The 3-Sentence Summary
Coaches at all levels can use video to check two metrics from their crews that Dr. Kleshnev created to evaluate technique: catch factor and rowing style factor. Catch factor is a more accurate measure of optimal boat check, and rowing style factor evaluates the coordination of the trunk and legs during the drive. Many medal-winning crews at the Olympics demonstrate optimal values for these metrics regardless of event or rigging.
- Basic concepts: Catch Factor, Rowing Style Factor
- Technique Demos
- Rigging: Gearing, blade types, and efficiency
1:57 Origin story of these “basic concepts”:
When I was an athlete, coaches used to tell me not to check the boat and keep it running. But we found the best crews check the boat really strongly but for a very short amount of time (highest magnitude of the negative peak of acceleration at the catch), and then accelerate the boat very quickly to the “first peak” when the heels connect with the stretcher.
3:52 This led to the development of the “trampoline effect,” in which the rower bounces off the stretcher. Demos of trampoline effect and its opposite.
When we bounce off the stretcher precisely, the boat moves more efficiently.
6:20 Then the methodology “catch through the stretcher”:
- Catching through the handle causes problems (opening with the back, not using larger muscles first…)
- Catching through the stretcher results in 46% faster blade velocity given the same handle velocity.
- Other terms: just hold the handle, hang on the handle.
10:44 This led to the “catch factor” metric:
Catch Factor = the time between when the handle changes direction at the catch and when the seat changes direction at the catch. The seat travels to the bow before the handle by this amount of time. Optimal value is 15ms for scull, 25ms for sweep. Pure technique, not related to blade type, rigging. (Catch is before entry.)
12:55 Rowing Styles are defined by coordination and timing of the trunk and legs.
15:23 When should we use the trunk? When the knee angle is 90 degrees, at the “transition point.”
18:26 This led to the “rowing style factor” metric:
Rowing Style Factor = the ratio of the seat travel to the handle travel during the first 20% of the drive length (until the “transition point”).
Optimal value = 90% (10% of the handle movement comes from upper body). 100% seems to include some amount of shooting the slide
20:04 Video examples of technique and catch factor
26:45 How does changing foot stretcher angle change the transition point?
Higher stretcher angle usually reduces drive length. Flatter stretcher increases drive length but more force is in the vertical component.
28:17 Do you have drills that can help rowers get to 90%?
Russian catch drill demo. Don’t pull the handle, keep the trunk angle constant.
Half slide drill demo. Start with trunk at half slide.
Tokyo Olympic Crew Analysis
30:45 Analysis of rowers from Tokyo Olympics with demo video. Unfortunately video quality was low (variable fps, random zoom and frame positioning), so we can only estimate catch factor.
|Timestamp||Crew||Rowing Style Factor||Catching through…|
|35:02||New Zealand W1x||~100%||Stretcher|
|50:38||Croatian M2- (the exception)||~80%||Handle|
|52:31||New Zealand W2-||~100%||Stretcher|
|56:00||New Zealand M8+||~90%||Stretcher|
Most crews don’t open the trunk up much before the transition point, and they catch through the stretcher (though it was difficult to estimate on video).
1:01:07 How does one continue to move the handle forward when the seat is stopped without diving?
It’s more of a shoulder stretch (sculling) or shoulder rotation (sweep). It’s elastic.
1:03:03 Not enough information around trends in rigging.
1:05:27 Gearing: Ratio of velocities of output to input (not forces). Components:
- Static oar gearing (ratio of outboard to inboard)
- Dynamic oar gearing (oar angles – the longer the angle the heavier the gearing)
- Blade slip decreases gear ratio
- Rower-oar geometry (between arm and blade shaft)
1:09:37 Static oar gearing: Shorter inboard/longer outboard/oar makes oar heavier and vice versa. Gearing numbers don’t vary significantly from the standard. They are generally ±3% in sculling and ±4% in sweep. Gearing is not proportional to boat speed.
1:12:37 Dynamic gearing is based on the “wedge” effect: if the angle of force application is different from 90 degrees, then propulsive force decreases, but propulsive velocity increases (speed skating, sailing, birds).
Due to lift forces, propulsive efficiency is higher at the blade entry vs. the middle of the drive.
1:14:46 Conclusion: Control oar angles to control dynamic gearing. General rule: every 1-degree increase of catch angle increases the gearing ratio as much as 1cm longer outboard or 0.5cm shorter inboard.
1:17:04 New project: measuring efficiency of blade types.
1:19:18 Example research question: how does the shorter outboard in the Fat2 blade affect efficiency and performance?
- Gearing was lighter, but propulsive power and efficiency were lower than other blades.
1:20:48 Starting to investigate indicator of propulsive efficiency.
1:23:06 Contact Info