This article was first published in Cycle Coaching #2, 2001. Most of the
research with SRM Power Cranks has been conducted by sports scientists.
Richard Hanson used them for time trials for most of the 2000 season.

I always figured that it would be very useful to know exactly how much effort I was expending at any given time whilst riding my bike. So I bought a pair of SRM Power Cranks and here is what I think so far.

The cranks demonstrate very clearly exactly what I am producing through the pedals. In the first month of using them they revolutionised the way that I approached training. Suddenly I could achieve very accurate training outputs in all weather and terrain conditions. I do most of my winter training solo and the SRM Cranks are superb as a source of motivation whilst out alone for hours in pre-season riding. Before using the cranks I would have relied on heart rate as a guide to overall effort. However in the last few seasons I have found that this was not accurate enough. Whilst stringing several hard sessions together over the period of a few days I found that my heart rate would stay static or sluggish for the first half of any session and then only rise moderately for the second half of the ride, despite the amount of effort I was producing.

The SRM cranks record and display on a handlebar mounted meter, current power in watts, heart rate, cadence, distance, time and speed. Averages and maximums can also be accessed for power, speed, cadence and heart rate. It is also capable of recording intervals and producing the above information for a specific interval. With the system comes a software package and all the above can be downloaded into a PC and reproduced in graph form after the ride. As the name suggests the cranks have two strain gauge stripes set within them and these constantly monitor the deformation on the chain ring when the rider applies pressure to the pedals. The system comes encased in a water-proof circular drive wheel with the chainrings attached, and this fits on to the bottom bracket like a normal set of cranks. The information on power, cadence etc is passed to the handlebar meter via the usual set up of a coil and wire fed down from the handlebar-mounted meter to the bottom bracket casing.

My approach to training has now become a lot more specific. I am now confident that I can go out on the bike and achieve very accurate sessions whilst at the same time recording and developing a complete training log of valuable data as I progress through the next few years. On a more practical short-term basis I have found that headwinds no longer demoralise me as the feedback that I receive shows that although I am riding slower I am still making the desired effort. Tailwinds are no longer as relaxing as they used to be. The cranks soon show the drop in power if I fool myself into believing that it’s me that is causing this great surge in speed. I have learned to average out the power whilst climbing hills rather than starting too hard and dropping off and consequently have had to use very big gears to keep the power on whilst descending the other side.

At present I ride time trials during the racing season and I have been able to calculate the amount of average power that I can produce for a given event from the maximum power that I can create. Whilst racing I use the cranks to produce a constant amount of power through the whole race rather than starting too fast and then struggling the last few miles. This has proved fairly successful on hilly courses and in windy conditions where it is all too easy to burn out before the end of the event.

Recording this data has also shown clearly the increase in power from early season races to mid season of about 12.5% in 25mile time trials. For example I completed my first 25ml TT on the 14 April 2001 and produced a time of 59min 16sec and a power output of 292w. I then trained and competed for the next seven weeks and completed a 25ml TT on the 10 June 2001, achieving a time of 56min 25sec and a power output of 329w. I then use this information as a benchmark to try and improve power output over the next month. If power output increases then the cycle repeats; if power drops, then I can look to see if any changes are needed in my training programme. The graph shows my power output in a 25ml time trial.

During mid-season training sessions I have been using the cranks to help develop power and endurance specifically for 10 and 25mile time trials. I have been able to go out on the road or on the turbo and complete session and interval work. One problem that I always faced doing interval sessions is trying to muster the same enthusiasm to push myself as I do during races. The cranks go some way to filling that gap between racing and training. For example, while racing I know that I can complete a 25ml TT at 330w and a 10ml TT at 350w. In order to improve my 25ml TT power output I would try to complete three 20 minute sessions at 340w each with a ten minute rest between each. For an improvement in performance in 10ml TT I will complete ten two-minute sessions on the turbo at 360 - 370w with two minutes rest between sessions.

By constantly monitoring the power output I find that I can create motivation in my training session as I can see that what I am putting through the pedals during that particular training session relates directly to my future performance in races. It would be fair to say that I have found SRM Power Cranks to be very useful in the few months that I have had them. They are excellent as a daily training tool and source of motivation in the short term.