Per Ng et al. 1998 Trunk Anterior Left

M. Obliquus Externus Abdominis

External Oblique (Obl Ext L)

The M. Obliquus Externus Abdominis (External Oblique) is a muscle of the trunk anterior region. It is responsible for lateral flexion and rotation of the trunk to the opposite side, spinal flexion, compression of the abdominal cavity. This muscle is not covered by the official SENIAM catalogue — placement is based on established clinical literature. This page documents the exact electrode position, anatomical attachments and a standardized test movement based on Hermens et al. (2000).

Function

Lateral flexion and rotation of the trunk to the opposite side, spinal flexion, compression of the abdominal cavity

Opposite side: Obl Ext R

Electrode position on the 3D model: M. Obliquus Externus Abdominis (muscle highlighted, sensor in place)

Preview — open the 3D viewer to rotate the model and check neighbouring muscles. View in 3D Viewer

Electrode Placement (SENIAM)

Below the lowest rib, 45 degrees to the horizontal

Orientation: Parallel to the muscle fibers (oblique, approx. 45 degrees)

Source: Ng et al. 1998 ↗

Ng JK-F, Kippers V, Richardson CA. Muscle fibre orientation of abdominal muscles and suggested surface EMG electrode positions. Electromyogr Clin Neurophysiol. 1998;38(1):51-58.

Methodological background of the source

Ng et al. (1998) determined the fibre orientation of the abdominal muscles and derived recommendations for surface electrode positions from it. The key point is aligning the electrodes parallel to the fibres — vertically for the rectus abdominis, obliquely for the external oblique. That fibre orientation is the core of the position documented here.

Recording notes per Criswell 2011, site „External Abdominal Oblique“, p. 349

Placement type: Quasi-specific site Neighbouring muscles contribute noticeably to the signal — allow for crosstalk.
Signal check: Rotate the torso; diagonal sit-up.
Crosstalk from: internal oblique · rectus abdominis · latissimus dorsi · quadratus lumborum
Artefacts: A thick adipose layer attenuates the signal.

Based on SENIAM recommendations (Hermens et al. 2000). Not an official SENIAM product. See all references → · How electrodes are placed (guide) · Glossary

Go deeper Specific, Quasi-Specific, General — The Three Types of Surface EMG Placement → 10 Factors That Distort Your EMG Signal → From Raw EMG to RMS — Rectification, Smoothing and Filtering Explained →

All 47 muscle protocols as a PDF — free

Print-ready for the lab or clinic: 75 pages of protocols (SENIAM + peer-reviewed), plus the SENIAM table, a placement checklist and a sensor comparison sheet as A4 sheets.

Anatomy

Origin External surfaces of ribs 5-12 Insertion Linea alba, iliac crest, inguinal ligament

Test Movement

Trunk rotation to the opposite side against resistance

This muscle has no SENIAM-standardized electrode position. Placement should be based on anatomical knowledge.

MVC reference test (Konrad 2005)

Position: Side-lying with legs and hips fixed; flex the trunk up and fix it early in the flexed position.
Fixation: Legs and hip fixed with belts or manually.
Resistance: Fixation itself (isometric hold); an added trunk rotation may raise the oblique activity.
Control exercise: The rectus abdominis test is the important check exercise.

Konrad: this test needs good coordinative skill; the obliques may fire higher when rotation is added to the flexion.

Konrad P. The ABC of EMG. Noraxon; 2005, p. 32. Konrad describes this test at group level; it applies to all muscles of the group. · Why and how to normalise to MVC

Measure M. Obliquus Externus Abdominis activity live

The electrode is placed — what next? easyEMG visualises muscle activity in real time, with SENIAM-compliant placement guidance, up to 4 channels at once and biofeedback training right afterwards.

In training, what matters for this muscle is targeted activation and left/right symmetry.

EMG biofeedback training → What is EMG biofeedback?

Frequently Asked Questions

Where do I place the EMG electrode on the M. Obliquus Externus Abdominis?

Below the lowest rib, 45 degrees to the horizontal. Orientation: Parallel to the muscle fibers (oblique, approx. 45 degrees). Not covered by SENIAM — placement per Ng et al. 1998.

Which test movement activates the M. Obliquus Externus Abdominis?

Trunk rotation to the opposite side against resistance. It serves as a signal check before recording: with correct electrode placement the EMG amplitude rises clearly during this movement.

Is the M. Obliquus Externus Abdominis a SENIAM-recommended muscle?

No. The M. Obliquus Externus Abdominis is not included in the official SENIAM catalogue. The electrode position documented here follows the established protocol per Ng et al. 1998.