Power Output Compared To 500m Splits
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as you slide down during the recovery, what force is bringing you to a stop? as you start the recovery what gives you forward momentum. There are 2 distinct forces applied here. Once gain using newtonian physics these forces are created by the rower, who will need to expend energy for both of them.<br />If I take 1 second for my recovery, over a period of 1 sec. (1 sec drive, 1 second recovery) (for the sake of the argument, let's say my speed is constant during the recovery. obviously it will not be, so the potential energy figure will be even higher)<br />Energy=1/2*m*v^2 (simple high school equation)<br />=1/2*75*1^2=37.5J, similar physics applies on the drive i guess.<br />So to me using grade 10 physics the 37W is a very feasible number.<br />I don't understand why you think it is total nonsense. DO THE MATHS!
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The article in question holds a lot of variables constant in arriving at the 37w/stroke figure for a 75-kg rower. I'd be interested to know what happens to the numbers if you start to account for recoil, i.e. elastic energy stored in the leg muscles as you come up to the catch. My suspicion is that full compression makes a significant difference, but then again I don't claim to be a physicist. If Physicist (who is) should happen to read this thread and care to comment .... ?!
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<!--QuoteBegin-ajspook+Aug 11 2005, 05:32 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(ajspook @ Aug 11 2005, 05:32 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->Paul, I don't think you've still got your head around the power concept properly.<br />The 37W, is per stroke, per minutes, per 100m, what ever you want to make of it.<br />Did that make sense? <br /> </td></tr></table><br /><br />Okay, so you are just going to add 37watts to the reported Avg Watts? (as long as the other constraints are maintained)<br /><br />What exactly is the productive purpose of that?<br /><br />Perhaps I just don't understand all that's going on here, but the fact that MikeN and myself put together a little thing called ErgMonitor™, might suggest otherwise. <br /><br />What distance do you think you are lifting your body mass through (~1cm), and also what distance does it travel latterally for your calculations? (~0.5m, on low friction bearings)<br /><br />I also doubt that you took into account the tension on the bungee ("negligible" according to C2, while at the same time greater than the work being done to move your body on the drive, my conclusion is that 2 * negligible = negligible.)<br /><br />Finally, watts = joules / sec, you say you've got 37 watts, but there still needs to be something that defines the "sec". The drive is only a small portion of the stroke, the body mass is not moving for another small protion of the stroke, and gravity/bugee is moving the body mass for yet another portion. Or did you mean to say 37J rather than 37W?<br /><br />Cheers!
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LOL, I forgot to hit "Add Reply" last night, and now see that the discussion has progressed. (or has it?)
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<!--QuoteBegin-ajspook+Aug 12 2005, 11:05 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(ajspook @ Aug 12 2005, 11:05 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->...as you start the recovery what gives you forward momentum. ...Once again using newtonian physics these forces are created by the rower, who will need to expend energy for both of them.<br />.....<br />I don't understand why you think it is total nonsense. DO THE MATHS!<br /> </td></tr></table><br /><br />As you start the recovery the forward momentum is given by the stretched bungees wanting to revert to their unstretched form, and the slope of the slide. There is no need to "do the maths" when there is no maths to do, if you have good technique you don't use energy on the recovery. You started this discussion by asking what energy was used on the recovery, so I'm not going to argue over using extra energy to move your body on the drive, and obviously there is some (negligible) amount.<br /><br />If you're going to try to explain things using high school physics, at least quote the equations properly. 1/2mv^2 is kinetic energy, not potential energy. Yes, at the beginning of the recovery there will be potential energy present (mgh), and this aids your recovery, it's not something you produce to do the recovery!<br /><br />Pete<br />Chartered Mathematician
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<!--QuoteBegin-Pete Marston+Aug 12 2005, 08:15 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Pete Marston @ Aug 12 2005, 08:15 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin--><!--QuoteBegin-ajspook+Aug 12 2005, 11:05 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(ajspook @ Aug 12 2005, 11:05 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->...as you start the recovery what gives you forward momentum. ...Once again using newtonian physics these forces are created by the rower, who will need to expend energy for both of them.<br />.....<br />I don't understand why you think it is total nonsense. DO THE MATHS!<br /> </td></tr></table><br /><br />As you start the recovery the forward momentum is given by the stretched bungees wanting to revert to their unstretched form, and the slope of the slide. There is no need to "do the maths" when there is no maths to do, if you have good technique you don't use energy on the recovery. You started this discussion by asking what energy was used on the recovery, so I'm not going to argue over using extra energy to move your body on the drive, and obviously there is some (negligible) amount.<br /><br />If you're going to try to explain things using high school physics, at least quote the equations properly. 1/2mv^2 is kinetic energy, not potential energy. Yes, at the beginning of the recovery there will be potential energy present (mgh), and this aids your recovery, it's not something you produce to do the recovery!<br /><br />Pete<br />Chartered Mathematician <br /> </td></tr></table><br /><br />This is all irrelevant to erging as whatever force is used to move the body up and down the slide, it is not measured by the monitor or by Paul's Erg Monitor software (which I use and recommend). There is however, a force applied in moving the body back and forth and it can be quantified using Newtonian Physics, and you can expand the equations to take into account the bungee and the slope of the rail. You can get a real number. Is it negligible, I don't know, no one has ever told me how many Joules or Watts or whatever is in one negligible.<br /><br />Newtonian physics tells us that if we have a mass on a level, frictionless surface it will take a force to get it moving, the same applies to our bodies on an erg.<br /><br />Fred Dickie
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<!--QuoteBegin--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->There is no need to "do the maths" when there is no maths to do, if you have good technique <b>you don't use energy on the recovery</b>. </td></tr></table><br /><br />Pete,<br /><br />Can you explain this! <br />If "approximately" half the time taken to complete a full stroke is in the recovery how can this not use energy.<br />If you were to do a 30 min piece, then approximately 15 minutes of that would be stroke recovery. This joint flexion and extension required to move from the end of the stroke to recovery must require energy, or am i missing something!<br /><br />Cheers<br />Gary<br />
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Wait, let's not forget to measure the work to pump 300% more blood through your body, the energy to inhale and exhale the massive breaths you take (and the rate you take them), the energy to hold your head still, the force to grip handle. If you simply had your heart at 180, breathing like a stuck pig and gripping the handle as we do, you have quite a physical demand on yourself even if the PM2 said 0 watts. Going up the slide to get another whack at the wheel is just one more source "demand" to get the real work done (as I see it). I'm not sure what the importance of measuring them is exactly. We'll probably never measure in watts the cardiac and ventilation load of rowing a 2k. I've never been a big fan of calling in Newton to explain everything here (but it'd be nice). For instance, loading our joints isometrically is tiring to us and yet no work is done. Hold 400lbs over your head and measure the power sometime......
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We havn't had a good thread on the stroke recovery for a while and this was heading in a constructive direction and died. Pete (and others) i'd to hear more on your thoughts on the energy expenditure or lack of during the recovery. <br /><br />Cheers<br />GW
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Sorry GW, I'd forgotten I hadn't replied to you on this.<br /><br />If you go back to what I said to ajspook some days ago to try, sitting at the finish with the handle in your hands and see what happens if you take your feet off the footplates, also doing the same without the handle in your hands. Both times you slide down to the front. Did you have to expend energy doing this? No, the slide is sloped down to the front end, and the bungees want to bring the handle back too.<br /><br />If your technique is good this is what takes you back down the slide. Ok, so of course you do expend a little energy on the recovery, but I believe it is (or should be) negligible. You start off by straightening your arms - the bungees assist you in this. Then your rock forward from the hips - the bungees assist you in this. Then you allow your knees to bend, and the bungees and slope of the slide let you effortlessly return to the front of the slide ready for the next catch.<br /><br />Maths and physics can be used to show a lot of things that aren't really true in practice. Like the example someone mentioned already - how much work is done holding a heavy weight stationary? It's zero because you're not moving it anywhere, but you're still having to expend energy.
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Pete,<br /><br />IMO there must be an energy output in "controlling" the recovery. <br />The initial movement of pushing your hands away without letting them drop, then contracting your spine angle to get the handle past your knees requires a degree of effort. <br />The middle phase of the recovery is mostly momentum. <br />However i think that the end of the recovery requires additional energy to "brake" as you come into the catch. Especially as the last muscle group activated in the recovery is the legs and then they are the "brakes" as they prepare for the drive at the catch.<br />Just my thoughts, and enjoying a good thread!<br /><br />Cheers<br />gary
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Gary,<br /><br />I'd put that "breaking force" as part of the drive force really, as it is effectively a pushing force with your legs, and very small compared to the force you'll then be driving with.<br /><br />Holding your arms straight, rather than letting the hands drop on the recovery. Yes, must require some energy, but less than to let the hands drop, then pick them back up before the catch?<br /><br />Pete
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<!--QuoteBegin-Pete Marston+Aug 16 2005, 07:32 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Pete Marston @ Aug 16 2005, 07:32 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->sitting at the finish with the handle in your hands and see what happens if you take your feet off the footplates, also doing the same without the handle in your hands. Both times you slide down to the front. Did you have to expend energy doing this? No, the slide is sloped down to the front end, and the bungees want to bring the handle back too. </td></tr></table><br />Your erg must be tilted far more and bungees much stronger than mine.<br /><br />Considering the end point of a drive, reversing that momentum, then sliding back down the slide to the catch, you can do this in one second?<br /><br />I am truly impressed if you can.<br /><br />To verify this, perhaps you could remove the straps and heel stops from the foot plates, then give one strong drive to the handle. That should be enough for this test.<br /><br />Have someone standing by with a stopwatch at the end point of your (normal) drive, who times you from there to when you get back up to your usual catch position.<br /><br />Again, if you can do this in less than one second I shall be duly impressed.<br />
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Who said anything about completing the recovery in less than 1 second? Why would you want to do that?
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A rate of 32 spm and a 46.7 percent ratio between drive to overall stroke would give you 1 second for recovery.<br /><br />Eskild Ebbessen, Elia Luini, Graham Benton, and Pavel Shurmei all have drive ratios in this range, and an average much higher than 32 spm, thus taking less than 1 second for recoveries.<br /><br />Since 32 spm is quite a low rating for a 2k, less than 1 second for recovery should certainly be manageable for this test.<br /><br />Or just row a 2k this way, with no straps or heel stops, and let us know what you get. <br /><br />I am very interested to hear your results!