How muscles get their names
Most muscle names tell you something specific about that muscle: shape, size, action, location, or attachment points. Decode the name and you understand the muscle.
The 3 muscle types
Skeletal muscle — voluntary, striated. Attaches to bones via tendons. This is what we train. Cardiac muscle — involuntary, striated. Heart only. Trains via cardiovascular exercise. Smooth muscle — involuntary, non-striated. Walls of blood vessels, intestines, etc. Not directly trainable.Naming conventions decoded
By shape:- Deltoid = triangle (Greek delta Δ)
- Trapezius = trapezoid-shaped
- Rhomboid = rhombus-shaped
- Quadratus = square
- Serratus = saw-toothed
- Pectoralis = pectus (chest)
- Gluteus = buttocks
- Brachii = of the arm
- Femoris = of the femur (thigh)
- Maximus, medius, minimus (large, medium, small — see gluteus group)
- Major and minor (rhomboid major/minor, pectoralis major/minor)
- Longus and brevis (long, short — peroneus longus/brevis)
- Biceps = 2 heads (long head + short head)
- Triceps = 3 heads (long, lateral, medial)
- Quadriceps = 4 heads (rectus femoris + 3 vasti)
- Flexor (flexes a joint)
- Extensor
- Adductor
- Levator (lifts)
- Pronator / Supinator
The sliding filament theory (briefly)
Muscle fibers contain myofibrils. Myofibrils contain alternating thin (actin) and thick (myosin) protein filaments. When the muscle is stimulated, myosin heads pull on actin, sliding the filaments past each other and shortening the muscle. ATP fuels this. Calcium triggers it.
This is what every rep is doing at the molecular level. Hypertrophy = adding more myofibrils. Strength gains = better recruitment and synchronization of motor units.
Why naming matters
"Biceps brachii" tells you it's the 2-headed muscle of the arm. "Vastus lateralis" tells you it's a vast (large) lateral (outside) thigh muscle. Once you know the language, you don't have to memorize 600+ muscles — you can decode them.