Power Meters 2 – The FORCE

On Wednesday, I wrote about power meters and there advantages.  Today, I would like to explain how you can learn from a power meter without even owning one.  If you do own one, great, this will help you gain a greater understanding of what you can learn from one.

To review, a power meter is simply that, it gives you the amount of power you are putting out at any given time in the unit of measurement called Watts.  If you produce power for long periods of time then you get work done.  Each race course requires differing amounts of work to complete it.  The higher your power, the sooner you will get the work done and finish the race.  To review the whole article click here.

You need to think like a power meter in order to learn from it without actually owning one.  A big advantage of owning a power meter is that it helps you to pace a race better.  That is a topic in and of itself so I will not digress at this point in time.  However, one component of pacing is learning to distribute force effectively throughout a race and that is what I want to talk about.

Back to physics for a second:

simplified: Power = Force time Velocity

This is how cyclists produce power.  By contracting our muscles we are able to produce force and we are able to do so at different velocities.  Muscular Force X the velocity it is produced = Power.

This equation tells us:

> The more force you exert the more power you get.

> The faster you exert the force the more power you get.

We can get tired both ways.  If you exert a lot of force (i.e. weight lifting) then you can get tired very fast.  If you exert a certain level of force but at very high velocities (sprinting) then you can also get very tired quickly.

In a hilly race, how you distribute your force can effect your pacing and hence the outcome of the race.  Think of it in terms of weight lifting.  If you lift a lot of weight then you get tired in a short amount of time.  The same thing can happen in a race.  If you exert a lot of force (on hills or into the wind) then you will get tired faster than if you were able to exert less force.  This is where cadence comes in.  We know we can average a certain amount of power over a certain course.  Where people often get in trouble is when they hit a very strong head wind and do not change gears.  There cadence may go from 87 down to 67 and they keep grinding away for many minutes. 

Cadence is directly related to velocity in our equation above.  At higher cadences we do not have to exert as much force to get the same power output as we do for lower cadences.  So, at 67 revolutions per minute we exerting a lot more force than at 87 revs per minute.  As a result, we jeopardize our pacing strategy and become susceptible to excess fatigue and dropped power over the final sections of the bike leg. 

Another scenario you may or may not have learned by now but many beginner’s fall trap too….is that when they hit a hill they think they can maintain a similar speed to what they were doing on flatter ground.  However, we know that it takes considerably more power to climb a hill.  More power at the same cadence then requires more force.  Too much force exerted and we blow up.  The bottom of the hill always feels easy, give it a minute or two or five and if you started too hard…well, you end up in trouble and people you just passed, pass you back.

This is why I often tell my athlete’s to maintain the same pressure (=same force) on the pedals when they start climbing a hill.  Most of them use heart rate monitors which is a great tool to pace but heart rate has a lag period.  Meaning, that they will exert a lot of extra force before there heart rate picks up.  By that time, they have wasted a lot of energy which may hurt them later in the race.

My final application to training is this…Some “experts” believe in big gear training while other “experts” do not.  I like using big gear training in my programs because it is a really good form of strength training that is sport specific.  By dropping your cadence down to 70 and eventually down to 50 revs per minute and maintaining your power means you have to exert a lot more force.  Hence, a form of sport specific strength training.  This is the exact same thing that happens when you do hill repeats.  Cadence drops, power is maintained or increased and the amount of force required greatly increases. 

To wrap up, paying attention to the amount of force (pressure to the pedals) you are exerting can help you pace yoru race better.  You may be in great cardiovascular shape but if you put out too much force too soon you will “lose your legs” later in the race or even cramp up.

—Scott