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Cycling Training Tips

Polar S-410 Gives a Rough Estimate of Energy Expenditure

Many heart rate monitors and bike computers has a feature to measure the energy cost of the exercise. But can we believe these numbers? I have always been sceptical to these calculations since they are based on very few variables (percentage of maximum heart rate and total time). I have always said to my riders that they can use these numbers for fun, but don’t count on them when they cook dinner. There is probably huge variability in the quality of calorie metres, some gives a rough estimate and some doesn’t.

Can heart rate monitors be used to calculate energy expenditure?

Yesterday I found a study published in Medical Science of Sports and Exercise that tried to figure out how accurate the energy expenditure calculator of the Polar s-410 heart rate monitor was. They used three different calculations of the energy expenditure: 1) Polar s-410 using predicted values of VO2 max and maximum heart rate. 2) Polar s-410 using actual values of VO2 max and maximum heart rate. 3) Indirect calorimetry (You might have heard about this one in school”¦)

The results showed that the Polar s-410 did a quite good job for the men with no significant differences between the three calculation methods. The women’s numbers were overestimated when using predicted values of VO2 max and maximum heart rate. The estimation was better when they used the actual values but still overestimated with 12%.

Read the full article about Polar S-410

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How To Use a Heart Rate Monitor for Cycling

A heart rate monitor is one of the most used tools for pacing strategy during intervals or competitions, analyzing of performance and detection of overtraining. Polar heart rate monitor watches make very precise measurement of the current pulse. This information can be very useful for an experienced user who understands the exercise physiology behind heart rate regulation.

Getting started
One of the best ways to learn to use a heart rate monitor is to use one during training. Don’t buy one of the top models from Polar (cs600, s725 etc.) – these watches are not made for beginners. Instead try one of the basic Polar monitors for a beginning. These watches are cheaper and easier to deal with. There are also several other manufacturers of monitors and some of them are probably cheaper. My point is that for a beginner who has never tried heart rate monitors before, it might be a clever idea to buy one of the cheaper models for a beginning and then buy a more advanced heart rate monitor when you know which kind of data you are interested in. A Polar cs600 is a great tool for experienced riders, but is very likely to be overkill for a beginner.

Notify how your heart rate reacts
When you have bought a heart rate monitor: Get out on the roads! Spend a month with your regular training program, just wearing the monitor, but notifying how the heart rate reacts to the efforts. It is very interesting to study the heart rate and very quickly you will discover that you start to use the monitor for pacing. At this point you are already getting paid back for your investment, since you train harder and are more motivated during the ride.

Watch your own heart rate monitor – not your training partner’s…
The fact is that you can only compare heart rate values with your own previous registrations. The reason for this is that we all have a different anatomy of our cardiovascular system. But these systems are all based on the same physiological mechanisms. Thus, we can learn from each others’ physiological experiences and adaptations, but we can’t compare individual heart rate values. E.g. your resting heart rate is 58bpm while your friend’s heart rate is 42bpm, still I can’t say which one of you are in the best shape nor have the highest VO2 max.

Your maximum heart rate is correlated to your age, but that does not mean that we all fit in to 220-age formula. There is a huge standard deviation because we all are anatomically different. Just like with the resting heart rates, maximum heart rates does not predict performance.

Be patient
It is not necessary to use a special heart rate focused training program when you start to use it. As I said, just wearing the monitor for the first month is a very good education. I remember when I started to use a heart rate monitor for the first time back in the mid 90’s. At that time I had read some literature about general exercise physiology and heart monitors, but I lacked practical experience with the monitor. The result was that I made some target intervals for my heart rate which triggered the alarm system to beep most of the time. After a few of these rides I started to ride without target zones until I knew more about how my heart rate reacted during cycling. The lesson I learned was that you have to be patient and wait a while before you start doing intervals based on heart rate target zones.

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Maximum power output or watts per kilogram?

Today is the first stage in Tour de France 2008 with big mountains. This is always an exciting stage to watch because it is the first really indication of who will be able to win the yellow jersey. Nevertheless, we will ver likely only find out who will NOT be able to win the yellow jersey today. But it should certainly be interesting to watch.

You will probably hear the commentators talk about the skill climbing and maybe also a bit more technical about how many watts each rider has performed in tests before the Tour de France this year.

Watts the problem?
It seems like there are two values when people discuss power outputs: Watts and watts per kilogram. The first one is an absolute value that predicts performance in flat races while the second one is often used to predict performance on hills. Watts per kilogram is often used as a more sophisticated way to present physical performance because it represents a power output that is relative to your body weight. Experienced riders already know that when you climb, body weight matters. Thus, additional fat stores are more expensive to carry on mountain stages than on flat stages.

Watts per kilogram the golden standard?
Watts per kilogram is often a better indicator of overall performance than absolute watts. But it is not as precise predictor of performance as it could be. With some simple adjustments it would give you a better picture of how you will perform. What I am talking about is making some values that give the body weight slightly less impact when you predict climbing performance and add some impact to your body weight when you predict time trial performance.

It all depends…
The reason for these modifications is because climbing results cannot be predicted by watts per kilogram only. The problem appears when small riders achieve greater values in watts per kilogram, but don’t win the mountain stages. This can be explained by the fact that the external weight of the bike is carried by the rider independently of body size and several other factors that influence on overall performance e.g. gradient, wind resistance and tactics. Thus, it is not possible to simplify the prediction of performance by using the metric watts per kilogram. Yes, that is definitively one of the best predictors we have, but it can be optimized with some modification and other factors should also be at least considered.

Watts per kilogram^X would possible be a better predictor of performance because there are no events that can be predicted accurately by watts or watts per kilogram only. Body weight will always play a role and normally play the biggest role in the mountains (X closer to 1). Also it is worth to remember that body weight influences on time trial performance even though it is not very important in flat time trials with a constant high race velocity (X closer to 0).

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