Crit Race Comparison: Zwift vs Outdoors

This past weekend I raced outside for the first time in several months, and it struck me how very different the experience was from racing on Zwift. Since I like to debrief myself by writing some notes after a race, I thought it would make for a good blog post.

First, About Me

I’ll be the first to tell you I’m nothing special when it comes to racing. I got into cycling late (in my mid 30’s) and lack the time, inclination, and genetics to be an outstanding racer. I ride for fitness and fun, and when it comes to racing my goal is to be a competitive USAC cat 3 and Zwift B racer.

I finish in the upper 1/3 of the B’s in most Zwift races, but rarely come close to the podium unless the field is very small (see my results). And I’m just a cat 4 road racer outdoors, with no significant results to show as a 4 (see my results).

Two Races, One Rider

I’ll be comparing two races. Here are the numbers:

• Zwift WBR 4 Lap Flat Race, January 11 2018: 34 racers, 18 B’s on the fairly flat London Classique course (see it on Strava and ZwiftPower)
  • Distance/Duration: 17.61 miles in 37:40 for an average speed of 28.1mph.
  • Normalized Power: 302w

• Cal Aggie Elite 4 Crit Race, January 27 2018: Approximately 40 racers, with dry weather and just a touch of wind on a very flat course with a couple sharp turns (see it on Strava)
  • Distance/Duration: 16.17 miles in 39:41 for an average speed of 24.5mph
  • Normalized Power: 259w

Disclaimer: two different power meters were used in these events, since I Zwift using a dedicated bike with Garmin Vector 2 pedals as the power source. My outdoor racing bike has a dual-sided Quarq. In comparison tests I’ve found their numbers to be quite consistently close, but there is always a possibility for some variation.

The Start

I’ve never been in an outdoor race that begins like a Zwift race. In Zwift, you have to be ready for a hard effort for the first 1-3 minutes of the race as riders push to make the front group and drop the hangers-on. Outdoors, the start is often the slowest part of the race, even in a shorter crit.

Pack Positioning

This is the big one for me.

In Zwift, improving your pack position is as simple as modulating power levels to move yourself forward or backward in the group. But if you decide it’s time to move up outdoors, it takes more than just increasing your power. You have to get out from behind the rider in front of you and move forward safely, and this can be challenging in a tight pack.

In my outdoor race I was well-positioned, sitting second wheel halfway into the last lap. Then riders attacked on both sides of us, moving me from the front to the middle of the pack in just a few seconds. Had I been more alert I would have been watching for this move and ready to grab one of the attacking wheels as it came by.

Attacking

In Zwift, attacks off the front on flat courses rarely stick because the pack’s speed is so consistently high and the draft effect is strong. Consequently, you see less attacking on Zwift than outdoors. If anyone does attack in a Zwift race, they’ll usually wait until the last few minutes of the race and do it on a climb.

This was certainly the case in my races. Riders attacked on a regular basis outdoors, while the Zwift race saw very few attacks. More constant attacks means more variable power levels as you work to hold a wheel or bridge up.

Variable Power and Cadence

Comparing the cadence and power graphs of the two races makes it clear that the outdoor race was much more variable in terms of effort. One easy way to see this is comparing the variability index (VI) of my two rides, where my outdoor race was 1.07 compared to Zwift’s 1.05.

This makes sense for three reasons:

1. Coasting is common outdoors: stopping or dramatically slowing your cadence is the best way to maintain your pack position outdoors (stay off the brakes). But if you stop pedaling on Zwift you’ll quickly get dropped from the pack as the auto-braking kicks in, so nobody stops pedaling in a flat Zwift race.
2. Slowing for turns: nobody reduces their power going into turns on Zwift, but of course everyone stops pedaling and may even use their brakes on sharp turns outdoors. My outdoor race had two particularly sharp corners which always led to braking in the pack, and the resulting “stand up and hammer” to get back up to speed.
3. More attacks outdoors (already discussed above.)

Different Speeds

If you’re regularly scrubbing speed on corners, it makes sense that your average speed would be lower outdoors than on Zwift. Add in a bit of wind, more chances of getting out of the draft, and the possibility of a less than perfectly aero riding position and it’s no surprise that Zwift race speeds are higher than outdoor races of a similar effort.

In my two races, my normalized power was ~40 watts higher for the Zwift race, which also helps explain the speed difference.

Similarities

Those are the big differences, but are there similarities? Absolutely! Here are a few:

• Good strategy and course knowledge required: whether the world is virtual or real, it’s important to know how to best attack the race and use the course to your advantage.
• The pain: while outdoor racing does afford more opportunity for major injuries, a crash-free race burns just as much whether you’re indoors or out.
• That winning feeling: crossing the finish line first gives me the same euphoric rush whether its virtual or outdoors. (Of course, outdoors would be more exciting if you’ve got a good crowd cheering you on, but since I’ve only won as a cat 5 I wouldn’t know what that’s like!)
• That sinking feeling: that moment when you can’t give any more, and you see the pack ride away? It sucks on Zwift and it sucks outside.

What About You?

How would you say Zwift racing compares to outdoors? Where is it the same, and where is it different? Share your thoughts below! I’m especially interested in hearing from experienced outdoor racers.