Like any other exercise, load matters. If you allow more slack in the ropes (by stepping forward) you'll be forced to work with the weight of the rope itself. Stretching them out tight doesn't allow for any actual weight to be loaded on the movement of your arm strokes.
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Grab the ropes, walk back, then take two big steps forward so the ropes are NOT taut.
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Take an athletic stance and an upright posture.
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Set a Tabata timer on your phone for 10 rounds of 20 seconds of work with a 10 second break.
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Alternate each round between strokes of your choosing. But once you pick a stroke, you must maintain it for the whole 20 seconds; you can't switch until the round is over. Once the 20 seconds is up, feel free to switch to another pattern.