Understanding Human Movement in 3-D
It’s no secret that the human body is a pretty amazing machine, and we rarely stop and think about what makes it move the way it does. We don’t consciously analyze the various muscle and joint actions that enable us to run to the bus stop, pick up our children or reach for something on the top shelf of the cupboard.
However when we begin a fitness program, understanding how our bodies move becomes very important. Learning to complete exercises with the proper form is essential in avoiding injury and getting the most benefit from the particular exercise. Whether you’re working with a personal trainer or following a DVD based workout program, a basic understanding of the three planes of human movement is the foundation for understanding proper form and execution.
When we talk about how the body moves, we generally refer to it as it moves through three basic planes, the Sagittal, Coronal (or Frontal) and Transverse. As you look at the different planes, you may find it easier to understand that while we often saying we’re moving “in” a particular plane, in reality the movement is actually parallel to the plane, and it occurs on an axis that runs perpendicular to the plane, much like an axle that a wheel rotates on.
- Sagittal Plane. This plane divides the body into two halves; a left and right side. Movement in this plane is said to occur along a coronal axis. The primary movements that occur in this plane are Flexion/Extension.
- Coronal (Frontal) Plane. This plane splits the body into the front and back sides and we see movement in this plane occurring along an anterior-posterior axis. The primary movements that happen here are Adduction/Abduction. Other movements include Lateral Flexion and Eversion/Inversion.
- Transverse Plane. This plane divides the body in half to create a top and bottom half. Movement in this plane occurs along a longitudinal or horizontal axis. Movements include Internal/External Rotation, Left/Right Rotation and Horizontal Adduction/Abduction.
Understanding all the terminology that goes along with the planes of movement can be a bit confusing; it’s helpful to consider that we use a basic anatomical position as the starting point. This way when we talk about moving a limb in one direction or another we have a good frame of reference to begin with. This anatomical position is standing with the body erect, arms at your sides with the palms facing forward, as the figure below shows.
These are terms that are used to identify a specific location or landmark on the body. Rarely used in everyday conversation, knowing these will probably help you understand comments you doctor makes during your annual physical! Seriously though, some trainers may use these terms in describing body positioning for various exercises.
- Superior. This means a position above a reference point. The pectoralis major (chest muscle) is superior to the rectus abdominis (abdominal muscle)
- Inferior. Refers to a position below a reference point. The gastrocnemius (calf muscle) is inferior to the biceps femoris (hamstring muscle)
- Proximal. This is a position nearest the center of the body or point of reference. The elbow is more proximal to the shoulder than the wrist. The knee is more proximal to the hip than the ankle.
- Distal. The opposite of proximal, this is a position that is furthest from the center of the body or a point of reference. The wrist is more distal to the shoulder than the elbow. The ankle is more distal to the hip then the knee.
- Anterior. Refers to a position on or toward the front of the body. The quadriceps are located on the anterior aspect of the thigh.
- Posterior. As you might imagine, a position on or toward the rear of the body. The hamstrings are located on the posterior aspect of the thigh.
- Medial. This is a position that is closer to the midline of the body. The adductors (inner thigh) are on the medial side of the thigh.
- Lateral. Refers to a position that is relatively farther away from the midline of the body. The humerus (upper arm bone) is more lateral than the sternum (chest plate)
- Supine. Lying on your back.
- Prone. Lying face down.
Flexion and Extension in The Sagittal Plane
Flexion is a bending motion that occurs in the sagittal plane where the angle between two body segments decreases, the joint movement happens on the axis that we described above. Some common exercises that involve flexion:
- Bicep Curl (elbow flexion)
- Hamstring Curl (knee flexion)
- Knee Raise (hip flexion)
Extension is the opposite movement, a straightening movement where the angle between two body segments increases. Common exercises that involve extension:
- Tricep Pushdown (elbow extension)
- Pushups (elbow extension)
- Dumbbell Pullover (shoulder extension)
Take a moment, stand up and perform some of these movements without weights, for example stand as if you had a dumbbell in each hand and perform a supinated (keeping your palms forward/up) dumbbell curl. Curl your arms up until your elbow is at a 90 degree angle and return to the starting position. Do this a few times, notice that this movement is in the sagittal plane – your arms are moving parallel to that imaginary line that bisects your body separating the left and right halves. If no one else is in the room, try a few other of the moves to wrap your head around the nature of both flexion and extension in the sagittal plane.
Did you know? As you shorten the muscle in flexion, that is a concentric muscle action, lengthening the muscle when you return to the starting position is called an eccentric muscle action.
Adduction and Abduction in the Frontal Plane
The movements that occur in the frontal plane are side-to-side. It’s easiest to think of these movements as if you were performing them with your back against the wall, or if you were in a very-very narrow hallway with only inches of clearance in front of and behind you.
Adduction is movement towards the midline of the body and involves a decrease in the angle between the two body segments involved (very similar to flexion, except it occurs in the frontal plane). Some common exercises include:
- Cable Crossover
- Side-lying Hip Adduction
- Hip Adduction Machine (squeezing legs together)
Abduction is a movement away from the midline of the body. Just as extension lengthens the angle between two body segments, so do abduction. Common exercises involving abduction include:
- Lateral Raises
- “X” Jumps (for all you P90X Fans!) also called Star Jumps 🙂
- Side Lunges with Hip Abduction
Lateral Flexion and Eversion/Inversion in the Frontal Plane
Lateral Flexion is simply bending the spine (cervical, thoracic or lumbar) from side-to-side
- Dumbbell Side Bends
- Neck Flexion (Ear to Shoulder)
Eversion/Inversion is used primarily when describing movements of the foot and ankle. Eversion is rotating the ankle outward so the bottom of the foot faces outward; Inversion is rotating the ankle inward.
Rotational Movements in the Transverse Plane
Movements in the transverse plane are fairly easy to identify as they involved rotational movement. This can be limbs rotating inward or outward or full body rotational movements. Here are a couple examples of limb rotational movements: balance on your right foot and lift your left foot about an inch off the ground, rotate your foot to point your toes to one side or the other. Next, stand in the traditional anatomical position with your arm down and palm forward (supinated) rotate your arm so your palm faces behind you (pronated) and return. Other common exercises or movements in the transverse plane include:
- Trunk Twists
- Neck Twists
- Swinging a Baseball Bat
Flexibility, Stability and Mobility
Many fitness programs include an increased emphasis on flexibility, stability and mobility – being able to perform movement and function in multiple planes of motion simultaneously. Many yoga movements actively involve major movement in at least two planes of motion challenging your sense of balance and stability. These combination often are targeted at strengthening your overall core to provide a more stable base for all the exercises you may do.
The Bottom Line…
We live in 3-D, our bodies instinctively moving in and out of all planes of motion, often without much conscious thought. As we explore specific exercises I will provide instruction that includes reference to the plane(s) of motion we will be moving in and providing cues as to the nature of the movement that is required to complete the move with proper form. Having a base knowledge of how your body moves will help you maintain proper form throughout the various exercises you perform and avoid injury. Remember: Form is King 😉