1. Physics of Fencing The Biomechanics of a Lunge
William Goldhirsch
Biology 438
Spring 2012

2. Weapons

3. The foil

4. What is fencing?

5. Physics of Fencing The main motion in fencing is the lunge
Deconstruct the lunge, see if the analysis matches the conceptual understanding.
2) The goal of the lunge is to hit your opponent…how much force is in this foil? How safe is fencing? For example, it is known that to set off a foil, you must put a minimum force of 4.9 newtons to press down the tip…how does this compare to the total force?

6. Video-Edited

7. Original Video

8. Lunge
A lunge is the primary, offensive technique in the sport of fencing.
It is an attack…and it is fast.
All weapons use
it, and it is arguably
the most important
aspect in competitive
fencing.

9. How do you lunge? 1. The arm holding the foil begins to extend.
2. The foot facing the opponent kicks forward.
3. The back leg pushes forward by straightening – at the same time, the back arm is thrown back –the body is pushed forward.
4. The foil reaches its target, and the front heel hits the floor. The foot lands and the leg bends until the knee is directly over the heel.

11. Start-before analysis

12. Video Analyzed - Finish

13. Which muscles are used? In fencing…everything you can think of!
Focus on the lunge:
Quadriceps femoris muscle: the main worker of the lunge; provide much of the force (the back leg).
Calves: help the speed and explosiveness of the lunge, they help set up the lunge and then when recovering.
Anterior tibialis muscle: Body weight is put on this muscle when a fencer lunges (front shin).
Hamstrings: help speed and recovery
Gluteus muscles: Hold thighs and quads in place during lunge/recovery.
Shoulder/Biceps/Triceps/forearm – hold and extend/bend

15. Velocities (X) of muscles
Vi time is relative to the front arm, which starts at 0.

16. Velocities (Y) of Muscles (cm/s)

17. Do the results make sense?
Yes!
But, why?
Front arm starts first, followed by front leg and back leg/back arm.
Back leg has the highest Vmax. The front arm has the second fastest, and it’s over a longer period of time, whereas the back arm has a very fast velocity over a shorter period of time.
Body moves up and down together- want to move mostly in X direction.

18. Implications
Help fencers lunge better (better=more explosive and farther in x direction, less in y direction)
Need for fencing equipment to be elastic, form fitting (more on this later…)

19. Force F=ma Difficult to use, since: There must be another way!
Acceleration is different for different parts of the body
Hard to tell how much mass is truly accelerating, is it the whole body or just part?
There must be another way!

20. Measure

21. Force of Foil-Measure 1

22. Force of Foil - Measure 2

23. Force of Foil -Calculations
Foil shortens cm (~6.8 inches)
Using a scale, find force as the blade is bent and shortened cm
Scale = 8.5 lbs
8.5 lbs * (4.448 newtons/1 pound force)= newtons

24. Calculations
…in an area of only ~ in2 or ~ cm2 (the tip of a foil is very small! It is a circle with diameter of about ¼ inch)
Pressure = force/area
Pressure=( newtons)/ ( cm2)= newtons/cm2
…that’s approximately 173 psi!

25. Force D=vi*t + ½ a *t2 D=distance of lunge (known)=1.778 m
Velocity=0 m/s (initial)
T= seconds
Therefore, a=2.612 m/s2
If F=ma, then newtons=m*2.612
m= 14.5 kg or about (14.5/79.5)=18.2% of my bw
(Around 2-3 times bw -good thing we didn’t use f=ma right away! Probably not a great approximation)

26. Protection For foil, you wear: Lamé Jacket Plastron Knickers
Socks/shoes/t-shirt/underwear
Mask
Chest plate

27. Kevlar
Fencing protection works like kevlar! Actually, the knickers, jackets, plastrons, and bibs of masks actually use kevlar as part of its fabric.
-the high tensile strength of kevlar make it difficult to stretch, requiring a huge force to pierce…instead of letting a projectile go through, it spreads the force into stretching the fibers.

28. Protection Masks come in 350NW, 800NW, (visor=1600NW)
Jackets/Knickers/Plastrons come in 350NW and 800NW
FIE = All 800NW and 1600NW
US competition=not really regulated
Range from 700NW-1600NW
Foil force = about 40 newtons!
You’re safe!...unless a blade breaks…

29. Conclusion
The physics of a lunge make it fast and explosive, thanks to the strong leg muscles.
The foil creates a decent amount of force, but much more pressure on the opponent.
Q&A- Has anyone ever been stabbed?
Yes, but always during times where the integrity of the material has been compromised.

31. About the Author

32. Works Cited http://www.ngfc.us/
The Science of Fencing: Implications for Performance and Injury Prevention: www. adisonline.com

33. Q&A