Q. I know your arms should not cross the centre line as they hit the water, but is this also true as you're pulling through the water?
A. When swimmers use their muscles to push the water backwards, that action causes a counter force that propels them forward. To achieve the most efficient stroke you must maximise your pull and push through the water.
Forcing your arms/hands to cross the midline of your body, commonly known as crossover, simply wastes effort because your arms and hands are now exerting a sideways force rather than a backwards one.
This forces the swimmer to wriggle from side to side, like a snake, which leads to increased drag because this side-to-side motion makes the hips and legs move left and right, rather than in a straight line. When the body doesn't wriggle (called good lateral alignment) only the head and shoulders push through the water.
Other crossover problems:
➽ Tendency to go off course, especially if your stroke is lopsided (one arm/hand crosses the midline more than the other).
➽ It becomes harder to achieve good rolling from the hips.
➽ It can lead to shoulder injury because the shoulder twists more than it should.
➽ It's a less stable position. In rough open-water conditions you will be tossed around more than if your arms under the water are in a wide position.
It is hard for swimmers to judge if they are doing any crossover in their stroke. Ask someone else to check your stroke to see if you are crossing over. If you are, try these drills:
1 During the pull phase of the stroke lift your thumb so it is at a right angle to your index finger. As you pull back under your chest, try lifting your hand up towards your chest, so your thumb scrapes along it. You will then know if you are crossing over and be able to adjust accordingly.
2 Take a kickboard and hold it with one hand straight out in front of you. Try swimming with just one arm and a leg kick. Focusing on one arm at a time will give you more opportunity to note where your arm/hand is under your body and you can adjust accordingly.
Simon Murie is the founder of SwimTrek (swimtrek.com), which offers open-water swimming and coaching camps, and holidays, in the UK and overseas. He is a qualified swim coach and an experienced swimmer, with a solo crossing of the English Channel to his name. He is passionate about introducing open-water swimming to the uninitiated as well as finding new locations for experienced swimmers and triathletes.