NCV / EMG LEARNING

Muscle localization

39 common muscles. Build comparisons across nerves within a myotome, then adapt to the clinical question.

Root entries indicate common contributions, with overlap and variation between references. Fixed needle sites or depths are not provided.

Muscles, roots, peripheral nerves and localization value
Muscle	Nerve / myotome	Action and localization	Interpretation and safety
Abductor pollicis brevisAbductor pollicis brevis · APB	Median nerveC8–T1	Palmar thumb abductionMedian wrist lesions; lower-trunk and C8–T1 comparisons.	Thenar anastomoses may alter innervation and CMAP.
First dorsal interosseousFirst dorsal interosseous · FDI	Ulnar nerveC8–T1	Index finger abductionDeep ulnar motor, elbow/wrist and C8–T1 comparisons.	Interpret with the history and findings in other muscles.
Abductor digiti minimiAbductor digiti minimi · ADM	Ulnar nerveC8–T1	Little finger abductionRoutine ulnar CMAP recording; compare with FDI.	Interpret with the history and findings in other muscles.
Pronator teresPronator teres · PT	Median nerveC6–C7	Forearm pronationProximal median and C6–C7; a non-radial C7 comparison.	Interpret with the history and findings in other muscles.
Flexor carpi radialisFlexor carpi radialis · FCR	Median nerveC6–C7	Wrist flexion with radial deviationC7 root and proximal median comparisons.	Interpret with the history and findings in other muscles.
Flexor carpi ulnarisFlexor carpi ulnaris · FCU	Ulnar nerveC8–T1	Wrist flexion with ulnar deviationProximal ulnar branch; compare hand and non-ulnar C8 muscles.	Interpret with the history and findings in other muscles.
Flexor pollicis longusFlexor pollicis longus · FPL	Anterior interosseous nerveC8–T1	Thumb IP flexionAIN, proximal median and C8–T1.	Deep muscle; identify nearby neurovascular structures.
Index flexor digitorum profundusFlexor digitorum profundus, digit II	Anterior interosseous nerveC8–T1	Index DIP flexionAIN comparison with FPL and PQ.	Different finger fascicles of FDP have different nerve supplies.
Pronator quadratusPronator quadratus · PQ	Anterior interosseous nerveC8–T1	Forearm pronationDistal AIN muscle; compare with pronator teres.	Deep muscle; no fixed insertion depth is provided.
Extensor indicis propriusExtensor indicis proprius · EIP	Posterior interosseous nerveC7–C8, predominantly C8	Index finger extensionPIN and a non-median/non-ulnar C8 comparison.	Interpret with the history and findings in other muscles.
Extensor digitorum communisExtensor digitorum communis · EDC	Posterior interosseous nerveC7–C8	Finger MCP extensionPIN and C7–C8 comparisons.	Interpret with the history and findings in other muscles.
Extensor carpi radialis longusExtensor carpi radialis longus · ECRL	Radial nerveC6–C7	Wrist extension with radial deviationRadial branches proximal to the PIN.	Interpret with the history and findings in other muscles.
BrachioradialisBrachioradialis	Radial nerveC5–C6	Elbow flexion in neutral forearm positionCross-nerve C5–C6 comparison with biceps.	Interpret with the history and findings in other muscles.
Biceps brachiiBiceps brachii	Musculocutaneous nerveC5–C6	Elbow flexion and supinationMusculocutaneous, upper trunk and C5–C6.	Interpret with the history and findings in other muscles.
Triceps brachiiTriceps brachii	Radial nerveC6–C8, predominantly C7	Elbow extensionHigh radial lesions and C7 comparisons.	Interpret with the history and findings in other muscles.
DeltoidDeltoid	Axillary nerveC5–C6	Shoulder abductionAxillary, upper-trunk and C5–C6 comparisons.	Interpret with the history and findings in other muscles.
SupraspinatusSupraspinatus	Suprascapular nerveC5–C6	Assists shoulder abductionCompare with infraspinatus to assess lesion height.	Requires reliable anatomical identification and a trained examiner.
InfraspinatusInfraspinatus	Suprascapular nerveC5–C6	Shoulder external rotationSpinoglenoid notch versus proximal suprascapular involvement.	Interpret with the history and findings in other muscles.
Serratus anteriorSerratus anterior	Long thoracic nerveC5–C7	Scapular protraction and upward rotationMedial winging and long thoracic assessment.	Chest-wall sampling carries pneumothorax risk; specialized training and appropriate imaging are required.
RhomboidRhomboid	Dorsal scapular nerveMainly C5	Scapular retractionProximal C5 branch versus upper-trunk comparisons.	Near the chest wall; requires a specific safety assessment.
TrapeziusTrapezius	Spinal accessory nerveCN XI; additional cervical sensory/proprioceptive contributions	Shoulder shrug and scapular stabilizationSpinal accessory lesions and lateral winging.	Consider pleural risk according to sampling region and body habitus.
Tibialis anteriorTibialis anterior · TA	Deep fibular nerveL4–L5	Ankle dorsiflexion and inversionCommon/deep fibular, sciatic and L4–L5.	Interpret with the history and findings in other muscles.
Extensor hallucis longusExtensor hallucis longus · EHL	Deep fibular nerveL5–S1, predominantly L5	Great toe extensionDeep fibular and L5 comparisons.	Interpret with the history and findings in other muscles.
Extensor digitorum brevisExtensor digitorum brevis · EDB	Deep fibular nerveL5–S1	Assists toe extensionRoutine fibular motor recording.	Local foot injury, atrophy and accessory deep fibular supply can interfere.
Fibularis longusFibularis (peroneus) longus	Superficial fibular nerveL5–S1	Foot eversionSuperficial versus deep fibular division comparison.	Interpret with the history and findings in other muscles.
Tibialis posteriorTibialis posterior · TP	Tibial nerveL4–L5	Foot inversion and assisted plantar flexionNon-fibular L5 comparison muscle.	Deep and near important structures; consider ultrasound when localization is difficult.
GastrocnemiusGastrocnemius	Tibial nerveS1–S2	Plantar flexion and assisted knee flexionTibial, sciatic and S1–S2.	Interpret with the history and findings in other muscles.
SoleusSoleus	Tibial nerveS1–S2	Ankle plantar flexionH reflex and S1-related comparisons.	Interpret with the history and findings in other muscles.
Abductor hallucisAbductor hallucis · AH	Medial plantar nervePredominantly S1–S2; myotomal references vary	Great toe abductionRoutine tibial motor CMAP recording.	Isolated spontaneous activity in foot intrinsics has limited specificity.
Vastus medialisVastus medialis	Femoral nerveL2–L4	Knee extensionFemoral versus L2–L4/lumbar plexus comparisons.	Interpret with the history and findings in other muscles.
Rectus femorisRectus femoris	Femoral nerveL2–L4	Knee extension and assisted hip flexionFemoral, lumbar plexus and upper lumbar roots.	Interpret with the history and findings in other muscles.
Adductor longusAdductor longus	Obturator nerveL2–L4	Hip adductionNon-femoral L2–L4 comparison.	Interpret with the history and findings in other muscles.
Biceps femoris, short headBiceps femoris, short head	Sciatic nerveL5–S1	Knee flexionAbove-knee fibular division of the sciatic nerve.	Distinguish it from the long head; their division supplies differ.
Biceps femoris, long headBiceps femoris, long head	Sciatic nerveL5–S2	Knee flexion and hip extensionSciatic tibial division; compare with the short head.	Interpret with the history and findings in other muscles.
Tensor fasciae lataeTensor fasciae latae · TFL	Superior gluteal nerveL4–S1, predominantly L5	Hip flexion, abduction and internal rotationNon-sciatic L5 comparison.	Interpret with the history and findings in other muscles.
Gluteus mediusGluteus medius	Superior gluteal nerveL4–S1	Hip abduction and pelvic stabilizationL5 root, sacral plexus and superior gluteal nerve.	Interpret with the history and findings in other muscles.
Gluteus maximusGluteus maximus	Inferior gluteal nerveL5–S2	Hip extensionProximal non-sciatic S1-related comparison.	Interpret with the history and findings in other muscles.
Orbicularis oculiOrbicularis oculi	Facial nerveCN VII	Eye closureFacial motor and blink reflex recording.	Facial sampling and specialized recording require appropriate training.
DiaphragmDiaphragm	Phrenic nerveC3–C5	InspirationPhrenic nerve and respiratory neuromuscular disease.	Specialized higher-risk sampling; requires a trained examiner and appropriate ultrasound assessment.

References and further reading

Neuroanatomy for Nerve Conduction Studies (2017) ↗AANEM · Anatomy course · Link accessed 2026-09-08
Electrodiagnosis of Radiculopathies ↗AAPM&R KnowledgeNow · Society educational review · Link accessed 2026-09-08
Upper Extremity Proximal Mononeuropathies ↗AAPM&R KnowledgeNow · Society educational review · Link accessed 2026-09-08
Lumbosacral Plexopathy and Sciatic Neuropathy ↗AAPM&R KnowledgeNow · Society educational review · Link accessed 2026-09-08
Advanced EMG and US of the Respiratory System (2024) ↗AANEM · Advanced course abstract · Link accessed 2026-09-08

Educational synthesis; independent neuromuscular specialist review is pending. Publication dates and compilation dates are distinct. This is an original teaching synthesis; consult the source for complete methods and criteria.