What Is Flexion And Extension

You’ve probably heard the terms flexion and extension tossed around at the gym or in the box by your personal trainer or coach. But what exactly does flexion and extension mean? Understanding the principles of human anatomy and biomechanics, is critical to training and performance. We’re going to explore more about human movement, and the importance of flexion and extension to your training. 

What Is Flexion And Extension 

Flexion and extension are two movements which take place in the sagittal plane. The sagittal plane is an imaginary line that bisects the body into two planes the right and left sides from the medial-lateral axis. Joint movements that occur within this plane, include flexion a bending movement in which the relative angle between two adjacent segments decreases, and extension a straightening movement in which the relative angle between two adjacent segments increases. Flexion and extension involve anterior or posterior movements of the body and or limbs.

For example, a forward bending motion from the vertebral column, would be considered anterior flexion, while extension involves a backward or bending back posterior directed motion.

In the limbs, flexion decreases the angle between the bones (bending of the joints) while extension increases the angle and straightens the joint. All anterior motions or bending at the joint is considered flexion and all posterior motions are extension. These motions include bending at the elbow, wrist, and the fingers. For the lower limbs, bringing your thigh and leg forward is flexion while any posterior or pushing back the leg behind the body is extension.

Flexion and extension occur in many joints within the body, including the spine, shoulder, elbow, wrist, hip, knee, foot, and hand. When referring to the ankle, flexion is known as dorsiflexion and extension is plantar flexion.

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What Is Hyperextension

Hyperextension is the extension of a joint beyond the normal range of motion, which typically results in injury. Similarly, hyperflexion is the excessive flexion of a joint. Hyperextension injuries are common at the knee and elbow.

Flexion And Extension Movement Examples

Now that you have a basic understanding of flexion and extension, what are some human movements that can easily be identified using these anatomical terms.

Let’s use a bicep curl as an example. Flexion is when the muscle is contracted and joints bend at the elbow, lifting the weight. Extension would be the straightening of the arm back to starting position, increasing the length and angle between the joint.  

In a squat, flexion and extension also takes place in the sagittal plane. Flexion, would be the descending motion, decreasing the length between the knee joints and the trunk, while extension, would be lengthening the joints as you stand back up.

Other examples of flexion and extension in the sagittal plane, include triceps pushdowns, calf raises, and front lunges.

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What Is Flexion And Extension: Takeaway

It’s important to become familiar with anatomical terms like flexion and extension especially as you progress in your training. Understanding basic biomechanics and human kinetics, will advance your athleticism and performance. By adhering to greater flexion and extension, you can increase range of motion, thereby lengthening the muscle, which is key in building more muscle mass and greater strength.

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