Rowing efficiency case study

rowing data comparison, rowing boat speed measure

Interesting data was obtained recently: two LW2x performed the standard BioRow® test protocol (RBN 2013/03) side-by-side, so the weather conditions should be the same. Both crews had the same boat build (Filippi with bow-mounted carbon wing-riggers), oars (Croker Super light), very similar boat age (made in 2012 and 2013) and average rowers height and weight (1.72m / 59kg for crew 1, and 1.75m / 58kg for crew 2). Both boats were equipped with BioRowTel system calibrated in the same way.

 

BioRowTel, rowing data, rowing boat speed, compare boat speed
Raw data collected from two 2x

On average, crew 1 (Table 1, in red) had 1.1% lower stroke rate, 0.9% shorter stroke length, 0.9% lower force and 8.6% lower power, but 0.52% higher boat speed compare to the crew 2 (in blue). Therefore, drag factor of crew 1 was significantly lower in all samples (on average, 7.2% lower Net DF, and 9.7% lower Gross DF, RBN 2015/03).

The obvious question is: how it was possible at the same weather, equipment and crews’ weight?

What could be the reasons of higher rowing efficiency in crew 1 compared to crew 2? To answer these questions, biomechanical analysis was made at the sample 6 (31.5 and 31.9spm), where crew 1 was 1.3% faster.

Crew 1 analysed: Force and Velocity for Handle & Seat

rowing data, rowing crew compare,
Crew 1 rating 31.5 comparing athletes

At the catch, the crew 1 (Fig.1) had quite different timing at the handle (the bow rower was 20ms later at change direction, 1), but very good synchronisation at the seat (less than 2ms difference, 2), which means rowers push the stretcher at the same time. The stroke rower applied a much higher force during the first half of the drive (3); then, the forces were quite similar (4). Catch Factors CF were quite similar in this crew (-10ms in stroke, and -27ms in the bow), as well as Rowing Style Factor RSF (80% and 90%).

Crew 2 analysed: Force and Velocity for Handle & Seat

rowing data, crew boat speed, analyse boats
Crew 2 rating 31.9 shows less alignment in the seat timing.

In contrast, crew 2 (Fig.2) had slightly better synchronisation at the handle (bow rower was 18ms later, 1), but much worse timing at the seat (bow rower overtook the stroke by 35ms), which means their stretcher forces were not synchronised. So, the CF was very different: +16ms in the stroke and -35ms in the bow, as well as RSF (79% and 98%).

Force curves were quite similar in general, but the stroke rower had a significant gap after the catch (3), which means (after subtracting oar inertia force) she applied a negative (braking) force at the blade.

Overall boat speed comparison and reasons

rowing data comparison, rowing boat speed measure
Comparing both crews shows where differences occur
Comparison of the whole boat data (Fig.3) shows that the negative peak of the boat acceleration in crew 1 (1) was narrower, but deeper (because of better synchronisation at the seat and stretcher), which allowed lower boat speed at the catch and easier “connection” to the water (2).
The force curve (sum of two rowers) was more “front-loaded” in crew 1 (3), so they had a significant “first peak” of the boat acceleration (4), while the crew 2 didn’t have it at all.
Also, “front-loaded” force emphasis at lower handle velocity allowed crew 1 to produce nearly the same impulse at 10.1% lower power, so they were more energy efficient.

Concluding:

In the more efficient crew 1, better synchronisation at the seat and stretcher allowed:
  • Lower “energy transfer through the boat” (RBN 2012/04), which may decrease inertial energy losses;
  • Deeper, but narrower negative peak of the boat acceleration, which helps better “connection” at catch;
  • More “front-loaded” & efficient force curve and better pattern of the boat acceleration during the drive.
©2017 Dr. Valery Kleshnev www.biorow.com

6 thoughts on “Rowing efficiency case study

  1. Martin Hyndman says:

    Step 1: Get the data – check
    Step 2 – Wear an exoskeleton that forces the sculler to make the most efficient movements
    Obvious really.

  2. David Harralson says:

    From previous Valery Kleshnev articles, I realized a front loaded stroke side force profile produced a more efficient pair. Now, it appears the same might be true in a double. Interesting.

  3. Michael Macrossan says:

    “… she [stroke of slower boat] applied a negative (braking) force at the blade.”

    In other words, she was backsplashing. When you put the blade in the water so that it pushes water towards the bow, you are applying an external braking force to the system, adding to the hull drag. When you “tap the brakes” twice every second or so, you go slower. Case closed, I think.

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