The forward lunge is a popular unilateral exercise involving stepping one leg forward, lowering the hips until both knees are bent at approximately a 90-degree angle, and then pushing back to the starting position. This movement is highly functional, mimicking daily activities like walking and climbing stairs. While the lunge strengthens the lower body, its central function is to build strength and stability in the large muscles of the hip and thigh. The calf muscles play only a secondary, supporting role.
Primary Muscle Groups Targeted by the Lunge
The main driving force behind the lunge comes from the muscles that extend the hip and the knee. The quadriceps, a group of four muscles on the front of the thigh, are heavily recruited in the lead leg, especially during the eccentric phase, which is the controlled lowering of the body. They work to manage the deceleration of the knee joint as the body descends toward the ground.
The gluteus maximus is a prime mover responsible for hip extension, contributing significantly to the powerful push-off phase that returns the body to standing. Its activation is particularly high in the lead leg as it generates force against the ground. The hamstrings, located on the back of the thigh, also contribute to hip extension, assisting the glutes and helping to stabilize the knee.
The gluteus medius, located on the side of the hip, works constantly to stabilize the pelvis and prevent the lead knee from collapsing inward. This emphasis on unilateral stability is what sets the lunge apart from bilateral movements like the squat.
The Calf Muscles’ Role: Stabilization, Not Power
The calf muscles, comprised of the gastrocnemius and the soleus, are active during the lunge, but their role is primarily one of dynamic stabilization. They maintain balance and control the ankle joint throughout the entire movement. Electromyography studies suggest that the gastrocnemius typically achieves only moderate activation, often around 20 to 25 percent of its maximum voluntary force.
The gastrocnemius is a biarticular muscle, meaning it crosses both the knee and ankle joints. During the lunge, since the knee is flexed, the gastrocnemius is in a shortened position, which compromises its ability to produce maximum force. The soleus, which sits beneath the gastrocnemius and only crosses the ankle, also contributes to stability, especially in managing the slight forward and backward movement of the shin.
Significant calf development requires a large amount of plantar flexion, the action of raising the heel. The lunge movement, however, does not require the ankle to move through a large range of plantar flexion under high tension. Instead, the focus is on dorsiflexion, the bending of the ankle toward the shin, as the lead knee travels forward over the foot during the descent. Because the calves are not the force-generating muscles for lifting the body, the lunge is inefficient for prompting calf muscle growth.
Best Exercises for Calf Development
To specifically target the calves for strength and size development, exercises that maximize the range of motion in plantar flexion are necessary. The two main muscles of the calf require different approaches due to their attachment points. The gastrocnemius is best trained when the knee is kept straight, which puts the muscle in a mechanically advantageous position to generate maximum force.
Standing calf raises, where the legs are straight, are the most effective exercise for isolating the gastrocnemius. To maximize muscle recruitment, it is important to perform the movement slowly, ensuring a full stretch at the bottom and a momentary pause at the peak contraction. Conversely, the soleus is best isolated with bent-knee exercises, as this position relaxes the gastrocnemius.
Seated calf raises, where the knee is bent at a 90-degree angle, primarily target the soleus muscle. This deep calf muscle is important for endurance and ankle stability, and it responds well to higher repetitions. Achieving a full range of motion and avoiding bouncing motions at the bottom is important to ensure the muscle, rather than the Achilles tendon, is doing the work.