TIGER WOODS June ’15 - an ANATOMICAL & BIOMECHANICAL Analysis SIMPLIFIED
[By a golf instructor with BS (physics, math); MS (sports science ie anatomy, orthopedic assessment, biomechanics, exercise physiology, exercise testing & prescription, sports nutrition etc.); PhD (biomechanics - student).]
Musculoskeletal Anatomy = the study of the structure and capabilities of individual bones, muscles, joints (mostly at joint/segment level)
Biomechanics = the study of the structure and function (mostly at entire-limb or whole-body level) of living organisms
Address: Trail shoulder and knee forward of lead side = CANNOT make a PURE rotation of hips/trunk. Also, ANY forward bend of the spine AT ALL prevents pure rotation - an upright posture is more efficient and safer.
[PURE ROTATION is the only body movement which can give BOTH distance and direction through a summation-of-speeds principal. See: http://epublications.bond.edu.au/cgi/viewcontent.cgi?article=1376&context=hsm_pubs]
Backswing club parallel to ground: Trail shoulder already in internal rotation (will need a re-route to help club arrive from the inside). Trail pelvis raised (as seen from drop of lead knee), so the hips now cannot rotate into the downswing.
Backswing lead-arm parallel to ground: More shoulder internal rotation, more trail pelvis rise. Downswing squat position already beginning. Such a position only serves to ram the hip ‘socket’ (acetabulum) more firmly onto the ‘ball’ of the thigh bone (femur head). Once again pure rotation cannot result, the trail hip has to push the body forward to start lower-body motion.
Backswing Top: With a lot of wrist-bend resulting in a horizontal shaft, the golfer must do work against gravity to get the club and hands back to a position of maximum gravitational potential energy. Such a position is a WASTE of EFFORT!
Downswing lead-arm parallel to ground: From the top of Tiger's backswing, a lot of wasted effort results in getting the club to this position, which is finally one where his hands and the club are in a position of Maximum Gravitational Potential Energy and can do useful, TARGETWARD WORK (application of force over a distance).
With the terrific squat maintained at this stage by Tiger (OUCH say his back, hips and knees) hip/trunk rotation will be difficult and/or highly contrived, not natural.
Downswing club parallel to ground: The hips have spun open to a great extent, while the shoulders have stayed closed. Such a position requires exaggerated forward-flexion along with torquing of upper- and lower-spine in opposite directions (not to mention the neck in a third!) and causes a lot of low back issues.
Downswing pre-impact: Each golfer’s brain makes its own most-convenient compensations to allow a reroute-of the trail shoulder from internal rotation and a rotation of the pelvis from a lateral flexion (side-bend). Here, Tiger arches his spine to create space for the trail elbow to straighten in a manner closer to that elbow's design.
The trail knee juts out, a sign that if the arms were to straighten right now the club would not be delivered sufficiently 'from the inside' (see previous post for more on this topic). When the trail knee and thigh are pushed forward so much, the trail shoulder arrives at the ball 'internally rotated', as indicated by very rounded shoulders at impact, and thus a 'BS' impact. [According to this blog, unless the club arrives well from the inside, a ‘bludgeon’ or ‘smother’ results, not PURE IMPACT see https://www.youtube.com/watch?v=UosXcURDg0Y]
Impact: The combined length of the lead shoulder and arm at impact is a sign of better utilization of ground-reaction-force and makes a longer lever - some term it 'going normal'. Both are indications of better distance potential. HOWEVER, from the deep squat that Tiger gets into, there is not enough time to straighten out the torso maximally, so at impact he does not have as much height as he possibly can with a straighter starting posture and less squat-jump (the 'jump-up' part needs a very strong and young golfer to accomplish along with everything else a downswing must, within a 1/4 of a second!).
Also, the quantity of motion each body part has, eventually gets transferred to the ball. This 'quantity' is termed 'angular momentum'. In a swing in which the trail shoulder or hip move nearer and further from the position of the golfer's spine at address, the direction in which the 'quantity of motion' acts continually changes, much like spinning top gains wobble.
INCONSISTENCY and INJURY BOTH result from both excessive, useless motion AND from poor joint positions. It’s all very well to say ‘move the body thus’ or the ‘let the club do such-and-such’ However, the MIDDLE JOINTS such as the hips, knees, elbows and wrists get badly ‘jammed’ in the process. The 21st Century golf instructor needs a very sound understanding of not just the biomechanics of limb/whole-body structure but also of joint/segment level structure and function.