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Plank

Also called: Front plank, forearm plank

Simplified front view of the abdomen showing the segmented rectus abdominis running down the midline, the diagonal external oblique on each side, and the transversus abdominis wrapping around the waist beneath. — Core region — rectus abdominis, obliques, and transversus abdominis (simplified). A beginner-level schematic of the core's abdominal muscles: rectus abdominis, external oblique, and transversus abdominis.
Illustration: Anatomy Learning Platform (original) · CC0-1.0 (public domain dedication)

Primary muscles: Rectus abdominis, Transversus abdominis

Secondary muscles: External oblique, Internal oblique

Plane: —

Equipment: bodyweight

What it is

Holding a straight-line body position supported on the forearms and toes, bracing the trunk still.

Purpose

Builds the ability to keep the spine stable (resist sagging into extension) under a bracing demand.

Starting position

Forearms on the floor under the shoulders, body straight from head to heels, toes tucked under.

Step by step

Brace the abdominals and glutes to keep the hips level — not sagging down or piked up.
Keep the neck neutral, gaze toward the floor.
Hold the position for the target time while breathing normally.

Breathing

Breathe steadily throughout — do not hold your breath.

Coaching cues

"Straight line from head to heels, squeeze the glutes, don't let the hips sag."

Common mistakes

Letting the hips sag (low back overextends); piking the hips up too high; holding the breath.

Easier regression

Plank from the knees instead of the toes, or shorten the hold duration.

Harder progression

Increase hold time, or lift one foot briefly while maintaining a level trunk.

Alternatives

Dead bug, bird-dog (lower back region).

Who may benefit

Nearly everyone — a foundational trunk-bracing exercise appropriate at almost any fitness level with the right regression.

Who should modify or avoid it

Those with wrist or shoulder discomfort in a forearm position, or low back pain that worsens when the hips sag, should regress or shorten holds.

Why this exercise works

The plank challenges the rectus abdominis, obliques, and transversus abdominis to work isometrically together to resist the low back sagging into extension under the load of your own body weight.

⚠ Safety note

If the low back arches and you feel it in the spine rather than the abs, shorten the hold time or regress to a knee plank.

Sources

“The rectus abdominis and transversus abdominis compress and stabilize the trunk, resisting unwanted spinal extension under load.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.3 Axial Muscles of the Abdominal Wall, and Thorax

Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19