Washington, July 30 : A study on players'' golf swings has revealed several biomechanical factors that help identify the duffers from the pros.

Researchers at the Stanford University School of Medicine have for the first time identified several key rotational-biomechanic elements of the golf stroke in its entirety, from backswing to follow-through, were analysed, and then the data were used to generate benchmark curves.

Jessica Rose, PhD, associate professor of orthopaedic surgery and senior author of the study, and colleagues found that swing biomechanics were highly consistent among a group of professional players.

At certain phases of their swings, their movements were almost indistinguishable from one another.

"The set of biomechanical factors we examined were selected to capture the essential elements of power generation," Rose said.

The findings could be used to help improve golfers'' ability to hit the ball farther and do so without increasing their risks of injury.

Researchers collected data for the study using an array of eight special digital cameras in the Motion and Gait Analysis Laboratory at Lucile Packard Children''s Hospital at Stanford.

They recorded three-dimensional motion images of the golf swings of 10 professional and five amateur male players.

Among the five non-professional golfers, one was a college-level amateur with a handicap of 4; two were amateurs with handicaps of 15 and 30, respectively; and two were novices.

Researchers analysed several biomechanical elements of subjects'' golf swings, including S-factor (tilt of the shoulders), O-factor (tilt of the hips) and X-factor - the relative rotation of the hips to the shoulders, measured in degrees - which is considered key to power generation.

Among the 10 pros in this study, peak X-factor during a hard swing was highly consistent, varying just 7.4 percent from a mean of 56 degrees. Their club speeds at impact with the ball also were highly consistent, varying just 5.9 percent from a mean of 79 mph.

In contrast, peak X-factor of the three least skilled amateurs - the handicap-30 golfer and two novices - fell below the professional range: 48, 46 and 46 degrees, respectively.

These smaller X-factor angles correlated with slower club speeds at impact: 68, 66 and 56 mph, respectively.

In addition, the study describes S-factor, a term coined by the researchers, for the first time. S-factor is the angle or tilt of the leading shoulder relative to the level position.

The researchers found that peak S-factor occurred right after impact and was highly consistent among the pros, varying just 8.4 percent from a mean of 48 degrees.

The handicap-15 player and two novices had lower S-factors of 42, 42 and 33 degrees, respectively, while S-factors of the handicap-4 player and handicap-30 players both fell within the professional range.

The study also found that peak free moment - the golfers'' turning force, or torque, measured using a special scale - was highly consistent among the pros, varying only 6.8 percent from a mean.

"Peak free moment, X-factor and S-factor are highly consistent, highly correlated to [club head speed at impact], and appear essential to golf swing power generation among professional golfers," the authors concluded.

The findings have been published online July 29 in the Journal of Applied Biomechanics. (ANI)