Muscle ID and Function
The soleus runs beneath the gastrocnemius, which is the rounded muscle at the back of your lower leg -- the bulk of your calf. The soleus is smaller and flatter, originates on portions of the tibia and fibula and inserts into the Achilles tendon at the calcaneous. The soleus engages when you flex your ankle and point your toes. It can't, however, fully contract unless your leg is bent, according to ACSM personal trainer Christopher Ball. Because of this, exercises in a seated position will be most effective in working the soleus.
The seated calf raise is one of the best exercises for working the soleus, according to Ball. Without sophisticated gym equipment, you simply sit tall on a sturdy chair or workout bench, put the balls of your feet on an aerobic step, then raise and lower your heels. For more resistance you can hold dumbbells, a barbell or weight plate on the top of your thighs. This exercise can also be done one leg at a time.
Most gyms offer a number of machines designed to work your calves in a seated position. The seated calf raise machine is commonly used to perform the seated calf raise, typically using weight plates or a weight stack for resistance. A Smith machine, which has a barbell that slides vertically up and down within metal rails, is another option for performing seated barbell calf raises. Other selectorized weight stack machines require you to sit in a slightly reclined position to perform bent-knee calf extensions to target the soleus. With this exercise you basically extend your ankles, push pedals forward against the resistance, then reverse the movement.
The soleus is made up of primarily type 1 slow twitch muscle fibers, according to Mike Behnken, NASM certified personal trainer. This type of muscle responds well to high rep sets under moderate tension for a long period of time. For maximum benefit, Ball recommends you perform sets with a high number of reps at a slow pace -- 30 seconds per rep -- using a full range of motion until fatigued.