Calves

#Function

The calf is two muscles stacked, not one. Gastrocnemius is the larger, more superficial muscle, with two heads crossing both the knee and the ankle. Soleus lies underneath, crosses only the ankle. Both plantarflex the ankle (point the toes down), which is why both get called "calves," but their different joint-crossing means they respond to different exercises.

#Origin and insertion

Gastrocnemius originates above the knee, at the femur's condyles — a knee-crossing origin, which is the entire reason leg position matters for training it. Soleus originates below the knee, on the tibia and fibula — it never crosses the knee at all. Both insert together at the heel via the Achilles tendon.

#Why leg position changes which muscle you're training

Because gastrocnemius crosses the knee, bending the knee slackens it — a bent-knee calf raise removes gastrocnemius from a useful length and shifts almost all the work to soleus, which does not care about knee angle at all.

This is precisely the distinction between a standing calf raise (knee straight, gastrocnemius fully involved) and a seated calf raise (knee bent roughly 90°, gastrocnemius slackened, soleus isolated). They are not two ways of training the same thing — they are the correct way to train each of the two muscles separately.

#Why calves are commonly underdeveloped

Two structural reasons beyond simple neglect. First, most calf work uses a very short range of motion relative to the muscle's actual length change — a genuine full stretch-to-contraction range (heel well below the platform edge, full toe extension at the top) is rarely used. Second, soleus is disproportionately slow-twitch and responds better to higher rep ranges than the moderate reps typically used for other muscles.

#Exercise selection

Both exercises are needed for a complete calf stimulus — this is not a substitution table, it is two different muscles.

Source tier: the knee-crossing distinction between gastrocnemius and soleus is textbook anatomy, entirely uncontested.