Understanding Flexion & Extension to Enhance Your Workout Gains

flexion and extension

Biceps curls are flexion, while triceps extensions are extensions. 

Bodybuilding transcends merely hitting the gym hard to rack up massive gains. It’s about deeply understanding your body’s mechanics and leveraging this insight for optimal outcomes. Attuning to your body’s movement pattern can dramatically transform your workout effectiveness, leading to fewer injuries, a healthier physique, and elevated athletic performance.

The human body can perform five primary movements: abduction, adduction, rotation, flexion, and extension. These foundational movements are vital for crafting effective workouts and preventing injuries. Grasping and weaving these concepts into your exercise regimen safeguards your body while enhancing your strength and fitness.

This article delves into the specifics of flexion and extension for athletes, breaking down their definitions, differences, and benefits. We’ll explore concrete examples of these movements and offer strategies for incorporating them into your workouts for optimal gains.

What Is Flexion?


Flexion is the movement of a limb or joint by bending it. The bones come together during flexion, bringing two body parts as the angle between them decreases. This occurs when performing certain exercises or everyday movements like bending, running, sitting, or eating. Focusing on training flexion can lead to more sagittal mobility, as this study shows (1). Below are some exercises you can use to train flexion at different joints: 

What Is Extension?


Extension is the movement of a limb or joint by straightening them. On extension, the bones make the joints straighten as the angle between them increases. It’s the direct opposite of flexion. Extension happens when you perform specific exercises or do movements like jumping and stretching. It can also help prevent injuries. Research demonstrates that extension exercises like back extensions can help prevent the decrease in spinal range of motion and build strength (2). Below are some exercises that you can use to train extension at different joints:

  • Leg Extensions (extension occurs at the knees)
  • Back Extensions (extension occurs at the spine)
  • Push-ups (extension occurs at the elbows)
  • Hyperextensions (extension occurs at the hips)
  • Squats (extension occurs at the ankles, knees, and hips while coming up)
  • Triceps Kickbacks (extension occurs at the elbows)

Flexion & Extension in the Body

As an overview, flexion, and extension can happen at the following places in the human body:


Flexion and extension happen at the elbow joint. Elbow flexion and extension are ways you can do routines like bicep curls and triceps extensions. 

Wrist & Fingers

These movements happen at the wrist joint and fingers. They’re important for grabbing free weights, writing, adjusting hand grips, and tying shoelaces.


Flexion and extension happen at the shoulder joints and are helpful for overhead and behind-the-body movements. This is how you can do routines like the overhead tricep extension


For spine movements, flexion and extension happen when bending forward or backward, as with back extensions or reverse hyperextensions. This movement is also helpful for maintaining a good posture.


Flexion and extension happen when moving your head up, down, and sideways. Head movement also allows you to stretch.


This happens at the knee joint and is helpful with walking, running, jumping, and sitting down. Flexion and extension at the knees happen when you do multiple squat variations. 


Flexion and extension happen at the hip joints and help you stand and swing your legs. You use hip flexion and extension to do routines like the deadlift. 


Flexion and extension happen at your toe joints and are important for walking, running, and balance.

Differences Between Flexion & Extension

Simply put, flexion is a movement that reduces the angle between two body parts. It brings them close together. In contrast, extension is a movement that increases the angle between two body parts. It moves them far away from each other. It’s the direct opposite of flexion movement. The table below shows the difference between flexion and extension.

Flexion Extension
It’s a backward movement between two body parts. It’s a forward movement between two body parts.
The angle between two joints decreases. The angle between two joints increases.
The two bones tend to bend when bringing them together. The two bones tend to straighten and separate.
Examples are performing a biceps curl and your forearms touching your biceps Examples of extension are coming from a squat position and extending your knees to stand straight up.

Incorporating Flexion & Extension in Your Workouts

Bodybuilders and lifters can use flexion and extension movements to optimize muscle gains and strength during workouts. The best kind of workout should contain equal numbers and extension movements for balance. To achieve that, remember a principle: flexion is backward, and extension is forward.

So, when setting up your workout, find which exercises focus on each movement. For example, biceps curls concentrate more on the flexion of biceps muscles, while tricep kickbacks focus on the extension of triceps muscles. Doing these and then adding isometric holds when performing them can help strengthen and balance the arms (3).

Wrapping Up 

Flexion and extension are core movements that enhance your training regimen. Flexion reduces the angle between bones at a joint, whereas extension increases it. These mechanics are central to many resistance exercises, particularly in movements involving the hips, knees, elbows, and shoulders.

Maintaining a balance between flexion and extension exercises is critical to maximizing the effectiveness of your workouts. Achieving this equilibrium is fundamental for muscle strength development and joint stabilization. By integrating this strategy into your fitness routine, you’re adopting a holistic approach to your training. 

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  1. Elnaggar, I. M., Nordin, M., Sheikhzadeh, A., Parnianpour, M., & Kahanovitz, N. (1991). Effects of spinal flexion and extension exercises on low-back pain and spinal mobility in chronic mechanical low-back pain patients. Spine, 16(8), 967–972. https://doi.org/10.1097/00007632-199108000-00018
  2. Yaprak Y. (2013). The effects of back extension training on back muscle strength and spinal range of motion in young females. Biology of sport, 30(3), 201–206. https://doi.org/10.5604/20831862.1047500
  3. Lum, D., & Barbosa, T. M. (2019). Brief Review: Effects of Isometric Strength Training on Strength and Dynamic Performance. International journal of sports medicine, 40(6), 363–375. https://doi.org/10.1055/a-0863-4539
Terry Ramos
As a personal trainer and writer, Terry loves changing lives through coaching and the written word. Terry has a B.S. in Kinesiology and is an ACSM Certified Personal Trainer and ISSA Certified Strength and Conditioning Specialist. He enjoys playing music, reading, and watching films when he's not writing or training.