Download Kinesiology is one of your more challenging courses you will have

The Planes of Motion and their respective Axis of Rotation can be very confusing. Here
are a few analogies that might help to explain this concept.
The sagittal plane divides the body into right and left halves. Imagine that you have a
piece of glass that divides your body into right and left halves. What movement can
occur along the glass, but doesn’t break the glass? If I twist, the glass breaks. If I laterally
flex (bend side to side), the glass will break. If I do flexion and extension, the glass is
intact. Flexion and extension glides along the glass and cannot break it.
The frontal plane divides the body into anterior and posterior halves. Now imagine a
piece of glass that runs along this plane. What movement can occur without breaking
the glass? Flexion and extension would shatter the glass once I bent forward or
backward. Twisting would break the glass as well. Ab/adduction and lateral flexion
would glide along the glass.
The transverse plane divides the body into superior and inferior halves. I like to picture
this plane as an inner-tube a child would wear in the pool or a hula hoop. What
movement can this child perform? Flexion and extension would be very difficult, as well,
as lateral movements. A child can twist very easily with an inner-tube around their
waist; therefore, rotation is most commonly seen in this plane.
The diagonal plane is basically a combination of one or more planes. Most sporting
activities fall in this category. The best example of movement that occurs in the diagonal
plane is the golf swing or a field goal kicker. The axis of rotation will always be at a right
angle to the plane of motion.
The best example of an axis of rotation is the leg extension and bicep machine at your
local gym. Next time you are there, look for a colored dot where you line your knee for
the leg extension and your elbow for the arm curl machine. This is the axis of rotation
for those joints. The axis of rotation is exactly perpendicular to the plane of motion;
meaning it forms a right angle. So for the sagittal plane, the axis of rotation is the frontal
axis (which runs from side to side). For the frontal plane, the axis of rotation is the
sagittal axis (which runs from front to back). Finally, for the transverse plane, the axis of
rotation is the vertical axis (which runs up and down).
The best experiment to understand the axis of rotation is to take a piece of paper. Hold
this paper like it was the sagittal plane (dividing you into right and left halves). Then
stick a pencil through the side. Now twirl the paper around the pencil. This mimics
flexion and extension. You can do the same experiment for the frontal and transverse
plane.