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Power Cranks good for obtaining a good power stroke?

 
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Anonymous
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PostPosted: Sun Mar 27, 2005 11:00 pm GMT +0000    Post subject: Power Cranks good for obtaining a good power stroke? Reply with quote

Even after getting a pretty good bike/cleat fit, I still get occasional sharp pains in my left knee during hard flat road rides, especially into the wind.

However, I don't get them during hard hilly road rides of the same duration.

I've been trying to improve my pedal stroke, thinking I may be getting sloppy on the flat rides.

In the meantime, a friend pointed me to the Power Cranks website. If price wasn't an issue, would these be helpful in obtaining a good pedal stroke? They seem to make sense.

Thanks in advance.
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Anonymous
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PostPosted: Mon Mar 28, 2005 8:00 pm GMT +0000    Post subject: Reply with quote

Yes. They will help even out your power distribution around a pedal revolution. However, it is debateable whether this helps performance or not. Some research shows the cranks help some don't. I don't recall having seen a study that shows a negative effect so have at it if you think it is a good place to put your $$$. If you dont have a power meter though I'd say get that first.

Other things that work on pedal stroke:
1) Just unclip one foot.
2) Concentrate on pedaling circles. There are a million different ways to do this (i.e. pedal like you are scraping mud off your shoe, drive your knee towards the stem on every revolution etc).
3) Pedal at high cadence for extend periods of time (like 120-130 rpm)
4) Rollers

Arnie Baker has a book with some single-leg trainer workouts.
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Anonymous
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PostPosted: Fri Apr 01, 2005 4:02 pm GMT +0000    Post subject: Reply with quote

A huge thing that helped me learn to 'spin' when I had knee problems was switching to a shorter crank arm....It totally taught me to spin a much higher cadence efficiently and got rid of my knee problems.
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PostPosted: Mon Apr 04, 2005 2:05 pm GMT +0000    Post subject: Reply with quote

pik20b:

There is only one published report on Rotor Cranks. I have pasted the PubMed Summary below:

Med Sci Sports Exerc. 2002 Nov;34(11):1854-8.

A new pedaling design: the Rotor--effects on cycling performance.

Santalla A, Manzano JM, Perez M, Lucia A.

Universidad Alfonso X El Sabio, Madrid, Spain.

PURPOSE: To assess the effects of the Rotor (ROT), a new pedaling system that makes each pedal independent from the other so that cranks are no longer fixed at 180 degrees, on endurance cycling performance. METHODS: Following a randomized design, eight subjects (noncyclists; age (mean +/- SEM): 22 +/- 1 yr; VO(2max): 51.8 +/- 1.0 mL x kg(-1) x min(-1)) performed two bicycle-ergometer tests on separate days, one with the conventional pedaling system (CON) and the other one with ROT. Starting at 75 W, the power output was increased by 25 W at 3-min intervals until volitional exhaustion. Gas exchange parameters and blood
lactate were measured for every 3-min interval. RESULTS: At exercise intensities between 60 and 90% VO(2max), delta efficiency (DE) was significantly higher in ROT than in CON (24.4 +/- 1.9% vs 21.1 +/- 1.1%, respectively).
CONCLUSIONS: Although more research is needed, especially with trained riders, the Rotor system might improve delta efficiency during endurance cycling. Other performance determinants VO(2max), maximal power output) do not seem to be changed compared with the conventional system.

Publication Types:
Evaluation Studies

PMID: 12439093

The tip drewmedlock gives regarding the shorter cranks can be helpful as well. Not only will the shorter cranks make higher RMP spinning easier, you will flex your knee less at top dead center of your pedal stroke and put less stress on you knee. Additionally it is important to make sure you saddle height and seat position is optimized. If you seat is too low or too far forward you will over flex your knee with each stroke.

Another possible cause you knee pain as you astutely point out is the quality of your stroke. It is possible you may be using a smoother, higher RPM stroke when you climb and a choppier, lower RPM, gear mashing stroke when you are riding the flats in the head wind. Look at a head wind as a great big long hill and ride it as such, you may find your knee maladies improving with a simple change in your style of pedaling.

Thanks,
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Anonymous
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PostPosted: Tue Apr 05, 2005 12:21 am GMT +0000    Post subject: Reply with quote

Doc, we're talking about Power Cranks here.
http://www.powercranks.com/

That study is for Rotor Cranks.
http://www.rotorcranksusa.com/

Anyway, Power Cranks has some info on their site. I am too lazy to search pub med so I am not going to quote anything.

Bottom line, do Power Cranks increase pedaling efficiency? Yes, but so do many other training techniques. Since very few if any of us have used Power Cranks and there are very few studies done on them we cant tell you how effective they will be for you.

One thing I can tell you is that if you currently do nothing to improve your pedaling technique then Power Cranks will be a big improvement.

Paul
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The Bike Doc
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Joined: 08 May 2003
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Location: Corpus Christi and Warda, Texas

PostPosted: Tue Apr 05, 2005 5:02 am GMT +0000    Post subject: Reply with quote

PaulBurpo:

Thanks for correcting me on the Rotors versus the Power Cranks. There is one study published on Powercranks it was at submaximal output that showed benefit. It is summarized below from PubMed.

J Strength Cond Res. 2003 Nov;17(4):785-91.

Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency.

Luttrell MD, Potteiger JA.

Department of Health, Sport and Exercise Science, University of Kansas, Lawrence
66045, USA.

Powercranks use a specially designed clutch to promote independent pedal work by each leg during cycling. We examined the effects of 6 wk of training on cyclists using Powercranks (n=6) or normal cranks (n=6) on maximal oxygen consumption (VO2max) and anaerobic threshold (AT) during a graded exercise test (GXT), and heart rate (HR), oxygen consumption (VO2), respiratory exchange ration (RER), and gross efficiency (GE) during a 1-hour submaximal ride at a constant load.
Subjects trained at 70% of VO2max for 1 h.d(-1), 3 d.wk(-1), for 6 weeks. The GXT and 1-hour submaximal ride were performed using normal cranks pretraining and posttraining. The 1-hour submaximal ride was performed at an intensity equal to approximately 69% of pretraining VO2max with VO2, RER, GE, and HR determined at 15-minute intervals during the ride. No differences were observed between or within groups for VO2max or AT during the GXT. The Powercranks group had significantly higher GE values than the normal cranks group (23.6 +/- 1.3% versus 21.3 +/- 1.7%, and 23.9 +/- 1.4% versus 21.0 +/- 1.9% at 45 and 60 min, respectively), and significantly lower HR at 30, 45, and 60 minutes and VO 2 at 45 and 60 minutes during the 1-hour submaximal ride posttraining. It appears that 6 weeks of training with Powercranks induced physiological adaptations that reduced energy expenditure during a 1-hour submaximal ride.

Publication Types:
Clinical Trial

PMID: 14666944
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PostPosted: Fri Apr 08, 2005 11:34 am GMT +0000    Post subject: Reply with quote

Thanks for the information.

I've been trying to work on my pedal stroke by listening to the chain sound and feeling for constant chain tension.

I think I'll keep working on the 'free' solutions via rollers and dedicated pedaling practice. I guess I was fishing for a magical solution.

Thanks again. Very Happy
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