What muscles does the TRX knee tuck work?

The TRX knee tuck primarily targets the rectus abdominis and hip flexors while also engaging the obliques and deep core stabilizers. The shoulders and arms work isometrically to maintain the plank position throughout the movement.

How do I keep my hips from sagging during TRX knee tucks?

Actively brace your core before each rep and think about pulling your ribcage toward your pelvis to maintain tension. Focus on controlled leg extension rather than speed, and reduce reps if you cannot maintain a neutral spine position.

Can I do TRX knee tucks if regular planks are easy?

Yes, TRX knee tucks are an appropriate progression once you can hold a solid plank for 45 to 60 seconds without form breakdown. The added instability and dynamic movement make them significantly more challenging than static planks.

Knee Tuck (TRX)

The knee tuck on TRX is a core exercise performed from a push-up position with feet suspended in the cradles, pulling the knees toward the chest while maintaining a stable plank. It suits lifters looking to build abdominal strength and control through dynamic hip flexion under instability.

Muscle group: Core
Primary muscles: abs
Equipment: Other

How to do the Knee Tuck (TRX)

Set the TRX straps to mid-calf height and place both feet into the cradles while facing away from the anchor point.
Walk your hands forward into a push-up position with arms straight, shoulders over wrists, and body in a straight line from head to heels.
Engage your core and pull both knees toward your chest by flexing at the hips and knees, allowing your hips to rise slightly.
Pause briefly when your knees reach your chest, maintaining tension in your abs.
Extend your legs back to the starting plank position in a controlled manner without letting your hips sag.

Form tips

Keep your shoulders stable and directly over your wrists throughout the movement to prevent rocking forward and back.
Pull your knees as close to your chest as possible to maximize abdominal contraction rather than stopping short.
Maintain a neutral spine by bracing your core and avoiding excessive arching in your lower back during the extension phase.

Common mistakes

Letting the hips sag during the extension phase reduces core engagement and places unnecessary stress on the lower back.
Rocking the shoulders forward as you tuck shifts the work away from the abs and compromises stability.
Using momentum to swing the knees in and out diminishes time under tension and reduces the effectiveness of the exercise.

Sets and reps

For strength, perform 3 to 4 sets of 6 to 10 controlled reps with a pause at peak contraction; for hypertrophy, use 3 to 4 sets of 12 to 15 reps with steady tempo.

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Frequently asked questions

What muscles does the TRX knee tuck work?: The TRX knee tuck primarily targets the rectus abdominis and hip flexors while also engaging the obliques and deep core stabilizers. The shoulders and arms work isometrically to maintain the plank position throughout the movement.
How do I keep my hips from sagging during TRX knee tucks?: Actively brace your core before each rep and think about pulling your ribcage toward your pelvis to maintain tension. Focus on controlled leg extension rather than speed, and reduce reps if you cannot maintain a neutral spine position.
Can I do TRX knee tucks if regular planks are easy?: Yes, TRX knee tucks are an appropriate progression once you can hold a solid plank for 45 to 60 seconds without form breakdown. The added instability and dynamic movement make them significantly more challenging than static planks.

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