I’m going to float a theory out there to see what other people think. I’ve been riding PC’s now nearly exclusively since September. I’m pretty well adapted now, and can do my long rides on them with minimal discomfort. The last few weeks though I haven’t been able to resist the temptation to bust out the tri bike with regular cranks for a few rides. I’ve experimented with “regular” pedaling vs PC-style pedaling on regular cranks, and I think I’ve come to an interesting observation about the real source of benefit from PC’s….
Anecdotally, everyone always comments that your rear side really hurts when riding PC’s. I’ve long-since noticed that to be really smooth and fluid on the PC’s I need to rest all my body weight on the saddle and not support any of my weight from my arms or legs. I didn’t put it together, though, until I got on regular cranks that this is, in fact, the chief source of benefit from PC’s. On regular cranks I have a tendency to support body weight with my legs whenever I’m really hammering or in the latter stages of a long ride when I’m starting to get really uncomfortable. It takes a lot of leg power to do this. Imagine riding with your butt supported about 1 millimeter above the saddle. In order to be able to do this you need to provide enough resistance with the recovering leg to permit the driving leg to not only drive the crank but to also lift the body. If you rode with your butt 1 millimeter off the saddle you’d feel it in your quads very quickly. I believe that this is going on to a much smaller degree all the time with regular cranks. It is this resistance by the recovering leg to permit saddle unweighting that is causing inefficiency, in my opinion- not just the weight of the recovering leg or not pulling up. I do believe that there is some benefit to using the hip flexors to raise the recovering leg, and that there is some associated benefit to running from training the HF’s this way. However, I’m asserting that the primary benefits of PC’s to cycling can be had by making sure that all of your weight is on the saddle and that you’re not using your legs to unweight the saddle. I think that pedaling in circles and applying power during the recovery stroke are secondary to this benefit. I’d really like to hear opinions on this.
jkatsoudas wrote: It is this resistance by the recovering leg to permit saddle unweighting that is causing inefficiency, in my opinion- not just the weight of the recovering leg or not pulling up.
I think you are right, at least for newbies (like us). It is true that you sit “heavy” on the saddle while on PC’s. I think, with a couple of years of training, you might be able to actually add power to the pedal stroke with your hip flexors, THEN, the benefits would be more than just removing the 1mm float tendency that we seem to have when riding regular cranks.
However, the run benefits are simply too good to be ignored…that just has to be hip flexor and/or improved neuromuscular efficiency (i.e., better timing of the firing of your running muscles) going on. This run improvement happens so quickly, I’m thinking it’s an improved timing aspect.
Who knows? It probably depends upon the most glaring weakness at the starting point for each individual.
If you weigh 150 lbs then the totality of the forces up on the body from the bicycle must be 150 lbs. The only places of contact with the bicycle are the handlebars, seat and pedals. On ordinary cranks, one is pushing down with both legs (even on the recovery) such that the forces on the handlebars and seat do not have to be particularly large to come up to the total. One PowerCranks, the first thing that happens is you stop pushing as hard on the downstroke to help keep the caadence down and don’t push down at all on the back stroke, even maybe pulling up some which would be seen as a negative force. This greatly magnifies the weight that must now be supported on either the handlebars or the seat. Until one gets to the point that they can start pushing down with considerable force the butt will take the brunt of this, which takes some getting used to.
Now, I think you may have something here in your analysis. In most mechanical systems, work requires applying a force through a distance. Mechanically, it requires no “work” to unweight the butt from the saddle since it doesn’t move anywhere, so it requires no energy. However, this is a biological system we are talking about. Biologicaal systems require energy to do everything so simply applying force, even though it is doing no “work”, requires energy. Unweighting the butt with either the legs or arms is a wasteful use of energy from the point of view of propelling the bicycle. By eliminating this loss, PowerCranks can help the rider get more of the total body energy expended into the pedals todrive the bicycle.
I have been training with powercranks for about six months now and continue to simply record my observations, preliminarily to someday drawing some conclusions about their relative benefits or not. After six months, as my training and intensity has started to ramp up, one unexpected thing I am observing is that when I switch to regular cranks, I have significantly increased endurance and strength when climbing out of the saddle. I have always been a good climber, and have an extensive running backround (although I have exclusively cycled for the last five years). My sense is that my hip flexors are now able to greatly contribute to the out of the saddle riding. What think you?