Monthly Archives: August 2010

Managing the recovery

Boat velocity vs rower power for different types of recovery

The figure shows the boat velocity vs power chart for different types of recovery. Each data point represents a calculation at different ratings between 25 spm and 35 spm. Keeping the force constant and varying the rating, the higher powers are obtained by racing the slides more. I modeled 4 types of recovery:

  1. Constant handle speed
  2. Sinus function handle speed
  3. Triangle handle speed (linear acceleration and deceleration of handles)
  4. “Realistic” handle speed (roughly modeled from rowing videos)

Note that I model the velocity profile of the handle. Of course, the body center of mass responds differently, the center of mass being slower than the handle at the start of the recovery where only the arms move, and faster during the second half of the recovery.

The figure shows that – within the accuracy of the model and at constant rower power – the average boat speed is independent of the recovery style. Knowing how coaches like to stress the importance of the recovery, this seems a counterintuitive result. However, my results are in agreement with Van Holst, who concludes quite strongly: “It seems useless to coach on a very pronounced mode of seat motion.”

Actually, coaches are right to pay attention to the return, but not for energy efficiency reasons. It is the quality of the return that determines the accuracy of the catch. This effect is strongest in sweep rowing: If the crew does not manage the recovery phase in perfect sync, the boat balance will be disturbed. Apart from the balance, there are more subtle effects. I believe that any disturbance resulting from imperfect crew synchronization or abrupt body movements during the return compromises the quality of the catch, which will have an effect on the stroke quality.

You can try this with your crew by training them to start from the release position. Another way of illustrating the effect is by training start sequences. The first stroke is usually done with less power and more attention to balance than the second one, because a bad first stroke can ruin the first return, which in turn ruins the first catch (of the second stroke), and so forth.

Free Range Kids

Just a note about something only remotely related: FreeRange Kids.

I was on the dock yesterday teaching a few 10 year olds their first strokes in a single scull. It was big fun and nobody got wet. For a couple of kids, it was a big confidence-booster.

Luckily, where I live we don’t need a Free Range Kids movement.

Masters Regatta Munich

No new rowing physics this week, just a finish foto featuring the author of this blog stroking the Masters 2x B in the Euro Masters Munich regatta:

We finished at third place with a few centimeters difference. From the stroke position I had the feeling we had lost the battle, but our Vespoli is a much longer boat than the opponent’s Stämpfli.

Back to physics: Presuming their weight equal to ours, our opponents must have used less energy as their first and second 500m differed by only 0.18sec, where ours differed by 1.59sec. Our last 500m was faster than our first 500m.