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Zwift vs Outdoors (Century Ride)

Updated: Jan 19, 2020

Indoor cycling has exploded within the last few years thanks to smart trainers and virtual training platforms. I use the Wahoo KICKR Smart Trainer and train on Zwift. Like alot of cyclists, I wanted to see what all the hype was about.

The first thing I noticed was how real the "feel" was riding the smart trainer. Having a flywheel vs. the old rear wheel trainer was a game changer. Riding my old indoor trainer felt like riding in sand. It didn't feel natural, it was hard and BORING! Forty-five minutes were all I could handle mentally and physically! The cost for a smart trainer ranges from $800-$1,500 but worth every dollar for those serious about winter training.

The most common question I hear is,“how does Zwift training compare to riding on the roads?” To answer that question, I looked at my training power data and compared two similar 100-mile rides. One of them outdoors and the other on Zwift. Here is what I found:

Above is my power data graph from a local century ride last August (98 miles, to be exact). My average speed was 24.7mph with a finish time of 3hrs 57 mins. Although the speed was high, my power data told a different story.

My average wattage for the entire ride was only 202 watts with Normalized Power of 257 watts. These power numbers are well below my Functional threshold Power (FTP) and less than I expected. I was shocked to see that I spent over two hours (50%) of the ride in my lowest power zone or not pedaling at all! There was a energized group of Midtown team riders who were hammering the front, driving the pace for +2.5 hours. I sat in the pack and drafted with less effort while we hauled down the road at +25mph (I am getting old so I need all the rest I can get). The last hour of this ride got intense and fast! My average power was over 300 with several minutes above 450 watts chasing attacks and hanging on. I was lucky to have conserved my energy during the first three hours to have the power needed to hang on to the finish. When I finished this ride, I was fried!

Even though my average speed was higher than normal my power output was lower than expected. Drafting in a big pack can conserve up to 40% of your energy. Coasting down hills also gives your body time to rest and recover. Most of the pain and power came in the last hour which made this ride feel much harder them the data showed. The data never lies.

Summary Data:

Distance: 98 miles

Time: 3:57:46

Average Speed: 24.7mph

TSS (Training Stress): 218

Average Power: 202 watts

NP (Normalized Power): 254 watts

Average Heart Rate: 118bpm

Max Heart Rate: 154 bpm

Intensity: 74%

Calories Burned: 2,870

OK, now let’s look at a similar 100-mile ride I did on the Zwift indoor virtual platform. You can see from the graph above this indoor ride included 13 laps on the same course loop.

The first thing that jumped out at me was the pink power line. It looked nothing like the fluctuating power chart from my outdoor century ride. The indoor power was fairly consistent throughout the entire ride. In fact, my power NEVER dropped to zero watts the entire ride. I was pedaling and putting power down every second for 100 miles! There is no coasting in the virtual world when you are on a indoor trainer. Power drives speed! This constant effort, especially long indoor rides, builds your muscular endurance and power fitness to higher levels that you will feel right away.

My indoor century average power was 60 watts HIGHER than my outdoor century! I didn't expect to see such a big difference. The indoor power average was 262 watts and my outdoor average power was only 202 watts. That is a huge difference in physical effort. The indoor century was not easy but it didn't crush me either. I would call my indoor ride as “comfortably uncomfortable.” So, my outdoor ride felt harder than the data revealed and my indoor felt easier but the data says it was harder. What's up?

There is no question, the indoor ride was harder on my body than the outdoor ride.

I averaged higher power, higher intensity, higher heart rate and burned more calories on my indoor Zwift ride even though it may have felt a tad easier. Some reasons for this is I never pushed my power beyond my threshold indoors. Outdoors I burned a lot of matches and pushed myself well over my threshold multiple times which created pain and exhaustion. In addition, I only spend 37 minutes in my lowest power zone indoors compared to 2 hours outdoors. The cumulative effort of my indoor ride simply created higher stress and training load in less time.

Personally, I had never ridden more than 2 hours on a indoor trainer but the Zwift virtual cycling community provided the enjoyment, motivation and challenge to keep me going longer than I thought I ever could. No flats, no crashes and not stops. Perfect!

Summary Data:

Distance: 102 miles

Time: 3:46

Average Speed: 26.9mph

TSS (Training Stress): 233

Average Power: 262 watts

NP (Normalized Power): 269 watts

Average Heart Rate: 128bpm

Max Heart Rate: 154 bpm

Intensity: 79%

Calories Burned: 3,569

Note: My avg speed was higher on zwift (26.9 mph). One reason is because I was riding in large pack with no wind, no intersections or stop signs to slow the train down. Everyone in the pack was putting out power at the same time. That combined energy makes for high speeds in any world.

If you have your own indoor training tips or experiences in the virtual cycling world please share your comments!

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