Lunges are a compound exercise, which articulate your knee and hip joints and activate over 10 different muscles in your lower body. The primary muscles used in lunges are your quadriceps. Each quadricep muscle comprises four smaller muscle segments, which attach to different parts of lower body skeletal structures. Take shorter lunge strides to maximize quadriceps activation while performing lunges. Increase the intensity of your lunges by holding a set of dumbbells or loaded barbell.
The rectus femoris muscle is one of the quadriceps muscles, which extends from your pelvic bone to the base of the patella at each knee. This muscle works in conjunction with the other quadriceps muscles to extend your knee while performing lunges. Flexing your hips to lower your body while lunging also recruits the rectus femoris. The rectus femoris is a particuarly powerful knee extender when your hips are extended, and it is the only quadriceps muscle that crosses your hip joint. Flexing your hips weakens the knee extension strength of the rectus femoris.
The vastus lateralis is the outermost segment of your quadriceps, which extends from the outer top of each femur bone to the patella at your knees. You can feel your vastus lateralis by touching the outside top of your thighs. The vastus lateralis is particularly helpful for extending your knees when your knees are flexed. Extending your knees as you raise your body during lunge exercises activates the vastus lateralis.
The vastus intermedius is an inner segment of your quadriceps, which is located deep in your thighs and underneath the rectus femoris muscle. Your vastus intermedis extends from the front top of your femur to your knees. Extending your knees as you raise your body during lunge exercises activates the vastus intermedius. The vastus lateralis works in sync with the vastus laterlis, and provides part of the force required to extend your hips when your knees are flexed.
The vastus medialis is the innermost segment of your quadriceps. Like the other segments of your quadriceps, the vastus medialis helps extend your knees while lunging. The portion of the vastus medialis that is immediately above your knees, the vastus medialis oblique, is particularly important for stabilizing your knee joints. The oblique portion of your vastus medialis has a teardrop shape. The vastus medialis adds most of the definition and mass to the inner legs.