The Crab Conundrum

For many rowers in their first couple of competitive seasons, “catching a crab” is the biggest fear in the boat. After a while, as your most recent crab recedes into history and becomes a distant memory, rowers tend to stop worrying about it – until suddenly one day for no obvious reason, it strikes again.  Crabs are rare among senior rowers, but not unknown. They happen during the Oxford / Cambridge boat race, at national championships and at Henley.  So here’s the conondrum, why does this novice error occasionally strike even very experienced crews? And what should coaches do about it?

This video – big thanks to WA Rowing Club, Perth – shows an experienced crew catching a crab (crab at 1:42 NSFW – loud music):


There are actually two types of crab.  The ‘common’ crab happens during the power phase of the stroke when the rower is unable to extract the blade from the water.  The speed of the boat pushes the handle of the stuck blade into the rowers body.  If they are lucky it simply knocks them flat and passes over their heads.  If they are unlucky, the handle can lift the rower out of his or her shoes and eject them over the side of the boat.  The other type of crab (as shown in the video) happens during the recovery when the blades are, or should be, in the air. If the leading edge of a blade catches the water at the wrong angle, the blade enters the water, the suddenly increased drag stops the forward motion of the spoon and again the movement of the boat brings the handle towards the bow, striking the rower’s body with the effect described above. From the coach’s point of view it is important to know which type of crab a rower has caught as the remedies differ.

The cause of the common crab is usually that the blade is not square in the water, either because the catch was not square or because the rower was feathering the blade underwater. Both of these novice errors can be fixed quickly and simply if timely action is taken by the coach. Unfortunately, a common response from novice rowers trying to avoid catching a crab is to pull their finishes lower into their laps in the belief that this will help get their blade out of the water. What this actually does is to lower their rigger toward the water at the extraction, giving them less space to ‘tap down’ into – so the problem of getting the blade out of the water actually gets worse. Pulling the finish higher, so raising the rigger and creating more room for the tap down is actually the more effective response.

A crab on the recovery is often caused either by over-feathering or (particularly with novices) by failure to keep the knees down during the first part of the recovery.  If the knees come up early, the hands have to rise to get over them – and if the hands rise then the spoon has to drop toward the water. Again both these errors are relatively easy to fix by appropriate coaching if they are spotted in time.

Some coaches train crews to row their recoveries with blades very close to the water. Personally I’m not sure that this offers a real performance advantage, but it does increase the risk of a crab if the boat hits rough water or the wake of another boat.  I coach crews to use the same hand height  on the recovery whether they are using square or feathered blades.  This gives the boat a margin of safety should the conditions require it.

For most rowers, catching a crab is not a predictable occurrence.  It happens suddenly and unexpectedly and even the rower concerned my not be sure at which stage of the stroke the crab happened.  Without video evidence, diagnosis and specific remedial coaching can be difficult.  In these situations it is important not to exaggerate the problem in the rower’s mind.  A rower who is concentrating on not catching a crab  is probably not rowing at their best and the more the coach focuses on the crab the more pressure the rower is under. That pressure is more likely to lead to further errors and you risk creating a vicious circle. No-one catches a crab deliberately and I believe that the most common cause is a lapse of concentration – possibly elsewhere in the boat.

With senior crews I simply ignore the occasional crab.  If it isn’t due to basic errors of technique then you do more good by sticking with the training plan for the outing rather than chasing what can be a very elusive error.  Particularly in the run-up to a competition, good crew morale and the achievement of the right balance of attention and relaxation is more important.

It IS important always to check the rigging after a crab – particularly if it happened while the boat was moving fast.  A crabbed blade can bend rigging out of shape. If the crew are sharing boats it is also worth checking that someone else hasn’t changed rigger heights, spans or blade pitches – again possibly on a different seat.

Provided that the problem isn’t in the equipment or the technique you have taught, I think catching a random crab remains one of rowing’s ‘black swan events’.  Bad luck if it happens to you, good luck if it takes out the competition.  As a coach, you just have to live with it.

3 thoughts on “The Crab Conundrum

  1. Your idea that the rower should keep a constant handle height during the recovery actually has a performance reason.

    As you point out, having the blade close to the water increases the probability of catching water during the recovery. My coaches call keeping the blade close to the water “training wheels”, and a competent rower does not need training wheels.

    The other reason to keep a constant handle height is for performance. At the finish, the blade gets extracted one blade height high. If the rower then brings the blade down close to the water, that takes rotational energy to perform (although the rower does not recognize it) and this subtracts from the total forward momentum of the boat. Also, the hands have to push down before the catch so that the oar can be squared, and this takes energy away from the forward boat momentum. This up and down hand movement rocks the boat during the recovery unless perfectly synchronized.

    Also, it complicates the brain and muscle communication and coordination around the catch time, requiring the rower to push down on the oar handle before beginning the square-up and placing the oar at the catch. It is difficult enough to impress on the rower to square up and place the oar before applying pressure on the foot stretcher.

    Believe me, I had a technical problem in that, although I thought my hands moved level, they drifted up during the recovery. This screwed up my square-up and placing the oar at the catch. I made the rowers to the bow side of me wet more often than not as I flipped up water, in addition to always having my side pitch down due to my hand movement.

    Rowing a pair emphasized the problem, and accentuated the advantages of level hands. Now, the eight sets up better, rows faster, and feels more stable.

    When coxing, during what I call the calibration phase of the warm-up, I emphasize keeping the oar one blade depth above the water during the recovery.

  2. Thanks for your comment. A big backsplash at the catch is a problem I’ve had too and it isn’t always an easy problem to fix. I agree that a recovery ‘one blade depth above the water’ is a good coaching rule and if you use the same hand height for feathered recoveries as you use for square balde recoveries that is what you get. It is a fact however, that you will see some elite crews who row with very little air under their blades on the recovery, and people find it an easy style to copy. As a coach I find that the solution is to select a rower at stroke who is consistently correct. Then you can simply say ‘row like stroke’.

  3. Pingback: How to avoid “catching a crab” in rowing

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