The back leg is extended and positioned behind the body. The back foot may face forward, or to the side at up to a 45 degree angle. The back knee may be slightly bent, or bent quite a bit and lowered down nearly to the floor, depending upon the strength and knee flexibility of the exerciser.
The upper torso is kept erect and centered over the hips. Look straight forward and keep the head lifted. The arms and hands may take a variety of positions.
The lunge exercise works the muscles of the thighs, buttocks. hip flexors and extensors, calves, lower back, and the hamstrings. All lunges primarily strengthen the muscles of the front of the thigh (quadriceps).
The lunge exercise is often performed using one's bodyweight alone; however, many athletes hold dumbells, kettlebells, or barbells in their hands as they step forward into the lunge position and then back to a standing position.
Yoga uses many lunge postures: Warrior poses (Virabhadrasana), Cresent Moon (Anjaneyasana), Equestrain (Ashwa Sanchalanasana), etc. The Equestrian pose also stretches the illio psoas muscle in the back leg side.
Tai Chi Chuan uses many forward lunge postures: Parting the Wild Horses Mane, Brush Knee, Single Whip, Ward Off, Fair Lady Works the Shuttles, etc.; and side lunge postures: Lazily Tying the Coat, etc.
Taijiquan and yoga lunge poses often do not drop the back knee so low the ground, tend to keep the back leg straighter with the knee slightly bend, and the back foot at an angle. This position is much safer for older persons. Bodybuilders, weightlifters and younger active athletes tend to keep both feet facing forward, dip the back knee closer to the floor, and hold dumbbells in their hands.
Lunge Exercises: Videos, How To, Safety Tips and More. By Mike Behnken.