by Jesper Bondo Medhus on August 12, 2007
Power meters are very expensive and for many people it is a big decision to buy one. Polar
offers one of the cheapest power measurement systems on the market, so it was interesting for me to see how it performed compared to the much more expensive SRM crank system. SRM crank system uses torque and angular velocity to measure power output, while Polar uses the vibration and speed of the chain to calculate power output.
British scientists made a study with 12 trained men who made 12 all-out efforts separated with short recovery periods. This study setup is very demanding for the power meters, since the stress on the bike is very high. The purpose of the study was to compare the agreement between these two different systems. The results were published in Journal of Sports Science, August 2006.
Polar underestimates power output
The main finding was that Polar underestimated the power output and did not agree with the power output from SRM. One of the great problems with the Polar was that it was greatly influenced by chain vibration and sampling rates.
These findings agree with the experiences I have been told about Polar. If you ride on cobble stones it is not reliable at all and it is necessary to change chain often. It is obvious that you can not get a precise system like SRM and only pay 1/10. For me Polar offers a cheap entry level for riders who would like to explore power outputs without spending all their money. I believe that you can make analyzes of races and get a good feeling of how races are. But I am not sure, that Polar is good enough for pacing in intervals. Maybe I should go try one?!
Reference:
Hurst HT, Atkins S. Agreement between polar and SRM mobile ergometer systems during laboratory-based high-intensity, intermittent cycling activity.
J Sports Sci. 2006 Aug;24(8):863-8.
by Jesper Bondo Medhus on August 10, 2007
Inspiratory muscle training is done against an external resistance when you breathe. There are several products (POWERbreathe, PowerLung, Ultrabreathe etc.) on the market claiming they can significantly improve your endurance. I have done some studying in Cochrane Library and Pubmed to figure out what we know about inspiratory muscle training for trained cyclists.
Inspiratory resistance training improves maximum inspiratory pressure
Nearly all studies find that it is possible to improve the maximum inspiratory pressure, but it remains uncertain whether this improvement actually affects cycling performance. Most studies have in common that they have used very small study groups with less than 10 participants in each group in the randomized placebo controlled studies. I am pretty sure that inspiratory muscle training does affect maximum inspiratory, but these respiratory muscles are also trained during hard aerobic exercise.
Respiratory muscles get exhausted during hard exercise
The first time I was introduced to exhausted inspiratory muscles was after a long race with a very high intensity. When I took a deep breath afterwards, I could feel pain in my inspiratory muscles. My conclusion was that vo2 intervals and racing probably gives your respiratory muscles a great stimulus.
Inspiratory muscle training – Yes or no?
As I have previously discussed, it remains uncertain whether strength training improves aerobic endurance. It seems like we have a similar problem with respiratory resistance training: Strength training for inspiratory muscles and skeletal muscles both increases maximum strength, but it remains unsure if there is a benefit for you in a competition.In a Cochrane review it is concluded that “Currently there is insufficient evidence to suggest that inspiratory muscle training with external resistive breathing devices provides any demonstrable clinical benefit in patients with asthma.”
So until we get more scientific evidence, I can not advice you to use respiratory resistance training regularly because there is not (enough) evidence for its benefits. On the other hand there is no doubt that instruments like Powerbreathe, PowerLung or Ultrabreath can train your respiratory muscles in a way you can’t train them during endurance training. I can’t think of any unwanted side effects to respiratory training, so if think it sounds interesting you can give it try. They are non-invasive and inexpensive, so it might be a cheap improvement for your performance.
by Jesper Bondo Medhus on September 26, 2006
Your body position and the bike’s aerodynamics play a big role in time trials. A couple a years ago I read a comparing of different body positions and what influence it had on the finishing time in a 40k time trial. I am not sure, but I think I saw these results back in 1997, so this is not breaking news, rather nostalgic news.
Aerodynamics is important in time trials
An interesting question is how much time you can save by using expensive aero wheels, an aero frame or saving some pounds? There are probably more precise answers to these questions than this report calculates for you, but it gives you an idea of what difference these changes can give you.
One of the interesting findings is that slower riders will benefit more from a lighter bike than top riders will, while aero wheels and frames will give the biggest advantage to faster riders. This is probably because the aerodynamic drag requires a relative larger percentile of the workload at high speeds.
Optimized aerodynamics is better than weight savings
The conclusion for this report is that the biggest changes in aerodynamic drag and in cycling performance come from changes in body position. A more aerodynamic body position can improve your 40k time trial by over 6 minutes (that is really something!) The report also concludes that improving the bike’s aerodynamics is more important than weight savings. A pair of aero wheels can reduce you 40k time trial time with 1 or 2 minutes.
Read the report about cycling aerodynamics
by Jesper Bondo Medhus on September 24, 2006
Carbon cycling shoes look better than traditional cycling shoes made of plastic. But the question is, do they perform better or are they only more expensive? Well, I found a scientific study that tested the stiffness, which is a very important detail when I decide which cycling shoes to wear. Comfort and weight are also important factors, especially comfort. It is though important to remember that shoes with the best comfort often lack stiffness. It is very difficult, if not impossible, to achieve a high degree of stiffness and comfort at the same time.
Carbon cycling shoes are stiffer
In the study shoe stiffness measurements were collected under controlled conditions in the laboratory with a dynamic hydraulic tensile testing machine. Measurements of plantar pressure were done using a special sensor in the soles while subjects pedalled at a controlled power output. The results from these tests showed that the carbon cycling shoes produced a significant, 18% higher peak plantar pressure than plastic cycling shoes. So carbon cycling shoes are stiffer and that is also what riders tell me when they have switched to this more expensive foot wear.
by Jesper Bondo Medhus on August 22, 2006
How effective can a set of short-term sprint intervals compared to regular endurance training at a comfortable pace be? It is well known that interval training can be time saving, but in July 2006 there was published an interesting study in The Journal of Physiology. The scientists compared the outcome of low volume sprint training [...]
