Uphill cadence rate, bad for my knees??

[tanggoman]

I have a question for our resident experts here... I was climbing a fairly decent grade yesterday, around 15-20% grade, with a 34FX27R gear ratio. I can only maintain a 70-75 rpms. What is the ideal cadence for this type of climb that will not strain too much the knees? Thanks!

 

[gntlmn]

Originally posted by tanggoman
I have a question for our resident experts here... I was climbing a fairly decent grade yesterday, around 15-20% grade, with a 34FX27R gear ratio. I can only maintain a 70-75 rpms. What is the ideal cadence for this type of climb that will not strain too much the knees? Thanks!

The answer is not that simple. Consider this scenario: speeding up for a while and doing 90 - 100 rpms in the same gear. Would you be putting less strain on your knees than you are now in this gear? I think not because you are going faster, and still pushing the same gear. Conversely, if you slowed to 60 rpms in the same gear, would you be putting more stress? I think not either because you are going slower. So gearing, I suspect is a factor as well.

Another way to look at this is the following: if you spin always at 100 rpms, for example, you will be putting less strain on your knees than you would at any lower spin rate. This is because you would have to be in a higher gear if you were to maintain the same speed at a lower cadence during your entire ride. If you are in a higher gear at each step of the way, the knee strain is going to be greater.

What riders have a problem with is that it takes more aerobic energy to spin faster than slower. This is because energy is being expelled as you lift your legs up and down through the motion of your spin. This increases as you increase your cadence. You are moving your legs through their range of motion at a greater rate. This is easy to imagine by asking yourself what is easier to do without pedals while sitting in the saddle: spinning at 80 rmps or 100. The answer is simple. This is without considering the force you apply against the pedals. This is why many riders are reluctant to use higher cadences, especially if their form is bad. Even with good form, don't quote me on this because I'm not sure, but I think you may have to increase by 5% your aerobic output to maintain your speed on a climb with a cadence of something like 90 instead of your 80 or so. But if you train this way, you will be able to maintain this because your legs will have less strain on them.

I don't know the answer to your question, but I would suspect you might want to gear down to get a higher rpm if you cannot maintain 90-100 rpms in the current gear. I have heard that range many times.

 

[dhk]

Agree with gntlmn; you have to gear down to reduce the pedal force required to climb the steep grade, regardless of the cadence. It's not hard to estimate the pedal force required for a given % grade.

But, 70-75 rpm really isn't bad for climbing. On 10% grades, I'm often sitting (and standing) at 40 rpm in 39/26. Standing will give the knees a break also.

Dan