workouts of your plan (Stryd Auto-Calculated Critical Power).

 

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Our book ‘The Secret of Running’ is for sale in our webshop. Also available in German as ‘Das Geheimnis des Laufens’, and in Italian as ‘Manuale completo della corsa’

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Dutch elite cyclist Tom Dumoulin surprised the running world on November 14, 2021 by participating in the 10K of the Groene Loper Run in Maastricht (The Netherlands) and immediately becoming second in the sharp time of 32:38.

In an ordinary cotton shirt and without carbon shoes, he seemed to run at ease with the leading group. The winner Wouter Simons, a fanatic runner and triathlete from Genk, Belgium, was deeply impressed: “he hardly breathed, what a class”. On social media it rained praise, including from Dutch champion Michel Butter!

Tom’s performance inspired us to make a comparison of the performance of runners and cyclists. The two sports are of course similar in the sense that the leg muscles have to do most of the work and the power of your human motor (especially your heart lung system and your leg muscles) is decisive.

For cyclists, running strengthens the bones. For runners, cycling has a low risk of injury and is beneficial for training the metabolism and heart lung system. It can be an alternative to recovery training. You often see that cyclists also run and runners also cycle. To get to the absolute top you have to specialize. We don’t know of any examples of athletes who excel in both sports.

In this article we will calculate the performance of top runners and top cyclists and analyze the running and cycling performance of Tom Dumoulin and some other cyclists.

How high is the power of the human engine of runners and cyclists?

In our books, we have shown that the power of the human motor is similar in both sports. In both sports, we have derived the limit of human performance from the world records and world best performances, such as the climb to the Alpe D’Huez.

The very best performance in both sports corresponds to a maximum power of 6.4 Watts/kg (as FTP, so the power that you can maintain for 1 hour). The table below gives an overview of the FTP values at the different performance levels. The table also shows the speed corresponding to the FTP values mentioned, both in cycling and in running. The calculated speed applies to the standard conditions, so an ideal flat asphalt course, no wind and for cycling a modern road bike.

Top cyclists such as Tom Dumoulin regularly reach a level of 6 Watt/kg in the Grand Tours. The maximum value of 6.4 Watt/kg is only approached in exceptional cases (top form of the very best cyclists).

Tom Dumoulin wins the prologue of the Giro d’Italia 2015 in Apeldoorn (The Netherlands). We calculated his ADV at 6.05 Watt/kg (archive photo The Secret of Cycling)

How fast can top cyclists theoretically run with their power of 6 Watt/kg?

We calculated that with our standard model for running for a flat course without wind on a hard surface, the result is in the table below.

Based on our calculations, Tom should be able to run almost 5 minutes faster than the 32:38, no less than 27:51 according to the table! That seems like a fabulous time, but we have to remember that Tom is also a fabulous top cyclist.

If we calculate Tom’s actual time back with our model, the 32:38 corresponds to an FTP of 5.12 Watt/kg, so a lot (15%) lower than the 6 Watt/kg that he does achieve in the grand tours. What factors can explain this big difference? We see at least 3:

1. Tom will probably be a bit heavier at the moment than in the cycling race season. For example, if he is currently 2 kg heavier than his race weight, that explains already almost 3%
2. Tom will certainly not be in top shape at the moment and certainly will not have dug as deep as in the Tour de France. Author Hans himself has experienced that in periods of lesser form he can lose up to 15% in performance.
3. Tom is probably a better cyclist than runner. His metabolic efficiency will be optimal in cycling and he will undoubtedly run less economically, so his energy consumption (ECOR) will be higher than a trained top runner. Author Ron has the reverse experience: on the bike his power is considerably lower (more than 20%) than while running. Author Hans has been cycling (since his running injury) for more than 2 years now: in the course of those 2 years his cycling power has increased to the same level as his running power was before his injury.

Other examples of running cyclists

Other appealing examples are professional cyclist Michael Woods, who once ran a time of 3:57.48 at the English Mile (1609 m). This performance corresponds to an FTP of 5.99 Watt/kg and is almost exactly the same as his bike FTP.

Tom Pidcock, the competitor of Mathieu van de Poel on the MTB, recently ran a 5K in 13:25 according to the internet! Although this time is not certified, it does correspond to an FTP of 5.93 and is also of the same order as his bike FTP. Incidentally, there are also reports that his course was downhill and too short due to GPS issues.

Most cyclists only run during the winter period and do not really focus on top times. It is known that Lance Armstrong ran the marathon after his cycling career in 2:46:43 (New York 2017) and Abraham Olano in 2:39:19 (San Sebastian 2006). These are of course nice performances, but absolutely not comparable to the world level they had as cyclists (FTP only 4.68!). This is even more true for Adam Yates who ran the Barcelona Marathon in 2:58 (FTP 4.38 Watt/kg) on 8 November 2021, this will have been a training for him and not a top performance. The same applies to Wout van Aert who recently ran the 10 EM of Antwerp in 1:11:11 (equivalent to an FTP of only 3.90 Watt/kg).

Author Hans also remembers the experiences of ex-pro Matthijs de Koning, who rode the Tour de France in the team of Joop Zoetemelk. After his cycling career, Matthijs started running with the Altis Masters in the 80’s, together with Hans, among others. Both ran half marathons of 1:12 at that time, which corresponds to an FTP of 5.16 Watt/kg. Matthijs cycled the big climbs in the Tour in ‘the grupetto’, so that his FTP will have been less than 5.5 Watt/kg. Matthijs was also a great ‘fighter’, who never gave up. He once performed a legendary catch-up race at the Dutch triathlon of Almere: he came out of the water as 100th, overtook 90 people when cycling and finished 2nd after the marathon!

In conclusion, it should be noted that in both sports, the real top performances are almost always delivered after years of intensive training, in which both the heart lung system and the leg muscles and the running or cycling economy is maximally developed.

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Our book ‘The Secret of Running’ is for sale in our webshop. Also available in German as ‘Das Geheimnis des Laufens’, and in Italian as ‘Manuale completo della corsa’

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In our book The Secret of Running we explained the power of the 4 energy systems of our human motor. The table below gives a summary of the maximum powers that are theoretically feasible with the world best athletes. First, we refresh for you what energy systems our human engine possesses and the fuel we have in the process. We conclude with a consideration of what you can still do on the last lap and in the final sprint.

Energy systems

Which energy system is used, the human motor itself automatically controls. At rest and when little power is needed, fatty acids are used as fuel. As more power is needed, so with an increasing speed in running, glycogen (carbohydrates) is also aerobically converted. Fatty acids and glycogen are the normal energy systems in long-distance running. The faster you run, the more power you need and the more glycogen you use. In an earlier article we have calculated what the required power and percentage of glycogen is for the world records on the long distances, see the table:

We see an unambiguous and logical relationship: the longer the distance (and therefore the lower the speed), the lower the percentage of glycogen and the higher the percentage of fatty acids.

But what about the (final) sprint?

Today we will discuss the (final) sprint in which the 2 most powerful energy systems also play a role, namely the anaerobic conversion of glycogen and the direct conversion of ATP. As can be seen from the table, with these energy systems you can produce much more power and therefore run faster.

The problem with this is, as is well known, that you can only keep this up for a short time. The anaerobic stock of energy in the muscles is very small, for ATP  in theory 12 kiloJoules and for the anaerobic conversion of glycogen in theory 21 kiloJoules.

In practice, it also appears that only part of this stock can be mobilized, in total order of 20 kiloJoules. With a runner of 60 kg, this is in theory already depleted after 20/60*1000 = 333 meters!

This is also the explanation for the fact that the speed at the track distances above 200 meters (and certainly above 400 meters) decreases rapidly and that the final sprint is always only started in the last lap of 400 meters. As can be seen from the table, however, you can mobilize a much greater power at the (final) sprint, so that the last lap is always run much faster.

World top runners who run laps of 62 seconds in the 5000 meters accelerate to 52 seconds in the last lap! Their speed thus increases from 23.2 km/h to 27.7 km/h!

How can you calculate how much energy you can mobilize for the final sprint?

In principle, you could do this with muscle biopsies. However, this is not easy and it is also questionable to what extent the results correspond to the actual situation in a race. However, Andrew Jones and Anni Vanhatalo of the University of Exeter (UK) have developed a very practical method to derive this from previous race results  at the distances from 1500 meters to 15 km.

Their method distinguishes between the ‘long-term’ energy systems (which they expressed in a CS, the critical speed that you can sustain) and the ‘short-term’ energy systems (which they expressed in D’ in meters).

The figure below gives as an example their determination of CS (5.91 m/s, so 21.3 km/h) and D’ (351  meters) for Haile Gebreselassie. The points in the figure show Haile’s PRs at the distances from 2K to 15K. The slope of this line is the CS and the intersection with the Y-axis is the D’.

We think this is a very useful method whose results are credible. Both the CS of 21.3 km/h and the D’ of 352 meters for Haile who has 21.3 km as hour record and was known for his strong final sprint. A big advantage is that in this way everyone can easily plot their own PRs to determine their D’.

Hans van Dijk has plotted his own  PRs  (from long ago, in the 1990s)  at the distances from 1500 meters to 15 km in the figure below. His CS at that time was 5.06  m/s (18.2 km/h) and his D’ 276  meters. These values are credible and correspond to his experiences. Hans had a good final sprint and ran an hour race in 18 km.

How can you calculate the final sprint and the effect of the race tactics?

Recently an interesting article by Brett Kirby and others  appeared in which this was convincingly demonstrated. This is an analysis of the World Athletics Championships 2017 in London. Mo Farah won, as expected, the 10000 meters, but at the 5000 meters he was ‘only’  2nd. In the final sprint, the Ethiopian Muktar  Edris turned out to be faster.

The authors of the paper hypothesized that Edris won against Farah because he could mobilize more energy supplies from the anaerobic systems. To test this, they used Jones and Vanhatalo’s model to calculate the CS and D’ of the participants in the 5000 meters and the 10,000 meters. The results are shown in the tables below.

The table of the 5000 meters immediately shows that Edris had the highest value of D’ (351 meters, against Mo Farah 268 meters). In the final sprint he was stronger than Mo. Farah could have won the race if he had run faster during the entire race, because his CS was higher than  Edris’s. This was also evident from the results of the 10,000 meters, where Farah won in a fast race from a.o. Kanworor  and  Hadis, who had a higher D’, but couldn’t keep up with the pace during the race due to their lower CS.

How fast can you go in the last round?

The authors also calculated how the stock of the ‘short-term’ energy systems D’ was consumed during the race. If you are forced to run faster than your critical speed CS during a fast race, D’ decreases. The figures below show the decrease of D’ during the 10,000 meters.

You can clearly see that the Kamworor did  not get a chance in the final sprint despite his high value of D’ at the start. The pace in the race was above his CS, causing his D’ to drop to 0. Mo Farah also had to dig deep, but in the last lap he had just some energy (and therefore a positive D’) left.

We also do not want to withhold a final convincing result from you, namely the relationship between the remaining D’ when entering the last lap and the lap time of the last lap, see the figure.

We find this a very impressive relationship with fast lap times of 52 seconds at a remaining D’ of 175 and ‘slow’ lap times of more than 60 seconds, when the D’ is completely used up (0 or less, then one only runs on the aerobic systems with the CS).

Conclusion

Long-distance performance are almost entirely determined by the ‘long-term’ energy systems (aerobic combustion of fatty acids and glycogen).  However, the ‘short-term’ energy systems (direct conversion of ATP and anaerobic conversion of glycogen) are of great importance in the final sprint, because they can temporarily deliver a significantly greater power.

How much energy you can mobilize in the final sprint can be easily deduced from your PRs at the distances from 1500 meters to 15K. The result is a theoretical ‘sprint’ distance D’ in meters (order of 150-350 meters).

A higher value means that you basically have a good final kick. However, the result of the race and how fast you can go on the last lap is also determined by the race tactics. In a fast race, your D’ can become exhausted during the race, so you can’t keep up with the pace.

With these calculations it turned out to be possible to convincingly explain why MoFarah could win the 10,000 meters at the 2017 World Athletics Championships, but not the 5000 meters. The 5000 meters was a ‘slow’ race, allowing  Edris  to finish with a high D’ and fast final kick.

There also appeared to be a convincing relationship between the remaining D’ at the start of the last lap and the lap time of the final lap. If you don’t run faster than your CS during the race, you can make maximum use of your final sprint in the last lap.

With the described method, it is in principle even possible to make a prediction of the winner (the one with the best combination of CS and D’) before a race AND to adjust this prediction during the race depending on the pace of the race and the exhaustion of D’ among the runners.

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Our book ‘The Secret of Running’ is for sale in our webshop. Also available in German as ‘Das Geheimnis des Laufens’, and in Italian as ‘Manuale completo della corsa’

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