How to Perform the TRX Crunch

Proper Form, Variations, and Common Mistakes

Verywell / Ben Goldstein

Also Known As: Suspended Knee Tucks, Reverse Crunch

Targets: Abs, Core, Chest

Equipment Needed: TRX Suspension Trainer

Level: Intermediate to Advanced

The TRX crunch is an alternative way to work abdominal muscles using suspension straps and your own bodyweight. The exercise targets your abs but also challenges the core, chest, and shoulders as you are suspended from an anchor point.

Performing an abdominal crunch while suspended challenges your body in conditions of instability. This forces you to constantly engage your core and stabilizing muscles to perform the movement. Instead of a basic crunch lying on the floor, you are suspended in a full plank position drawing your knees toward your chest.

The exercise not only works your abs but helps to improve your balance, stability, and overall strength. Adjusting the level of difficulty for this exercise is an easy shift of your body position. The adjustable bands are suitable for the novice exerciser to the advanced athlete and can be modified to fit nearly every fitness level.

TRX training claims to provide an effective full-body workout with simple equipment. This is one of the many popular reasons people are trying suspension training. It’s also a great way to add variety and challenge to an existing ab routine or training program.

If you’re new to this exercise and TRX training, it’s recommended to perform workouts in stable conditions before adding the instability of suspension straps. It may also be a good idea to enlist the guidance of a qualified personal trainer or TRX coach.


The TRX crunch is an alternative way to work the abdominal muscles. This exercise targets the abs but also challenges your core, chest, and shoulders during the movement.

The balance component of this exercise forces you to engage your core to maintain proper body position throughout the movement. Developing a strong core can help improve posture, balance, and relieve low back pain. It also improves the neuromuscular response (reflexes) and stability which can come in handy if you take a misstep off a curb or need to react quickly to a falling object.

Performing the TRX crunch, like all suspension exercises involves multiple muscle groups making it a fast and effective way to get in a full-body workout. Quick and challenging workouts are just one of the many benefits of suspension training.

The TRX crunch and other suspension exercises are shown to have numerous positive benefits and studies have indicated the following: 

  • Lean mass gains
  • Improved strength
  • Improved stability/balance
  • Increased core strength
  • Improved cardiovascular health
  • Decreased body fat
  • Improved blood pressure
  • Corrected body imbalance
  • Improved athletic performance
  • Reduced fall risk
  • Better gait (walking)
  • Improved functional fitness (day-to-day activities)
  • Practical and effective exercise alternative
  • Increased exercise confidence 

Step-by-Step Instructions

The great thing about TRX training is portable cables that offer the ability to workout anywhere. It just requires an area where they can be securely attached and you are ready to exercise.

Follow these simple steps to perform the TRX crunch:

  1. Attach cables to an anchor point above your head adjusting the straps to hang down about one foot from the floor or ground.
  2. Assume ground facing away from the anchor point (GFA) position and place your feet securely in the foot cradles. Maintain downward pressure with the tops of your feet facing the ground and toes pointed away from your shins.
  3. Lie on your stomach and prepare to assume a full plank or forearm plank position (shown). To prepare for the full plank, place your hands shoulder-width apart like preparing to perform a push-up. To prepare for a forearm plank, the forearms are placed on the floor, shoulder-width apart.
  4. Tighten your core and glutes, exhale and raise into a full plank (advanced) or forearm plank (intermediate). Maintain a neutral spine not allowing your hips to sag or back to arch.
  5. Slowly pull your knees toward your chest and under your hips. Keep your feet together during the movement and avoid swinging of the suspension straps.
  6. Inhale and slowly lower your body to start position maintaining a tight core and neutral spine.
  7. Repeat the exercise for a determined amount of repetitions.

Common Mistakes

The TRX crunch is performed in unstable conditions and special attention is required for proper form and technique. The following are common mistakes to avoid during this exercise:

Sagging Your Low Back and Hips

Allowing the low back and hips to sag could be an indicator of exercise fatigue or unreadiness to perform the TRX version of this exercise. You should be able to maintain a tight core in order to stabilize the low back (lumbar spine) throughout the exercise. The important thing is to be aware of your body mechanics at all times for exercise effectiveness and safety.

If you are using the full plank position but are having a hard time maintaining a tight core and stable back, switch to a forearm plank.

Incorrect Foot Position and Pressure

It is important to keep your feet together while applying downward pressure in the foot cradles. This sets up the exercise to be performed correctly without the suspension straps swinging back and forth during the movement.

Arching Your Back

Not keeping your back straight during the movement could be another indicator of exercise fatigue or unreadiness to perform the TRX version of this exercise. Perform the exercise with a neutral spine and tight core to ensure proper form and avoid the risk of injury.

Uneven Suspension Straps

Proper exercise setup is important for exercise effectiveness and safety. Ensure the suspension straps are even before placing your feet in the cradles.

Modifications and Variations

The TRX crunch can be performed in a variety of ways to accommodate your fitness level.

Need a Modification?

If you're new to performing a suspended ab crunch and TRX training, you may want to apply a few modifications as follows:

  • Master the basic abdominal and reverse crunch in stable conditions on the floor before progressing to the TRX version. This will increase exercise confidence and overall strength before adding the instability of suspension straps.
  • Hold a plank position with your feet in the suspension straps without pulling the knees towards the chest. This will introduce you to the unstable conditions from suspension straps and build up your core strength. 

Up for a Challenge?

TRX training is a progressive exercise method suitable for all fitness levels. This means you can increase the intensity of your workout as you become stronger. The following applied modifications make the TRX crunch more advanced:

  • Move your body further away from the anchor point to create more resistance during the exercise. You will feel increased tension in the straps and have to work harder to pull your knees toward your chest. 
  • Alternate a push-up and crunch variation and really kick up the challenge. This two-part routine increases workloads to the chest, shoulders, and core muscles.
  • Perform the TRX pike instead of the crunch. This requires even more core engagement and increased challenge to your balance, stability, and ab muscles.

Safety and Precautions

The TRX crunch is performed in unstable conditions and requires keen body awareness during the exercise. Because of this instability, it’s important to pay attention to your body position and movement at all times.

The following tips will help you perform the TRX crunch correctly and reduce the risk of injury:

  • Take the time to properly adjust your suspension straps about one foot from the floor and ensure that both straps are at equal lengths.
  • Maintain a tight core and straight back at all times during the exercise to reduce the risk of low back discomfort/injury.
  • Be aware of any sag in your hips or arched back during the exercise. This could be an indicator of being tired, fatigued, or not enough core strength to perform the movement.
  • Keep your feet together during the exercise and downward pressure on the foot cradles to avoid swinging of the suspension straps.
  • Work at your fitness level for this exercise to increase overall strength and balance before adding more challenge.
  • If you experience pain or discomfort that doesn’t feel right during the TRX crunch, discontinue the exercise.

Try It Out

Incorporate this move and similar exercises into one of these popular workouts:

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Darla Leal
Darla Leal is a Master Fitness Trainer, freelance writer, and the creator of Stay Healthy Fitness, where she embraces a "fit-over-55" lifestyle.