I'd like to return to the argument about imbalance and the cost of reaction against it. Recall Hank's suggested thought-experiment of drilling through the centre of a paddle shaft and putting an axle in there. Then we can easily spin the paddle on that axis. But if the hole is drilled obliquely, at such an angle that the axle is horizontal and each blade dips into the water on its own side of the boat, it's hard to hold that axle steady, and the faster the paddle is turning, the harder it is. Normally (except when we're trying to roll?;-) the paddle blade barely dips below the surface, so if our hands are held low, the blade is well out from the boat, and for an "efficient" vertical stroke our hands ar held higher. The higher our hands are, and the faster the stroke, the more physiological work we are doing to support the paddle against both gravity and its own angular momentum. This is in a sense work at zero efficiency, because it's only the part of the work that we do to support the paddle, the part that would not be work if we rigged up some sort of mechanism to hold the paddle. Thus we do less work by lowering the hands (gravity: independent of speed), or by making the stroke more vertical (reaction against turning: increases rapidly with speed). For any cadence, then there is a paddling angle, the point we choose between a vertical and a horizontal stroke, for which the amount of physiogical work in holding the paddle is a minimum. If I'm touring along the edge of a marsh looking at dragonflies, my least-work stroke will be nearly horizontal. Passing a less-interesting bit of shore, my stroke rises a bit, and when I notice the thunderclouds overhead, it becomes nearly vertical. A lot of work has shown that animals (including people) automatically change gaits, as their speed varies, to minimize physiological work, measured as oxygen consumption. As the treadmill speeds up, we break from walk to run. But we know that animals can be taught to hold a specific gait even when it costs more -- race walkers and trotting horses are examples. Paddling is not an inborn activity; we need to consciously learn it. Some of us learn to do it in a specific way, and others "listen" to our bodies more, and automatically vary our "gaits". There have been comments that could be summarized as "Shut up and paddle". But when we paddle, sometimes we let our minds go blank, sometimes we enjoy our surroundings, and sometimes try to improve our technique. Trying to analyze what we are doing, and how it could be done better, whatever we choose "better" to mean, is a legitimate part of paddling, provided it does not become obsessive. And, as has been pointed out, if it is obsessive when we're off the water, so what? What better coiuld we be doing? Besides, as we age we must substitute better technique for waning strength, or, perish the thought, slow down. Bruce Bruce Winterbon bwinterb_at_intranet.ca http://intranet.ca:80/~bwinterb All states have laws to protect the rich from the poor. Few attempt the more difficult task of protecting the poor from the rich. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Wed Jul 22 1998 - 18:47:24 PDT
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