Muscle anatomy

Every major muscle: origin, insertion, function, and — the part most guides skip — where on its length-tension curve each exercise actually loads it.

In this module

How to read this sectionOrigin, insertion, and the resistance-profile logic that connects anatomy to exercise selection.QuadricepsFour heads, one with a genuine blind spot that most training never closes.HamstringsTwo jobs, and most programs only train one of them at length.GlutesOne muscle with four jobs, and the exercise that loads its hardest-to-reach one.ChestTwo heads, one continuous muscle, and why 'upper chest' and 'lower chest' need different equipment to train properly.Back — latsThe muscle that is longest overhead, trained by most programs in its shortest position.Back — upper back and trapsThe muscles that have almost no stretched position, and why that changes how you should train them.DeltoidsThree heads, three different jobs, and one that most dumbbell exercises train through only a third of its range.BicepsTwo heads, and the shoulder position that decides which one is actually stretched.TricepsThree heads, and the largest one is trained badly by the exercise most people do most.CalvesTwo muscles, one straight-leg and one bent-leg, and most people only train one of them.