Good-morning
The movement of the Good Morning exercise resembles bowing to greet someone "good morning". It involves the hamstrings but is primarily used to strengthen the lower back.
The degree of knee bend used will change the focus. Nearly straight-legged involving the hamstrings most.
Importance
The good-morning is an essential exercise in the Westside Barbell method and is often trained to near limit maximums. Developing strength in the lift aids in the recovery of a "bad" squat, reducing the risk of injury. Properly applied, it can also strengthen an individual's deadlift; for this reason, it is a key exercise in the conjugate method of training this lift.
In Olympic weightlifting, the good-morning is used as the most efficient assistance exercise to train the second phase of the clean or snatch pull and bases of squat positions in snatch drops and clean squat positions. In this variation, the lifter will descend, reverse direction, and accelerate the ascent, rising up onto the toes at the conclusion of the lift. This mimics the rapid hip extension and subsequent toe-rise during the clean and jerk or snatch.
Form
The lifter starts with barbell or two dumbbells are held on his shoulders, behind his head. The lifter bends forward, bowing at the hips while keeping the back straight. The motion is at it's half way point when the lifter's torse is almost parallel with the ground, after which he returns to the upright position.
The spine does not twist or round at any point during movement. The lifter should rather concentrate on pushing the hips back while keeping the spine straight or arched.
Safety
The good-morning is a controversial exercise as some will claim that it leads to lower back injuries. Famously, Bruce Lee seriously injured himself while performing the exercise after an inadequate warm-up and overconfidently selecting his working weight. On the other hand, the good-morning can also strengthen the lower back and prevent injury when properly applied.
Rounding the back can result in back injuries. To aid in preventing a rounded back, the lifter's chin should remain upright. A common technique is to focus the eyes on a spot at about belt height during the lift, reversing direction after lowering when a eyes come in line with the spot. At the bottom of the range of motion, this keeps the chin up and the head tilted back, facilitating a flat or slightly arched spine.