The calf; those diamond shaped muscles that pop out from the heel of your foot right up to the back of your knee. If you have them you are very lucky, they are a genetic gift from the GODS! Zeus! Hades! Odin! Whoever! When you train them right they hurt like bloody hell.
I know, I know, slightly over the top but for someone who did not get the gift of “the Calf” I have had to train them 3 to 4 times per week for over 13 years to get an acceptable result - something I am happy with. The calf is made up of two main muscles, the Gastrocnemius and Soleus used mainly in pushing the foot off the floor from the ball of the foot - plantar flexion. You can find out more about the calf muscle here I always do 3 sets to failure after every upper body work out and always rotate between Toe Presses, workout 1, Seated Calf Raise, workout 2, and after a back and trap workout I do a smith machine calf raise but holding the bar at waist level rather than across the shoulders - Snatch Grip Calf Raise. This has the double effect of not only building the calves but of stretching out the traps that I have just worked. https://youtu.be/0iREQJc5mWQ I also like loading the leg press up and do 3 sets of heavy Toe Pushes on other days just to mix it up. The calf needs lots of different stimulation not just a standard rep range, think about it, you walk, run and jump and do thousands of reps all day with these two muscles and they are stubborn as hell to get any growth out of. Just keep pushing away changing things up. Again consistency is the key.