Optimum force curve

[JLB123]

Trying to work out what the optimum force curve is. In particular, very interested if anyone knows of any literature on the subject / pictures of high level rower's force curves.

Way I see it there are 4 main variables to the force curve:

1) Stroke length. Self explanatory.

2) Peak force. Maximum force applied at the stroke.

3) Peak position (%). Point in the drive at which peak force is reached. E.g. if stroke length is 1.5m, 50% implies peak force is reached .75m into stroke.

4) Smoothness. Shape of the curve. I.e. you could have a curve which climbs very steeply then falls steeply, or one which climbs slowly then falls slowly. Not necessarily related to peak position. Example: in the picture below, compare the Rosenberg and DDR styles



In terms of shape (i.e. worrying about points 2,3 and 4), it's unclear what is the best shape. Mathematically the optimum power curve is a box, implying peak position should be as early as possible, curve should be very flat, and peak force should be relatively low (obviously having the highest possible peak force is also good, but for a given boat speed, a flatter power curve with an earlier peak implies a much lower peak force than a steep curve with a later peak (again compare the area under the graph in the Rosenberg and DDR styles). In short, the Grinko style is best.

However, there seems to be a fair bit of support for the argument that a later peak is better (particularly on the water, where the catch and finish are relatively ineffective due to the blade angle meaning a greater component of the force is pushing the boat sideways rather than forwards), implying force exerted around the mid-point of the stroke is more efficient, so the optimum power curve would have a later peak position (c.50%), and less power at the start and finish (implying a steeper curve), and, in order to get the same boat speed, a higher peak force. In short, the Rosenberg style is best.

Of course, you could also argue that some compromise between the two is necessary i.e. the DDR style is best

So, if anyone knows of any research, force curves helpful to answering this, would be v. grateful.

[lindsayh]

there is a great discussion on this topic about 4 threads down on this sub forum that has been going for a week or 2

[jamesg]

catch and finish are relatively ineffective

Not with modern blades. There's a wing (hydrodynamic) effect with very little slip. Seen from above the blades move forwards, not astern.

This could have some effect on those curves and choice of style. They say "DDR" so might be of archeological interest only.

An instant catch gives me very high load at the start of the stroke, even after chopping lumps off the ends of the blades. This leaves me very little choice of style, it's all legs at the catch, none of the rest of me is strong enough. Most sculler videos show this very clearly, with hatchets.

On the erg we only need to try the various styles: the Watt readout shows the effects immediately. Logic to me suggests using the largest muscles when there's more work to be done, and the Watt reading confirms. So legs, swing, arms, not that it's ever so clear cut.

[JLB123]

there is a great discussion on this topic about 4 threads down on this sub forum that has been going for a week or 2

Had seen that - actually trying to focus more on the facts than opinion (otherwise I reckon I'll never get anywhere!)

catch and finish are relatively ineffective

Not with modern blades. There's a wing (hydrodynamic) effect with very little slip. Seen from above the blades move forwards, not astern.

I've heard this a lot, but not sure what the basis for it is - do you know if there's any evidence? I assume hatchets have radically improved this vs. macons, but equally, I've never actually seen anything showing this to be the case (and would have assumed C2 would have published something if they had it). Not saying I disagree, just not sure either way.

[jamesg]

That's why they're used. I saw, years a go, a set of photographs taken from above, and the blades clearly moved ahead.

When the blades move axially though the water, the shape of the blade and the speed of the water along the blade cause lift (Bernoulli). In the middle of the stroke this effect is lost, and the blades are less efficient.

http://www.concept2.com/files/images/oa ... bridge.jpg

[tortoise]

Mathematically the optimum power curve is a box, implying peak position should be as early as possible, curve should be very flat.

For a given speed, there are an infinite number of force curves that would do the job. The erg doesn't care what the shape is, as long as you don't break the chain. The best shape for YOU is the one that's easiest to maintain. Given sufficient resources, one could analyze your body as a system of levers and motors, but it is uncertain that this would give a better result than going by feel.

[hjs]

Mathematically the optimum power curve is a box, implying peak position should be as early as possible, curve should be very flat.

For a given speed, there are an infinite number of force curves that would do the job. The erg doesn't care what the shape is, as long as you don't break the chain. The best shape for YOU is the one that's easiest to maintain. Given sufficient resources, one could analyze your body as a system of levers and motors, but it is uncertain that this would give a better result than going by feel.

There can,t be one optimal curve. Given the differences in peoples build etc. As long as its without flaws but fluend forget about it.