Exercise Science Review 1-5, Levers and Mechanical Advantage

Posted by on Jan 19, 2013 in Exercise Science, Review Topics | 0 comments

This is perhaps one of the most challenging topics of the Exercise Science section.  In physics class, I always forgot whether a lever was class I, class II, or class III.  On top of this, you need to know points of origin of muscles and where they insert.  Basically, you have to know Anatomy AND Physics, two topics renowned for their difficulty…though I am exaggerating.  These are really two subtopics of both fields, and we should be able to get through them just fine with some careful thinking and good images (lol @ my photoshop skills).

To fully understand this post, you may need to review what Torque is, what a Lever is, and what Mechanical Advantage (or leverage) is.

Levers

  • Class I - A lever in which the load (dumbbell for example), and the applied force (by muscle in this case) act on the same side of the fulcrum.
  • Class II - A lever in which the load and the applied force act on the same side of the fulcrum, with the applied force having greater mechanical advantage (a longer moment-arm) than the load.
  • Class III - A lever in which the load and the applied force act on the same side of the fulcrum, with the applied force having lower mechanical advantage than the load (and thus a shorter moment arm).

Levers

The three different classes of levers

Now how does all of this apply in the human body?  Take the bicep curl…where is the fulcrum, the load, and the applied force?  You have to know these things in order to classify this movements class of lever.

Levers-Curl2

What class of lever is this?

As you can see, knowing where the biceps inserts is key to being able to identify the location of the applied force.  Figuring that the elbow is obviously the fulcrum, the biceps is the applied force, and the dumbbell is the load, we can correctly identify this as a third class lever.

Levers-Curl3

Biceps curl is an example of a third class lever

I won’t go through every possible example throughout the human body, but rest assured that any movement is probably fair game on the CSCS Exam.

Study your anatomy!  To prepare, think about various muscles and movements, and try and identify their fulcrum, insertion point, and lever class.