The Biomechanics of a Tiger

This is the 3rd of a three part series on Excellence through an examination of Tiger Woods.

It is well known that the displacement of a golf shot is a direct function of the club head velocity (CHV) at the point of impact. Now, Linear CHV however, is a function of angular velocity of the club head and the length of the arm-club lever at the point of impact. While the length of the arm-club lever can only be minimally modified, the angular velocity of the club head can greatly be influenced by the body’s mechanics.

A golf swing can be broken down into 5 phases:

Takeaway
Backswing
Downswing
Acceleration
Follow-through

Very little occurs during the takeaway.

At the top of the Backswing, limited hip ER or Tibial IR will be revealed if the lead leg’s heel lifts off the ground. In addition, if the trail hip IR is decreased, the ASIS will rotate in a posterosuperior direction, and the knee will extend from the desired 20 deg of flexion. Significant activity from certain musculature is requried:

Lead Arm – Subscapularis and Serratus Anterior
Trail Arm – Upper Trapezius
Lead Side – Erector Spinae and Obliques
Trail Side – Biceps Femoris

During the Downswing, 2 levers (arms, club), 1 pivot (shoulders), and 1 hinge (wrists) are involved. The wrists are a major contributor of CHV. The Trail-side hip extensors, ABDuctors and lead-side Adductor Magnus initiate pelvic rotation. Eccentric trunk musculature contraction initiates the Downswing sequence. One of the most important aspects of this phase is that:

Pelvic Rotation initiates before Backswing is complete

Again, significant musulature activity is required.

Lead Arm: Subscapularis and Latissimus are very active
Pectoralis major becomes very active at 1/2 way
Trail Arm: Subscapularis, Latissimus, Pectoralis major are very active
Serratus Anterior, lead Rhomboid, and Levator scapula are active throughout

During the Acceleration phase muscle contributions include:

Lead Arm: Latissumus, Pectoralis, Rhomboids, Mid-Trapezius
Trail Arm: Serratus Anterior
Lead Side: Adductor Magnus, Biceps Femoris, Gluteus Maximus
Trail Side: Gluteus Maximus, Biceps Femoris, Obliques

It has been reported that wrist cocking is the strongest determinant of CHV (60% of variance between golfers)

As with most sports, in order to achieve maximal terminal velocity, a proper sequence of movement is required, such that

HIP ROTATION MUST PRECEDE SHOULDER ROTATION

(aka proximal to distal sequence)

Similar to the biomechanics of throwing, the purpose of the Follow Through in golf is to decelerate the body via eccentric contraction. Here, eccentric strength is required in the external hip rotators of the lead leg, and external glenohumeral rotators of the trail arm.

Flexibility is also important since the length of the Backswing has been shown to directly correlate with ball distance. Further, hip ROM should be emphasized rather than lumbar ROM. The “core” musculature should actually act as a hoop of stiffness that utilizes the recoil from the stretch of connective tissue secondary to the backswing. Not only will this save the low back from injury, but it will also enable the Ground Reaction and lower extremity forces generated to be transmitted to the hands and subsequently the head of the club.

I will elaborate on the injuries associated with improper mechanics in a future post, however, please take the time to enjoy a moment of excellence by viewing this video of Tiger in slow motion.

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