Punching force is one measurable metric for effectiveness in martial arts training, though it does not measure the effectiveness of a given technique. Force is measured in newtons, which express the amount of energy needed to move a given mass a given distance. Impact energy is expressed in pascals, which is a unit of pressure, and divides force in newtons by the surface area of the impact surface.
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Things you need
- Video camera with a known frames per second recording speed
- Punchbag with a known weight in kilograms
- Backdrop with 10 centimetre stripes painted on it
- Athletic tape
Hang a target of a known weight from the ceiling; for example, a 100kg punchbag.
Set up a video camera with a known frames per second speed -- 30 fps is typical -- to observe the bag.
Put a backdrop behind the bag in line with the camera that has 10 centimetre stripes, alternating between white and dark grey.
Turn on the camera and punch the bag. After each punch, make sure the bag is put at rest before the next punch. Repeat this step multiple times.
Review the film footage, advancing one frame at a time. Most digital cameras and digital video editing software allows you to advance video footage one frame at a time. Determine how far the bag moves from each punch in one frame. Repeat this for as many frames as you can, summing the distances and dividing by the number of frames used. This will give you the average distance moved per frame.
Multiply the average distance in meters moved per frame by the number of frames per second your camera records. This is the velocity the bag moves in meters per second.
Multiply meters per second by the weight of the bag. You will have calculated the total force delivered to the bag by the punch, in kilogram meters per second, which happens to be one newton.
Wrap the surface of the martial artist's hand in athletic tape, and press lightly into a sponge; the water will temporarily mark the surface of the tape. Cut the moistened part of the tape off; this will be a proxy for how much surface area struck the bag. Measure this piece of tape -- if it's 5cm by 8cm, for example, it has 40cm^2 of surface area.
Divide newtons of force from step 3 by square centimetres of impact, then divide by 10,000. This yields the pressure in pascals.
Tips and warnings
- To convert pascals to pounds per square inch, multiply them by 0.000145037738.
- Several commercial training tools exist that give a punching target, and measure the force and impact area of the punch to yield the amount of energy delivered and give pressures in pounds per square inch.
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