Why Should You Use A Power Meter in Training?

The Benefits of using a Power Meter

How do you make the best use of your training time? In short, we at Halocycles.uk would say use a power meter! Why? Well, they are single biggest thing that improves performance – mainly because they make training more objective and efficient.

How Does A Power Meter Do This?

  • Power is the absolute measurement of the work you are doing.
  • It measures the total work you have done over a period of time.
  • It helps you make the best use of your time on the bike.
  • It helps you target your training – making it more specific
  • Acts as a great motivator, making indoor training especially more targeted.
  • It helps you identify weaknesses and track improvements
  • It helps you work out when you are too tired and can stop you over training
  • In the end – makes you learn more about your body.

Power is the absolute measurement of the work you are doing.

It’s as simple as that. A power meter measures the work you are doing in an absolute sense. No matter what system you use and for this discussion it doesn’t matter, a power meter measures the power you are putting through the pedals, and assuming losses are pretty minimal, driving the bike forward.

Everything we are going to talk about with respect to training with power comes from that simple idea. Before we go on it is worth looking at the other ways of measuring work that have been and in my opinion, gone.

Distance and Speed
First there was the speedometer and mile counter. The classic, I have been doing 400 miles a week or I did 120 miles on Sunday boast was a way of measuring how much work we have done. In some respects it worked on a macro level, 100 miles a week as opposed to 300 miles does quantify a different level of work. And if you were a rider capable of riding 300 miles a week – week in, week out then you would expect to be stronger than someone only doing 100 miles per week. But that’s where the benefit stopped.

Distance had no way of judging how hard you were going. In some respects average speed added a little bit more info but it is so dependent on environmental factors that it is almost meaningless.

Heart Rate
The next thing to come along was heart rate. This was the revolution of 25 years ago and took training to another level.

It gave us the ability to train at different levels and intensities. Pioneering sports physiologist, Peter Keen developed 4 zones of training when he was working with Chris Boardman prior to the 1992 Olympics – where Chris won the pursuit. It was the first tine that the general public could assess how hard they were riding and actively choose how to target their training.

But, heart rate is the body’s physiological response to a training load and work. It is not a measure of the work itself. It lags behind the effort and can be affected by many things, so is not always accurate. Hydration, fatigue levels, anxiety, hunger and temperature will all affect your heart rate. So, prescribing training on narrow heart rate values cannot always be totally accurate.

Don’t get me wrong. Heart rate is better than nothing, especially if you can use it in conjunction with how you are feeling, but power it is not. For most people and coaches now, power then is the gold standard way of measuring your effort.

Why Do We Want to Measure Our Effort?
In simple terms, we need to measure our effort because without doing so, we cannot know how hard we are trying, if we are improving or not and more importantly what type of training to do.

Power Measures The Total Amount Of Work You Have Done over a Period Of Time.
To understand that statement we need to think of what training really is: The purpose of training is to apply a physical load or stress to the body. This breaks the body down and then it grows back stronger after resting. The bigger the load you can give the body, before it breaks completely, the stronger you will be. So the first goal of training is to continually apply a bigger and bigger load to the body. The second goal of training is to make sure it is the right load.

Personally, I think one of the first benefits of using power is to measure your total amount of work. Every ride gives you a figure for the work done in kilojoules. Roughly one kj = 1 calorie, so it also helps you to work out how much food you need to eat to fuel your training. Just knowing the total amount of work done in a week or month can be a real motivating power.

I find that in the winter, when rides are pretty constant and steady then the best measure of whether you are doing enough work to improve is your monthly kj figure. October, November, December and even January. If you can plan and see an increase in work on each month, you know you are moving forward. It’s almost back to measuring in miles – but not quite. The next benefit tells you why.

Power helps you make the best use of your time on the bike.
This benefit comes directly from the fact that a power file from a ride measures the power you are producing on a second by second basis. If we go back to using distance to measure effort, then 60 miles sounds like quite a decent ride. But how much effort was that ride really? And is 60 miles, really 60 miles? I propose that its not.

With a power meter you are recording data every second. You should have cadence, speed, heart rate and power for every second of the ride and one of the simplest ways of looking at that data and judging how much work you have done is the time in zones chart for the ride. The following two pictures show two different 2.5 hour rides. The first was a recovery ride done as part of a big group in Majorca. The time in zones graph on the bottom left shows a lot of time spent in a zone I jokingly call lazy freewheeling…. Although the average speed was quite reasonable with the ride being 47miles, the total work and the Training Stress Score (TSS) were quite low.

The second ride was a week later and although only 42 miles were completed in roughly the same time the ride was much harder with most of the ride spent in endurance and tempo zones. The total work and TSS were much higher showing that this ride has a greater training load. If you can monitor this you can make your riding more efficient.

Power helps you target your training – making it more specific
Following on from making better use of your training time the next refinement is that a power meter will help you make your training more specific. The two rides above were unfocussed rides, there was no goal to them except just riding the bike. Any coach will tell you that every ride should have a goal, whether it is recovery, a big endurance day or high intensity time trial efforts. With a power meter on your bike you can target your training to what ever you or your coach choose.

You can ride at the levels set and then when you get home look back at the file and see how well you did. The file below is a 2 hour tempo (Z3) ride. That was what was set and the rider did it exactly. Come the end of the ride it would have started to hurt but just being able to see what power he was doing the rider managed to complete the set training.

Power acts as a great motivator, making indoor training especially more targeted.

Motivation. This is a great aspect of training with power. Because we can define very specifically some of the efforts, its easy to know what to do and this is a major motivation factor. Indoor trainers are not the easiest of things to use and people are often scared of them. But if you go into a session with a defined set of intervals at a defined power level then that can make a massive difference. 4 x 5min threshold efforts sounds a lot better than just ride hard a few times…..

Power helps you identify weaknesses and track improvements

This is one of the big things power can do for you – help you identify your weaknesses. Take the indoor training efforts. If your coach has set you 6 x 3 min efforts and you can only mange 3 then you know you are less used to intense efforts and they fatigue you more than expected.

On the other hand, if you are trying to do 20 minute sweet spot efforts and just collapse after 10 minutes then you can see that you need to practice these more. In races, time trials or the bike session on a triathlon you can look back at power files and see if you got the pacing right. Did you go too hard to start and then die off?

Looking back at race files can give you a clue as to how to ride them in the future. Some people can go above threshold easier than others. If you look back and see that on the races where you went too hard for a while you just exploded, then you know that pacing is incredibly important for you. If on the other hand a few minutes above threshold doesn’t seem to damage you too much then that is great to know. 

In terms of improvement, as you get stronger you will find reaching certain power levels gets easier. If you time trial a lot you will see steady state power levels increase. If not, conducting tests will enable you to see that you can produce more power than you used to. In short, tracking the numbers of all your races and rides gives you the chance to see how your body has changed, hopefully for the better, over time.

Power helps you work out when you are too tired and can stop you over training

As you spend more time riding with and using power one of the more sophisticated benefits is the ability to spot when you are getting too tired and perhaps overtraining. On a simple level, if you are set 6 x 3 minute intervals at 300 watts say and after the second interval you can’t keep the power that high, then on that day you are tired and you should stop training. That is a great, objective way to know if you need to rest, and often just backing off for 24 hours can make all the difference.

One measure of work that we haven’t talked about is something called Training Stress Score – TSS. This is a measure of the work of a ride relative to your FTP. If you ride at your FTP for an hour then your TSS score is 100. It doesn’t matter what the level of your FTP is, mine might be 280 and yours 380 but if we ride at that level for an hour it causes the same amount of stress on our bodies. Once we start using TSS and seeing how much we do in a week then we can start to assess if we are doing too much and also how big days affect us. If you have been training at around 400 TSS per week and suddenly jump up to 700 then you would expect to feel very tired and actually need a rest. Over time you can begin to find what levels make you tired, what levels make you ill and what levels you need to come down to for a taper.

If we remember back at the start I said that the goal of training is to gradually increase the load that your body can absorb. Using TSS gives you a very precise and objective way of measuring and achieving that.

In the end – Power makes you learn more about your body.

Finally, what power meters really help you do is learn to understand your body, how it works, what it can cope with and how best to make it go faster on a bike. You can use a power meter in different ways at different times of the year. In the winter you can watch your monthly work totals go up. Pre and early season you can use it to build threshold power and practice race winning attacks. Leading up to target events you can fine tune your form and then finally concentrate on rebuilding endurance that constant racing can sometime erode for the last part of the year. It is the ultimate cycling tool.

As ever, if you want to know more about power meters and Infocrank call Peter on 07973 909455.