Seated Single Leg Calf Raises
You do this exercise just like the seated calf raises, except that you use a dumbbell instead of a barbell and exercise one leg at a time. You can do this with a machine or without a machine.
Here are video demo on how to do Seated single leg calf raises
Dumbbell Single Leg Calf Raises
You do this exercise same as dumbbells calf raises. Hold the dumbbell in the hand as the same side of the calf you are going to work. Stand on a platform with toes and foots of ball on the one leg whose calfs your are going to work. Now raise the heels by pushing your toes on the platform and lower them slowly as you reach the max position.
Video Demo showing how to do Dumbbell Single Leg Calf Raises
Hack Machine Calf Raises
Position yourself on regular hack machine as you are going to perform regular squats. Adjust the weights according to your capacity and do the the same as you do in calf raises. Raise and lower your heels to work your calfs
Video Demo on How to do Calf Raises on hack squat machine