new rower, much slower 500m split than gym rowers

[Slidewinder]

Very interesting, and all seems to make perfect sense - presumably, then, everybody who has a replacement cord notices this apparent change in performance?

In the forum archives many users have reported differences in times recorded on different machines - most notably between new machines or machines with replacement cords compared to well-used machines. These reported experiences are always dismissed by other posters as "psychological".

Continuing the reasoning of my previous posting, and using the same figures, here is an easy to understand illustrative example for those still in denial about this: Let us have a 500M rowing ergometer race between two people. The two ergs being used will have the strength of their elastic cords measured to ensure that the force required to stretch them is identical. This is important because, as stated, the monitor does not measure the energy to stretch the elastic cord, so the force to stretch each cord must be identical on both machines, a constant, to guarantee that the race is fair - any difference in cord strength and it is no longer a level playing field.


In this race however, a 20 pound bag of potatoes will be suspended from the high 30 foot gym ceiling, and one of the ergs will be connected to it so that over the course of the 500 metres the person on that machine will have to hoist that bag of potatoes almost the full distance from the floor to the ceiling. Will this race be fair? If both competitors expend the same amount of energy, then according to the monitor, will the competitor required to hoist the bag of potatoes win or lose?

[johnlvs2run]

The PM does not measure the energy expended to stretch the elastic cord, therefore the effort to lift that extra virtual weight is not recorded on the monitor of your home unit. Therefore, even if your expended energy on your home unit and on the cruise ship units are identical, the monitor on your home unit will record a slower time. This is not psychological.

Yes, this is true. You make a very good point. When I changed the cord on my old model B, the resistance was indeed noticeably higher. However, without checking my logs, the difference was not more than 2 seconds per 500 meters, and the cord will adjust with time. A 20 second difference is way too much to explain by the cord. First of all, the HIIT session should be repeated to have an idea of any actual difference.

[Allan Olesen]

At a 1:40 split time, at 36 spm, this is 60 strokes in that time. If your average stroke length is 4.5 feet, in that time you will be moving the handle a total of 270 feet during the drive portion of the stroke. If the elastic cord in your home unit requires 2 pounds extra force to stretch than the elastic cords in the heavily used cruise ship units, that 2 pounds of extra force over the 270 feet stroke length distance is equivalent to lifting a 20 pound weight through a vertical distance of 27 feet. The PM does not measure the energy expended to stretch the elastic cord, therefore the effort to lift that extra virtual weight is not recorded on the monitor of your home unit. Therefore, even if your expended energy on your home unit and on the cruise ship units are identical, the monitor on your home unit will record a slower time. This is not psychological.

Very interesting, and all seems to make perfect sense - presumably, then, everybody who has a replacement cord notices this apparent change in performance?

Slidewinder has been advocating this for years, and it does have some merit, even though the opposing argument also has some merit: If you row at a rate where you have to actively pull with your feet to return to the catch, the increased tension will make you use less power on this.

Anyway, even when accepting his argument, we have to look at the proportions:

The additional work for 60 strokes of length 4.5 feet (1.35 m) at an additional force of 2 pounds (8.9 N) is 60*1.35*8.9 = 730 J. This work is done over a duration of 100 seconds, so the additional power to overcome the additional force is 730/100 = 7.3W.

So how much is 7.3 watt?
At a pace of 1:40.0 minutes/500 meter, you are outputting 350.0 watt.
At a pace of 1:39.3 minutes/500 meter, you are outputting 357.5 watt.

So the additional power for overcoming the additional tension is equivalent to less than 0.7 seconds/500 meter.

These are not the seconds, you are looking for.

[marcmartineau]

20 minutes HIIT (40 sec at 34-40 SPM followed by 20 second recovery 20 SPM). In that 40 sec, I was reaching sometimes 1:37 to 1:40 split time, something that I can’t get on my new Model E, even if I pull as hard as I can !
5 min recovery at 20-22 SPM low wattage.

At a 1:40 split time, at 36 spm, this is 60 strokes in that time. If your average stroke length is 4.5 feet, in that time you will be moving the handle a total of 270 feet during the drive portion of the stroke. If the elastic cord in your home unit requires 2 pounds extra force to stretch than the elastic cords in the heavily used cruise ship units, that 2 pounds of extra force over the 270 feet stroke length distance is equivalent to lifting a 20 pound weight through a vertical distance of 27 feet. The PM does not measure the energy expended to stretch the elastic cord, therefore the effort to lift that extra virtual weight is not recorded on the monitor of your home unit. Therefore, even if your expended energy on your home unit and on the cruise ship units are identical, the monitor on your home unit will record a slower time. This is not psychological.

Yes I did do the same HIIT on my home rower and that’s where I found that I can’t get the timing that I had on the cruise ship rowers. More than that, I was reaching a total of approx 8000 meters over my entire workout on the ship (including the warm up and cool down), but at home, I reached approx 6900 meters !

Reason for my initial question. Your explanation Slidewinder makes sense to me, as of course and certainly, that the elastic cord on the ship rowers is way more stretched than mine that is new (well refurbished unit bought directly at COncept 2 factory).

Thanks for this explanation !

[johnlvs2run]

20 minutes HIIT (40 sec at 34-40 SPM followed by 20 second recovery 20 SPM).

What was the difference in your 20 x 40 second averages?

[marcmartineau]

20 minutes HIIT (40 sec at 34-40 SPM followed by 20 second recovery 20 SPM).

What was the difference in your 20 x 40 second averages?

On the ship’s rowers, I was able to reach 1:40-1:45 split time at 36-40SPM (couldn’t do that for very long though...) and, on my home rower, the minimum that I reached is 1:57 in the same 40 sec. It is mostly around 2:03-2:09 split time.

[johnlvs2run]

On the ship’s rowers, I was able to reach 1:40-1:45 split time at 36-40SPM (couldn’t do that for very long though...) and, on my home rower, the minimum that I reached is 1:57 in the same 40 sec. It is mostly around 2:03-2:09 split time.

Did you not keep the averages? I'd try that session again to make sure. Then, if you're convinced there's a 12 to 17 second difference, that's way too much.

[Noseve]

Would be nice if the PM5 - which knows the history of stroke count, stroke lengths, drag factors, watts etc experienced by the cord - could be programmed with an algorithm to factor its wear into a performance rating which is transferable between machines.
It would appear that a barely-heavyweight (like me, at 170lb) on a brand new machine (like me, 3 weeks old) has no way to realistically compare his/her pound-per-pound performance with others. Certainly not using the C2 ranking facility, anyway.
This wasn't something that played a great part in my buying decision, but it could have been very motivating, obviously.
Suppose I shall just have to enter competitions if I'm that bothered about it (trouble is, how do I know when I'm ready...)

[johnlvs2run]

I personally feel that cord variation, being at the most maybe 1 second per 500 meters, is not a significant factor, certainly not when compared to the vast difference in people's weights, and the fact that weight is not accounted for in the rankings.

It would appear that a barely-heavyweight (like me, at 170lb) on a brand new machine (like me, 3 weeks old) has no way to realistically compare his/her pound-per-pound performance with others. Certainly not using the C2 ranking facility, anyway.

Actually, this can be done with some diligence, which I've done personally for the 70+ rankings.

[Anth_F]

On the ship’s rowers, I was able to reach 1:40-1:45 split time at 36-40SPM (couldn’t do that for very long though...) and, on my home rower, the minimum that I reached is 1:57 in the same 40 sec. It is mostly around 2:03-2:09 split time.

Okay thats a significant difference if those number variations are correct. From being able to pull 1:40's on one machine, then can't get below 1:57 pace on your own machine is very bizarre stuff.

Surely it can't be just the shock cord that is the cause of this!!!!!!

[Noseve]

I personally feel that cord variation, being at the most maybe 1 second per 500 meters, is not a significant factor, certainly not when compared to the vast difference in people's weights, and the fact that weight is not accounted for in the rankings.

My fault - I was mid-compose and interrupted by a call, then came back and posted, not having read the intervening post explaining the sub-1 second/500m difference. Shall ignore the non-issue of cable wear.

[Allan Olesen]

On the ship’s rowers, I was able to reach 1:40-1:45 split time at 36-40SPM (couldn’t do that for very long though...) and, on my home rower, the minimum that I reached is 1:57 in the same 40 sec. It is mostly around 2:03-2:09 split time.

That difference is equal to a 2:3 ratio in Watts.

The ergometer has 3 magnets on the flywheel, sensed by a stationary coil. I wonder what would happen if one of those 3 magnets are missing or outside the range of the coil, so you only get signal from 2 magnets. I would hope that the PM5 picked up on the uneven intervals between impulses from the coil and reported an error - but I don't know.

[marcmartineau]

I was thinking about this...

Does the air temperature has an effect on air flow ? Guess it wouldn’t change a thing if drag factor is the same but just thinking out loud...

[Allan Olesen]

I was thinking about this...

Does the air temperature has an effect on air flow ? Guess it wouldn’t change a thing if drag factor is the same but just thinking out loud...

Yes, air density plays a role. It can be affected by air pressure and temperature. But that is why we use drag factors instead of damper settings. If you adjust the damper until the drag factor is the same, you have cancelled out any influence from air pressure or temperature.

[Slidewinder]

Slidewinder has been advocating this for years, and it does have some merit, even though the opposing argument also has some merit: If you row at a rate where you have to actively pull with your feet to return to the catch, the increased tension will make you use less power on this.

Anyway, even when accepting his argument, we have to look at the proportions:

The additional work for 60 strokes of length 4.5 feet (1.35 m) at an additional force of 2 pounds (8.9 N) is 60*1.35*8.9 = 730 J. This work is done over a duration of 100 seconds, so the additional power to overcome the additional force is 730/100 = 7.3W.

So how much is 7.3 watt?
At a pace of 1:40.0 minutes/500 meter, you are outputting 350.0 watt.
At a pace of 1:39.3 minutes/500 meter, you are outputting 357.5 watt.

So the additional power for overcoming the additional tension is equivalent to less than 0.7 seconds/500 meter.

These are not the seconds, you are looking for.

I understand the physics, but there are a couple of factors not taken into account here.

I acknowledge that the elastic cord assists in moving the user's mass forward during the recovery portion of the stroke, but that energy does not flow back into the user's muscles, restoring strength and vigour. Regardless of the assistance given in returning to the start position, pulling on a strong elastic cord is more tiring than pulling on a weak one. Everyone knows this from experience.


Addressing the argument you support by calculations: At the limit of one's exertion, a requirement to provide an extra 2 pounds of force to maintain a target time could be all that is needed for a competitor to "hit the wall" and slump back to a slower pace. I have seen powerful weightlifters after a series of bench press reps, unable to complete a final lift, but a skinny safety man takes the bar and effortlessly assists the weightlifter to raise the weight onto the rack. All that was needed was just another couple of pounds of force to complete the lift, but he just didn't have it in him. He was whipped. Similarly, let two people have a rowing ergometer race as described in my example - both going at the limit of their strength and endurance - and then add to one a 20 pound bag of potatoes that must be hoisted about one-half a vertical foot at every stroke (the approximate equivalence of the 2 pound extra force required to stretch the elastic cord in the example given). This person is already at the limit of exertion, therefore with this extra load, it will be impossible for him/her to maintain the pace. I predict that the resultant rapid onset of exhaustion would result in a far slower time than the .7 seconds/500 metres predicted by calculation. Those calculations assume a human to be a machine, tireless and without limitations. This is incorrect, and a probable source of error.


No one in this long thread has offered a better explanation than this for the difference in user times between different machines.