In some ways, accuracy is the easiest thing in the world to describe. Something is either true or not. 300 watts is 300 watts or it is not!
However, the concepts can be quite confusing sometimes, so I just want to work on one issue today. The question is, “Can you measure the radial forces?”
Firstly, what are the radial forces?
They are the forces that are applied to the crank which presses it inwards or outwards, usually by foot placement at different times during a ride or sprint.
The short answer is that InfoCrank does not measure any forces except the tangential force – that’s what drives the bike forward and constitutes the energy the cyclist applies in order to move the bike.
Technically, this is because our software, strain gauge placement in a Wheatstone bridge formation and bonding techniques all combine in such a way that no other force can register. No; we do not measure radial forces. In fact, we nullify them completely.
Just assume for a moment that we built an InfoCrank that did not nullify the radial (and other) forces? What most people do not realise is that we would still just get a number purporting to be watts. What we would not know is how much of that number was actually watts and how much was something else.
Our rider may sprint and his foot may move outwards which would show up as increased watts but no one knows if it is or not.
Therefore, the only way to measure radial force is to purposefully measure it. Measuring all the forces and then trying to build out algorithms to separate them is one of the main reasons most power meters are vastly inaccurate in real life. Real life is complicated.
With an InfoCrank, no matter how the pressure is applied to the pedal, the power result is the same. It does not differ if your foot is 25mm from the crank or 35mm, or if you have a different pair of pedals. 300 watts is 300 watts – that is your energy put into making the bike go forward.
But what if we built an InfoCrank in such a way that we measured both tangential and also radial force? Now our 300 watts is going to vary up and down and we are going to have no idea how much of that is due to differing foot pressure and how much is driving the bike forward. We are going to have to build an algorithm and assume all sorts of things such as riding style, leg tiredness and seat height to try and isolate out the radial force. What a mess!
So, no we don’t measure radial force or any other force except tangential. If you want us to, we will build a specially instrumented crank or pedal to do so but that would be when you discover that no one really wants to know radial force and certainly they do not want to pay for it…
It’s a really good idea to supplement your endurance training and high intensity training with some exercises off the bike to help build your strength. The actual time you need to spend on strength exercises is really very short, but very important if you want to make your muscles stronger, not just faster.
Here’s one of our favourite isometric exercises – we challenge you to give it a try and see if you notice the difference in your quads.
Due to its nature, cycling is to a large extent a non-load bearing activity, however humans are designed to take load, so we need to do some load bearing exercises. You can use weights if you wish, but one of the best weights is the human body.
An isometric exercise is where the muscles are placed on under tension but are not contracting (in the below example not rotating on the crank). This isometric exercise is best when your bike is fixed on a trainer.
Lock the bike down safely so the cranks can’t move, you might for instance apply the rear brake as tightly as you can.
Then position your cranks at around 30 degrees and apply all the pressure you can till you lose form.
Stop, perform the same exercise on the other leg, then rest and repeat.
Build up both time and pressure.
You can measure the instantaneous torque with your InfoCrank (via the VINC app available from the Google Play store) and then strive for new records every week. It’s likely you can probably only hold the maximum torque for 15 seconds, so doing a couple of sets is not a real time issue – but the payback is huge.
Here you can see a set of two Isometric exercises and then a Zoom into one exercise. These charts and data are available for subscribers to VINC Pro – get in touch to find out more.
Using a power meter enables you to carefully monitor and structure your training sessions in order to gain as much benefit as possible from any given session. When increases in power can be measured and accurately tracked over time, it becomes possible to better understand your body and how it responds to different types of workouts.
Power meter technology is what has enabled cyclists of the modern era to become increasingly specialized and accentuate the precise physical characteristics necessary to dominate in any given discipline, be it road, track, mountain bike or BMX.
Very broadly speaking, cycling events can be split into two categories – power-based events such as the Track Team Sprint or BMX, and endurance-based events such as the Track Team Pursuit or Tour De France. This is not an entirely clean characterisation as a degree of endurance is required in power-based events as well as vice-versa, but where one or the other predominates we can reliably say it falls within its respective category.
Mark Cavendish may be said to be a hugely successful sprinter, but he is by no means a power based athlete in the conventional sense. Surviving a three-week Grand Tour takes exceptional levels of endurance, but we can also say that alongside all other Grand Tour riders, Mark is an exceptional sprinter. After three or four hours of endurance-based racing, he possesses the relative power advantage to cross the line first.
Power output is the best indicator of how a cyclist may perform when they are attempting to maximise their speed, yet absolute speed within cycling is a truly multi-faceted and complicated beast since it is entirely dependent on context. Aerodynamic drag, body position, weather conditions, discipline, duration of effort and terrain are just a handful of factors that any cyclist will wish to understand before he or she decides if a given speed is worthy of respect.
If power output matters, what is actually being measured when measuring a cyclist’s power? In simple terms, the power of a cyclist is contingent upon how much force they can push their pedals round as well as the speed at which they are doing so – maximum power is obtained when the force on the pedals multiplied by the crank’s cadence (RPM) gives the highest figure. We can say:
Pedalling Power = Force On Pedals x Speed Of Pedals = 200N x 3m/s = 600W
N = Newtons
m/s = Metres Per Second
W = Watts.
Any increase in either cadence or force will therefore result in an increase in power. To be able to visualise how much power is being generated, simply divide the Watts figure by 10 and convert it to Kilograms – such a weight will be lifted by 1m in 1 second. So in our example, a cyclist producing 600W is producing enough power to lift 60kg by 1m in 1 second. That’s the same thing as lifting an average sized human female 1m vertically in a second! But what does all this tell us about the power output of the different types of professional cyclist?
Unsurprisingly true power-based cyclists such as track sprinters and BMXers generate the most power. In fact, on the GB Cycling Team the most powerful athlete in 2012 was the BMX rider Liam Phillips. Liam was able to generate more power than Sir Chris Hoy due to his super-fast and explosive cadence. Amazingly elite level BMX riders can generate in excess of 2200W during their 1.5 second run down the 8 metre start hill. They accelerate from 0 – 60km/h in this time, which is as fast as pretty much any supercar available today, and lift the equivalent of 200kg a vertical height of over 1 metre.
To put this in context, that is three average sized fully grown men elevated 3 feet! If you consider this alongside BMX athletes’ ability to hit 15m long jumps at 50 km/h and land them within 10cm every time, you begin to see the true talent of these athletes. They truly are exceptional. They can’t of course maintain this power output for sustained periods, but that is not the point in BMX. They fight first to the bottom of the start-hill, and then to the end of the first straight. Whoever enters that first corner first becomes the man or woman to beat.
At the other end of the endurance and power continuum, you find Grand Tour riders who look to be able to sustain the highest power possible for a three-week duration, as opposed to bursts of 1.5 seconds. Most top Grand Tour riders will produce a fifth of the power of Liam, but they can hold that power for maybe an hour or more on a given climb or time trial.
Bradley Wiggins produced 440W on average for his entire hour record, which is a staggering feat, and for endurance events such as this the mental toughness required to maintain such an output makes the feat even more remarkable. For most mere mortals, holding a power number between 150W and 200W for an hour would be a respectable achievement.
So, we can see then that although power output is an excellent indicator of how fast a cyclist is able to propel themselves, we can also see that power output alone tells us very little, we need to understand the context too.
Most physically fit people could generate 440W, but none of them could do so for an hour. Different professional cyclists produce varying amounts of power within different disciplines to meet the physiological demands of their specific discipline.
But unless you wish to become an elite level BMX athlete, at which point you will need to develop truly exceptional bike-handling skills, it’s sustaining the power numbers that really makes the difference to your performance. This is why it’s always crucial to decide what your goal is ahead of time and train scientifically toward that outcome.
The Verve InfoCrank is the most accurate and repeatable power meter available today, and is used by most of the world’s dominant track cycling nations, as well as triathletes, rowers and eSports cyclists.
In the world of competitive cycling and coaching many things are said about the accuracy of power meters. What is acknowledged by all is that knowing and training the power of the athlete is the single most important determinant for success. The energy (watts) expended by the cyclist in driving the bicycle forward determines everything else.
But confusion runs rampant and logic is totally lost due to the misinterpretation of the simple word – accuracy.
Most athletes and their coaches try to explain accuracy in terms of consistency. They say that the only thing that matters is that the results from their power meter are somewhat consistent.
In this case, half right is totally wrong. It is logically impossible to know (as an athlete or coach) if your power meter is consistent if you do not know if it gives true results. That is why the actual definition of accuracy is defined as having two parts:
Trueness. – is the closeness of a measurement quantity to that quantity’s true value. In other words, it is the extent to which the measurement is error free.*
“Precision” – is the degree to which two or more repeated measurements show the same results each time. Sometimes precision is referred to as the reliability or consistency of the measurement.*
It is possible if you have extensive testing facilities to determine whether your device shows consistent results, without necessarily ever showing true results. But for the cyclist on the road and the coach looking at results, it is impossible.
With the advent of the InfoCrank, acknowledged as the power device that is both true and precise the whole time, there is a sea change about to happen. The InfoCrank has been independently tested for both torque (measured 256 times each second) and for power (watts) which combines the torque and the cadence to a level of accuracy (both parts of the definition) that in simple terms, the number on the screen of the athlete is always the correct wattage number.
For the first time, leading federations and coaches are realising that they now have a tool to help with selection of athletes for teams. Because they have trueness and precision all the time on every bike, they can directly compare each athlete and make selections accordingly.
Many commentators may have assumed that this was happening before, but it was not the case. Some federations knew that their devices were quite consistent, but not directly comparable bike to bike or rider to rider. This has now changed.
However, some competitive amateurs also knew it, but not because of expensive measurement tools. Riders who use certain indoor spinning machines with a crank based power device go to extremes to mark their favourite machine. They have learned that their perceived effort differs machine to machine and has no relationship to the number being shown on the head unit.
A break-through is now easily predictable. Over the next years, say leading up to the Tokyo Olympics, there will be very significant improvements in cycling performance and not because of the chemists and doctors.
With only consistency (at most) to go on, it was quite a random exercise to have anyone other than podium athletes really train at the specified level. The data was only viewed after the event, so normally only averages were observed. As the cyclist changed bikes from the road to the track or vice versa, the numbers differed greatly as they did in different environments.
The Cyclist did not know as they rode their intervals how closely they were maintaining their workload and so nearly all riders, even with all the technology available, have been training on Perceived Effort with numbers to prove it. This is why well-known professional riders say they do not ride with their power meters. They are very well tuned to Perceived Effort and the power estimator does not add particular value to them.
Have a look at the 50 second excerpt below from a steady ride (on a real climb) where the athlete was attempting to maintain 250 watts. The InfoCrank showed the right number each pedal stroke as it has been independently tested to do.
The other power device (claimed to be accurate to 1.5%) showed numbers that varied second by second in a 100 watt range, both negative and positive. For the rider who wants to measure his effort, he truly has no idea what power is being ridden.
Many coaches might be satisfied with the uploaded data after the event, because after all the fluctuations, the average result is OK. The rider, the one who is riding the effort in order to improve, never had any idea what pace he was riding and does not know until later.
No wonder that professional riders when asked what they want from a power meter, say simply, “ I just want the right number”.
The advances in cycling performance will come from a combination of things that follow from having true and precise numbers all the time.
Firstly, the Bio Feedback loop, (what the legs are feeling, what the head unit is showing and what the eyes are seeing) will enable the athlete to control their efforts more closely than just by using Perceived effort and power estimations.
This in turn will enable controlled breakthroughs in thresholds and improvements in maintaining them. The coaches will be key here as they adapt from averages to true numbers.
The pedal stroke itself will come in for significant improvement as that same feedback loop uses the intra-pedal stroke accuracy to voluntarily improve individual muscle performance and train fine motor skills. The biomechanics, the bike fitters, the physiologists will all be key here as they ensure that the rider and the machine are optimised for his/her event.
All that will need to have to happen for a quantum leap in cycling performance to occur is to listen to the riders – They want the right (true) number and they are getting the point!
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