JOURNAL OF SPORTS SCIENCE & MEDICINE
LOW HANDICAP GOLFERS GENERATE MORE TORQUE AT THE SHOE-NATURAL GRASS INTERFACE WHEN USING A DRIVER
Paul Worsfold, Neal A. Smith and Rosemary J. Dyson
University of Chichester, Chichester, West Sussex, UK
© Journal of Sports Science and Medicine (2008) 7, 408 - 414
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|The aim was to determine the rotational torque occurring at the
shoe-natural grass interface during golf swing performance with different
clubs, and to determine the influence of handicap and golf shoe design.
Twenty-four golfers (8 low 0-7; 8 medium 8-14; and 8 high 15+) performed
5 shots with a driver, 3-iron and 7-iron when 3 shoes were worn: a modern
8 mm metal 7-spike shoe, an alternative 7-spike shoe and a flat soled shoe.
Torque was measured at the front and back foot by grass covered force platforms
in an outdoor field. Torque at the shoe- natural turf interface was similar
at the front foot when using a driver, 3-iron and 7-iron with maximum mean
torque (Tzmax 17-19 Nm) and torque generation in the entire backswing and
downswing approximately 40 Nm. At the back foot, torque was less than at
the front foot when using the driver, 3-iron and 7-iron. At the back foot
Tzmax was 6-7 Nm, and torque generation was 10-16 Nm, with a trend for greater
torque generation when using the driver rather than the irons. The metal
spike shoe allowed significantly more back foot torque generation when using
a driver than a flat- soled shoe (p < 0.05). There was no significant
difference between the metal and alternative spike shoes for any torque
measure (p > 0.05), although back foot mean torques generated tended
to be greater for the metal spike shoe. The golf shot outcomes were similar
for low, medium and high handicappers in both metal and alternative spike
shoes (metal: 87%; 76%; 54%; alternative: 85%; 74%; 54% respectively). The
better, low handicap golfers generated significantly more back foot torque
(metal spike: 18.2 Nm; alternative: 15.8 Nm; p < 0.05) when using a driver.
Further research should consider back foot shoe-grass interface demands
during driver usage by low handicap and lighter body-weight golfers.
Key words: Cleat, golf, iron, shoe, spike, traction.
The golf swing, performed to project the golf ball into flight, is a complex dynamic movement. The degree to which the force produced by the body musculature is transferred to the ball depends upon the reaction force from the ground against the feet (Carlsoo, 1967). Traction at the golfer's feet has traditionally been achieved by using relatively long 6 or 8 mm metal spikes (Figure 1), which fix into the outer sole of the shoe in order to indent or penetrate the turf of the golf course. However, traditional metal spikes compress and grip grass roots, grass or soil, with the likelihood of creating spike marks. The increased popularity of golf has resulted in more surface damage to courses and putting greens (Hammond and Baker, 2002), and caused the wearing of traditional metal spike golf shoes on many courses to be forbidden or restricted. Such bans resulted in the development of alternative spikes for golf shoes, such as shown in Figure 2. Alternative-spike traction is provided by surface protrusions (or cleats) that penetrate only several millimetres into the turf, and were thought by Slavin and Williams, 1995 to be associated with a higher probability of slip. Some shoemakers incorporate additional raised mouldings of various designs between the spike positions to increase outer shoe sole traction during the swing in order to reduce the chance of the foot slip. The modern alternative spike sole design relies on surface area and form to grip the ground rather than long spikes. With the potential for injury and performance impairment arising from an accidental slip, in such a fast, powerful movement as the golf swing, there is the need for realistic, ecologically relevant testing to reassure and inform players, coaches and designers of the performance characteristics of modern golf shoe designs.
golf play, the better golfer is given a lower handicap which reflects
their golfing ability. The expectations and demands of the low handicap
golfer from footwear are likely to be different to those of a high handicap
player. The low handicap player is likely to perform fewer golf swings
but the needs for effective power generation, control and accuracy are
paramount. The game of golf also involves the selection of a number of
different types of club, designed to aid particular forms of ball flight,
in order to reach a hole with the lowest number of shots. The club used
for longest shots is the driver and it has the longest shaft and largest
club head. The 3-iron and 7-iron are metal irons, which have different
lofts to assist ball projectile flight. The 3-iron is often the longest
iron carried for long fairway shots. The 7-iron has a shorter shaft and
is used for medium to short approach shots. Knowledge of how these key
game factors interact during the performance of the golf swing, particularly
in relation to the torque generation at the modern golf shoe outer sole
to natural turf interface, would aid in questions arising concerning golf
shoe selection and design. Laboratory based human studies conducted on
artificial turf surfaces have underpinned the scientific knowledge (Barrentine
et al., 1994;
Dillman and Lange, 1994;
Hume et al., 2005;
Williams and Cavanagh, 1983).
This has inherent limitations because of the induced change in the mechanism
of outer shoe sole spike penetration and compression. Williams and Sih,
who investigated ground reaction forces when wearing different types of
golf shoes on artificial turf, highlighted the need for shoe assessments
to be made on a natural grass surface. Worsfold et al., 2007
have reported greater vertical ground reaction force in spiked golf shoes
at the shoe-natural turf interface when irons were used in comparison
to a driver. It was also noted that greater mediolateral forces occurred
across each foot when the driver was used in comparison to the irons.
Use of the longer driver club to achieve powerful distance shots involves
the generation of more rotational force, and this is likely to impact
and interact with maintenance of an adequate support base. Further research
is required to confirm the relevance of rotational force (torque) at the
shoe-natural grass interface during performance of the golf swing.
Twenty-four right-handed male golfers (mean mass 75.3 SD 9.1 Kg) volunteered for the study and all reported playing three times or more a month. Eight golfers had a low handicap (0-7), eight had a medium (8-14), and eight had a high handicap (15-26). Following university ethical clearance and consideration of the experimental procedural information, each subject provided written consent to participation. All participants were reminded that withdrawal from the study at any time without prejudice was possible. Subjects were allowed as much time as they needed to become accustomed (typically two hours) to the experimental shoes and environment.
The Mauchley's test of sphericity; Levene's test of homogeneity
and Kolmogorov-Smirnov test of normality all revealed non significant
findings. Straight shots were achieved in 89%, 71% and 46% of cases by
the low, medium and high handicap players respectively. The golf shot
outcomes were similar for the low, medium and high handicappers in both
the metal spike shoe (87%; 76%; 54% respectively) and in the golf shoe
with alternative spikes (85%; 74%; 54% respectively).
| In contrast
to previous research, this study examined ground reaction torque during
golf swing performance on a natural grass surface in an outdoor field setting.
The interaction of the shoe outer sole and spikes with the natural grass
turf will therefore have been quite different to studies which utilised
artificial surfaces (Barrentine et al., 1994;
Dillman and Lange, 1994;
Williams and Cavanagh, 1983).
In this study the metal or alternative spikes will have penetrated the grass
root structure and therefore the golf stance stability will have been supported
in the critical backswing and in the dynamic downswing and follow-through,
and it is likely this would be perceived by the golfer. The outdoor testing
location would also potentially better replicate the visual and long distance
shot natural to the golf course environment than an indoor testing station.
The more ecological approach to testing might also influence body posture,
with potentially shoe spike penetration and a longer distance visual focus,
influencing body posture and movement during the golf swing.
Previous research, using artificial surfaces indoors, focused on orthogonal ground reaction force, and reported maximal forces at each foot, and the weight transfer from the back foot during the backswing to the front foot in the downswing and follow-through (Barrentine et al., 1994; Dillman and Lange, 1994; Koenig et al., 1994; Williams and Cavanagh, 1983; Williams and Sih, 1998). Worsfold et al., 2007 discussed these previous studies and noted the predominant greater maximal front foot ground reaction force measures and asymmetric force generation pattern reported or summarised in most studies other than that of Barrentine et al., 1994. Worsfold et al., 2007 reported, for a natural turf based study of golf swing performance, that the maximal vertical forces were less when a driver was used (back foot 0.49 BW; front foot 0.84 BW) than when the 3-iron and 7-iron were used (back foot 0.82 BW; front foot 1.1 BW).
Although the levels of front foot Tzmax in this study (20 Nm approx) were similar to those reported from the artificial turf study by Barrentine et al., 1994, the reported similar torque levels of outward rotation at the back foot (peak 22 Nm) and front foot (peak 23 Nm) when using a driver, are not supported by this research. Barrentine et al., 1994 reported on handicap level in relation to torque and described similar maximal values for back foot and front foot in the range of 17-26 Nm for all handicaps when Goodyear welted golf shoes were worn. However for PGA and low handicap players, outward rotation was 17-18 Nm for the back foot, and 23-26 Nm at the front foot. Hence, within the better golfers in Barrentine et al.'s study there is evidence of slightly greater maximal outward rotation at the front foot compared to the back foot, but the front to back foot differences in the Tzmax values recorded in this current research were greater.
For all clubs in this natural grass turf based study, Tzmax was greater at the front foot (17-19 Nm) than at the back foot (6-7 Nm). The torque generated was also greater at the front foot (40 Nm) than at the back foot (10-16 Nm). The generated torque values reflected both the negative clockwise and positive anticlockwise rotations of the feet. For the back foot case, the differences between the two torque parameters in figures 7 and 8, for the driver, reflected the greater mean torque generated during the backswing in the metal spike shoe (8 Nm) in comparison to the alternative spike shoe (6 Nm). Worsfold et al., 2006a compared the metal 7-spike shoe and the alternative 7-spike shoe characteristics using mechanical testing methods on natural grass turf. In comparison to the alternative spike shoe the metal spike shoe provided more forefoot linear (7%) and rotational (31%) traction, and in complete foot to natural turf contact traction was greater for inward rotation (11%) and outward rotation (18%). Hence, the increased torque generation in the back swing observed when the low handicap players wore the metal spike shoe was likely to have been linked to the greater traction in outward rotation provided by the metal spike golf shoe outer sole on natural grass turf. Dillman and Lange (1994) cited research by Richards et al. (1985) which identified that low handicappers had more weight on the shoe heel at the top of the backswing, which would suggest they would be more dependent on complete outer shoe sole traction than less experienced golfers.
There is evidence that detailed dynamic numerical research analyses using groups of subjects can aid in the identification of shoe design characteristics influencing human movement during performance of a golf swing. An alternative 7-spike golf shoe was reported to allow the generation of significantly greater maximal vertical force and torque during golf swing performance with a driver on natural turf than an alternative 6-spike shoe design which had one less alternative spike in the central forefoot toe position (Worsfold et al., 2006a). Case study approaches (e.g. Williams and Sih, 1998) and qualitative observational reports without descriptive statistics or statistical analyses (Koenig et al., 1994), can result in the basis of knowledge being anecdotal in nature (Worsfold et al., 2007).
In this research when using the driver club, better low handicap golfers generated more torque in each type of shoe at the back foot (Table 1). When driving, the difference in torque generation with the metal spike shoe (18.2 Nm) compared to the alternative spike shoe (15.8 Nm), was likely to be linked to the different outer shoe sole performance characteristics determined during mechanical testing.. The metal 7-spike and alternative 7-spike shoe in this investigation provided good traction, and slip did not occur. However this research has shown that, at the back foot the torque generation was greater in the metal spike shoe, and this was particularly of value to low handicap players who had greater torque generation demands. It is recommended that golf shoe designers should consider designing outer sole traction to particularly cope with the torque demands at the back foot interface when low handicappers perform long distance shots with a driver, especially since only approximately 0.5 BW peak vertical ground reaction force acts through the back foot and weight transfer also occurs. In future research and design, consideration should also be given to low handicap golfers of lighter body weight to ensure that their specific torque generation requirements at the back shoe-natural grass interface are addressed.
This experimental research study has revealed that the anecdotal increased force associated with golf driver usage compared to iron usage is misleading, and that the rotational force (torque) generated at the shoe-grass interface is an important component when using the driver. However, ground reaction force variations are important in maintaining stability, and in weight transfer patterns (typically peak 0.3-0.4 BW between feet) that are potentially important in golf coaching (Worsfold et al., 2008) and improving performance.
The results of this experimental study need to be borne in mind when considering the advisability of determining golf shoe selection on indoor testing of golf swing performance, particularly if artificial grass surfaces (or carpet, smooth flooring) are involved in the process. Inclusion of natural grass turf within a testing facility could vastly improve the applicability of golf shoe evaluation and selection.
|During the golf swing there is considerable torque generation at the golf shoe-natural grass surface interface. For the driver, 3-iron and 7-iron, the maximal torque (17-19 Nm) and torque generated (40 Nm approximately) were greater at the front foot than at the back foot (6-7 Nm and 10-16 Nm respectively). When using the driver, the metal spike shoe allowed the generation of significantly more torque at the back foot than a flat sole shoe, supporting the importance of outer sole traction in driver swing performance. Also when using the driver, low handicap golfers generated more torque than both the medium and high handicap players. Golf shoe designers should consider designing outer sole traction to particularly meet the demands at the back foot outer sole-natural grass interface when low handicap and lighter body weight players perform distance shots with a driver.|
|We would like to thank Adidas for providing footwear for this
research, and financial support was provided by the University of Chichester.
Dr Paul Worsfold is now working at the University of Chester, Chester, Cheshire,
Employment: Lecturer in biomechanics. University of Chester.
Degree: BSc (Hons), PhD.
Research interests: Sports footwear design and development, biomechanics of soccer, cycling and golf, and notational analysis in sport.
Employment: Senior lecturer in biomechanics, University of Chichester.
Degree: BSc (Hons), MSc, PhD.
Research interests: Footwear design and ergonomics, non-linear movement analysis, and biomechanics of soccer and racket sports.
Employment: Reader in Sports Science, University of Chichester.
Degree: BSc (Hons), PhD.
Research interests: Neuromuscular physiology/ biomechanics and water based activities.