• Question: In martial arts, particularly ones like judo, akido and ju-jitsu, they do a lot of break falls; a controlled way of landing from a throw that reduces the impact damage to the body. These can range from a roll to slapping the floor with your arm. I was hoping you might be able to explain how this actually reduces the force? I thought that perhaps a roll lengthens the time of the impact which could somehow reduce it, and perhaps the way you land might link to maximising the surface area reducing the pressure. But I'm not too sure, especially on why we slap the floor. Whilst on the topic of sport, does shouting when fighting or playing tennis actually improve your playing?

    Asked by 07stoombs to Alexander, Josh, Serena, Simone, Stuart on 21 Jun 2013.
    • Photo: Alexander Munnoch

      Alexander Munnoch answered on 21 Jun 2013:

      Regarding the falls it is a matter of maximising surface area.

      e.g. Force = Pressure / Area
      So if you fall with the same force over twice the area, you’ll feel half the pressure!

      As regards the shouting, I think it can ‘serve’ as both a tension release and a way of emptying your lungs but I don’t know the specifics.

    • Photo: Simone Sturniolo

      Simone Sturniolo answered on 21 Jun 2013:

      I agree with Alexander. I also think that a roll, for example, is a way to exploit the force of the impact instead of letting it hurt you: if you roll, you have small friction and can even use the momentum to get back up, or get out of the way of further hits. If you slam and slide on the ground, on the other hand, you suffer higher friction and it all goes to damage you. About slapping the floor, I think it’s a way of controlling your falling trajectory, most likely. After all, our body has certain parts that are better at suffering an impact without taking serious damage than others (I’d rather fall on my side than on my head!).
      I’m not a martial artist though, so I don’t know. If you do practice sports like this, try repeating the controlled falls on your own as a training exercise and feeling the forces acting on your body yourself! You’ll probably figure it out better than we can do :).

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