“Man!  That guys watts per kilo must be off the charts!” is something you may hear at the local group ride or race and is usually directed towards a skinny dude that everyone dislikes once the road starts to turn uphill.  Think of grand tour winners (Chris Froome, Nairo Quintana, Marianne Vos, Anna van der Breggen, etc.) or those who are usually seen in polka-dots.  Basically, the athletes who wear extra small jerseys, but the sleeves still flap in the wind!

Watts, as previously discussed, are how much energy the cyclist is producing to propel his/her bike forward.  The more wattage the cyclist can produce, the faster they should be able to go.  A kilogram (kilo for short) is a metric measure of weight equal to 2.2 pounds.  So, to figure out your “watts per kilo” you first need to figure out what your average wattage over a given time period is and divide that by your weight in kilos.  This will result in a number that you can brag about (or maybe not) to your friends and explain why you always beat them on the climbs.

To give this more depth, an “untrained” rider can be predicted to produce ~1.8 w/kg in a 20 minute FTP test, and a “world champion” can be predicted to produce >6.5 w/kg during the same test! (1)

Why is having a high watt per kilo rating beneficial?

Simple!  It allows you to climb hills faster while at the same time expending less energy.  Imagine pushing a wheel-barrow up a hill.

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The less mass in it (i.e. body fat), the easier it will be to push and your legs won’t be as fatigued at the top.  This is why all grand tour winners, prolific climbers, and most professional cyclists look like a bag of bones with quads attached; they are able to use far less energy and move a lot quicker if they are as lean as possible.  This is also why the “weight-weenie” phenomenon has been gaining ground over the past few years; the lighter you can make your bike, the faster you can climb.  However, as the old saying goes, “I would rather lose a pound off my ass than off my bike.” 🙂

Keep in mind though that the lighter you are means you possess less overall power and brute force.  You won’t be at the pointy end of the bunch during a criterium sprint, you will get smoked in most track events, teammates will start to block you at the base of climbs during group rides (and you wont be able to do anything about it with your spaghetti arms), and people will constantly tell you to “eat a cheeseburger!”.  When push comes to shove though, in most of the larger road-races and stage races you can put far more time into your competitors in the mountains than the flats.

When can a high watt per kilo rating be unadvantageous?

Being a lean and powerful endurance athlete has more pros than cons, but sometimes brute force and momentum play bigger roles in races.  Some examples are track cycling, criteriums, and most cyclocross races where the bigger and stronger cyclists can push their weight around (pun intended).  Having increased mass means you need to produce less power to keep your momentum and therefore use less energy motoring on flats or descending compared to the skinny dudes.  This also means you can power up to speed faster and fly up short, but steep climbs without too much trouble.

To really drive this point home, take a look at Robert Forstemann’s legs, the German track cyclist who kills it in the sprint events, compared to Chris Froome’s legs, the reigning Tour de France champion…

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Credit: Harry Engels, Getty Images
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Credit: The Telegraph

I am pretty sure you can figure out what pair of legs belongs to which athlete!  Froome technically has more w/kg compared to Forstemann and can definitely climb mountains a lot faster, but line these two up for a sprint and Froome will be eating dust.

So, what are watts per kilogram?  A measure of how strong a cyclist is based on how much energy they can produce and how light they are.  This is an important number for athletes looking to excel at stage races, hill climbing events, and single day races that involve a lot of elevation gain because they will be able to ascend and attack from a group using less energy than their “heavier” counterparts.

For more information on GC Coaching and how we can help you increase your fitness using power, please visit www.gaffneycyclingcoaching.com

References:

(1) Coggan, A. (2008, October 10). Power Profiling. Retrieved December 1, 2015, from http://home.trainingpeaks.com/blog/article/power-profiling

About the Author Shayne Gaffney

Shayne holds a bachelors degree in biology, is a USA Cycling Level 2 Certified Coach, USA Olympic Committee Safe Sport Certified, and a Category 3 road and cyclocross racer. He is the owner of GC Coaching and the creator and director of P2 Cycling. He can be contacted directly via info@gaffneycyclingcoaching.com

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