A couple of months ago I started using an indoor cycling program called Zwift. For the full review of my setup and my initial impression, here’s the post. I took a little bit of break at the start of December, but since the New Year I am back in the saddle, literally.

Week 1 Success, on to Week 2!

Zwift has been simply fantastic for me so far. It’s motivated me to go down to the basement four nights a week and ride for a solid hour. The built-in training programs have been great (I am currently working on a plan called FTP-Builder), and I love how they make workouts available. How the do it is they make a workout “available” for you at certain times, and they are only available for 24 to 36 hours. This motivates you to find the time, without locking you into a specific day. I love that flexibility.

As I am just getting into the whole cycling business, there are a couple of nerdy metrics that I am still wrapping my brain around. The first, is measuring a riders actual output. The unit of measurement that tracks output is called watts. A single watt, is roughly 1/746 horsepower. Watts are calculated by how much torque a rider is putting on the pedals. To track this, you need some-sort of power meter (very expensive), or in my case, Zwift uses my cadence and speed sensors to calculate it out.

Understanding watts opens up other nerdy metrics to keep track of, the most important being your FTP, or functional threshold power, is simply the maximum average watts you can sustain for one hour. To test this, is simply awful. The best way is to literally ride at your max effort for one hour. So I did that, and found out my FTP is roughly ~210 watts.

So is that good? How do I compare (yes I am highly competitive for no good reason). To figure out how you stack up to other riders, there is yet another measurement. This is your power to weight ratio or watts/kg. To figure this out is fortunately easy, you take your current watt output, and simply divide by your weight in kg. So if I am riding at my FTP, 210, and my current weight (~215 lbs or ~97.5kg) my formula is 210/97.5. This equates to 2.15 w/kg. This number is important, because of wind resistance and a little thing called gravity. Riders with a better watt to weight ratio can ride up hills much easier, thus being faster.

So how does my 2.15 w/kg stack up? Well, in Zwift, 2.15 puts me in the bottom bracket D group. Bummer. The below chart from Cycling Weekly:

Rider type5 mins20 mins1 hour
 Professional7.06.16.0
 Amateur3.73.33.0
 Recreational2.52.11.8

Essentially, I am riding at slightly better than recreational. I’ll take it! Having a firm metric like watt/kg is perfect for a nerd like me, because I can actually measure improvement over time. I am also excited because as I bring my weight back down to a respectable number, as long as I keep working out my watt/kg will improve as well.