Lunges are are generally performed to strengthen and sculpt the thighs and buttocks. While they may be considered a body weight exercise -- that is, an exercise that uses your body weight as resistance -- they can also be done while holding weights to increase the difficulty. Lunges make an effective warm-up exercise because they work large muscle groups, improve hip mobility and elevate heart rate. This exercise can be utilized to work out your hips, butt and several other muscles.
All three of the hip, or gluteal muscles, are worked out during lunges. The gluteus maximus is the primary muscle worked and is used extensively to extend the hips. You can target this muscle more intensely during the exercise by using very large steps. The gluteus medius and minimus work to level and stabilize your hips throughout the movement.
The quadriceps, or thigh muscles, are another primary muscle group worked with lunges. They can be worked more intensely by using smaller steps forward. All four of the quadriceps muscles work together to extend the knee during the upward phase of the movement. The hamstrings muscles work to dynamically stabilize the knee joint during lunges and also aid the gluteus maximus with hip extension.
Although lunges are typically thought of as a lower body exercise, they also do a number on a couple of abdominal muscles. The transverse abdominis muscle is used to compress and support the abdominal wall during the lunge movement. The obliques work hard to keep your torso upright and stable as you move your hips from side-to-side with each lunge step.
The gastrocnemeus and soleus muscles of the calf are both worked differently during lunges. The soleus is worked in the rear leg to plantar flex, or lift your heel off the ground. The gastrocnemeus is used to dynamically stabilize the knees throughout the exercise.
The lunge is considered a basic exercise, but you still need to be adamant about using proper form. Allowing your knee to move past the end of your toes during the exercise could result in knee injury. Because all of your weight is distributed on one knee at a time, it is important not to use heavy weights when performing lunges or injury may result.
Jen Weir writes for several websites, specializing in the health and fitness field. She holds a Bachelor of Science in exercise science from Montana State University, is an NSCA-certified strength and conditioning specialist and maintains a personal trainer certification from the American College of Sports Medicine.