Biomechanical properties are truly the source of most all aspects of your weightlifting and training. They are the methods behind the madness so to speak. A cool thing I learned in physics, which I think you all will enjoy learning about as well are these crazy boogers called levers. The way levers work is rather simple, however the way they work in the body is extraordinary. First, I will discuss the three types of levers and then I will talk about how they relate to your training and some cool analysis of levers within the human body that allow you to be awesome and not even know it.
All levers consists of an axis of rotation about which the movement is occurring, the force that is being applied to cause the movement and the resistance, that of which is acting against the force. The first type of lever is the First class lever. A first class lever consists of the fulcrum or axis of rotation being located between the force and the resistance. Real world examples include seesaw and scissors to name a few. The second type of lever is the second-class lever. The second-class lever is one in which the resistance is located between the axis and the force being applied. Examples of this would include wheelbarrows. Last but not least, the third type of lever is the Third class lever. In a third class lever the force is located in between the axis and the resistance. An example of a third class lever would be tweezers.
Now that you know about the different types of levers, lets look at some real life examples within the human body and related to training. Some examples of the first class lever in the human body is the action of the triceps when performing elbow extension. The body’s action during a push-up is characteristic of that of a second-class lever. The feet at the floor act as the axis, the pushing up of the arms of the force and the center of gravity of the body being the resistance located between the force and the axis. The third class lever is the most prominent type of lever that we find within the human body. This is so because of how muscles are attached to bone and essentially pull on bones to produce desired movements. They are third class because the actual joint itself is the axis of rotation and the insertion of the muscle is not directly on the joint itself. For example, when looking at the elbow joint during flexion, the biceps brachii and brachialis muscles pull on the ulna not directly on the elbow joint itself but slightly away from the joint but still proximal to the joint. The insertion of theses muscle is where the force is being applied, the axis being the elbow joint and the resistance being the weight of the forearm and any weight that is placed in the hand.
That being said this brings me to a cool analysis of the human body in relation to comparing individuals. A tall lanky individual with longer limbs goes up against a shorter stockier individual with shorter limbs, who will be able to lift the most weight relative to his/her body weight? Given that these individuals have essentially the same relative strength, one will actually have more potential to lift more weight than the other. Why? The properties of levers provide a simple explanation with this scenario. The equation for this idea is:
Force x force arm = resistance x resistance arm
In the instance of weightlifting, and purposes for our scenario, the force is the action of the muscle on the body, the force arm is the distance between the insertion of the muscle to the axis of rotation or the joint, the resistance is the amount of weight being lifted and the resistance arm is the distance from the weight being lifted and the axis. That being said the scenario with the short-limbed person verses the long limbed person, the shorter limber person actually has the potential to be able to lift more weight than the longer limbed person. For example say the shorter-limber individual has a forearm length of 36cm, the force arm length of 2.54 cm, and is lifting a weight of 5kg.
F x 2.54 cm = 36cm x 5kg
F = 70.87kg
This means that the shorter-limber person’s biceps will have to apply 70.87 kg of force at the point of the insertion to lift the 5kg weight. However, if a longer limbed person with a resistance arm of 40cm were to lift the same 5 kg weight this would be what happens.
F x 2.54cm = 40cm x 5kg
F = 78.74kg
As you can see, the shorter person will technically be able to apply a smaller force to lift the same amount of weight as the person with longer limbs! And could therefore, lift a larger amount of weight in kg with an equal force of that of the person with longer limbs. Crazy, CRAZY facts! Sorry to all you big and tall people, the world must really me heavy to you! This isn’t to say that all people with shorter limbs are stronger than people with longer limbs. It simply implies that when removing all other environmental and genetic factors, they have the potential for being able to lift more weight!
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