Zwift has just announced a series of events next week in partnership with Scott. “Scott Week” is a celebration of all things cycling, with events focused on road, tri (TT), and mountain disciplines.
This isn’t a race series. Rather, it’s a series of group rides hosted by pro riders from each cycling discipline. The week ends with an exhibition race on Crit City between 3-person teams of Scott pro riders (see below for details).
Kit Unlock
Take on any of the available events, whether it’s a group ride or group workout, and you’ll unlock the stylish in-game SCOTT Kit.
Celebration Group Ride
Scott Week begins with the “Celebration Group Ride” on Sunday. This ride will be over one lap of London’s Triple Loops route (40.8km/25.4 miles, 544 meters/1785′ elevation). This ride includes three categories to choose from.
This is the only open event of Scott Week which has a finish line, so expect many riders to treat it as a race even though it’s classified as a group ride.
Stage Details
Stage 1 (Road)
Group rides are 60 minutes long on the Innsbruckring route. Cyclists from the Mitchelton-Scott Men’s and Women’s World Tour teams will join Zwifters on these group rides – see each event for details.
This stage’s group workout is inspired by Esteban Chavez. It is a high-intensity workout which works on VO2 max power. Esteban uses this session to accumulate time at VO2 max power before entering a block of racing. This is a good session to work on FTP power. The workouts are 55 minutes long on Watopia’s Waistband – see workout details in the Companion app.
This stage’s group workout is from professional SCOTT triathlete Alistair Brownlee, and is ~60 minutes long on Watopia’s Tick Tock route. This ‘hour of pain’ group workout is the ultimate indoor training session to be completed in an hour. See workout details in the Companion app.
All riders will be on Scott Plasma TT bikes.
Stage 3 (MTB)
Group rides are 60 minutes long on Watopia’s Road to Ruins route, and will be hosted by pro riders from the SCOTT-SRAM team.
This stage’s group workout is from UCI Cross Country Mountain Bike World Champion Nino Schurter, and the workouts are 60 minutes long on Watopia’s Jungle Circuit route. See workout details in the Companion app.
Scott Week ends on Sunday June 28th with an invite-only exhibition race featuring pro Scott athletes from road, mountain bike, and triathlon.
The race will be streamed on GCN, GMBN and GTN. Each team will consist of three athletes, one from each discipline, and include both genders. The race is over 12 laps of Crit City, with points being awarded to the top five finishers in each lap (for both men and women) as well as for the first five to cross the finish line. The team with the most points wins.
If you’ve been following this “How the Race Was Lost” series, you know that I, like many Zwifters, race for different reasons on different days. Usually I race to win: I find the event best suited for me, and I ride to give myself the best chance at 1st place. Other times I might join a race in order to get a specific type of workout – putting in repeated short attacks, for example. Sometimes I’ll do a hard, long race, knowing I stand zero chance at winning, but also knowing that the only way I’ll go hard for three hours is in a race!
I might also race with teammates – riding a TTT, or putting in work for a rider who stands the best chance at winning. And occasionally, I find myself in self flagellation mode, looking to find a race that hits me right in the weak spots so I can be pushed to the limit in my area(s) of weakness and hopefully get stronger.
That was my plan for today’s race: 13 laps around Yorkshire’s Queen’s Highway in a race of Team Fusion’s “BEUNSTOPPABLE” series. No race in Yorkshire had ever been kind to me, and I anticipated more of the same today.
Recon + Warmup
This was a mid-morning race, so I ate my favorite breakfast (oatmeal with pecans and blueberries) a few hours beforehand. As race time approached I chewed two pieces of caffeine gum and rubbed PR lotion on the legs, then headed over to Yorkshire to ride my warmup while doing a bit of recon.
I’m quite familiar with Watopia‘s roads, as well as Richmond, Crit City, and most of London. These maps I can navigate in my mind, pointing out every rise and turn. I’m definitely less familiar with portions of Innsbruck (the climb loop), the upper roads of NYC, parts of Bologna, and the upper loop of Yorkshire. While I’ve ridden in Yorkshire a fair amount, it’s always been for events – I don’t really go there when free-riding. Those events typically only hit the smaller, upper loop of the course once or twice, so while I was familiar with the general layout of the Queen’s Highway route, I wanted to know all the nooks and crannies. Time for some recon work.
Route recon
There were other racers on course, and we had a nice chat. Here’s what I found in my pre-race recce:
There is no portion of this circuit which is flat. In general terms, the first third of the loop is downhill (from the sprint banner to the bottom of Cornwall Road). Then the next third consists of a couple of rollers. The final third is a gentle climb back to the sprint banner. Wash, rinse, repeat.
The second half of the descent seemed steep/fast enough for a short supertuck. This might prove useful.
The two rollers before the longer climb to the sprint banner could be managed nicely by maintaining momentum – hammering a bit at their base in order to build speed which could be carried over the crest
In the sprint section, the road flattens before turning left toward the sprint banner. Then it pitches up for a final steep kick to the banner. This would be a logical attack point, because you could hammer for a bit and gap riders who were gassed from initial longer climb. But… that kick to the line is followed by a long descent, which would make it hard to stay away. My conclusion: attacks would naturally happen here, but they wouldn’t stick.
After half an hour and five laps of Queen’s Highway, I was ready to race the loop. Let’s do this!
Pre-ride banter!
The Start
This route’s lead-in is around 1.8 miles long, taking you over the challenging bits of the Queen’s Highway loop before you hit the sprint/lap banner for the first time and your laps begin to count down. I averaged a reasonable 317 watts from the start line to the lap banner, making the front selection which broke our starting pack of 66 neatly in half.
I had my eye on only two riders in the pack: Kristian Nissen (Fusion Development), who was ranked at the top of our B field, and my friend Dafyyd Williams (KRT) who was ranked #2 and I knew to be a very strong rider.
ZwiftPower rankings – this wasn’t going to be easy!
Dafyyd attacked across the lap banner a few laps in, but I just sat in the pack who easily reeled him in on the descent. “Boring,” Dafyyd messaged to all riders. Perhaps. But I didn’t think I would be able to hang with the front for the full 13-lap event, so I wasn’t going to waste my legs trying to join him!
The Middle
Our group found a good rhythm after a few laps. PowerUps were disabled, which made the group even more sedate. The only way the group could have really been broken up would have been by a strong attack by multiple riders on back 2/3 of the loop – but nobody seemed willing to do that.
For my part, I was just happy to be able to hang with the group on the uphill portions of the route! Here’s how I rode the loop – keep in mind I’m a bit heavier than most (~81kg) so, compared to a lighter rider, the descents are friendlier to me, and the climbs a bit more punishing:
The descent from the sprint banner was easy enough – just go hard enough to stay with the pack
Supertuck at the bottom of the descent, gaining plenty of speed so I could just put in a few good pedal turns in order to crest the first roller with the pack
Descend that first roller, then put in a few more good turns as the road tilts upward for the second roller. (For whatever reason, I always ended up at or near the front at this part of the course, which was fine with me – my well-timed momentum-carrying power bursts were making it easy!)
Settle in for the longer climb up toward the start banner, maintaining good pack position
Put in a final hard kick on the last pitch to the banner
Descending Cornwall Road
I kept waiting for one of the well-represented teams (BMTR or Fusion) or one of the stronger riders to put in a hard attack. But it never came! On the 9th lap of 13 it finally sunk in – I could make it to the end of this race! No one was more surprised by this than myself.
The Finish
No strong attacks came in the penultimate lap, although Nissen moved up near the front of our pack. He was obviously a smart racer – but what was his strength? I hadn’t done enough digging to know if he was a sprinter who would win in the last 15 seconds, or perhaps better suited to the long attack with strong 1-5 minute power. I kept a wary eye on him, deciding I would try to follow his wheel if he attacked any time after the descent on the final lap. (If he attacked any sooner I figured the group would pull him back before the race was done.)
Nearing the final climb
We began the final climb, still a group of ~30 riders. I was well-positioned within a few wheels of the front, but little did I know how unprepared I was! Nissen jumped… hard. His numbers went orange, he gapped our group, and even though I pummeled the pedals with everything I had, I couldn’t get back onto his wheel.
I averaged 436 watts for the final 90 seconds of the race, chasing Nissen up that cursed climb. My legs were so gassed that my final “kick” to the line was more of a heel-click. I finished 7th according to Zwift, but 4th on ZwiftPower. Not a win, but I was very happy to have hung in until the end. Nissen took first with his strong, long attack. Well done, sir.
One strategic exercise I enjoy is figuring out a sort of “attack profile” for each portion of a race course. In each section, a racer can ask: are attacks likely to happen here? Will those attacks stick? And the all-important question – is this a smart place for me to attack?
I rode this race 100% defensively, never looking to attack, because I was quite sure I wouldn’t be able to hang with the front to the end. If I was to race this again, especially if I was working with teammates, I would probably attack on the middle third of the circuit, on the rollers. Because it’s here that a well-timed kick can give you the momentum needed to quickly gap the group. Even if you don’t stay away, they’ll probably burn a few matches bridging the gap up the climb.
Overall, I was pleasantly surprised with my experience on the Queen’s Highway. Losing a bit of weight and getting a bit stronger allowed me to stay in contention, and the constantly changing pitch made for a an exciting race. I would race here again!
Zwift has just announced this year’s Norseman series – a 6-week ride+run training series culminating with the weeklong Norseman Festival of Climbing. With COVID-19 canceling the IRL Norseman race, this will be the only Norseman experience for 2020!
Training Series
From June 15th through July 26th, Zwift is hosting the Norseman Training series which consists of group ride and run workouts, events, and races. Each of these activities will hit key timezones worldwide, with four different sessions per day.
The bike and run workouts were developed in collaboration with Norseman and feature specific messaging and coaching around different parts of the Norseman course. Notable Norseman finishers and ambassadors will also lead some group rides and runs!
The training series culminates in The Norseman Festival of Climbing, a week-long celebration of hill climbs around Watopia with a chance to win two entries to Norseman 2021!
The route schedule will be released soon, but each route will build upon the elevation of the previous day.
Prize Drawing + Kit Unlocks
Zwifters completing any of the Norseman rides on August 1st will be entered into a drawing to win an entry to the 2021 Norseman race.
Completing any of the August 1st Norseman rides also unlocks the Norseman cycling kit.
For runners, completing any of the August 2nd Norseman runs will unlock the Norseman Run shirt.
The other Norseman rides and runs throughout the week will not enter participants into the drawing or unlock the kits.
Last week Zwift rolled out a set of events based on the IRL Chasing Cancellara series. Like last year, the series begins with a set of workouts hosted by Fabian Cancellara, who is an Olympic gold medalist, 3x Paris–Roubaix champion, and multiple Tour de France stage winner (in case you didn’t know). And it ends in a big main event, which thousands of Zwifters have already signed up for! Here are the details…
Main Event Switchup
The final event happens on June 28th at 7pm BST/2pm EDT/11am PDT.
But this year, the big finale has been flipped on its head! Instead of Fabian starting and everyone else chasing, riders sign up for a category, and groups are let go in a staggered order (with slower categories starting first). Cancellara will start last, and he has to work to catch all of us over one lap of Dust In the Wind.
Like other Zwift chase/handicap races, riders will need to suffer as a team to stay away from hard-charging Fabian. It won’t be easy – Cancellara averaged 440w (5.76 w/kg) for 72 minutes when he won Olympic TT gold in 2016!
Say hello to Flora Duffy. The 32-year-old triathlete has been wildly successful in her triathlon career with multiple world championships over many disciplines. She’s the 2016 and 2017 ITU World Triathlon Series world champ. She’s a five-time winner of the XTERRA World Championships. She’s represented Bermuda at three Summer Olympics—2008, 2012, and 2016.
Now, not all triathlons are equal. There’s ITU, Xterra, 70.3, and more; Flora has dominated all of the disciplines, which is no small feat! So in Ep. 29, we pick her brain on how she’s done it, and how we should all mix up the sort of racing we do.
About the Podcast:
The Zwift PowerUp Tri Podcast is hosted by former pro triathletes Matt Lieto and Jordan Rapp, lending their in-depth knowledge of the multisport to the Zwift Tri audience.
Kristin Armstrong talks with TWENTY20 General Manager Nicola Cranmer. With 16+ years at the helm of women’s pro cycling teams, we count 4 Olympic medalists and 17 World Champions with her backing… and more trophies on the way.
Her show-stopping women of TWENTY20 are regular Zwift users, smashing max power limits and honing their mental game. Nicola also looks into her crystal ball and offers predictions for the future of bike racing.
Zwift released a minor update to its Companion app yesterday. Here’s a quick video from our favorite Aussie Lama summarizing the changes:
“Only Zwifters I Follow” Event Filter
When the new “Only Zwifters I Follow” filter is enabled, events will only show up if one or more Zwifters you follow are signed up for the event. This makes it easier to join friends on upcoming races or group rides!
Filtering for B races
Filtered results
Two friends are signed up!
Add Events to Android Calendar
You can now add Events and Meetups to your device calendar on Android. Great news for the Android crowd!
iOS Version Note
It’s worth noting that Zwift Companion version 3.15 (and 3.14, actually) on iPhone/iPad require iOS 11 and newer. If you are on iOS 9 or 10, you will only be able to go up to Companion version 3.11.1.
Opportunities to challenge oneself are always abounding on Zwift. There are big Zwift events, as well as unofficial events and solo challenges. Here are 5 events this weekend you may want to check out.
Special thanks to Jesper at ZwiftHacks with his Events app which provides powerful event filtering tools that help us create this list each week.
Haute Route Dolomites Challenge
This is an individual challenge, not an official Zwift group event. The challenge? Climb 3300m in a single ride between 12:00am Friday 12th June and 11:59pm Sunday 14th June in your local timezone.
To mimic the elevation of the Queen Stage for Haute Route’s canceled 2020 Dolomites event, riders must climb 3300 meters (10,826′) in a single ride in order to complete this challenge. The challenge only runs from Friday-Sunday in your local time, too, so you’ve got to plan accordingly.
What does 3300 meters look like on Zwift? Well, you could ride:
3x up Alpe du Zwift, plus another 194m
Almost 8x up the Epic KOM forward (or almost 6x if you include the Radio Tower “bonus climb”)
More than 24x up London’s Box Hill
66x up Watopia’s first climb, the Hilly KOM!
If you complete the challenge (and jump through the hoops of filling out a form or two) you will be entered into a drawing for a 3-day Haute Route event in 2021, plus prize packs from Precision Hydration. Be sure to visit the link below for details, so you can get registered properly.
You may remember 8 year old Samantha Frost from her Tour of Fire and Ice ride last month. She is cycling to battle arthritis in her knees and back, and this weekend she’s taking on the challenge of riding 25 Volcano Circuit laps. That is a full distance of 102.5km or 65 miles!
Zwifters are invited to join and support her. This is a great time to earn that “On Fire” badge, too! (Join Samantha by looking up “Samantha Frost (age 8) on the Companion app and sending a follow request.)
Ride organizes say, “We are also asking people to sponsor her for each lap she completes. As much or as little as you like. The only thing we ask is that the money she raises is sent to your own local arthritis association of Your choice in her name or the Everyday Hero page below.”
This is not an official Zwift event. Sammy begins at 7:30am New Zealand standard time, which is Saturday 8:30pm BST/3:30pm EDT/12:30pm PDT. Learn More >
Catrina’s Ladies Only Century
Ladies, join ride leader Catrina Weiss for a 100-mile ride on Watopia’s Waistband! Catrina says, “This is NOT a NO DROP ride. With that said we do try in my rides to keep the pace steady and drop back if we know early enough to bring back dropped riders. We encourage all women who have done 59+ miles on Zwift or IRL to join this ride as it will be super fun.”
Jonathan Parker and Matt Bottrill are undertaking a 6 hour non-stop Zwift challenge to raise £2,000 for Cyclists Fighting Cancer. Support this effort by making a donation and/or joining Jonathan and Matt for some or all of the 6 hours of pedaling!
Jonathan Parker holds the official world record for the fastest solo cycle ride from London to Paris (12 hours and 31 minutes). Matt is a multiple National Time Trial champion who has set some of the fastest times ever ridden in the UK.
Hot tip: they’ll be riding London’s PRL Full Route, so if you complete the route you’ll only have another ~800 meters of climbing left to complete the Haute Route Dolomites Challenge (see above)!
I’m a sucker for slick design. I’m also a sucker for wordplay. So when I first saw the branding behind the WKG events, I thought, “I should try those out. They look pro.” Then I saw the race named “Critty Critty Bang Bang” and I knew it was only a matter of time before I found myself in those start pens!
This was the day. And it was going to be a crazy race. There were hundreds of riders signed up for 14 laps of Downtown Dolphin, and all categories would be visible, which meant I’d be pushing to my max to try to hang with the stronger A’s as long as possible. Let the suffering begin. For PR’s! For glory!
The Warmup
This was a mid-morning event for me, which meant I was able to eat breakfast and get a decent warmup instead of rushing around a dark house at 5am. Refreshing!
As usual, I chewed two pieces of caffeine gum and rubbed some PR lotion into my legs. Then it was off to Tick Tock for a 30-minute warmup. But as I rode through Fuego Flats I started looking at the signup list for this event, and realized that there were a lot of riderssigned up. Over 100 B’s, nearly 100 A’s, and that didn’t include those who would just show up last-minute without signing up.
This was a combined-category race, meaning we would be able to see all riders from all categories, but we would be scored in ZwiftPower based on our category. That meant the B podium would probably belong to the riders who were able to hang with the faster A’s longer than the other B’s. With a big and strong A field I didn’t think I’d be able to hang with the front for the entire race, but I decided I would push until I blew up in order to hang with the front as long as possible. Because you don’t know your limits until you truly push through them.
“Damn the torpedoes! Full speed ahead!”
I decided to head to the start pens early, since riders are placed further and further back the later you join. I wanted to make sure I didn’t have to ride through any more riders than necessary at the start as I tried to make the initial selection.
The B pen, 12 minutes before race start. Crowded!
Even though I jumped into the B pen with more 12 minutes to go, things were already crowded. That meant I would have to push even harder to make that first selection of A’s, B’s, and suspicious C’s and D’s. So be it. Let’s race!
The Start
The clock hit zero, and it was hammer time. I set a segment PR on my first lap, averaging 386 watts. I hung in for the second lap as well, but just barely… 349 watts for that. And as we hit the false flat after the lap banner, I couldn’t hold on any longer, and on the third lap, a group of ~80 rode away.
Where Am I?
My screen showed me in 80th out of 402. But that was 402 riders total, from all categories. This is something that annoys me about mixed-category races – the fact that there’s no easy way to know where I’m at in relation to all the other B’s. I could see from the minimap that there were plenty of B’s in the group that just dropped me. But how many? 79? 10? I knew around 70 A’s had signed up… did that mean there were around 10 B’s up ahead?
The only ways to find this information out by yourself are:
Pulling up ZwiftPower’s live view of the event, or
Clicking through the rider list on your screen to get the perspective of riders up ahead.
But both of those solutions are far from ideal, as they force you to take focus off of what’s actually happening. Anyone want to play DS for all my races?
The Middle
So there I was, on the 3rd lap of 14, with the leading group up ahead and some stragglers grouping up behind who would surely sweep me up soon. I eased my power, knowing I wasn’t going to bridge up to the front group or stay away from the larger group behind.
Where did I stand now? I knew we would be seeing some of the B’s in the front group get dropped and join our chase group – there was no way so many B’s could maintain that frenetic pace. But how many would we sweep up, and how many would remain out of reach?
On my 4th lap the group of A’s and B’s that had been swelling behind me came through, so I grabbed their wheels. This group seemed to be ~15-20 riders in size, but to be perfectly honest, it was already getting hard to tell who was where! With over 400 riders moving at different speeds around a small 1.2-mile circuit, there was a nearly constant stream of riders ahead and behind, and my only indication of standing was the overall placing number, which (again) didn’t tell me where I was actually ranked against the B’s.
I started paying attention to some of the stronger riders staying near the front of our group, so I could track them as we moved through packs of slower riders. I didn’t want to get gapped in all this mayhem and dropped from this chase group, especially since it was possible that a B podium winner or two might come from our group.
Happily, the pace was doable, although certainly not easy. I was getting useful powerups, conserving as much energy in the draft as possible, and watching as we slowly caught B riders getting dropped from the hard-charging A group. We were making progress, catching single riders and small groups as our group continued to swell in size. The front of our chase group went from ~85th to ~50th between laps 4 and 7, and my conviction grew that a B podium was within our grasp.
The Finish
By the time we hit the final lap, our group had swelled to 30+ riders. The powerup gods had given me only bonus points for the past three laps, and they begrudgingly gifted me a feather for the final lap. Not what I was looking for, but I used it on the prime climb to save a little energy while I tried to stay within a few wheels of the front of our group.
A strong rider or two always seems to go hard from the top of the bricks, and this race was no different. I didn’t chase them, though, preferring to sit in the draft and let others catch those off the front. Soon enough we were down the twisty descent and it was time to shift, stand, and hammer out the final sprint. I gave it all I had, which admittedly wasn’t much after such a hard start and the longer race. I crossed the line in 47th overall, 10th in the B’s. Three B’s from my chase group had outsprinted me, but at least two of the B’s ahead were well over category limits, so I knew I had at least 8th place. What would ZwiftPower say? Final answer: 6th place.
I was pleased with my power numbers for this event, having set a new PB for 2020 in the ~3 to ~5 minute range. Like I said earlier, I joined this race because I knew that mixing it up with the A’s would push me extra hard. It worked!
Takeaways
I’m still not a fan of mixed-cat racing. But I will admit that it’s useful if you’re a rider like myself who is strong enough to hang with the front of a B-only race without being completely on the limit. If that’s you, and you want to improve, then you have a few race training options, as I see it:
Race inefficiently. Decide that you’re going to ride on the front of the B group in the wind, and/or make lots of attacks during the race, just to push yourself to the max and get that extra training stress.
Race your weaknesses. For me, that means signing up for races with climbs, so I’m forced to push myself to the edge just to hang with the front of the race.
Race against stronger riders. Mixed-category events are great for this, because when you get dropped from that front group, you’ll find riders behind to work with. If all you do is race up a category in a category-separated event, you may get dropped and be alone for the rest of the race, since no slower categories are visible on course.
I’ve been using all of these strategies lately in various races, and I know it’s making me a stronger racer.
You’ve started zwifting… first of all, welcome! One of the first things you are going to notice as you speed around Watopia is that the name of the game is power. Everything in this virtual world runs off of those precious watts that you are able to generate as you turn the pedals. If you aren’t lucky enough to have your hands on a power meter, the kind engineers of Zwift have come up with a solution for all of us! That solution is zPower.
zPower is a calculated power value based on the speed of your bike and the resistance of the trainer you are riding on. Editor’s note: although the terms are used interchangeably by Zwifters, there is a slight difference between zPower and virtual power on Zwift. Jaden is technically using virtual power, but he uses the term zPower throughout this post. For more on this, read “Virtual Power Basics for Zwifters“.)
When I started on Zwift, I did all my training and racing using zPower, and one of the first questions that I asked myself was: “Is the power value anywhere near my true power?” The more I trained the more I wanted to be able to compare my numbers with my friends and see how I would stack up in group rides and races. I wanted to know whether the numbers I was getting for FTP, training zones, etc. were close enough to my actual power to be useful.
I am basing this article on a video I created, if you’re interested in getting the information in video format, check it out and don’t hesitate to subscribe to the channel:
Hope you enjoy the video, but in case you’re more interested in the text version of the story, here it is:
The Test
The first thing I needed to do was compare two different power data charts in the same time frame. To do that, I ran Zwift as I normally would, sending speed, cadence, and heart rate to the AppleTV to run my avatar. Separately, I used the new power meter on my bike (4iiii Precision) sending data directly to my Wahoo Bolt. After I finished the test, I was able to use ZwiftPower to compare two different power graphs based on data from Zwift (downloaded from Strava) and from my Wahoo Bolt head unit, downloaded from the Wahoo app.
When you add both of these data files into ZwiftPower’s analysis tool, you get some cool comparative information. The first thing you see is this graph (the purple line is zPower, and the light blue line is the 4iiii Power Meter):
We will get to the specific sections in the graph more closely soon, but before we get to that there are some other elements of the analysis that I wanted to highlight.
For an average power, I was very impressed with Zwift! A difference of only 6.1 watts (4.26%) averaged over the whole test was actually quite impressive, so kudos to the team for working hard and making something great. I won’t talk much about normalized power, but as you can tell in the graph it is also within about 4% as well, which I would consider very accurate for an estimation.
Maximum power is definitely a key point here, with an almost 10% discrepancy. The actual power meter read a significantly higher max power, which from what I can tell is due to the ability of a rider to push significant power into the pedals instantly, but the resulting wheel speed (what zPower is actually based on) does not increase quite as fast. If your sprint lasts for a long time, you may see the zPower number climb up to match that maximum, but if the power peaks and then drops, as mine does in this sprint test, your zPower numbers will not be able to catch up, and will not spike as high a power meter can.
To review the actual data, I divided the overall test into three segments that told three different stories about the difference between Zwift zPower and an actual power meter. Here are the three main test sections that I looked closely at:
Steady State
Most of the test was run as an (attempted) steady state ride, hovering around 200W. My intention here was to see what zPower could do if the speed was constant. As you can see on the graph, both of the values are tracking pretty closely together, with the zPower consistently lower, and the difference there was by about 10-25 watts. This may seem significant, especially on the higher end of that range, but the fact that it was tracking closely even though it was low helps me know that at least for workouts you will still feel the difference between hard and easy.
The other thing to notice on the steady state portion of the test was that my actual power data is quite jumpy. I’m fairly new to this power meter data, but from what I have learned from others with much more experience is that this is normal. When you first start measuring power, it’s reasonable that your natural pedal stroke will create slight variances in power even when riding at a steady state. The reason that the Zwift value is able to be so consistent, is because they are basing theirs off of wheel speed, which is more constant.
Intervals
I did some really quick interval work during the test, so I could see what the zPower readings would look like when you ramp up power, stay at that level for some period of time, and then bring it back down again. I think this result is interesting because it is the only meaningful time that the zPower value is higher than my actual power meter.
The difference in the graph partially represents a slight lag, so my power increases as soon as I put more pressure into the pedals, which makes sense, but my speed will only increase gradually, thus increasing the zPower. The interesting thing to note is that my continued high-power effort increased my speed fairly significantly, and even though I was holding a consistent power, I was still accelerating. That is why for a few seconds, my zPower will continue to rise past the top of my actual power numbers. The same small lag is noticed on the tail end of the interval, as I ramp the power back down again.
Sprinting
The most significant difference between the values that I saw was when I tried a sprint. I only ramped my power up to around 800 watts, but it was quick enough to see how zPower would react to the changes. As expected, since my speed increases slower than the effort I’m putting in, my real power increase is very sharp. The zPower is much more gradual.
Since I spent so little time at the power peak, it is reasonable that Zwift wouldn’t reach the same value, but the difference was about 70 watts, which represented an almost 10% difference. In a significant race-ending sprint, that wattage difference could be a big deal. Another interesting piece to note is that the decrease is much more gradual on the zPower side. When I stop putting in effort, my watts will instantly go to zero. However, and depending on your specific trainer, the flywheel you have will keep some of your momentum in the trainer and your wheel will continue to spin for some amount of time as your speed decreases.
Conclusion
After running this test, I was honestly very surprised at the accuracy that Zwift is able to achieve through a data-based estimation. It’s actually very impressive! I know the same accuracy results will likely not be the same for everyone (see the ‘Recommendations’ for tips on how to improve zPower accuracy) but from my testing I can say that I was impressed.
Knowing how power meters work, and how the calculations are made by zPower, can be a great tool to have when you are training on Zwift and are curious as to why you can’t put out huge wattage in a sprint as quickly as your fellow racers, or why you are able to keep a much smoother and consistent power curve than those with direct power meters are. I very much enjoyed diving into this data, and if you are interested in checking out my actual data set, I have made it public on ZwiftPower! Just keep in mind that I am still in training, so the power numbers are still those of an amateur cycling enthusiast.
Recommendations
There are likely a few people reading who are curious whether the results that I got are going to be similar to the results that you see. Since quite a few variables are involved, I’ll share three things that you can do to help your trainer give the most accurate zPower numbers possible (see Zwift Support for more information)
Use a compatible trainer. The Zwift website has a list of the trainers (non-smart) that they have done extensive testing with. That data is the reason that Zwift is able to calculate an accurate power. I personally use the Giant Cyclotron Mag trainer. If you use a magnetic trainer (or any trainer with a variable resistance) Zwift will tell you which resistance value to use. Make sure to use it!
Keep the trainer tight. When you tighten the trainer to the wheel, you want to be sure that it will not slip during the workout, because that will create inconsistent speed ratings. I do this by turning the wheel directly as a test to see if you can hear any slip. If turning the wheel manually causes that skid sound, it’s a good idea to give it another quarter-turn until it’s solid. If your wheel is slipping, Zwift will usually catch it and put a pop up in-game to alert you, and it could kill your power until you tighten it (it’s the worst if you’re in the middle of a race… so best to just make it’s tight from the beginning).
Pump the tires to a normal PSI. This part isn’t tricky, but it is easily forgotten. Just as you would before an outdoor ride, check the PSI in your tires and make sure it is at a normal value, similar to what you would ride outside.
Ride on!
What About You?
Have you ever compared Zwift’s zPower estimates with a power meter? What did you conclude? Share below!
