In our experience when swimmers try and make their stroke as long as possible they normally over-reach at the front of their stroke.
从我们的经验来看，当泳者尝试并使他们的划臂尽可能长时，他们在划臂的前端过分地往前够。
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If you consistently over-reach on your backstroke pull, double-arm makes this very tough to do, because you have to cross your arms during the recovery to accomplish that.