How is this different from the Box-Assisted Pull-Up?

Here the box sits under the bar and one foot stands flat on it, so that leg can push like a step-up and give a lot of help. In the Box-Assisted Pull-Up the box sits behind the bar and both feet rest on it by the toes, which gives far less leg drive, so it is the next step once you need less help here.

Which leg should rest on the box?

Either leg works. Most people use whichever leg feels more stable and keep it the same across sets so the amount of assistance stays predictable.

How hard should I push off the box leg?

Just enough to smooth out the hardest part of the pull, not enough to stand yourself up. If the box leg is doing most of the work, lower the box or switch to a version with less assistance.

Do I need a box for this exercise?

Yes, a sturdy box or step is what the standing leg rests on. Without one, train the hang-only versions instead, such as a Band-Assisted Pull-Up or a full Pull-Up.

What comes after this exercise?

Reduce the pressure through the box leg set by set, then move to the Box-Assisted Pull-Up, which gives less leg help, before working toward a full Pull-Up.

Box-Assisted Single-Leg Pull-Up

What Is the Box-Assisted Single-Leg Pull-Up?

Box-Assisted Single-Leg Pull-Up is a compound exercise that primarily targets the back, particularly the latissimus dorsi, while also engaging the biceps, rear shoulder muscles and core. It is a beginner-level movement that sets a box directly under the pull-up bar: one foot stands flat on the box with the knee bent, and the other leg hangs free, so a single leg can help drive the body up to the bar.

Because the working foot sits under the body, that leg can push like a step-up and take as large a share of the load as the lifter needs, which makes this the most generous of the box-assisted options. It is a sensible first step for someone who can't yet move through any part of a pull-up unaided, before the Box-Assisted Pull-Up, where the toes rest on a box behind the bar and the legs help far less, and then a Band-Assisted Pull-Up, a machine-based Assisted Pull-Up, or a full Pull-Up.

The pulling pattern itself mirrors a standard pull-up: the lats drive shoulder extension and adduction, the biceps and brachialis flex the elbow, and the rhomboids, lower trapezius and rotator cuff muscles stabilize the shoulder blade throughout the pull. Because only one foot is grounded, the core and hips also work to keep the body from twisting toward the supported side.

The aim is to let the back and arms lead every rep and use the leg only to make up the difference. A leg that does most of the lifting turns the exercise into a step-up holding a bar, so reduce the leg drive set by set as pulling strength improves.

Muscles Worked

MuscleActivation

Latissimus Dorsi: Primary
Biceps Brachii: High
Brachialis: High
Infraspinatus: Medium
Lower Trapezius: Medium
Rhomboid Major: Medium
Teres Major: Medium
Erector Spinae: Low
Pectoralis Major: Low
Rectus Femoris: Minimal

Instructions

Set a sturdy, non-slip box directly under the pull-up bar, tall enough that you can reach the bar while standing on it with one knee bent.
Place one foot flat on the box and grip the bar with an overhand, shoulder-width grip, arms fully extended.
Let the other leg hang free beside the box.
Pack your shoulder blades down and back and brace your core before starting the pull.
Pull your chest toward the bar by driving your elbows down and back, letting your back and arms lead the movement.
Press through the foot on the box only as much as needed to keep the rep moving; the box leg straightens as you rise.
Pull until your chin clears the bar, then pause briefly at the top.
Lower back down under control until your arms are fully extended, bending the box knee again.
Repeat for the set, then switch the foot on the box.

Common Mistakes

Turning it into a squat
Driving hard through the box leg so the knee extends and the torso rises before the elbows bend lets the leg do most of the work instead of the back and arms.
Letting the free leg swing
An uncontrolled free leg adds momentum to the rep and makes it harder to judge how much the box leg is actually helping; keep it bent and still.
Using an unstable or slick box
A box that shifts or a slippery top changes how much support the foot gives from rep to rep, making the assistance inconsistent.
Shrugging the shoulders at the hang
Starting each rep without packing the shoulder blades down and back loads the neck and rotator cuff instead of the back.
Pulling with the arms first
Leading with the biceps and reaching the chin toward the bar, rather than driving the elbows down and back, shifts work away from the lats.
Overloading the push late in the rep
Suddenly stomping down through the box leg only at the sticking point, instead of applying light, steady pressure throughout, makes the rep jerky and inconsistent.

Injuries

Box-Assisted Single-Leg Pull-Up is a low risk exercise when performed with proper technique. The shoulders are the main strain point: letting the shoulder blades roll forward or shrug up toward the ears at the bottom of the hang can irritate the rotator cuff tendons or the subacromial bursa, especially over repeated reps. Repetitive elbow flexion under load can also aggravate the forearm tendons at the elbow if the grip is too tight or volume climbs too fast.

The box itself adds two risks a standard Pull-Up does not have: a wobbly or slick box changes how much support the foot actually gives from rep to rep, and driving too hard through the standing leg's knee turns the rep into a one-legged squat rather than a pull. Use a stable, non-slip box at a fixed height, pack the shoulder blades down and back before pulling, and keep foot pressure light and steady rather than stomping down late in the rep.

Someone with existing shoulder impingement or elbow tendon pain should regress to a machine-based Assisted Pull-Up or a Band-Assisted Pull-Up, which load the joint more gradually. Stop the set if pinching shoulder pain, sharp elbow pain or a loss of scapular control appears.

Overview

Primary Focus: Back
Equipment: Pull-up bar, plyo box, and body weight
Modality: Strength
Difficulty: Beginner

Alternative Exercises

Frequently Asked Questions

Q: How is this different from the Box-Assisted Pull-Up?: Here the box sits under the bar and one foot stands flat on it, so that leg can push like a step-up and give a lot of help. In the Box-Assisted Pull-Up the box sits behind the bar and both feet rest on it by the toes, which gives far less leg drive, so it is the next step once you need less help here.
Q: Which leg should rest on the box?: Either leg works. Most people use whichever leg feels more stable and keep it the same across sets so the amount of assistance stays predictable.
Q: How hard should I push off the box leg?: Just enough to smooth out the hardest part of the pull, not enough to stand yourself up. If the box leg is doing most of the work, lower the box or switch to a version with less assistance.
Q: Do I need a box for this exercise?: Yes, a sturdy box or step is what the standing leg rests on. Without one, train the hang-only versions instead, such as a Band-Assisted Pull-Up or a full Pull-Up.
Q: What comes after this exercise?: Reduce the pressure through the box leg set by set, then move to the Box-Assisted Pull-Up, which gives less leg help, before working toward a full Pull-Up.