Muscle activity during the golf swing (P2)
The acceleration phase starts from the horizontal club to the impact of the ball (late part of down swing). This phase of the swing sees the pectoralis major muscle bilaterally being the most active muscle (93% MMT bilaterally) in the upper body. On the right side, the second most active muscle is the upper serratus anterior (69% MMT). On the left side, the levator scapulae is the second most active muscle (62% MMT).
In the lower body, the acceleration phase sees the left biceps femoris (83% MMT) being the most active muscle with the left upper and lower gluteus maximus, along with the vastus lateralis being the second most active muscles (58% MMT). On the right side, the abdominal oblique (59% MMT) is the most active muscle, followed by the gluteus medius (51% MMT).
Early follow through
The early follow through starts at impact to when the club is horizontal to the ground. In the upper body, the most active muscle during the early follow through is the pectoralis major bilaterally (74% MMT), followed by the right subscapularis (64% MMT) and the infraspinatus on the left (61% MMT). The most active muscle in the lower body during the early follow through is the left long head of biceps femoris (79% MMT), and left vastus lateralis (59% MMT). The right gluteus medius (59% MMT) is the most active right sided muscle, followed by the abdominal oblique (51% MMT).
Late follow through
The late follow through starts when the club is horizontal to the ground and ends at the completion of the swing. The most active muscles in the upper body during the late follow through on the left are the infraspinatus (40% MMT) and the pectoralis major (39% MMT). On the right side, the most active muscles are the subscapularis (56% MMT), followed by the upper and lower serratus anterior (40% MMT).
In the lower body, the most active left sided muscles are the semimembranosus and vastus lateralis (42% MMT each), followed by the adductor magnus (35% MMT). On the right, the vastus lateralis muscle (40% MMT) is the most active muscle followed by the gluteus medius (22% MMT).
The classic golf swing, predominantly used in the early part of the twentieth century, involved a relatively equal amount of lumbopelvic and shoulder rotation during the back swing. The follow through position was characterised by a relatively neutral spinal position and the momentum of the player moving forward.
The modern golf swing was made popular by Jack Nicklaus and is currently used by most current professional players. It involves a limited lumbopelvic rotation in the back swing resulting in a greater relative rotation of the torso compared with the classic swing. The follow through is characterised by a hyperextended spinal position, known as the reverse ‘‘C’’.
The momentum is directed upwards. This swing is thought to deliver more power to the shot and a higher ball trajectory. It is the most popular golf swing, both in the professional and amateur ranks.
The clinician often sees patients presenting with a golf related injury. Many of these injuries occur as the result of golf swing mechanics and are soft tissue injuries. An understanding of golf swing mechanics is important in determining the aetiology and management of golf related injury. The back swing is characterised by a rotation of the shoulder girdle to the right, with right arm abduction flexion and external rotation and corresponding left arm adduction, flexion and internal rotation to take back the golf club. The right scapula retracts and the left scapula protracts as they move around the trunk in a clockwise movement. Thus the muscles most active in the back swing are located in the upper body. The upper and middle trapezius are the most active muscles on the right. On the left side, the subscapularis and serratus anterior muscles facilitate internal rotation of the arm and protract the scapula.
The lumbopelvic region has limited rotation to the right in the modern swing, with the pelvic muscles providing a stable base for the trunk to rotate. The lumbopelvic movement results from hamstring group activation as the body weight transfers to the right side. The left oblique also contracts to aid this trunk rotation in the back swing.
The down swing is often reported as being made up of two arbitrary components, the forward swing (the early down swing) and the acceleration phase, which begins when the club is parallel to the ground. The early phase of the down swing is characterised by the return of the body back to the ball in preparation to hit it. In the modern golf swing, the hip initiates this movement and rotates the pelvis to the left. The right gluteals are very active in the extension of the right hip. The right biceps femoris contracts strongly to aid in the transfer of body weight back to the left side. The left pelvic muscles are active to provide a pivot point for the left lumbopelvic rotation, and weight transfer is enhanced by the activity of the vastus lateralis and adductor magnus.
In the upper body, the arms rapidly return the down swing in preparation to hit the ball. This combined movement of left rotation of the shoulder girdle and scapular rotation in an anti-clockwise direction around the trunk results in large activity of the left medial scapulae stabilisers/retractors. Muscle activity on the right side is high in the pectoralis major in the initiation of internal shoulder rotation and flexion, and the upper serratus anterior contracts to assist scapular protraction.
The acceleration phase of the golf swing continues the down swing to the ball impact. This phase of the swing is the most active phase of the entire golf swing. The major movers of the shoulder girdle, the pectoralis, are the most active muscles. The right side continues the activity achieved during the early down swing, while the left pectoralis appears to maintain an eccentric contraction to control the left arm abduction and external rotation. On the right side, the upper serratus is still active to protract the scapula. On the left side, the levator scapulae are also active to help with the scapular tilting. In the forearms, there is what is termed the ‘‘flexor burst’’ during this phase. This refers to a large increase in wrist flexor muscle activation just before the point of impact.
The acceleration phase also sees activity of the lower body, which is characterised by the left lateral leg and lumbopelvic stabilisers being strongly activated. The muscles are active to provide a solid base for subsequent rotation of the trunk in the process of hitting the ball. On the right side, the obliques are the most active muscles and assist the rotation of the trunk back to the ball from the right rotated (back swing) position. At the level of the hip, the gluteus medius is also active to aid in this rotation.