How long should I hold a TRX Single-Leg Plank?

Start with 10 to 20 seconds per side and add time only while your hips stay level and your back stays flat. Several short, clean holds are better than one long hold that ends with sagging hips.

Is the TRX Single-Leg Plank harder than a regular plank?

Yes. The suspended foot is less stable than the floor, and lifting one leg takes away half the base of support, so the core has to resist both sagging and rotation. If you cannot hold a TRX Plank well yet, work on that first.

Should the lifted leg be straight or bent?

A straight leg or one with a slight bend at the knee, held at about the height of the cradles, is enough. Going higher usually arches the lower back instead of adding useful work.

How is it different from the TRX Reverse Plank?

The TRX Single-Leg Plank is face down on the forearms and works the abdominals against gravity, while the TRX Reverse Plank is face up and works the glutes and the back of the body more.

Why does my foot slip out of the cradle?

The straps are usually too long or the cradle is sitting too far down the foot. Shorten them so the cradle sits snugly around the ankle and over the top of the foot.

TRX Single-Leg Plank

What Is the TRX Single-Leg Plank?

TRX Single-Leg Plank is a compound exercise that primarily targets the core and also engages the glutes, shoulders and hips. It is an intermediate-level movement: you hold a forearm plank with one foot in the suspension trainer's foot cradles and the other leg lifted off the floor behind you. With only one foot supported, the hips want to rotate, tip and sag, so the abdominals, obliques and lower back work hard to keep the body in one straight line.

The suspended foot is what makes the plank harder than its floor version. In a study of 21 adults, a plank with the feet in TRX straps produced higher abdominal muscle activity than the same plank on the floor, and lifting a leg removes half of the base of support on top of that. The study tested two suspended feet, not one, so treat the single-leg version as a harder step beyond it.

Lifting the leg adds a hip-extension demand. The glutes of the lifted leg work to hold it up, and the trunk muscles resist the tendency of the pelvis to rotate toward the unsupported side. The forearm position keeps the load on the shoulders lower than a straight-arm plank while the serratus anterior and deltoids stabilize the shoulder blades.

This exercise suits people who can already hold a solid TRX Plank with both feet in the cradles and a level pelvis. If it is too hard, build up with the floor Plank or the two-foot TRX Plank first. When it becomes easy, try the more dynamic TRX Body Saw and TRX Pendulum. Holds are best kept short and clean, since form is the first thing to fail as the core tires.

Muscles Worked

MuscleActivation

Rectus Abdominis: Primary
External Oblique: High
Gluteus Maximus: High
Deltoid: Medium
Erector Spinae: Medium
Rectus Femoris: Medium
Serratus Anterior: Medium
Gluteus Medius: Low
Pectoralis Major: Low
Biceps Femoris: Minimal

Instructions

Set the suspension trainer so the foot cradles hang about 1 to 2 feet (30 to 60 cm) above the floor, with both straps the same length.
Kneel facing away from the anchor point and place one foot in the cradles, with the straps around the ankle and over the top of the foot.
Place your forearms flat on the floor, parallel and pointing forward, with your elbows directly under your shoulders.
Push your forearms into the floor and extend your body into a forearm plank, with the supporting foot held in the cradles.
Brace your abs and squeeze your glutes until your ears, shoulders, hips and ankle form one straight line.
Lift the free leg off the floor behind you to about the height of the cradles, keeping it straight or with a slight bend at the knee. Do not rest it on the straps.
Keep your hips level and square to the floor. Do not let them rise, sag or rotate toward the lifted leg.
Look at the floor just ahead of your hands to keep your neck neutral, and breathe steadily.
Hold for the planned time, then lower the lifted leg, bring both knees to the floor and release the foot. Repeat on the other side.

Common Mistakes

Sagging hips
Letting the hips drop toward the floor as the core tires puts the lower back into extension and takes the load off the abdominals.
Rotating toward the lifted leg
Opening the pelvis to the side as the leg lifts shifts the work away from the core and into the lower back and hip.
Lifting the leg too high
Swinging the free leg above cradle height arches the lower back instead of using the glutes and trunk to hold the line.
Collapsing between the shoulders
Sinking the chest toward the floor leaves the shoulders unstable, so push the forearms into the floor and keep the upper back wide.
Piking the hips up
Raising the hips above shoulder height shortens the lever and makes the plank easier, so the core gets far less work.
Resting the free leg on the straps
Letting the lifted foot lean on the straps gives back a second point of support and removes the single-leg challenge.

Injuries

TRX Single-Leg Plank is a medium risk exercise when performed with proper technique. The body is held as a long lever with only one point of foot support, so most of the demand lands on the lower back, shoulders and the muscles that control the pelvis. The usual strain points are the lower back, if the hips sag or the back arches as the leg lifts, and the shoulders, if the upper back collapses between the forearms.

To reduce the risk, keep your abs braced and your glutes squeezed so the pelvis stays level and the spine neutral. Adjust the straps so the foot sits securely in the cradle, and keep the lifted leg low and controlled rather than swinging it up high, which pulls the lower back into an arch. Hold for short, clean efforts and stop the set when your hips start to drop or rotate rather than pushing through a sloppy hold.

If you are new to suspension work, master the floor Plank and the two-foot TRX Plank first. Stop if you feel sharp pain in the lower back, shoulders or neck, or if the foot slips in the cradle.

Overview

Primary Focus: Core
Equipment: Suspension trainer and body weight
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: How long should I hold a TRX Single-Leg Plank?: Start with 10 to 20 seconds per side and add time only while your hips stay level and your back stays flat. Several short, clean holds are better than one long hold that ends with sagging hips.
Q: Is the TRX Single-Leg Plank harder than a regular plank?: Yes. The suspended foot is less stable than the floor, and lifting one leg takes away half the base of support, so the core has to resist both sagging and rotation. If you cannot hold a TRX Plank well yet, work on that first.
Q: Should the lifted leg be straight or bent?: A straight leg or one with a slight bend at the knee, held at about the height of the cradles, is enough. Going higher usually arches the lower back instead of adding useful work.
Q: How is it different from the TRX Reverse Plank?: The TRX Single-Leg Plank is face down on the forearms and works the abdominals against gravity, while the TRX Reverse Plank is face up and works the glutes and the back of the body more.
Q: Why does my foot slip out of the cradle?: The straps are usually too long or the cradle is sitting too far down the foot. Shorten them so the cradle sits snugly around the ankle and over the top of the foot.