Basic Physics of Rowing (2007)

This page was written by Anu Dudhia, who for many years was celebrated by the giant graffiti saying "ANU IS GOD" on the side of Donnington Bridge in Oxford.

I rowed in high school, and one of the things the coaches always wanted to see is for you to slide forward slowly in your seat as you move the oar between strokes.

The reasoning being that as you slide “forward” in your seat, you’re actually pushing the boat backwards with your momentum, since you face backwards in the boat.

It always struck me as strange advice though, because in a race you’re trying to get high stroke rates (35+ strokes per minute) and there’s not a lot of time between strokes to move your seat. And if you have to move your seat from A to B, there’s no real free lunch: Work equals force times distance, so you’re going to impart the same amount of momentum into the boat whether you move the slide slowly or quickly… it’s just a matter of how much time that work is spread out over, and that really shouldn’t make a difference to the boat.

Watching rowing in the Olympics it doesn’t seem like they’re worried about this at all. They just move from the back to the front of their seat quickly and it’s not some obvious effort to be gradual about it.

There were other dubious bits of advice too, like pushing with your legs first, then torso, then arms, but if you try to actually do that in reality it feels extremely awkward. And watching the pros do it on TV it doesn’t seem like they’re doing anything like this.

The move slowly thing is likely to account for jerkiness as a thing people do is rush up the slide and wait at the catch position. You want to get to the catch without the inertia of being forced forward so you can raise your hands get ours in and then push. From a physics perspective there’s also the possibility that rushing up the slide forces the stern down faster breaking the about however that Varys massively and I don’t know about it being proven.

Regarding the order of operations after the catch that’s because a stroke is similar to power clean sitting down. You are effectively maximising the lever arc.

> slide forward slowly

It's an efficiency thing, the linked page partially covers this in section 5. Going forwards slowly impacts the same momentum, but as it is done gradually it results in a greater overall boat speed because you avoid sudden speed jolts. And remember that going forwards quickly also means you must decelerate your body quite a bit at the catch! When a coach is telling you to slide forward slowly they are trying you to move forward at a constant speed, not so much a slow speed.

That being said, it is better to do slower and longer strokes. You're trying to move the boat, so all the moving of your body is wasted energy. Moving your body really quickly is very tiring, whereas you can sustain slower and longer strokes a lot longer. At an elite level you simply can't make the stroke any longer, and you can't get more power out of a stroke either because there are limitations to oar length. The only way for an elite rower to put more energy in the boat is to do more strokes, which means they have to speed up.

> pushing with your legs first

Your legs are a lot stronger than your torso and arms. If you do arms first, the power being put into the boat by the legs is limited by your arm strength. When you leave the arms extended, you are simply hanging on them without the muscles engaged, allowing you to go full leg strength. This is 100% still the case at an elite level, but it is harder to see due to the higher stroke rate, and the fact that they engage the arms/torso before the legs are completely flat.

That's the irony of rowing: when you are doing it properly it looks completely effortless.