Timeline for What's the lowest safe cadence on a climb?
Current License: CC BY-SA 3.0
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| Jul 23, 2015 at 12:32 | history | edited | Daniel R Hicks | CC BY-SA 3.0 |
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| Jul 22, 2014 at 12:49 | comment | added | R. Chung | @DanielRHicks: you're right that max pedal force isn't constant across all cyclists but the classic dataset collected by Kautz (isbweb.org/data/kautz, or anonymous.coward.free.fr/rbr/kautz.png) shows that max pedal force is roughly twice avg. pedal force (in the Kautz data, max is 1.85x avg), whence the rule of thumb cited above. This has been verified by more recent pedal-based power meters like the Garmin Vector. | |
| Jul 22, 2014 at 11:31 | comment | added | Daniel R Hicks | @R.Chung - I don't know how you'd be able to calculate the maximal force, since even the best cyclist's stroke is not smooth, especially at low RPM. You might calculate, say, RMS force, but that could easily be off by 2-3x. | |
| Jul 22, 2014 at 7:39 | comment | added | R. Chung | It's easy to calculate the maximum force at the pedal but it's hard to calculate the "safe" force at the knee since that depends on your knee. A reasonable rule of thumb is that max pedal force is around 12*watts/rpm, and that applies whether riding on the flat, gentle climbs, or brutal climbs. Of course, on brutal climbs you'll need the right gearing to keep your power down -- with your current gearing up a 15% slope your power at 90 rpm wouldn't be 225 watts. | |
| Jul 21, 2014 at 16:03 | comment | added | Daniel R Hicks | I don't have the physiological data/knowledge to figure this out. One problem is that, even with good seat height, the knee is bent at a fairly sharp angle when the maximal force is applied, whereas when walking/running (the most-studied activities) the knee is at a much shallower angle. I did find this, though I didn't attempt to digest it: physicaltherapyjournal.com/content/67/9/1365.full.pdf | |
| Jul 21, 2014 at 15:52 | comment | added | sjakubowski | That is something that was missing from the answer and my understanding. Is there a range or best practice to be able to calculate safe force. I have all the raw data and variables at my disposal which is a big advantage and hope there exists something to point me in a safe direction. | |
| Jul 21, 2014 at 15:49 | comment | added | Daniel R Hicks | When you're doing that wattage on the flat you're applying a much lower force to your knees. Wattage = force times RPM. | |
| Jul 21, 2014 at 15:44 | comment | added | sjakubowski | But I am already measuring force and I can sustain that wattage. I can sustain that wattage on the flats spinning much faster and am not concerned as that is normal. The risk is the low cadence no? | |
| Jul 21, 2014 at 15:41 | comment | added | Daniel R Hicks | @sjakubowski - As others have indicated, it's not simply cadence that is the issue, but rather the maximum force applied. It's just that at higher cadence your aerobic capacity (usually) limits you before you can cause injury. But you might want to consider my rule of thumb which is to never sustain (for more than say 5 minutes) a cadence that is slower than your respiration rate. This seems to fit a wide variety of circumstances pretty well. | |
| Jul 21, 2014 at 15:35 | comment | added | sjakubowski | This is a great answer and I am tempted to accept (up voted) What is missing from it is what cadence am I reasonably safe from risk of this type of injury. Am I supposed to avoid this until I can safely make 60rpm? 70rpm? How I get there in terms of power or weight does it matter? | |
| Jul 21, 2014 at 15:09 | history | answered | Daniel R Hicks | CC BY-SA 3.0 |
