Brachialis – Anatomy Breakdown
Treadwell, DPT | Muscle by Muscle Series
Watch the Episode
Watch on YouTube: Brachialis – Anatomy Breakdown
In this episode, Dr. Austin Treadwell, DPT takes a closer look at the Brachialis — the deep engine of the arm.
It doesn’t get the spotlight like the biceps, but it’s doing the heavy lifting behind the scenes. Literally.
Overview
The Brachialis sits deep to the Biceps Brachii and is the primary flexor of the elbow joint.
Unlike the Biceps, it doesn’t cross the shoulder or rotate the forearm — it’s pure flexion power, built for torque.
Clinically, the Brachialis is critical for anyone recovering from elbow injury, tendinopathy, or lifting asymmetry.
In training, it’s the muscle that gives the arm its dense, rounded look when developed — and it’s the unsung hero behind heavy curls and pulling strength.
Origin & Insertion
Origin: Distal half of the anterior humerus
Insertion: Coronoid process and tuberosity of the ulna
Because it inserts on the ulna, not the radius, the Brachialis contributes regardless of forearm position — meaning it flexes just as powerfully in pronation (palms down) as in supination (palms up).
Function
Primary: Elbow flexion (regardless of forearm rotation)
Secondary: Joint stabilization during rapid or loaded elbow movements
EMG studies confirm that the Brachialis remains active across all grip orientations — peaking during neutral and pronated flexion patterns (Yoshida et al., 2024).
That’s why hammer curls are the go-to isolation movement: they bias the Brachialis more than the Biceps.
Innervation & Blood Supply
Innervation: Musculocutaneous nerve (C5–C6) and occasionally the radial nerve
Blood Supply: Brachial artery and radial recurrent artery
Clinical & Training Insights
Brachialis strains or adhesions can mimic distal biceps tendinopathy — differentiate with palpation deep to the biceps belly.
Hypertrophy of the Brachialis can visually widen the upper arm by “pushing” the biceps up and out.
Training variations like reverse curls, Zottman curls, or fat-grip holds challenge this deep flexor while reducing biceps tendon stress.
Rehab focus: eccentric and tempo-based elbow flexion through full range to restore load tolerance.
Clinical insight: Post-op elbow patients who emphasize Brachialis strengthening early regain flexion faster (Patel et al., 2023).
Clinical Relevance
The Brachialis doesn’t need flash — it needs function.
It’s often inhibited after elbow immobilization or biceps injury, leading to reduced grip strength and fatigue during loaded carries.
Restoring its strength and timing rebalances the elbow complex and protects both the distal biceps tendon and the forearm flexors.
Take the Next Step
You’ve got the anatomy down — now put it into motion.
If you’re a clinician, let’s talk upper-limb rehab and loading progressions.
If you’re an athlete or lifter, let’s talk arm mechanics and elbow strength.
And if you’re working through elbow pain or biceps issues — this is where anatomy meets recovery.
𖤓 Watch more breakdowns on YouTube: Treadwell, DPT – Muscle by Muscle Series
𖤓 Book a Virtual Consultation: TreadwellDPT.com/appointments
𖤓 Download free PT tools & anatomy resources: TreadwellDPT.com/resources
Much more in store; even more to come.
Stay tuned, stay locked. Treadwell, DPT. 🚀
