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More Power: The “Fat” Part of the Pull

November 5, 2012

I have for a long time struggled with the school of though that emphasizes “reaching farther” to “propel more”.  Not that there is not something to the whole “stroke length” part of the equation – V = Length * Rate, but more importantly, how does the Length term get maximized?  By reaching farther?  Generally speaking, I would say no.  The goal, to me, is to maximize the grip and force on the water during that part of the stroke when mechanical advantage is in your favor, that is, when your hand is moving more or less straight back (generally speaking, when it is underneath your torso).

The Fat Part
A basic analysis of the stroke tells us that we can propel most effectively when pulling backwards, and we can’t really do that during the entire underwater pull since our hand travels in some sort of curvilinear path.  Thus, we have encouraged the swimmers to seek feeling the greatest traction when the hand is roughly under the chin to somewhere along the hip, but not necessarily very far past the hip.  I stumbled upon an old study recently that outfitted trained competitive swimmers and novice swimmers with “sensor gloves” that measured the amount of force they were applying against the water at each point along the path that their hand flowed during the underwater portion of the pull (Takagi, 2002: http://www.taiiku.tsukuba.ac.jp/~takagi/document/ISEA2002.pdf).  The results are shown in figures 1 and 2.  To me, this says that the accomplished swimmers generate similar amounts of forces, and perhaps overall LESS force during the stroke, but concentrated in a narrow part of the stroke where there force is at its highest.  As it turns out, the part of the stroke where this concentration occurs is that portion where there hand is moving more or less straight back, enjoying its greatest mechanical advantage.  So, find the fat part of the stroke.

Figure 1: Diagram of force on the swimmers hand measured with pressure sensor gloves during the underwater portion of the crawl (freestyle) stroke.  The plot on the left hand side is that for an accomplished competetive swimmer, the plot on the right is that from a novice swimmer.

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2 Comments
  1. Pretty much how the pedal strokes works on a bike. Beginners are always trying to spin the perfect circle (long power phase) while the world class athletes are pushing as hard as they can for that brief period when they are well positioned to push hard. Generally, the ore world class they become, the more they do this. Even the graphs look similar to the ones above. Nice blog.

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