TRX Suspended Jackknife

The TRX Suspended Jackknife exercise is a dynamic tuck position, bringing your knees to your chest. It is a strong core activator while working the upper body isometrically to stabilize you through the movement.

Primary muscles worked

  • Abs

Secondary muscles worked

  • Shoulders
  • Lower Back
  • Glutes
Body Part

Body Part:




Step 1: With the TRX straps set at three inches above the ground, place your feet in the stirrups so the tops of your feet are facing the floor.

Step 2: With your hands placed on the floor at shoulders with, begin this exercise from the plank position (abs and glutes engaged, shoulders stacked above wrists, keeping a straight solid line).

Step 3: Begin the movement by engaging your shoulder girdle stability with your scapulae depressed.

Step 4: Shift your weight slightly forward so your shoulders are in front of your hands; at the same time, proceed to bring your knees into your chest, focusing on engaging the abdominal’s (not the hip flexors). You are still maintaining a strong plank position with your core and glutes tight.

Step 5: Return back to the starting plank position

Step 6: Repeat the knee to chest movement several times.


How to progress the exercise

Being that one arm is on the floor, there is more stability to this exercise, than doing the Chest Fly. This exercise can be prepared for doing the Chest Fly.

Additional Information

As for any fly exercise, shoulder stability is of great importance and must be the primary focus throughout the movement.

TRX Pro 4 Strap



Man performing the TRX mountain climber

TRX Mountain Climber

The TRX Mountain Climber exercise begins in a similar position as the Suspended Jackknife. The difference is you are performing a ‘Mountain Climber’ which is alternating knees to chest, as opposed to both at the same time. Great exercise for explosive training, which working shoulder and core stability.

TRX Pro 4 Strap

TRX Anti-Extension Fallout

The TRX Anti-Extension Fallout is precisely to avoid spinal extension by maintaining a very strong plank throughout the movement. The TRX Kneeling Fallout is an easier version of this exercise and should be mastered before performing the straight legged Fallout.

TRX Pro 4 Strap

TRX Hamstring Curl

The TRX Hamstring Curl is a preceeding movement towards the Supine Hip Extension to Leg Curl. It’s a good beginning posterior chain (Glutes, hamstrings, lower back) activator and is loved by runners around the world.


signup for latest news and offers