Fulcrum, Lever, What?

Part I

As most of my patients and athletes can tell you, I can weave the words, “Fulcrum, Lever, Sport” into just about any conversation. While this makes complete sense to me, there have been numerous times when ‘innocent bystanders’ have no idea what I am talking about. In this instance, the term ‘innocent bystanders’ refers to people who happen to be nearby - or even participants of the conversation - when MRoss starts ranting about Fulcrums and Levers and Sport in response to any conversation related to injury or functional fitness. They stand there trying to be polite while MRoss goes on and on, blah blah Fulcrum, blah blah Lever, blah blah Sport. In this, and the next, FLS BlogCast episode, I draw from two sections of my book, aptly titled, “Fulcrum-Lever-Sport: A Handbook of BioMechanics for Improved Performance and Injury Prevention” in order to explain these terms that I can’t seem to shut up about.

We, as human beings, act as biomechanical machines and rely on a series of fulcrums and levers. We need these fulcrums and levers in order to function—to be able to push, pull, squat, or lunge. To understand humans as biomechanical machines, it’s helpful to step back and examine a simpler mechanical machine: a children’s seesaw. A seesaw is comprised of a fulcrum, a lever, and the mass, or the child, at the end of the seesaw.

There are a few basic rules in the laws of physics that apply to this simple mechanical system:

·       Rule #1: The fulcrum needs to be strong enough and substantial enough to support the lever and whatever mass or load is put on the lever.

·       Rule #2: The fulcrum needs to be the most stable part of the overall system.

·       Rule #3: Fulcrum, then Lever, then Sport.

·       Rule #3a: Stability, then Mobility, then Function.

Rule #1

The laws of physics state that the amount of torque, or load, on the hinge point of the fulcrum is roughly equal to the length of the lever, multiplied by the mass/weight that’s exerted on the end of the lever. The longer the lever, the more torque that will be applied to the fulcrum hinge point.

For example, if you place five pounds near the fulcrum hinge point, the torque will be minimal. However, if you extend those five pounds further out on a longer lever, it will put more force on the length of the lever arm, which in turn, adds more torque. This also occurs when additional weight is added to the lever. The more weight there is, the more torque that will be applied to the fulcrum hinge point.

In order to support the torque put upon the system, the fulcrum needs to be more substantial than the lever. It needs to be designed to withstand extensive loading because it’s not a static system—it changes and moves. Over time, there will be a repeated amount of levering on the fulcrum hinge point. The fulcrum needs to be strong enough and sturdy enough to withstand this repeated movement for a long period of time.

If the torque exerted by the lever on the fulcrum hinge point is more than the fulcrum can withstand, catastrophic failure is likely to occur. For example, if two full grown adults attempt to use a children’s seesaw, the seesaw may potentially fail due to it being designed for children. If the load is too large, or the lever is too long, the fulcrum will collapse under the weight of the load because it’s not designed to support the weight that’s being put upon the system. Too large of a load on the lever can, and will, overload and destroy the fulcrum.                                                                  

Rule #2

The fulcrum needs to be stable, solid, and durable. Any instability, looseness, or laxity within the fulcrum hinge point can lead to catastrophic failure. While this won’t happen immediately, after time, with repeated levering, the fulcrum will eventually wear down and fail. To maintain efficiency, the fulcrum needs to be built out of rebar, steel, concrete, and solid material, with a solid, smooth, well-oiled hinge point. Any instability within this system will lead to substantial errors and ultimately, failure.

Rule #3

If a seesaw were to be built in the backyard, the fulcrum would be built first as the foundation. A solid, flat piece of ground would be sought out, and the necessary materials to build the seesaw would be purchased. When all the items were gathered, the specifications would be studied and the building timeline would be created. The fulcrum would then be built under these conditions with these materials, and nothing less.

These necessary steps would need to be taken in order to create a sturdy, successful fulcrum. Rule #3 is that the fulcrum must be built prior to the lever in order to maintain optimal functionality.

These steps need to be completed in order. For example, a lever wouldn’t be put on the ground with the assumption that the fulcrum would be created from underneath, because it would collapse under the weight of the lever before it could be created. The fulcrum needs to be constructed first and checked for durability. Once this has occurred, the lever is placed upon the fulcrum and checked for any unwanted looseness or instability. Then, and only then, would the seesaw be considered safe and ready for use. This is a very important aspect of the process. The seesaw would not be used for levering until the fulcrum is built and ready. It may take some time to build the fulcrum to where it is ready to lever, but using the seesaw before the fulcrum is ready would be a recipe for disaster.

For example, two children would be able to effectively seesaw with a system that is built following the proper steps. If the steps aren’t followed, or are completed out of order, the seesaw wouldn’t function. This would be the equivalent of placing children atop the lever before the fulcrum was constructed. It just wouldn’t work.

Creating a fulcrum and lever system follows a specific order of building basic machinery. This order needs to be followed to guarantee the utmost function and safety.

Rule #3a

Building the fulcrum first is done to guarantee stability. The static portion of the system (fulcrum) is created prior to the moving portions (lever). The fulcrum is built out of the necessary materials, the lever is checked for stability, and the hinge joint is checked for proper functionality. Following these steps will ensure it will function the way it’s designed to.

Similar to Fulcrum then Lever then Seesaw, this process can be known as Stability then Mobility then Function. When the pieces are properly assembled, completed in order, and are in ideal working condition, they will function as a seesaw.

In Part II, I will share how this relates specifically to human beings.

-MRoss