This post is all about planes of movement (Frontal,
Sagittal, Transverse/Horizontal). This is a fundamental concept. It was
introduced to me in my introduction to anatomy class and I’ve used it in
everything from biomechanics to kinesiology. I think people understand one
perspective (Plane or Axis) better than the other. This is a planar explanation
of this concept.
Let’s start off with definitions so easy you don’t even need to memorize them.
Sagittal plane – Slices you down the middle, dividing the body segment into right and left portions.
Frontal plane – divides the body segment into anterior and posterior portions.
Transverse plane – Divides the body segment into superior and inferior
portions.
Planes interact with an axis. A plane and axis are always perpendicular and they always follow this setup.
Sagittal plane = Frontal axis.
Frontal plane = Sagittal axis.
Transverse plane = Vertical Axis.
You can impose a plane on any body segment. A sagittal plane could be imposed on the forearm and hand. If we did that, the forearm would have the ulna on one side of the plane and the radius on the other; the hand would essentially have the middle finger “sliced” down the middle by this plane, leaving the pinky and index finger on one side and the thumb and pointer finger on the other.
So now that we have the planes in mind (hopefully), we need to look at the types of movement. Each movement depends on the joint that is in question. I’ll give the definition of flexion and extension, then an example to start us off.
Extension: Increasing the joint angle.
Flexion: Decreasing the joint angle.
[Joint: Elbow] Arm Curl
It helps to visualize the body segments around that joint. The elbow would have the forearm distally and the upper arm medially. Thus, when you bring your arm up (flexion), you can see how the joint angle decreases. When you bring your arm back down (extension), you can see how the joint angle increases.
Some tips and tricks that helped me remember these:
ABduction: being Abducted away.
ADduction: being ADded to the body.
Plantarflexion: Think of planting your foot on the gas pedal.
Supination: The radius and ulna are not crossed. Leaving your palms (s)up.
Now that we have the motions down, we can finally see how they act in planes.
If we look at the arm curl from early, what plane would the motion fall in? The plane can be imposed on just the arm. The movement can only take place in that plane.
Got your answer?
Drum roll…
ABduction: being Abducted away.
ADduction: being ADded to the body.
Plantarflexion: Think of planting your foot on the gas pedal.
Supination: The radius and ulna are not crossed. Leaving your palms (s)up.
Now that we have the motions down, we can finally see how they act in planes.
If we look at the arm curl from early, what plane would the motion fall in? The plane can be imposed on just the arm. The movement can only take place in that plane.
Got your answer?
Drum roll…
…
Extension was the correct answer!
This is a basic concept that will take you a long way in human movement and function. Understanding this idea is key to understanding how people move, how to train an athlete, or how to rehabilitate a patient.
