A calf raise is a common resistance exercise that strengthens the muscles of the lower leg through a motion called plantar flexion. This movement involves extending the ankle joint to point the toes and lift the heel, which is the action used when standing on the balls of the feet. People incorporate calf raises to build strength for activities like running, jumping, and walking, or to improve the overall appearance and stability of the lower limbs. Understanding which muscles are responsible for this action is key to effective training.
The Primary Movers: Gastrocnemius and Soleus
The back of the lower leg is home to a powerful muscle group known as the triceps surae, which literally means “three-headed calf.” The primary components of this group are the two largest muscles, the gastrocnemius and the soleus, which provide the force for the calf raise movement. These two muscles merge together at the bottom of the leg to form the Achilles tendon, the body’s thickest tendon, which ultimately attaches to the heel bone (calcaneus).
The gastrocnemius is the more superficial muscle, creating the visible, diamond-shaped bulk of the calf. It is a two-headed muscle that originates from the femur, or thigh bone, just above the knee joint. Because of this high attachment point, the gastrocnemius crosses both the knee joint and the ankle joint. This positioning influences its function, as it acts as a plantar flexor at the ankle and a flexor at the knee.
Lying underneath the gastrocnemius is the soleus muscle, which is flatter and wider. The soleus originates lower down on the leg, attaching to the tibia and fibula below the knee joint. Unlike the gastrocnemius, the soleus crosses only the ankle joint, making it a single-joint muscle. This difference explains why the two muscles respond differently to variations in the calf raise exercise. The soleus has a high proportion of slow-twitch muscle fibers, suggesting it is built for endurance and sustained activities like walking and maintaining posture.
Targeting Specific Muscles: The Role of Exercise Variation
The position of the knee joint during a calf raise determines which of the two primary muscles is most actively recruited. This mechanical difference allows for targeted training of the gastrocnemius or the soleus. The common standing calf raise is performed with the knee completely straight, which places the gastrocnemius in a position where it can generate maximum force. With the knee extended, the muscle is stretched across both joints, allowing it to fully contribute to the plantar flexion motion.
Conversely, the seated calf raise is performed with the knee bent, typically at a 90-degree angle. This bent-knee position effectively shortens the gastrocnemius muscle across the knee joint, which significantly reduces its ability to contract forcefully. This phenomenon is known as active insufficiency, where a multi-joint muscle cannot exert its full force because it is already shortened over one of its joints.
When the gastrocnemius is mechanically disadvantaged in the seated position, the workload shifts almost entirely to the soleus. Since the soleus only crosses the ankle joint, its function is not affected by the bend in the knee, making it the primary mover in a seated calf raise. Therefore, incorporating both standing and seated variations into a routine ensures comprehensive development of both the superficial and deeper calf muscles. This variation in joint angle is the most effective way to selectively focus on the strength and size of each muscle.
Supporting Muscles and Joint Action
The fundamental motion of the calf raise is plantar flexion, the anatomical term for pointing the foot downward away from the shin. While the gastrocnemius and soleus are the main engines, several smaller, deeper muscles also contribute to the action or help stabilize the ankle and foot. These supporting muscles ensure the movement is smooth and controlled, maintaining balance throughout the exercise.
One assisting muscle is the plantaris, a long, thin muscle with a slender tendon that runs between the gastrocnemius and soleus. While small and sometimes absent, the plantaris works alongside the larger muscles to assist with both plantar flexion and knee flexion. Its contribution to power is minimal, but it is anatomically part of the posterior lower leg.
Another supporting muscle is the tibialis posterior, located deep within the calf compartment. The tibialis posterior plays a significant role in stabilizing the ankle and supporting the medial arch of the foot during the calf raise. It helps to invert the foot (turn the sole inward), which is necessary to maintain proper alignment as the heel rises off the ground. These smaller, deep muscles are responsible for the stability and finer control of the foot and ankle, complementing the raw power generated by the primary calf muscles.