An anatomical lever system is using the body to increase intensity. For example, lifting a weight with the arm straight vs. the arm bent, increases the intensity. The lever being the arm. The further away from the body the load, the weight, is, the more intense, difficult, the exercise becomes. Any body part can be a lever, as long as it moves around a joint. The further from the joint the part is being lifted, the more difficult the exercise.
A mechanical lever system in exercise usually refers to using a piece of equipment to act as the lever. Think of leg extension machines at the gym. The laws of the lever system are still the same in both.
Here’s a great explaination of how the lever system applies to exercise:
Movement in the body is produced by a system of levers. These series of levers work together to produce coordinated action, some by actual movement (dynamic) and others by stabilization (static). The definitions of Lever, Motive Force and Resistance Force are:
Lever: Rigid bar that turns about an axis of rotation or a fulcrum (A)
Motive Force (F): effort or exertion applied to cause movement against resistance or weight
Resistive Force (R): opposes motive force
Anotomical lever system is divided into three classes, they are:
a. First Class. In a first class lever, the weight to be moved is at one end of the lever, the applied force is at the other end, and the fulcrum (the pivot or turning point) is between the two.
b. Second Class. In a second class lever, the weight to be moved is between the applied force and the fulcrum. This type of lever enables a weight to be moved with less force than would be required without a lever. (Many feel that there are no second class levers in the human body.)
c. Third Class. In a third class lever, the weight to be moved is at one end of the lever, the fulcrum is at the other end, and the applied force is between the weight and the fulcrum. This type of lever provides speed, but a greater amount of force is required for a given weight. This is the most common type of lever in the human body.
Hi David. Also with an anatomical lever the lever length is governed by how we are built (e.g. long or short arms etc.) whereas with a mechanical lever we can usually adjust the length of the lever arm and thus change the advantages of using a lever.
I hope that this helps.