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Home > Forum > Triathlon Forum > Turbo vs spin bike watts and muscular strain

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Turbo vs spin bike watts and muscular strain
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gerow
Apr 4, 19 1:46
Post #1 of 6 (942 views)
Hi all, wondering if anyone has any insight into something strange I've noticed with my bike training.

I've spent most of the winter training on a spin bike with a power meter. I'm pretty sure the pm is good, they're kept calibrated and a I know a lot of guys using them say they report similar numbers to their own pms/trainers. I have vector 3s on my bike, and recently also started training on a kickr snap at home. What I've noticed is that at lower power on the kickr snap I'm perfectly happy, but as soon as I get up towards and above FTP the muscular strain is so much higher that I can hardly keep my legs turning over.

I'm planning to retest on the trainer so I have a second number to train with on that, but was wondering whether anyone had had similar experiences, or had any ideas why the apparent strength/muscular strain was so much higher on the turbo.

Cheers
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Re: Turbo vs spin bike watts and muscular strain [georgeox] [ In reply to ]
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Ai_1
Apr 4, 19 2:17
Post #2 of 6 (920 views)
Are you using both in the same way?
For example, are you using similar cadence, and are you using ERG mode on the trainer?

Power is power so if your cadence is the same, and the pedal force is higher, then power is higher.
Of course there could be differences in your position between the bikes that's having an impact. A much bigger flywheel on one of the systems would effect how consistently you have to apply power around the stroke and would make things feel different, etc...
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Re: Turbo vs spin bike watts and muscular strain [Ai_1] [ In reply to ]
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burnthesheep
Apr 4, 19 5:07
Post #3 of 6 (870 views)
I thought the smart trainers were supposed to have some kind of force application in the design to give some semblance of "road feel". And this was a setting?
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Re: Turbo vs spin bike watts and muscular strain [georgeox] [ In reply to ]
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RowToTri
Apr 4, 19 5:45
Post #4 of 6 (839 views)
Is there a significant difference in crank arm length?

Spin bikes usually have a lot more intertia, which helps keep cadence higher because it does not slow down as much over the dead parts of the stroke.
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Last edited by: RowToTri: Apr 4, 19 5:45
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Re: Turbo vs spin bike watts and muscular strain [Ai_1] [ In reply to ]
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gerow
Apr 4, 19 6:00
Post #5 of 6 (817 views)
Ai_1 wrote:
Are you using both in the same way?
For example, are you using similar cadence, and are you using ERG mode on the trainer?

Power is power so if your cadence is the same, and the pedal force is higher, then power is higher.
Of course there could be differences in your position between the bikes that's having an impact. A much bigger flywheel on one of the systems would effect how consistently you have to apply power around the stroke and would make things feel different, etc...

I'm trying to sit at the same cadence... I usually spin pretty high but it's this turnover that seems to require a lot more effort. I've mostly been using ERG mode, need to try resistance mode a bit more to see if it makes much of a difference.
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Re: Turbo vs spin bike watts and muscular strain [RowToTri] [ In reply to ]
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gerow
Apr 4, 19 6:10
Post #6 of 6 (811 views)
RowToTri wrote:
Is there a significant difference in crank arm length?

Spin bikes usually have a lot more intertia, which helps keep cadence higher because it does not slow down as much over the dead parts of the stroke.

I think there's just 2.5mm difference between the cranks; 170mm on the spin bike and 172.5mm on mine.

I suspect the inertia is what's causing the difference in feel. The flywheel on the spin bike is slightly lighter than the snap, but it's much bigger, so you're right that it'll have a higher moment of inertia.

Guess I just have to get used to the different feeling and hope it doesn't take too long to get back up to my usual numbers!
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