The Application of Sports Science to the Golf Swing
By Eanna Rushe MS, CSCS, CGFI, MES
At the elite level the full golf swing is a marvel of science and technique. We look at professionals on the PGA and LPGA tours and wonder how do they drive the ball so far. There are many contributing factors, for example, equipment, physical conditioning and of course raw talent. Less obvious is the biomechanics of the golfers motion.
Biomechanics is the analysis of human motion that blends physics and physiology. It allows us to measure movement patterns and body segment speeds in the golf swing. For example, if you videotape your golf swing you don’t know how fast your hips are rotating or how fast the club shaft is releasing. Doing a biomechanical analysis of your golf swing allows us to quantify your golf motion in terms of how fast each body segment is moving, how you are creating power and if there are significant power leaks. When you look at a biomechanical model of a tour pro or long drive champion it becomes pretty apparent why they drive the ball so far. Their motion is highly efficient with very little power leakage.
Power Generation Process – Kinetic Link Concept
The kinetic link (sometimes referred to as the kinematic sequence) is the concept upon which speed or power is created. This concept applies to all hitting or throwing sports and it involves speed/momentum transfer from the large body segments to the smaller body segments. The golf-specific kinetic link can be visualized as a system composed of four segments and three links. The segments are the hips segments, the shoulders segment, the arms segment and the club shaft. The links are the muscles that connect each segment. For example, the trunk muscles connect the hips segment to the shoulders segment. Before the backswing is completed efficient golfers are already starting the downswing from the ground up. As their feet push into the ground forces are created that starts to accelerate their hips towards the target. This should not be interpreted as a big, wild leg drive. In fact quite the opposite is happening. It is a very tight, controlled motion. Once the hips reach their maximum speed they start to slow down or decelerate. This “braking” action transfers speed to the shoulders segment, which accelerates to a maximum value usually twice that of the hips. As the shoulders segment reaches peak speed they start to decelerate. Speed is now transferred to the arms, which accelerate even faster. As the arms are approaching impact they decelerate rapidly transferring a huge amount of speed or momentum to the club. The club then releases or uncocks into impact with maximum velocity. It is interesting to note that the arms reach peak speed before impact not at or after impact.
Common power leaks include:
- Hip Slide
- Hip Spin
A Hip Slide occurs when the hips move laterally or slide from right to left during the downswing. No rotational hip speed is created. Often times the hip slide is accompanied by a spine tilt to the right side. Now the muscles on one side of the trunk are lengthened while muscles on the opposite side of the trunk are shortened. This asymmetry causes inefficient power generation.
A Hip Spin occurs when the golfer tries to excessively rotate the hips on the downswing. Now the lower body outraces the upper body and too much lag is created between the hips and the shoulders. The potential energy that could have been used to accelerate the shoulders is wasted and power is lost.
An “Arm-Push” pattern occurs when the arms do not decelerate or slow down rapidly before impact. The arms are forcing or pushing the club through impact. In many cases the arms reach peak speed after impact. This action disrupts the normal speed transfer process from arms to club. The club release speed is significantly decreased and potential power is lost.
Hold the Angle
When we look at the motion of efficient golfers on videotape it appears that they are “holding” the club shaft in a cocked position deep into the downswing. Many amateurs in an attempt to create more power try to emulate this action. What you have to understand is that efficient golfers do not manufacture or try to hold this cocked position. The arms accelerating around the axis of the trunk on the downswing create this club lag or cocked position. When the arms decelerate before impact speed is transferred to the club. The club accelerates and the angle between the arms and club shaft increases rapidly into impact.
About the Author
Eanna Rushe is the founder of BioSport Technologies located in Greenwich, CT. He specializes in 3-D biomechanical analysis for golf and other sports, athletic development and sports performance enhancement. Eanna has a master’s degree in sports science. He is a certified strength & conditioning specialist. Eanna is also a member of the International Society of Biomechanics in Sport. He can be reached at 203-661-8330. The author would like to acknowledge Chris Welch for biomechanics references.