beng1

Through circumstance I have had to spend an hour a week at a local YMCA which has Keiser brand spin-bikes for it's members to use in spin classes and individually. The bikes are fitted with digital readouts showing RPM, Watts, time, distance and heart rate. I have no experience spending time in gyms of any sort, and no experience riding with any sort of wattage meters. The last time I had a digital readout on a bicycle was in the 1990s one year.

I thought it would be interesting to compare a ride on the Keiser bike to a real-world ride I have done hundreds of times on classic steel road bikes, a 12.1 mile loop of a flat local route that has been used for many sporting events for decades including time-trials and triathlons. After a few hundred laps of this course over the last few years I know that on an average warm day with no significant wind I can loop my 61 year-old butt around it between 19mph and 21mph depending on what sort of day I am having with one of four different bicycles I often use there.

So I got onto the Keiser after adjusting the seat position and started pedaling wearing sneakers, blue-jeans and a white v-neck T-shirt. I set the Keiser to "14th" gear so it was easy to spin and off I went on a virtual 12.1 mile ride. My position was similar to riding on the "hoods" on one of my bicycles. I ran my pedal rpm up to above 80, and I had to exert myself in "zone 2" to keep that cadence, where I was breathing harder than normal, but I could converse in short sentences if I had to. I had no intention of riding in "zone 3" where I would be breathing so hard I would be unable to talk. At the seven mile mark I switched to 15th gear and the watt meter went from reading around 170 to about 190 or 200 for the same pedal cadence between 80 and 90 rpm. I tried to keep the rpm in the lower 80s to make things easier on myself, I was sweating about the same as if it was a real ride on a warm day, and the pedal resistance and rpm was about the same as I was used to on the hundreds of rides of a similar length I had taken on my road bikes.

After 12.1 miles came up I stopped and the readout said my average pedal rpm was 82, my average watts was 172, and I had covered the 12.1 miles in exactly 30 minutes flat !!! Boy I wish.

Obviously there was something seriously out of whack with the calibration of the machine. With that sort of pedal rpm and effort in the real world, I would be much more likely to cover 12.1 miles in 39 or 40 minutes is my guess at about 18 to 19mph.

I played with a few cycling calculators entering data for myself and my 35-pound Huffy road bike I had used in a 12-mile TT last summer where it had averaged 19.5mph, and one calculator spit out 170 watts, another said over 200 watts though, the two averaging close to the 170 average of the Keiser. So maybe although the time reading was off by 30%, the watts were more accurate.

In the end I don't think the members of the gym are getting any good information off the Keiser bikes there. There are a number of the bikes at this gym, maybe up to a few dozen. If I get another chance next week maybe I will try another bike for the same distance and see if it reads completely differently or about the same. The bike I was using was in a room with about a dozen or so others used for actual spin classes, so I would think it's calibration would be important, or that someone in one of the classes would notice if various bikes they used gave wildly different times or distances for their regular classes.

If anyone else has any experience comparing Keiser or similar spin-class bikes with real-world riding experiences put them up.

Eric F 

It sounds like the indoor bike doesn't calculate for wind resistance of riding IRL. No surprise at all. Expecting an IRL experience on that bike is kind of a stretch, IMO.

Also, Zone 2 is easier than you're describing...but that's a different topic.

indyfabz

Let’s see the actual bike, instead of a stock photo.

shelbyfv

I don't think anyone expects a spin bike experience to have much relationship to cycling.

terrymorse 

Considering the uncertanties involved, nobody should think that the speeds estimated by a stationary bike are likely to match an outdoor ride.

But who cares? For workout purposes, speed makes no difference at all.

What matters is power versus time, and if the bike's power meter is calibrated, that should be accurate.

With today's rain and gale force wind advisory, I'll be doing a Zwift indoor ride today, and I won't even look at the distance or average speed.

[edited for tone]

beng1

So it is not sensible to think that man can land rovers on Mars and has been designing bicycles for a few hundred years, and developing digital technology for seventy years, and should also be able to manufacture an accurate exercise bicycle. Okay...........

beng1

I can certainly adjust the resistance of a stationary bike to feel like the resistance felt on hundreds of real-world rides over thousands of miles on more or less level riding in moderate wind conditions, especially with a tachometer to assure pedal cadence, and any other cyclist with the same experience under their belt could do the same. Try again.........or not.

shelbyfv

Offer your expertise (and a pot full of $) to the Y, maybe they'll buy something you like better.BTW, there's an "indoor cycling" section right here on BF !

terrymorse 

Try planning a Mars landing without knowing the mass of the payload, the value of "g", or the density of Mars' atmosphere.

Now try to estimate speed of rider+bike over some unknown road surface, with unknown wind conditions, unknown air density, unknown tire rolling resistance, unknown CdA.

A person going through this thought exercise ought to realize that both of these exercises will produce only a very rough estimate.

[edited for tone]

Jughed

Power is power - 170W is 170w regardless of type of bike.

But outside conditions vary greatly, indoor bike is steady. No wind, no hills, no weather...

The closest thing to reality would be a smart trainer connected to Zwift - where zwift feeds resistance data back to your trainer. In order to do 19.5 here, you need 195w, or 225w because of headwinds or grade.

A static trainer has very little correlation to real world conditions - except power.

For example, my last 19.5 mph outdoor ride was 227W average for 1.5 hours. 227W on my turbo trainer, with my bike and the same power meter pedals, is like 24MPH.

terrymorse 

And even power is "different" on a stationary bike.

Well, power is power, but a given power output feels harder on a stationary bike than on the road.

BillyD

Is this "sensible person" **** really necessary to have a conversation, Terry?

Eric F 

Your arrogant need to assert that you know more than anyone else got in the way of getting my point.

IRL, a big part of your power output is consumed by pushing through the air (I know you know this). On that indoor bike, I would guess that the distance calculation is based solely on revolutions of the wheel with no compensation for estimated aerodynamic drag. This would account for the difference in time to cover the same distance when comparing your IRL ride to the indoor bike. Could aerodynamic drag be calculated? Sure. Some virtual cycling programs do a pretty decent job of it. On the bike you're talking about, I'm not at all surprised that this compensation is not included.

Trakhak

Spin bikes are a few generations behind the state of the art. I resisted spending the money on a smart trainer for years, but then succumbed.

I don't mind doing indoor rides throughout the winter when I can't face the cold or wet, but the little inner voice that wonders whether I should be working harder or taking it easier or doing either for longer or shorter intervals really saps my concentration.

Now, I just fire up Xert (software that monitors my fitness, or lack thereof, and my progress, or lack thereof, and dynamically adjusts the workout accordingly) and do the prescribed workout. The software controls the resistance on the basis of my heart rate, cadence, and power output (and also incorporates the same and other data from the previous week, month, etc.).

Turns out my previous indoor rides on dumb trainers were usually uniformly in the a-bit-too-hard-for-too-long zone, paradoxically limiting my progress. Now, I finish every hard-ish workout feeling moderately fatigued while knowing that the next day's workout will be set in a very easy recovery zone.

Many people like smart trainers for the social aspect of virtual group riding or racing. Tried that once or twice, but it felt too random. I do structured workouts exclusively.

Eric F 

I do both structured workouts and group rides on Zwift. The social aspect of group rides is important to me. Not chatting, but just riding and interacting with other riders in real time. Even if I start off just riding solo at a targeted effort level, it's not uncommon for me to come across others who are riding at a similar pace, and a spontaneous group forms.

terrymorse 

Is that a scolding? Because it sort of sounds like a scolding.

Eric F 

A warning shot across the bow, perhaps.

terrymorse 

Fair enough, I edited to hopefully seem less insulting.

Eric F 

Considering the history of how that particular person interacts with other members, I didn't think it was out of line. That said, I'm just a member, not a Mod/Admin. My opinion is pretty irrelevant.

PeteHski

In my experience of gym bikes they are nearly always over-optimistic in their speed/distance calculations, even if their power measurement is reasonably accurate. They just have a very simplistic bike/rider model (maybe based on riding in a Velodrome on a track bike in a skin suit vs road bike - who knows what parameters?). Smart trainers are much more realistic in this respect and you can see what type of riding they are trying to represent, but their accuracy depends on what App you use i.e. their bike/world modelling. Zwift for example is generally optimistic on speed, riding in perfectly still conditions in a good aero position. But not unrealistic for those conditions.

indyfabz

Best to just ignore.

seypat

Indoor cycling is not meant to mimic the real world experience unless you're talking about zwift. Simply a way to get exercise/train. The gym I belong to pre covid would give free jerseys to people who wanted to represent the gym at the local cycling events. In one class of at least 30 participants, the instructor mentioned this. He asked for a show of hands as to how many people had real bikes and would be interested in repping the gym. Only one other person and I had real bikes and also rode outside. I mentioned that I had bikes to loan if others wanted to try it out. No takers. Most of the class had their own cycling shoes and some had on cycling pants. Go figure. Like a lot of real world cyclists, the social aspect is the draw.

seypat

The Keisers are nice. Lots of fit adjustability and accurate power readings.

https://www.keiser.com/fitness-equip...i-indoor-cycle

seypat

The gym I use has different hybrid classes such as cycle/core, cycle/stength with weights, etc, etc. The also have a group fitness class called Butts and Guts.

Then there's this. Looks just like real world cycling to me. Probably a lot of fun. Not for the serious cyclist like the one in the Performance video, though.

seypat

Indoor might be the better place to train the engine.