Rest a loaded barbell across your upper back as you would for a squat, then position the ball of one foot on an elevated platform with that heel hanging off the edge.
Brace your core, keep the working leg nearly straight, and use the other foot only lightly for balance.
Exhale and rise onto the ball of your foot, squeezing the calf hard at the top.
Inhale and slowly lower the heel below the platform until you feel a full stretch.
Complete all reps, then switch the barbell load to the other foot and repeat.