## Monday, March 29, 2010

### Physics 201

b
WORK= POWER X TIME

In one of my November 2009 blogs, entitled Physics 101, I defined "Power" and its importance in cycling.  Now, that you've (hopefully) grasped the concept of "Power", it's onto Physics 201 and the definition of "Work" and its importance.

We know that in order to increase our overall cycling fitness we have to perform more work on the bike.  More work, rest and recovery makes us stronger...right?  Not necessarily.  For now, lets take a look at the Power component in our equation above.  You would think that if one pedals at say a relatively low power for a long time which would be the same as pedalling at a high power for a short time..that one would create the same amount of work and thus improve overall cycling performance...right?

Not really..let me explain.  Here's an example:  Training ride 1- a 2 hour (120 minutes) ride at an average of 150 watts for a total Work of 1800 kJ.  Training ride 2- a 1 hour (60 minutes) ride at an average of 300 watts for a total Work of 1800 kJ.  Both training rides produce identical total work of 1800 kJ but the power or intensity produced during one ride (training ride 2) is double the other (training ride 1).  What's not clear in the Work equation (above) is that the higher, more intense, power training rides have more performance benefits.  i.e. the higher more intense workouts require higher force muscle contractions where more fast-twitch muscle fibers are recruited...in addition to 100% of the slow-twitch muscle fibers.  These muscle contractions are what makes your muscle stronger..thus making you FASTER on the bike.  It's the composition and work capacity of our muscles that is the limiting factor on how hard/fast we ride.

So, what's all this mean?  It means the "intensity" of the exercise (or training ride) and the "recovery" from that intense exercise is what makes you stronger..NOT just an overall High Work or workload...via high volume training.  It's what "hi-intensity" interval training is all about- High Power Short Time intervals.