Saturday, 12 November 2011

Power to Weight Ratio (PWR)

If this winter is anything like last winter, it will mean plenty of time off the bike.  Snow and ice were the main problems last winter, making riding conditions difficult and at times dangerous.
I've used Wattbikes plenty of times in the past at Manchester Velodrome and visiting the Wattbike stand at the Cycleshow recently, I was reminded of how good they are.  You can read more about them here

You can rent a Wattbike for £60 per month, so I thought I'd get one for the Winter to a) have a contingency against bad weather b) do some base mile work to lose some weight c) work on my pedal stroke and d) to see if I can increase my power (one of the key attributes of the Wattbike is the ability to measure power output aswell as pedalling efficiency). 

Today, I did my first three minute test, which is a way of measuring your power output.  You warm up for twenty minutes, then push the pedals in a timed three minute period to assess your power output (wearing a heart rate monitor to record your heart rate maximum at the same time).

By doing this, you can assess your power to weight ratio (PWR), this is derived by dividing your sustainable power by your weight (KG).  The power to weight ratio is one of the key metrics used by professional cyclists to assess whether they are capable of winning grand tours like the Tour de France.  Grand Tour winners tend to have a power to weight ratio above 6.7.

My three minute test showed my average power as 285W, dividing it by my weight (97.7kg) means my PWR ratio is 2.91.  I shouldn't be making any major plans to enter a grand tour yet!

Over the winter, I want to lose some weight, focus on my pedalling stroke and see if I can increase my PWR by 10%.  I can do this in one of three ways 1) lose weight 2) increase power 3) lose weight and increase power.  It's all easier said than done.

To lose weight, you need to lots of training in heart rate zone 1, which is between 60-65% of your heart rate maximum.  My heart rate maximum is 184 bpm, so my fat burning zone is between 110 and 120.  By limiting your heart rate in your training sessions, your body should use fat for fuel and it should help contribute to weight loss, as the theory goes.  If you then combine that with a sensible diet, the weight should start to come off.

So, between now and Christmas, fat burning is what it's all about.  I'll keep a record of my PWR over the coming months and see "watt" (get the joke) can be achieved.

More about how you rent a wattbike here


Having re-run the test a couple of days later, I realised I had capacity to go harder.  So, on re-test, my power output was 323W, meaning my PWR is 3.35 (around 15% improvement from the first ramp test).  So, that is now my benchmark for comparison.

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