Erg wattage vs Cycling wattage

[Tsnor]

I agree with you that moving X kilo's up and down a very frictionless slide still consumes some energy.

I think/assume that during the transition from legs to the back still some kinetic energy is transferred from my moving body to the flywheel and make it decelerate: i.e. I am decelerating and when rowing strapless, it can't be because my legs excert some negative force (by hanging on my hamstrings).

Easy to test this.

There is a pick drill where you use ONLY LEGS. Your hips don't move and your arms stay straight.

Try this pick drill strapless.

Bet beverage of your choice that you hit the end of the slide. Don't do a huge leg drive the first time, inch up on it, because there is nothing to stop you. (cheater footnote, I just verified you don't stop, so don't take the bet).

So why didn't the handle/flywheel stop you?

The flywheel's one way clutch only resists when the handle is being pulled hard enough to increase the flywheel spin rate. Once your backward motions on the slide slows to the rate of the flywheel or less there is ZERO resistance from the handle. And while the flywheel does slow down from the drag factor, the flywheel never stops spinning during strapless rowing so you never stop going backwards.

And yet you can row strapless. How? It's because your arms are pulling hard enough that they can keep the flywheel increasing spin so that it gives resistance to pull against. AND your legs stop pushing against the foot stretchers so the force you are applying with your arms can be used to slow you down, stop you and reverse your direction. The energy your arms provide is enough that it can keep both reverse your direction and keep the flywheel accelerating so there is resistance at the handle.

2nd interesting experiment. Moving backwards near the end of the slide try to come back to the catch position without using any ARM motion. Can't do it (unless you hook your heels on the stretchers and pull that way). The handle does not ever pull you back even if you are moving away, it can only slow you down at a rate less than or equal to its own rate of spin loss from air drag.

[Carl Watts]

Probably time for a few people here to think about why C2 do NOT let you use slides for a WR or World Record.

Thats right, simply putting the same static Erg on Slides suddenly gives you an advantage.

Thats impossible I hear you all scream, that Kinetic energy is going into the Flywheel !!!!

Yeah no it isn't. The Slides mean you are no longer moving your whole bodyweight up and down the slide in the same way so its easier for your body to put more power into the flywheel due to the reduced losses of the motion to produce that power.

The power into the flywheel = Total power at a given HR - Losses

Reduce the losses and your HR stays the same but more of that total power gets to the flywheel, its that simple.

Those that obviously benefit the most from slides are the heavier rowers, the heavier you are the more advantage the slides give you because your losses are higher moving your bodyweight. Your also going to get rewarded with better technique on the slides.

Think about it.

Despite all that extra steel in motion and wheels for it all to sit on and the elastic its still more efficient than the static erg.

I wouldn't like to put exact numbers on it but I would say the losses halve and you get an extra 10-15% power to the flywheel on a dynamic.

So at about 204W or 2:00 pace on a static now you have an extra 20 to 30W on the dynamic so you now have 1:56 pace for the same heartrate or 224W going into the flywheel.

Pretty sure C2 could give you some more exact numbers, but the difference is significant. I have seen it for myself on RowPro from a guy that said he cannot even row on a Static because of his back but can bash out 8300M for the 30 minute on slides. The biggest issue with slides is getting people to admit they are using them, kind of like the bikes with the LiPo batteries stuffed into the frame

Anyway I have had enough of this subject, time to move on.

[flatbread]

I do most of my erg sessions on slides, but I don't see a big difference in HR/watts between the two -- but that's UT1/UT2, not higher ratings+watts.

I'm more efficient on slides, it's not by 10%

that may be because of technical flaws

[Nomath]

Probably time for a few people here to think about why C2 do NOT let you use slides for a WR or World Record.

Thats right, simply putting the same static Erg on Slides suddenly gives you an advantage.
.....
I wouldn't like to put exact numbers on it but I would say the losses halve and you get an extra 10-15% power to the flywheel on a dynamic.

The possible advantage of the C2 on slides has been investigated several times in scientific studies. The performance differences are fairly small!
It is far below the 10-15% extra power that you take out of the blue.

The reason why C2 does not allow it in real competitions or WR's is probably that it would complicate organizing the event and blur the records. Possibly also because it would put a spotlight on one of their rivals, RowPerfect.

Below is a table from one of these studies, titled Rowing Ergometer with Slide is more specific to Rower's Physiological Evaluation. Authors F. de Campos Mello and others. Published in Research in Sports Medicine, 2014, vol. 22, p. 136-146.
Please read it !

Participants were 8 competitive ( state and national level) male rowers, aged 24 yrs. They used a C2 with and without slides. The test started at 150W and 50 W increments after each 3 min stage. Rowers were free in chosing the stroke rate.
As you can see, the maximal power is slightly lower with slides, but the difference is statistically insignificant. The VO2-max is also lower on slides, which the authors judge as statistically significant. The HR at maximal power is about equal.

What everybody agrees on, is that rowing on slides shaves the peak forces. Hence, it is more friendly for the limbs and joints.



If you are interested, I can give the titles of 3 more studies on this topic (i.e. comparison with and without slides).

[flatbread]

so it's more like 5% ?

[Nomath]

5% in what?
The authors of the paper find the maximal aerobic power difference insignificant.

[flatbread]

5% in what?
The authors of the paper find the maximal aerobic power difference insignificant.

watts @ OBLA

oxygen cost was the same, but it looks like there was a slight wattage advantage to the slides

[Nomath]

They didn't mark that result as statistically significant, which could have several reasons. Please read the paper.

[jamesg]

Our inertial power losses on the fixed rowerg depend on speed and frequency of motion. At 1m/s (if body mass speed is half the handle speed), 80kg, ke = 80/2 = 40J per stroke.

At rate 20, only the pull is that fast, so power needed for movement = 40*20/60 = 13W.
At rate 40 with body mass speed the same both ways, power loss would be 2*40*40/60 = 53W.

13W is about 10% of what I normally pull, 120-130W @ 20.

Slides and water ensure the catch is quicker, so shorter, by increasing acceleration, there being less mass to accelerate. If research shows this, no doubt Sir Isaac will be happy. If not he'll maybe wonder who's playing tricks on who, the researchers or their victims.

[flatbread]

1) I never took physics and don't understand it.

2) on that basis, anything I have to post or link should be taken with much salt.

all that said

That is, on a static erg, the rower is required to put in six times as much energy accelerating/decelerating just their bodyweight, compared to a boat or a dynamic erg where the energy is split between the bodyweight and the boat/erg.

Cas Rekers (designer of the Rowperfect) has performed tests comparing the 'indicated' power output with and without the flywheel fixed - the subject gained about 10-20% power output in the second case, representing the additional power that could be applied to the flywheel instead of accelerating the bodyweight.

from

http://eodg.atm.ox.ac.uk/user/dudhia/ro ... meter.html

[JaapvanE]

At rate 20, only the pull is that fast, so power needed for movement = 40*20/60 = 13W.
At rate 40 with body mass speed the same both ways, power loss would be 2*40*40/60 = 53W.

13W is about 10% of what I normally pull, 120-130W @ 20.

Anu Dudhia has written something about this as well in his work on ergometers (see http://eodg.atm.ox.ac.uk/user/dudhia/ro ... #section13), there he estimates that a rower "wastes" 37W.

I typically pull 180W, but I weigh "a bit" more, so that might explain some differences.

Slides and water ensure the catch is quicker, so shorter, by increasing acceleration, there being less mass to accelerate. If research shows this, no doubt Sir Isaac will be happy. If not he'll maybe wonder who's playing tricks on who, the researchers or their victims.

I don't know on slides, but on rowers like the RP3 (or the Concept2 dynamic?) the person's weight doesn't move significantly, only the erg moves, which is much lighter than my body, making this difference smaller.

[dabatey]

As well as a bit of power lost sliding up and down- how much i'll leave to you experts.

I would have thought that the way power is applied (1/3ish reps but 3ish x power) would inevitably lead to more muscle fatigue on the rower over time, and hence a lower average power output over that time compared to the cycle due to pacing to accommodate muscle fatigue.

[Nomath]

That is, on a static erg, the rower is required to put in six times as much energy accelerating/decelerating just their bodyweight, compared to a boat or a dynamic erg where the energy is split between the bodyweight and the boat/erg.

Cas Rekers (designer of the Rowperfect) has performed tests comparing the 'indicated' power output with and without the flywheel fixed - the subject gained about 10-20% power output in the second case, representing the additional power that could be applied to the flywheel instead of accelerating the bodyweight.

from

http://eodg.atm.ox.ac.uk/user/dudhia/ro ... meter.html

This statement of Cas Rekers has been checked in a scientific study by I Bernstein and coauthors reported in the paper An ergonomic comparison of rowing machine designs: possible implications for safety, published in the British Journal of Sports Medicine, 2002, vol. 36, p.108-112.
The paper can be downloaded free of charge from https://bjsm.bmj.com/content/36/2/108

Participants : 6 elite male rowers, average age 30.
Equipment : RowPerfect with floating flywheel head and the similar RowPerfect with flywheel head clamped ('fixed').
Exercise : 20 mins rowing in both modes at a target steady heart rate that ensured that the subjects exercised above their anaerobic threshold and developed fatique.
Result (summary of Table 2) : The work done in the floating mode was the same as in the fixed mode. In the floating mode the stroke rate was 10% higher and the work per stroke was about 10% lower. The mean peak force was 12% higher in the fixed mode and the stroke length was considerably longer.
It is postulated that the longer stroke length and the greater forces with the fixed head are risk factors for soft tissue injuries.

More details in the paper.

[Nomath]

One of the best studies ever of the kinematics of rowing, both on a stationary ergometer and on a floating ergometer :
F. Colloud, P. Bahuaut, N. Doriot, S. Champely, L. Cheze
Fixed versus free-floating stretcher mechanism in rowing ergometers: mechanical aspects
J. of Sports Sciences 2006, vol.24 , p.479-494
Download free of charge from http://bionics.seas.ucla.edu/education/ ... 006_02.pdf

Participants : 25 elite rowers, male, average age 24 yrs
Equipment : RowPerfect with a floating stretcher mechanism and RowPerfect with a fixed stretcher mechanism. Additional force sensors in the handle, in the foot stretchers and in the seat to measure the forces during the stroke. In addition: a video system to register body and hand positions.
Exercise : 15 strokes at race-pace test (35 strokes/min)
Result : The average power was 8.5% lower when the rowers used the free-floating mechanism than the fixed mechanism.

The above result is not so interesting, although telling in the discussion about the alleged power advantage of dynamic ergs.
More important is that the installed force sensors on the handle, stretchers and in the seat provide a very precise picture of the movements and the forces during the stroke applied on the three support points: handle, seat and foot stretchers.

Have a look at figure 7 : the acceleration of the rower's center mass after the catch on the stationary erg (solid lines).
The figure shows that the initial backward acceleration becomes zero after a handle displacement of only 40 cm (the full stroke is about 140 cm). Thereafter the body mass decelerates at ca. 2-3 m/sec².
Question to the intimi of Sir Isaac : how can this happen?
The answer is : by applying a braking force on the handle.
And because the ergometer is doing what it is made for, namely measure work (= force x displacement) done at the handle, the braking force is doing work that counts!

I repeat, possibly ad nauseam : all kinetic energy for moving the body in the drive phase has been fully recovered before the drive comes to a stop. Nothing is lost.

[jamesg]

Question to the intimi of Sir Isaac : how can this happen?

By changing body shape.

When the slide stops, the cg also stops; but not the handle, if we use standard style. The brake force from the flywheel is Newtonian action and reaction when we pull the handle: no pull, no reaction. The flywheel can only decelerate when our applied action is smaller than air brake torque.

The work put into the handle reduces our kinetic energy and increases that of the flywheel; this looks like a free switch, but it cannot be done without our contracting muscle, so cannot be equated to an elastic exchange with energy recovery.

On slides or similar, the work not done in body mass acceleration to a lower speed, can only get into the handle if we decide to put it there, by pulling longer and or harder. It won't be automatic.

The usual effect when shifting from fixed to dynamic is a large increase in rating. After years of fixed ergs, it takes a little time to remember and switch back to rowing.

I find this very difficult afloat, but no doubt this is the result of mixing extreme age, a shell and two C2 hatchets; these give a quicker catch than any machine and using erg style with them is devastating. If I take no care at the catch, the work increases enormously and I'm dead after ten strokes even at rate 19. Research subjects (always élite) certainly know this (but maybe not the researchers) and take their precautions.