Concept2 Forum

The formula that I use in Excel to calculate average watts/stroke matches perfectly with my PM2 results, yet that same formula yields the same watts/stroke regardless of my stroke rate.<br /><br />This doesn't seem right; because at any given pace, a higher rating means that you are applying less power per stroke to the handle than at a relatively lower rating. Doesn't it?<br /><br />Yet the formula I am using doesn't take stroke rate into account, even though the result matches the PM2 results.<br /><br />Confused ,<br />Mark<br /><br />P.S. This is the formula that I use:<br /><br />Average Watts per Stroke = 2.8/(totaltime*60/totaldistance*1442)^3

<!--QuoteBegin-Mark Keating+Jan 13 2006, 07:14 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Mark Keating @ Jan 13 2006, 07:14 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->The formula that I use in Excel to calculate average watts/stroke matches perfectly with my PM2 results, yet that same formula yields the same watts/stroke regardless of my stroke rate.<br /><br />This doesn't seem right; because at any given pace, a higher rating means that you are applying less power per stroke to the handle than at a relatively lower rating.  Doesn't it?<br /><br />Yet the formula I am using doesn't take stroke rate into account, even though the result matches the PM2 results.<br /><br />Confused ,<br />Mark<br /><br />P.S.  This is the formula that I use:<br /><br />Average Watts per Stroke = 2.8/(totaltime*60/totaldistance*1442)^3 <br /> </td></tr></table><br /><br />Joules are the basic unit of energy that can be measured from the known characteristics of the flywheel, Mass, Moment of inertia and Change in angular velocity relative to freewheeling (DF).<br />(It's all fairly complicated, but Newton figured it out a long time ago.) <br /><br />Avg Watts/stroke = (Total Joules absorbed by the flywheel during the stroke cycle)/(60/(Strokes/Min))<br /><br />or<br /><br />Avg Watts = Stroke Joules/stroke seconds<br /><br />Pace is just a conversion of Watts to "virtual boat speed".<br /><br />Since we can only input Joules on the Drive, and this results in equilibrium, you can look at the inputs required at different rates.<br /><br />Pace ~2:00, R20, Stroke Time = 3 sec, 600J/3 = 200Watts = Heavier Drive with high ratio<br />Pace ~2:00, R30, Stroke Time = 2 sec, 400J/2 = 200Watts = Lighter Drive with low ratio<br /><br />

Divide your watts by your weight, and this will show you your intensity for the distance.

<!--QuoteBegin-Mark Keating+Jan 13 2006, 05:14 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Mark Keating @ Jan 13 2006, 05:14 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->This is the formula that I use:<br /><br />Average Watts per Stroke = 2.8/(totaltime*60/totaldistance*1442)^3[right] </td></tr></table><br />Hi Mark,<br /><br />read the formula again - you are calculating average per time

Paul,<br /><br />This equation is used by the PM2 to calculate Ave Watts/<i>individual</i> stroke, <i>but not the average watts/stroke for a given session</i>, correct?<!--QuoteBegin-PaulS+Jan 13 2006, 10:42 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(PaulS @ Jan 13 2006, 10:42 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->Avg Watts/stroke = (Total Joules absorbed by the flywheel during the stroke cycle)/(60/(Strokes/Min)) </td></tr></table><br /><br />What I am wondering, basically, is why, using this equation in my spreadsheet<br /><br /><!--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-->Average Watts per Stroke = 2.8/(totaltime*60/totaldistance*1442)^3 </td></tr></table><br /><br />outputs the same result as my PM2, even though stroke rate is not (or does not appear to be) one of the variables?<br /><br />It makes me wonder if the PM2 truly displays the average watts per stroke for an entire session.<br /><br />Mark<br /><br />P.S. And Godfried, didn't your mother teach you not to tease people like me?

<!--QuoteBegin-Mark Keating+Jan 15 2006, 12:45 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Mark Keating @ Jan 15 2006, 12:45 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->And Godfried, didn't your mother teach you not to tease people like me? </td></tr></table><br />My mother told me she was never at home when her mother was teaching. <br /><br />So I guess that runs in the family. <br /><br /><br /><br />I just think the equation calculates average watts/hour.

<!--QuoteBegin-Mark Keating+Jan 13 2006, 03:14 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Mark Keating @ Jan 13 2006, 03:14 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->The formula that I use in Excel to calculate average watts/stroke matches perfectly with my PM2 results, yet that same formula yields the same watts/stroke regardless of my stroke rate.<br /><br />This doesn't seem right; because at any given pace, a higher rating means that you are applying less power per stroke to the handle than at a relatively lower rating.  Doesn't it?<br /> <br /> </td></tr></table><br /><br />Using "average wattage per stroke" simply does not make sense, it is a completely invalid measurement. <br /><br />Your wattage is simply your _current_ power output. You cannot measure a total amount of power used for a given action, you can measure total energy (joules), but NOT total power (joules / sec). <br /><br />Say you are averaging 100 watts in a session lasting for 30 minutes. Your average wattage will be 100, therefore your average wattage per stroke will be 100 as you are using 100 joules per second on average.<br /><br />Hope this helps somewhat.<br /><br />

MK<br />If you want to know how much Work you did in an average stroke, divide Power in Watts by Rating.<br /><br />Power has dimension Work/Time;<br />Rating has dimension 1/Time;<br />So writing: Power/Rating = (Work/Time)/(1/Time) = Work, and in our case, Work per Stroke.<br /><br />The unit is the Watt-minute, because ratings refer to one minute, and we could call it W' for brevity. 1W'=60J, because 1 Joule = 1 Watt-second by definition.<br /><br />200W at 20 is 10W'/stroke, and I think this is a nice training level for most amateur HWs. To put it in perspective, G Benton did his Birc 2k at about 17W', rating 29, while the LW examples J Rupp uses pull at about 11 in their races (if the rating is 40). No idea what they do in training. I'm happy if I can stay at 8.5 - 9.<br /><br />Almost all training plans relate Pace to Rating, and if you convert the Paces that these plans show to Powers (using W=2.8V^3, where V is in m/s)), you get an almost constant Work/stroke level for each single reference 2k time.<br /><br />This we could call Work based training. The idea is pull equally hard and long at all ratings. This is the numerical expression of the idea "train as you would race": you pull with exactly the same stroke all the time, just up the rating if you want to go faster. When the Work/stroke drops off, there's no point in upping the rating any more, so race rating selection is automatic. This suits the erg very well, because we have the numbers in front of us.<br /><br />The other training method is Xeno's, HR based: watch your Heart Rate and use it to keep in the <2 mmol area. In his recent thread on what to do in the last 8 weeks before a race, he suggests 34 w/os of 60-80 minutes at that level, and uses some faster paces in only 15 pulls, for durations <20' and many very short, mostly within the long pulls. Effectively this is the same as pace based, but we add the HR control. This suits scullers who have plenty of water and need super-fine technique so that the boat goes fast with the least possible effort (see XM's comments on what happens at 500, 1000 and 1500m in a race).<br /><br />The basic bone of controversy is, I think, whether we can replace long slow endurance work (where long means >60') with faster and shorter work (the no pain no gain idea). Those who have gold medals earned on water, seem to think not. For me at least, pain gets in the way of training because it stops me before time.<br /><br />If there's a secret, it's technique. The long pieces place a very heavy accent on technique. There's nothing like being 5km from the boathouse and dead tired to teach us how to scull efficiently.

<!--QuoteBegin-DavidW+Jan 14 2006, 07:59 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(DavidW @ Jan 14 2006, 07:59 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->Using "average wattage per stroke" simply does not make sense, it is a completely invalid measurement. <br /> </td></tr></table><br />Thanks David, that is what I was starting to think too - but high school physics was a lonnng time ago!

<!--QuoteBegin-jamesg+Jan 15 2006, 02:22 AM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(jamesg @ Jan 15 2006, 02:22 AM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->MK<br />If you want to know how much Work you did in an average stroke, divide Power in Watts by Rating.<br /><br />Power has dimension Work/Time;<br />Rating has dimension 1/Time;<br />So writing: Power/Rating = (Work/Time)/(1/Time) = Work, and in our case, Work per Stroke.<br /><br />The unit is the Watt-minute </td></tr></table> <br /><br />Thanks for the clarification james. I've been tracking that value as well, I believe it's all starting to make sense - finally.<br /><br />Mark

<!--QuoteBegin-Mark Keating+Jan 15 2006, 02:08 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(Mark Keating @ Jan 15 2006, 02:08 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin--><!--QuoteBegin-DavidW+Jan 14 2006, 07:59 PM--><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'><b>QUOTE(DavidW @ Jan 14 2006, 07:59 PM)</b></div></td></tr><tr><td class='quote'><!--QuoteEBegin-->Using "average wattage per stroke" simply does not make sense, it is a completely invalid measurement. <br /> </td></tr></table><br />Thanks David, that is what I was starting to think too - but high school physics was a lonnng time ago! <br /> </td></tr></table><br /><br />It does sound very strange, but used about an "energy acceleration" it makes sense. Like in "how many wattages per stroke do I increase by when starting the race"<br />Average wattage per stroke: Well after 3 strokes my intensity is 700w so my acceleration in terms of average wattage per stroke is 700/3 = 233w/stroke.<br /><br />Erging, not only does it keep you physically fit, but also mathematically, if you push for that as well. <br /><br />I'm sure it has been said before, though, "wattage per stroke" is just a hint on how to calculate your SPI: wattage/SPM

There's an SPI calculator here:<br /><br /><a href='http://www.machars.net/spi.php' target='_blank'>http://www.machars.net/spi.php</a><br /><br />