Planes of Motion: Body

ByCrossFitJanuary 10, 2019


As discussed on 190105, infinite planes pass through the body and divide it into sections. “Cardinal planes” are those that divide the body in halves. The cardinal sagittal plane divides the body into right and left halves. The cardinal transverse plane divides the body into upper and lower halves. The cardinal frontal plane divides the body into front and back halves.

A diagram showing the body’s cardinal planes (sagittal, transverse and frontal), as well as the body’s center of mass; i.e., the point at which all three planes intersect.

Figure 1: The cardinal planes of the body and the body’s center of mass.

The point at which all three cardinal planes—or their axes—intersect defines the point around which body mass is equally distributed. This point is called the center of mass.


Every segment of the body has a mass. For example, an individual weighing 81.7 kg (180 lb.) will have a head that weighs about 5.3 kg (11.7 lb.). When we move a body segment in a direction—moving an arm forward, for instance—the weight of that segment moves away from its equilibrium state (or the state of standing at rest).

A diagram showing how the body maintains equilibrium during simple movements such as shoulder flexion and complex movements such as a squat.

Figure 2: The body maintains equilibrium in simple and complex movements by balancing the movement of mass.

When the arm segment’s 3.9 kg (8.6 lb.) move forward, an equivalent mass must move rearward to maintain balance. In general, the body is programmed to do this unconsciously. In a complex, multi-segment movement such as the air squat, more segments move and the magnitude of weight displacements is larger, but the principle is the same: Forward and backward displacements of body-segment weights must be equivalent to maintain balance.

Comments on Planes of the Body


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Peter Shaw
October 1st, 2021 at 1:39 am
Commented on: Planes of the Body

The more complex and dynamic a movement, the harder it is to balance. Especially with added load!

Isometrics can really help learn the right position at each phase of movement.

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Rosanna Edison
January 12th, 2019 at 6:56 pm
Commented on: Planes of the Body

I wish I could find my balance when doing pistols as easily as I do when performing air squats.

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Sean Rockett
January 12th, 2019 at 11:55 pm

Completely different exercise and stress. Start with supporting yourself and build from there

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Matthieu Dubreucq
October 21st, 2019 at 11:31 pm

You can start with a partial range of motion pistol to a box. Slowly bring it down.

Also if you understand the article you can easily also help yourself by holding a weight in front of you. It will keep you balance in the Frontal plane. Slowly reduce the weight as you get use to it.

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