Front plank muscles worked

Every role here is for this technique: on the forearms and toes, elbows under the shoulders, body held in a straight line from head to heels.

What muscles does the front plank work?

The prime movers of the front plank are rectus abdominis, external oblique, internal oblique and transversus abdominis. They hold the trunk straight against gravity. The synergists are iliopsoas and the quadriceps. Six stabilizers hold joints and segments still, among them serratus anterior, the sternal part of pectoralis major and the anterior deltoid.

See it on the body: Muscles Worked by Exercise 3D Explorer →

Joint actions and their prime movers

The joint actions of the front plank and the prime movers that produce each
Joint action	Prime movers
Holding the trunk straight against gravity	Rectus abdominis, external oblique, internal oblique and transversus abdominis

Every muscle by role

A prime mover produces the lift’s main joint action against the load; a synergist assists that action, or adds a secondary action the lift needs; a stabilizer contracts mostly isometrically to hold a joint or a segment still. A role describes what the muscle does in the technique above, not how hard it works or how much it grows.

Prime movers 4

Prime movers in the front plank, with what each does
Muscle	What it does here
Rectus abdominis	Stopping the hips sagging, without changing length
External oblique	Stopping the hips sagging, without changing length
Internal oblique	Stopping the hips sagging, without changing length
Transversus abdominis	Raising abdominal pressure to stiffen the trunk, without changing length

Synergists 2

Synergists in the front plank, with what each does
Muscle	What it does here
Iliopsoas	Holding the hips in line, without changing length
Quadriceps	Keeping the knees straight and the hips up, without changing length

Stabilizers 6

Stabilizers in the front plank, with what each does
Muscle	What it does here
Serratus anterior	Holding the shoulder blades against the ribs
Pectoralis major, sternal part	Holding the chest up over the elbows
Anterior deltoid	Holding the shoulders over the elbows
Gluteus maximus	Keeping the pelvis level with the trunk
Gluteus medius	Keeping the pelvis level
Erector spinae	Balancing the abdominal wall so the spine stays neutral

Lowering and lifting

What the prime movers of the front plank do in each half of a rep
Phase	What the prime movers do
Holding	The abdominal wall stays the same length against gravity

Rectus abdominis, external oblique, internal oblique, transversus abdominis, iliopsoas and the quadriceps hold without changing length, though they are prime movers and synergists rather than stabilizers.

Where these prime movers also work

Rectus abdominis: a prime mover in no other lift here.
External oblique: a prime mover in no other lift here.
Internal oblique: a prime mover in no other lift here.
Transversus abdominis: a prime mover in no other lift here.

Sources

Ekstrom, Donatelli and Carp (2007), J Orthop Sports Phys Ther 37(12):754
Neumann, Kinesiology of the Musculoskeletal System, 3rd ed. (2017)

The cited studies that measured muscle activity used electromyography, and a larger signal need not mean more force or more growth (Vigotsky et al. (2018), Front Physiol 8:985). The roles draw on those studies for which muscles a lift involves and how two lifts differ, never to rank one muscle against another.

See these muscles in 3D

Visualiser · Biology Muscles Worked by Exercise 3D Explorer Choose a lift and a real body lights its prime movers, synergists and stabilisers, front and back, with the same muscles in 3D. Visualiser · Biology Muscle Origin, Insertion and Action Explorer Paint a muscle’s origin and insertion on real 3D bones, or click a bone to see what attaches to it.