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Extend and Flex Exercise 2023

Extend and Flex exercises are simple stretching movements involving repeatedly extending or flexing individual body parts. 

They work to loosen up muscles and joints, improve the range of motion, and prepare the body for further exercise. 

  • Extend (Extension) is when you move two body parts further away from each other, making your joint angle smaller. 
  • Flex (Flexion) is when you do the opposite, bringing two body parts closer to each other and making your joint angle larger. 
  • For easy understanding, Flex refers to closing a joint (decreasing the angle), while Extend means opening a joint (increasing the angle).
  • These two exercises will help build different muscle groups and improve joint stability. 

When you flex those muscles and pose, squeezing your muscles tight, it creates tension within your muscles. 

The longer you can hold that tense pose, squeezing your muscles as hard as possible, the more working muscle fibers activate and the stronger your muscles will become. 

The key is focusing on the squeeze and holding that flexed position for as long as possible to fatigue your muscles and stimulate muscle growth.

Army PRT Extend and Flex Exercise

The Army Extend and Flex Exercise is a part of the United States Army Physical Readiness Training (PRT) program, which is designed to reduce injuries in soldiers.

  • Extend and Flex is the third exercise in the Army Recovery Drill
  • Here is a breakdown of the movement as it would be conducted in a formation.


  • This exercise develops mobility of the hip flexors, abdominals, hip, and lower back, hamstrings, and calves.

Army Extend and Flex Exercise
Army Extend and Flex Exercise

Starting Position: 

  • The front leaning rest position.

Position 1:  

  • On the command, “Ready, STRETCH,” lower the body, sagging in the middle, keeping the arms straight and looking upward. 
  • Hold this position for 20-30 seconds.

Starting Position:  

  • On the command “Starting Position, MOVE,” assume the starting position.

Position 2:  

  • On the command, “Change Position, READY, STRETCH,” slightly bend the knees and raise the hips upward.
  • Straighten the legs and attempt to touch the ground with the heels. 
  • Move the head in line with the arms, forming an A with the body. 
  • Keep the feet together and hold this position for 20-30 seconds. 
  • On the command “Starting Position, MOVE,” return to the starting position.

Check Points:

  • In position 1, the thighs and pelvis rest on the ground.
  • Relax the back muscles while bearing the body weight through the straight arms. 
  • The toes point to the rear.
  • In position 2, the legs are straight, the arms are shoulder width apart, palms down on the ground. 
  • Relax the shoulders and push to the rear with the hands, forming an “A” with the body. 
  • Try not to round the shoulders.
  • Keep the feet together throughout the exercise.


  • N/A


  • Soldiers who cannot extend the trunk in position 1 while keeping their arms straight and hips on the ground may assume the modified position 1 shown above. 

Muscles Worked by Army Extension and Flexion

Extend and Flex Muscles
Extend and Flex Muscles

The Army Extend and Flex exercise works the following muscles:

Muscle GroupRole in Army Extend and Flex Exercise
HamstringsStretches during forward flexion movement.
Lower BackEngaged during flex forward from the waist.
Chest and ShouldersStretches as arms extend to the sides and towards the back.
Core MusclesMaintains balance & control throughout the movement.
Upper Back
(Trapezius and Rhomboids)
Engaged when arms extend out and back.

What Muscles Can Extend and Flex?

There are many muscle groups in your body that can bend and extend; some you likely use many times a day without even thinking about it, others not as much.

When you exercise and condition these muscles, your movements can become more efficient and flexible. So, training these muscle groups regularly is important for building and strengthening them.

Each area has specific exercises you can do:

  • Elbows: bend and straighten your arms
  • Knees: squat, lunge, and leg presses
  • Neck: chin tucks, neck extensions
  • Hips: hip extensions, bridges, clamshells
  • Spine: back extensions, trunk twists
  • Shoulders: shoulder presses, flies, raises
  • Wrists: wrist curls and extensions
  • Ankles: calves raise, and toe raises

How to Add Extend and Flex Exercises to Your Workout

  • Extend and Flex are straightforward concepts, but keeping them in mind when planning your workouts can boost your results.
  • Aim for an even mix of bending and extending exercises in your routine. This will allow you to build balanced strength while minimizing your risk of injury.
  • For example, doing bicep curls (bending) and tricep extensions (straightening) each week will strengthen both sides of your arms.
  • Use the principles of extending and flexing within the same muscle group for an even bigger strength and power boost. 
  • The key is to emphasize the lowering portion of each exercise every week.
  • For instance, spend the same time lowering the bar during bicep curls as lifting it. This way, the Muscle stays under tension longer. So, every rep packs more strength and power.


  • In conclusion, remember that extend means backward, and flex means forward. 
  • Flexion is where two parts of the workout come together. If it does the opposite side, it’s an extension.
  • Extend and Flex exercises are simple stretching movements involving repeatedly extending or flexing individual body parts. 
  • They work to loosen up muscles and joints, improve the range of motion, and prepare the body for further exercise. 
  • I hope this helps. Cheers!!
George N.