Understanding Power to Weight

April 11, 2016 |

In the above video Power Education Specialist Benjamin Sharp explains why Power-To-Weight is major in cycling. It’s one of the most determining factors when it comes to your fitness compared to your competition (specifically your competition’s FTP).

Why does Power-To-Weight matter so much? Well, the forces we need to overcome when riding our bikes. Since we have power meters we’re looking at data all the time. But unfortunately the actual watt number isn’t the only determinate of performance. The major force we’re overcoming, especially when the road tilts up is gravity.

The easiest way to determine this is to take watts and divide it by our body weight to get Watts per Kilo or W/Kg.

To look at this we’ll take two riders, Pat and Andy. We’ll look at their FTP in watts and dived that by their weight in kilograms to get their watts-per-kilo at threshold.

Pat: 345W ÷ 81.4Kg = 4.2 W/Kg

Andy: 320W ÷ 69.5Kg = 4.6 W/Kg 

This shows that Andy is actually producing more power at his bodyweight at FTP than Pat.

To show how this plays out, we’ll do to microintervals. The first will be on a flat road where Pat has an advantage because he is putting out more watts. However in the second workout we’ll head to the hills. Now, as as the road pitches up Andy will be at an advantage, because with the added effect of gravity, Andy is actually the one putting out more power per his body weight.

If you want to figure out your W/K at FTP, here’s Benjamin Sharp’s tips on how to FTP test.


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