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#131
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Beware of PowerCranks
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#132
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Beware of PowerCranks
On Jul 31, 7:54 pm, Doug Taylor wrote:
On Tue, 31 Jul 2007 11:30:58 -0700, wrote: In my opinion, the limiter is the ability to deliver oxygen to the mitochondria so the mitochonria compensate by using another mechanism with lactic acid as an end point. Once there are enough mitochondria in this situation the amount of lactic acid being produced overwhelms the bodies ability to compensate for this and the "failure cascade" starts. Pardon me if I switch topics, but now that Frank is posting I want to get back to the subject ofPowercranksand strength training . Jobst Brandt has opined - I hope I am not misconstruing him - that the full circle muscular movement thatPowercrankstrain, is not really used when pedaling a bicycle. Good old stomping is how regular cranks work mechanically. I'm still a beginner on myPowercranksand usually manage a low cadence. I trained them on the basement trainer over the winter, and now use them only about twice a month (hint: they are absolutely perfect to use when taking a spin with your S.O. if she, or he, is a less strong cyclist. They slow you, or at least me, down enough so that we actually can ride together.) Anecdote: I took out my single speed maintain bike this evening for the first time this season and the first time ever after usingPowercranks. Anyone who climbs on single speeds knows that the gearing is much higher than what would be used on a multi geared bike, and that standing and grinding at a very low cadence, rather than sitting and spinning, is what gets you up and over. I found that an approximation of a circular pedaling motion works much more efficiently than stomping in this venue, and that I was noticeably stronger over terrain that in the past was much more difficult. So, anecdotally and subjectively, I'm thinking these puppies have made me stronger. FWIW. First, Jobst is wrong. Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? People get confused when they look at measured pedal forces and they see everyone with negative forces on the back stroke and very large forces on the down stroke. They construe this to mean that stomping is the way to go. What they forget is the effects of gravity on those measured forces. By way of example Let's say you measure your forces and find that you are putting 50 lbs of force on the down stroke each revolution and a negative 5 lbs on the up stroke. From this you think you are a masher. However, If you consider that each leg weighs perhaps 25 lbs what this really means is you are really pulling up with 20 lbs force when you see those negative 5 lbs on the pedal and that 25 lbs of the downward force is actually the weight of the leg such that you are only actually pushing with 20 lbs of muscular force on the downward portion. So you are actively pushing with 25 lbs force and pulling with 20 lbs force, what almost anyone would call close to pedaling in circles, even though the forces on the pedals do not look like that at all. If all PowerCranks does is make the rider completely unweight then they only have to pull up another 5 lbs and now they are pushing with 25 lbs force and pulling with 25 lbs force, what anyone would consider pedaling in circles I am sure, even though the forces on the pedals would be 50 on the downstroke and 0 on the up. |
#133
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Beware of PowerCranks
On Aug 3, 2:14 am, wrote:
Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? [...] What they forget is the effects of gravity on those measured forces. You're saying that on the moon your cranks would be one-sixth as effective? |
#134
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Beware of PowerCranks
On Aug 3, 1:37 am, wrote:
On Aug 3, 2:14 am, wrote: Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? [...] What they forget is the effects of gravity on those measured forces. You're saying that on the moon your cranks would be one-sixth as effective? One-sixth as effective as what? bicycle cranks? training devices to train "circular" pedaling on earth? training devices for space? |
#135
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Beware of PowerCranks
On Aug 3, 6:35 pm, wrote:
On Aug 3, 1:37 am, wrote: On Aug 3, 2:14 am, wrote: Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? [...] What they forget is the effects of gravity on those measured forces. You're saying that on the moon your cranks would be one-sixth as effective? One-sixth as effective as what? bicycle cranks? training devices to train "circular" pedaling on earth? training devices for space? I don't know. I'm asking. You're saying that everyone but you forgets acceleration due to gravity. So can you estimate the difference in power an astronaut could make if he used a regularly-cranked ergometer on the ISS? |
#136
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Beware of PowerCranks
On Aug 3, 10:21 pm, wrote:
On Aug 3, 6:35 pm, wrote: On Aug 3, 1:37 am, wrote: On Aug 3, 2:14 am, wrote: Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? [...] What they forget is the effects of gravity on those measured forces. You're saying that on the moon your cranks would be one-sixth as effective? One-sixth as effective as what? bicycle cranks? training devices to train "circular" pedaling on earth? training devices for space? I don't know. I'm asking. You're saying that everyone but you forgets acceleration due to gravity. So can you estimate the difference in power an astronaut could make if he used a regularly-cranked ergometer on the ISS? regarding your comment that everyone but me "forgets" acceleration due to gravity - Have you ever seen anyone else mention that the forces on the pedals do not actually represent the muscular forces involved? I haven't, at least in any of these threads. I am not sure what an astronaut can or would do on the ISS. Their problem is going to be that unless they are somehow glued to the seat their forces have to be completely balanced or they are going to fly off the seat. I am sure this takes a little (or a lot of) getting used to and since their main job is not to see how good they can get on the exercise bike but, rather, simply maintain enough muscular and cardiovascular fitness such that they might be able to actually stand up when they return to earth, I suspect most of them see substantial drops in power compared to what they could do on the earth before they went into space. |
#137
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Beware of PowerCranks
On Aug 4, 7:51 pm, wrote:
On Aug 3, 10:21 pm, wrote: On Aug 3, 6:35 pm, wrote: On Aug 3, 1:37 am, wrote: On Aug 3, 2:14 am, wrote: Everyone pedals in circles to some degree, in that they do some work on the back stroke, the only question is how much do they do? [...] What they forget is the effects of gravity on those measured forces. You're saying that on the moon your cranks would be one-sixth as effective? One-sixth as effective as what? bicycle cranks? training devices to train "circular" pedaling on earth? training devices for space? I don't know. I'm asking. You're saying that everyone but you forgets acceleration due to gravity. So can you estimate the difference in power an astronaut could make if he used a regularly-cranked ergometer on the ISS? regarding your comment that everyone but me "forgets" acceleration due to gravity - Have you ever seen anyone else mention that the forces on the pedals do not actually represent the muscular forces involved? I haven't, at least in any of these threads. I am not sure what an astronaut can or would do on the ISS. Their problem is going to be that unless they are somehow glued to the seat their forces have to be completely balanced or they are going to fly off the seat. Then what would an astronaut be able to do on Mars? |
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