Many say that the calves rank as a stubborn muscle group. Genetics always play a role, but this muscle group seems affected most. Authorities often use a heavy man or woman with big calves example to justify their theories. They argue that the high volume of walking along with the heavy bodyweight develops them. Along these lines, most experts suggest more volume to get bigger calves. They argue that this muscle group has many slow-twitch muscle fibers.
This requires endless sets of high repetitions. Dramatic solutions include doing sets of heel raises, seated heel raises, and donkey calf raises between every set of an exercise, every day. You have to point your toes in various directions to address different heads of the muscle. You need advanced techniques: drop sets, partials, etc. You need to squeeze at the top to really feel the tension. You need a deep stretch at the bottom. Try to get a full range of motion.
Although this looks sound since it appears as a tough-as-nails and somewhat complicated solution, it seems suspicious. Consider that heavier people have proportionately more muscle and fat than the average person. Not every fat person possesses these big calves. Slow-twitch muscle fibers have little potential for growth. Those possessing more of them have less potential for muscle size in all cases.
You optimize size and strength through heavy weights that address the fast-twitch muscle fibers most responsible for growth. Advanced techniques may cause a lactic acid buildup and more soreness the next day. This does not lead to more tension, the main stimulus for muscle growth.
The gastrocnemius and soleus muscles converge on a single tendon. This brings into question if changing foot position can make any great difference. Only with very light loads unrelated to strength training would the tension in any specific area develop more or less.
The strength of your muscles depends on what length they work. The only thing that changing your foot and body position can do is change the potential length you can use. Seated heel raises put the gastrocnemius, the largest calf muscle, into active insufficiency. This means the sites where muscle contraction occurs overlap too much, like a ball of yarn. This can lead to severe cramping and other muscle injuries. The smaller soleus muscle underneath the gastrocnemius works harder only due to the disabled status of the larger muscle.
The squeeze at the top of a heel raise also works the calf region in this poor shortened position. It only feels tougher since your muscle works weakly, which makes the weight feel heavier. Stretching at the bottom has the same flaw. It works the muscles at a stretched weak length. You need to emphasize the middle portion of any lift to work the muscles best.
Heel raises will irritate your ankles. You can only tolerate heavy weights due to the mechanical advantage at the ankle. The calves function to absorb shock and transfer force from larger muscles, not to move heavily through a great range of motion. Heel raises maximize shearing forces on the ankle. This occurs due to the direction the force is applied. It can harm your joints overtime.
With much thought, I instead suggest the following program for building bigger calves:
Yes, you need squats only. Instead of trying to isolate your calves, treat them as part of a functional lower body unit. Most people fail to squat with proper form. They squat with their butt out from under their back. This turns the squat into a good morning exercise, failing to recruit the powerful quadriceps and calf muscles. Instead, fight with all your might to keep your chest up as you descend and lift. This will allow plantarflexion to occur, which activates all the major muscles. It also occurs at the medium length ideal for tension during the squat. It maximizes compression over shear force, which protects your ankle. Muscles seem to contract harder when other muscles contract along with them. This helps explain why compound movements work better for growth than isolation, as long as you use good form.
Sprinting and jumping for your interval training will also develop the calves. Even walking will develop your calves. Jump roping has a legendary reputation for building the calves, since it uses them precisely as your body intended. This works them in the proper role as shock absorbers. The most explosive athletes actually tend to have small calves. The posterior chain comprised of the glutes and hamstrings drives athleticism. High calves seem to affect black athletes especially, with their longer Achilles tendons. Look at the fastest sprinters in the world to see how that fares for them. Muscle belly size determines possible growth. Therefore, they remain small. Large calves may even harm speed.
Some include work for the tibialis anterior. This involves some form of toe raise, often using resistance bands. I suggest against this. This muscle developed for an unloaded motion. It raises the foot when traversing. Doing it heavily will harm the ankle. Other muscles laterally and medially on the leg work as stabilizers during any lower body movement. They did not adapt to grow big and you do not need specific exercises for them.
If you have the option, choose your parents. If that does not seem possible, then do your best and accept whatever results occur. Perform squats properly, with heavy weights, to best develop the calves. Make sure to use low heel shoes. Do athletic activities while getting your heart rate up. Both these forms of exercise involve your calves as intended, and will therefore build them up safely and quickly.