Force Curve Lessons and Advice Sought

[Frionel]

So I've been using the force curve to evaluate the strengths and weaknesses in my stroke. What I've found is that when I achieve a "model" force curve, with a clean, even, parabolic shape, it really requires an explosion of power from the catch and strict discipline in pulling back. I really had no idea how inefficiently I had been rowing and now need to take the dampener down to a 1-2 range in light of these discoveries, from the mid-range where I had been keeping it, or I get gassed really quick.

So on one hand I feel like I'm finally understanding, even after years of C2 ownership, why rowing is thought of as such an efficient workout. Thank you, force curve. But on the other hand. I'm wondering what "light" rowing or "recovery" rowing means in the context of the force curve. Obviously when you opt to not explode back you tend to end up with a more elongated force curve, which makes complete sense (it's just physics), but is the goal in all workouts to achieve maximum efficiency with the force curve, and so when you dial down your stroke rate, you're really just controlling the rate of return to the catch before the next explosive pull? In other words, is a light row more defined by dialing down the stroke rate way down without losing any of the power/efficiency of the pull, or is it expected that you will slow all components of your form, meaning you definitely do less explosion and generate less power.

[ahooton]

In the same boat mate, I also have only recently discovered power curve.

When I am working hard at say 1:50/500 or faster, the curve is perfect. When I’m going slower however it tends to turn into a hump. I asked my coach about it and she said it’s fine. You will obviously be less explosive when rowing at a slower pace, hence you won’t have that dramatic rise at the beginning of the curve. Obviously for efficiency purposes you’d want that every stroke with a long slow recovery. At this point though, i think it just depends on the way you prefer to row steady state.

There will be people who know far more than I about it, who can give further insight.

[p_b82]

I'm certainly no expert but here's my take on it.

When I want to get my force curve into the expected "good" shape I need to be rowing with 8.5-10Wmin strokes (aka 170-200W @r20) - when I row at a low effort per stroke, I take the force out the leg drive and it affects the curve. both in the peak height (less force) and the shape of it - shallower to start. (above 10Wmin I have it skewed to the left & I'm often shortening the stroke as I'm rating up too)

What I "should" do is also take the same effort out the back swing to keep the effort components proportional, but I don't like to do that as I find it harder to ramp the effort up again (and my back sulks when I do) and keep good form.

I think once you get to a certain point of fitness it is easier to keep the Effort per stroke (Wmin) the same, and control the pace via the rate - so you always use your strong strokes, and you control your effort that way. (I'm not there, so I also reduce my work per stroke to drop my pace).

Light rowing would be keep the curve smooth, so you're keeping good sequence, but just not generate as high a peak.

When in recovery mode I think it is more about making sure you don't stress the part that needs to be protected, and I don't think that the shape of the curve is as important under those circumstances. (When I was recovering from a back injury I didn't use any backswing/hip hinge and it changed the shape of the curve)

[Tsnor]

There is no perfect or most efficient force curve. Some people's strokes are front loaded, some peak later. Its not clear that a front loaded "explosive" force curve is more or less efficient that a smoother one, or a left leaning or a right leaning haystack. In a multi-person boat you need to have same shape. Erging pick the one you like. Here are some rowing styles defined by their use by OTW champion rowers in the 70s. They are different. https://www.row2k.com/features/5531/row ... -kleshnev/

... I'm wondering what "light" rowing or "recovery" rowing means in the context of the force curve. Obviously when you opt to not explode back you tend to end up with a more elongated force curve, which makes complete sense (it's just physics), but is the goal in all workouts to achieve maximum efficiency with the force curve, and so when you dial down your stroke rate, you're really just controlling the rate of return to the catch before the next explosive pull?

For light or long/slow days: Explosive power for the stroke followed by a very long recovery seems like it would defeat the goal of very low load. People typically do long/slow (1) so they can do more hours without overreach and (2) get some useful adaptations that may not happen under heavy load (more capillaries? more mitochondria?). Heavy strokes followed by very long recovery to get down to long/slow splits seems counterproductive, but no evidence to support that. Low rate rowing (the logical extension of keep the same power and getting long/slow splits) is definitely different than long slow rowing. If I had to row 12 spm for long/slow days it would kill me. I sit at 20 spm and control drive power.

[Dangerscouse]

So I've been using the force curve to evaluate the strengths and weaknesses in my stroke. What I've found is that when I achieve a "model" force curve, with a clean, even, parabolic shape, it really requires an explosion of power from the catch and strict discipline in pulling back. I really had no idea how inefficiently I had been rowing and now need to take the dampener down to a 1-2 range in light of these discoveries, from the mid-range where I had been keeping it, or I get gassed really quick.

So on one hand I feel like I'm finally understanding, even after years of C2 ownership, why rowing is thought of as such an efficient workout. Thank you, force curve. But on the other hand. I'm wondering what "light" rowing or "recovery" rowing means in the context of the force curve. Obviously when you opt to not explode back you tend to end up with a more elongated force curve, which makes complete sense (it's just physics), but is the goal in all workouts to achieve maximum efficiency with the force curve, and so when you dial down your stroke rate, you're really just controlling the rate of return to the catch before the next explosive pull? In other words, is a light row more defined by dialing down the stroke rate way down without losing any of the power/efficiency of the pull, or is it expected that you will slow all components of your form, meaning you definitely do less explosion and generate less power.

I'm not saying this as an expert, but i like to have strict muscle memory for every stroke, as when it gets horrible there's less chance that it'll fall apart.

I prefer to slow down the recovery, and keep a fairly consistent drive, albeit with less power explosion, but i also like to try and keep within a range of pace / power for any given stroke rate. Obviously this doesn't always happen, but I perceive steady state as moments to ingrain the movement and not just to go through the motions

[iain]

There is no consensus and "explosive" strokes may vary from a typical 2k stroke to "power strokes" that would not be sustainable for >1 min. As "SPI" (which I call by its physical description - work per stroke) discussions abound. Amongst good rowers there is a wide range of how they vary the work per stroke from it staying constant (broadly similar drives with the difference in rating solely from recovery speed) to maintaining the same ratio of the time recovering to the drive (work per stroke broadly increasing with the square of rating). That is without considering how any changes o the stroke are achieved!

The low rate SS approach does seem to assume that the "recovery" required is of the CV system and that the strokes are good strong strokes but not maximal strokes and so elevate HR less than the faster paces required at higher ratings to generate the same tiredness in the muscles. Personally Oi find that muscular recovery is also required.

[JaapvanE]

There is no perfect or most efficient force curve. Some people's strokes are front loaded, some peak later. Its not clear that a front loaded "explosive" force curve is more or less efficient that a smoother one, or a left leaning or a right leaning haystack.

I have some experience in analysing force curves. One point to make first: C2's force curves are limited in their use as they seem to lack a decent granularity and are displayed for two seconds on a display with horrible resolution. Not a really good approach. I typically look at forcecurves with over twice the number of datapoints post-training, at a much higher resolution, and then you see more. Typically, we use RowsAndAll's forcecurve analysis tool, that also visualises the median of all strokes, making it a good representative stroke (with decent scales). That is a much better tool than a quick display when under stress.

The statement above is not exactly true when looking at physics. In essence, the area under the force curve represents the work done in the drive. As no work is done in the recovery, dividing that work through the entire stroketime results in power. So, one might argue that, as long as the times stay fixed, any shape with the same volume under it is identical in work.

However, that is not the full story. The cube law is also present within the stroke. So, accelerating too quickly early in the drive creates a fast flywheel that has a large dragforce trying to slow it down. That can result in a collapse of the forces in the second part of the drive (no haystack there). So aiming for a flat, right leaning curve is more efficient as it delays the fast part of the stroke to later sections. See also https://youtu.be/IVuw_lAt_Xw (this guy is an Olympian, so he probably knows what he is talking about).

Admittingly, looking at elite rowers, you see frontloaded and backloaded strokes. However, that is at elite level. Their technique is good. In most force curves I see from non-elite rowers, you see a frontloaded curve that is actually suboptimal as they explode at the catch: too much power at the front end, followed by a weak follow through. Typically, you see it as a dent in the force curve after the peak. So the volume isn't optimally distributed.

Key issue is: the dent is difficult to spot when training on a low resolution monitor. It actually looks pretty decent when sweating and moving. When you see it on a high resolution screen post traing, you see it instantly.

I actually made a set of curves where you can see the difference between three types of strokes at 2:05/500m at high resolution. Only if you see the longer flatter curves overlayed, you recognize issues (as we are using it in an upcomming book on the subject, I can't display it here). Peaking too early in the drive is hard to recognize from the force curve shape alone, but quite a common issue.

In a multi-person boat you need to have same shape. Erging pick the one you like.

That is actually an area if intense academic debate, where there is some good evidence pointing the other direction as well. Optimal crew composition and placement is incredibly complex, and moving "as one" may have downsides.

[Tsnor]

.. Typically, we use RowsAndAll's forcecurve analysis tool, that also visualises the median of all strokes, making it a good representative stroke (with decent scales). That is a much better tool than a quick display when under stress.

As always your post is full of content.

Agree RowsAndAll's forcecurve analysis tool is excellent. So is biorower's force curve work which shows up a lot on Aram Training youtube channel (along with video analysis of OTW rowers).

However, that is not the full story. The cube law is also present within the stroke. So, accelerating too quickly early in the drive creates a fast flywheel that has a large dragforce trying to slow it down. That can result in a collapse of the forces in the second part of the drive (no haystack there). So aiming for a flat, right leaning curve is more efficient as it delays the fast part of the stroke to later sections. See also https://youtu.be/IVuw_lAt_Xw (this guy is an Olympian, so he probably knows what he is talking about).

Admittingly, looking at elite rowers, you see frontloaded and backloaded strokes. However, that is at elite level. Their technique is good. In most force curves I see from non-elite rowers, you see a frontloaded curve that is actually suboptimal as they explode at the catch: too much power at the front end, followed by a weak follow through. Typically, you see it as a dent in the force curve after the peak. So the volume isn't optimally distributed.

Key issue is: the dent is difficult to spot when training on a low resolution monitor. It actually looks pretty decent when sweating and moving. When you see it on a high resolution screen post training, you see it instantly.

I actually made a set of curves where you can see the difference between three types of strokes at 2:05/500m at high resolution. Only if you see the longer flatter curves overlayed, you recognize issues (as we are using it in an upcomming book on the subject, I can't display it here). Peaking too early in the drive is hard to recognize from the force curve shape alone, but quite a common issue.

At a really gross, crude level the force curve reflects legs/hips/arm sequencing. At a more nuanced level it shows power output from these overlapping components -- but for new rowers sequencing (or lack of sequencing) drives the shape.

OP was changing his style to get a bell curve. My post was to remove OP's certainty that they needed to target a bell curve. Agree completely with your point that there are other styles that might be better than a bell curve. Also agree with OP that concept2 etc. talks about bell curve.

The force curve will also be different sprinting because the underlying legs/hips/arm sequencing is different for a short sprint - less layback, maybe shorter drive length from shins not reaching vertical, etc.

This 2022 USrowing coaches education video is rough to listen to (strong accent). 2022 Coaches Conference : Rowing Styles : What is the Most Optimal Style & Considerations? It'll go over why I said there are several valid styles without invalidating your point. I linked starting 4 mins into the talk.
https://youtu.be/-xTYWaSlh9I?si=IO4XMsoNEaMJQffj&t=239

In a multi-person boat you need to have same shape. Erging pick the one you like.

That is actually an area if intense academic debate, where there is some good evidence pointing the other direction as well. Optimal crew composition and placement is incredibly complex, and moving "as one" may have downsides.

"..some good evidence pointing the other direction as well..." means it might be optimal to have different rowing styles in the same boat ?? Any papers or credible articles you can point to? This is a big surprise to me, but I like the concept. (Sort of like the discovery cycling that short cranks are better, fat low pressure tires are better, stretching before racing hurts you, etc. Amazing what you find when you actually measure stuff instead of going with what everyone knows is right).

[jamesg]

what "light" rowing or "recovery" rowing means in the context of the force curve.

It'll be smaller, since what happens is the stroke has less mechanical Work in it. Paddle "Light" is done for warm up and getting back home. "Recovery" is also lightish, but longer, where technique but not necessarily Work, is what counts. One likes to hear the boat sing, but without heavy breathing.

On the erg we have to imagine this. Ideal drag can help with rhythm, since it lets us control the pull speed.

[jamesg]

might be optimal to have different rowing styles in the same boat ??

That's a stopper, to be sure. See the Princess Elizabeth races in recent years or any good 4x. Even their eyes seem to be all fixed on the same point.

[JaapvanE]

"..some good evidence pointing the other direction as well..." means it might be optimal to have different rowing styles in the same boat ?? Any papers or credible articles you can point to? This is a big surprise to me, but I like the concept. (Sort of like the discovery cycling that short cranks are better, fat low pressure tires are better, stretching before racing hurts you, etc. Amazing what you find when you actually measure stuff instead of going with what everyone knows is right).

Sorry, I couldn't find them again. For me, the main focus was finding math that describes optimal force curves on ergs, as on ORM we wanted to show where people can improve. That made the articles interesting to read, but out of scope for me. As you also explained well: there isn't a perfect curve. A "perfect curve" essentially is one that is smooth (i.e. lacks dents due to bad transitions) and has as much volume as possible.

The key thing I recall is that in a boat, human synchronisation isn't perfect. A typical example is the person in the stroke seat is a tiny bit earlier than the rest (we are talking microseconds here). So accepting that, but still having compatible (i.e. overlapping) force curve peaks overall helped.

From a pure physics perspective I always wondered about the need for 100% synchronisation. A side effect of the cube law is that high variation in boat speed in a stroke requires a lot more energy. So by having tiny variations in force curve peak positioning, boat speed could be accelerated more smoothly instead of getting a huge push at a single moment. But here, practicality of people moving at different times will cause weird effects.

[jamesg]

The point about timing is that the boat is not fixed to the ground; so if good, we all work together and all feel the same inertial effects. Which are small compared to eight large oarsmen.

[iain]

The point about timing is that the boat is not fixed to the ground; so if good, we all work together and all feel the same inertial effects. Which are small compared to eight large oarsmen.

I'm no expert, but while there may be a benefit from slight differences:

1) in a sweep boat, the force applied on both sides needs to be the same or the boat will rock, so pairs need to be synchronised
2) if you are ahead of the rest of the crew in a larger boat then he catch is very heavy, indeed a common exercise for inexperienced oarsmen is having each try and row a held boat alone, the force required to accelerate the boat is so high that the oarsman is pushed up out of their seat unless they are leaking power at the catch. Please would you explain how having the stroke ahead would benefit the crew.
3) As in 1)we need to remember that the boat has more than one dimension, the boat lifts at the bow during the drive which reduces its drag, is this built into the models considered?

While I can see that a theoretical approach of each pair rowing in time but staggered might be more efficient, I am cynical that this could be timed correctly as it is much more complex than rowing together where feel and sound reinforce the coordination. I too have noticed that the best crews appear to be near perfectly coordinated.

[Tsnor]

... For me, the main focus was finding math that describes optimal force curves on ergs, as on ORM we wanted to show where people can improve.

Math has to account for efficiency of various human muscles. At one point math predicted for cycling that lifting on part of the stroke (using clipless pedals) and using elliptical chainrings to get more continuous power was more efficient. Nope, turned out not to be true. For rowing area under curve is not a good measure of efficiency (but it will give total power - just not how efficiently that power was generated). Example: If leg muscles are more efficient then back, the the first part of the force curve should be higher - you'd want more force to come from legs.

The key thing I recall is that in a boat, human synchronisation isn't perfect. A typical example is the person in the stroke seat is a tiny bit earlier than the rest (we are talking microseconds here).

Surprised by this. I'm more apt apt to be early following stroke than late, its called "rushing the stroke". There's not even a term for being late (other than late). For elite teams if there was a structural imbalance in catch timing the coaches would fix it. Aside - when catch or release timing is off you really feel it. Catch hits you as you are floating on your slide wheels under zero power (letting the boat run under you), its an obvious change to how fast you are approaching the catch. Something you've done 100s of times that practice is suddenly different in a bad way. You also feel it when back/hip swing gets in sync, feels great.

From a pure physics perspective I always wondered about the need for 100% synchronization. A side effect of the cube law is that high variation in boat speed in a stroke requires a lot more energy. So by having tiny variations in force curve peak positioning, boat speed could be accelerated more smoothly instead of getting a huge push at a single moment. But here, practicality of people moving at different times will cause weird effects.

Exactly --> "... people moving at different times will cause weird effects". (1) If some people in the boat are rushing (catch early), then the rest of the boat can't get a full stroke. The boat moves away from the rest of the rowers as the early people move the boat relative to the other rowers. Very obvious feel, you can see peoples heads bob forward and back (wasted energy) if the boat is out of time, and the coxswain is rattled around. The trade-off of less power production for less friction loss doesn't work. (2) There is not enough room in the boat for some pairs to be on the drive while others are on the recovery. If you are not in sync you get an oar in your back.

[Tsnor]

Even their eyes seem to be all fixed on the same point.

This is huge. Doesn't seem like much, but really changes breathing and boat set. We sometimes do drills where people move their heads just to remind us how important it is.