Relationships Between Field-Based Measures of Strength and Power and Golf Club Head Speed : The Journal of Strength & Conditioning Research

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Original Research

Relationships Between Field-Based Measures of Strength and Power and Golf Club Head Speed

Read, Paul J.1; Lloyd, Rhodri S.2; De Ste Croix, Mark1; Oliver, Jon L.2

Author Information
Journal of Strength and Conditioning Research 27(10):p 2708-2713, October 2013. | DOI: 10.1519/JSC.0b013e318280ca00
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Abstract

Introduction

The primary goal of the golf drive is to maximize displacement of the golf ball, which is a direct function of linear velocity at the point of impact between club head and the golf ball (14). An established method of measuring golf driving performance has been to determine the magnitude of club head speed (CHS) (5,7,11,16,17), which is dependent on many factors including the amount and direction of ground reaction force produced (1), and the use of the kinetic chain sequencing (28).

Within the available literature, increases in CHS have been reported after strength training and plyometric interventions (5,7), correlating with lower handicaps (8), and overall golf performance (31). Despite the apparent associations between physical abilities and golf drive performance, reliable field-based assessments to predict CHS remain unclear. Previous investigations to determine the strength, flexibility and power characteristics of elite golfers have demonstrated high reliability (25). However, 15 tests were used and a number of the measures required specialist laboratory-based equipment, which may have time and cost implications. Therefore, the development of an effective or efficient range of field tests with high levels of validity and reliability will allow effective long-term tracking of athletic development within elite golf programs.

Investigations into the relationships between physical performance and CHS have involved a range of approaches. Keogh et al. (16) analyzed a range of anthropometric flexibility and muscular strength measures of low and high handicap players (0.3 ± 0.5 and 20.3 ± 2.4 respectively), reporting that a golf-specific cable wood chop displayed the highest overall association (r = 0.70) with CHS. Additionally, trends were evident that low handicap players achieved significantly greater (30%) bench press scores. The impact of chest strength is further evident as Gordon et al. (11) noted increased strength of the chest measured using an 8 repition maximum on a pec deck machine, as a significant indicator (r = 0.69) of CHS in low handicap players (4.9 ± 2.9). This is likely due to the fact that the pectoralis major is highly active in the acceleration phase of the downswing (15). Although the above mentioned strength tests have reported significant correlations with CHS, it should be noted that they are time inefficient and require equipment which may not be available in a number of golf facilities delivering strength and conditioning programs. Therefore, inexpensive reliable field-based performance measures optimizing efficiency in testing may be a more prudent strategy in the physical assessment of golf athletes.

Hellstrom (12) assessed the profiles of 30 male elite golfers (+5 to 0) and reported significant correlations between a range of performance measures and CHS, with back squat (r = 0.54) and vertical jump peak power (r = 0.61) displaying the greatest associations. The results of Hellstrom (12) suggest that physical factors such as whole body dynamic strength and power have greater associations with CHS and should be considered by players and strength and conditioning coaches alike to enhance golf drive performance. A limitation of this study was the exclusion of a trunk rotational exercise within the test battery, a movement pattern inherent to effective golf performance, represented by lower handicap scores (22). The importance of trunk rotary strength and power has been highlighted previously, with lower handicap players (<0) displaying significantly greater (p < 0.001) hip and torso strength than higher handicap players (10–20,25), with the majority of work done on the golf shaft generated from the torso (19). Additionally, significant correlations (r = 0.54) have been noted with a medicine ball rotational throw (MBRT), an assessment of dynamic rotational power (11). When interpreting the results of the above research, it should be highlighted that the correlations reported are moderate (range, r = 0.5–0.8). As such, there is a large amount of unexplained variance. To the authors knowledge, no previous research has extended beyond single linear regression equations to examine the possible combined effects of multiple variables on golf CHS.

Assessing relationships between physical performance tests and CHS may be critical for the purposes of training, testing, and ultimately performance enhancement. It has previously been speculated that accurate assessment and training methods will enable golfers of all levels to achieve their playing goals (27). Owing to the simplicity, time efficiency, and minimal equipment requirements, field-based methods are often desirable for physical performance testing. However, currently there is not a suggested battery of field-based performance tests to determine the CHS of golfers. Therefore, the aim of this study was to examine the reliability of a range of field-based physical tests and subsequently examine their relationships with CHS.

Methods

Experimental Approach to the Problem

A correlation study design was used to investigate if significant relationships are present between field-based measures of physical performance and CHS. Within the research, CHS was the dependent variable, whereas anthropometric measures, squat jump (SJ) height and peak power, unilateral and bilateral countermovement jump (CMJ) heights and peak power, and seated and rotational medicine ball throws were selected as the independent variables. In addition, multiple trials of each field-based performance test were collected to assess the reliability of the measures. During the study, subjects attended on 3 separate occasions with a minimum of 48 hours between sessions. Day 1 involved a familiarization session for all performance tests and CHS analysis, and anthropometric testing was also completed. On day 2, data were collected for CHS; and on day 3, data were obtained for vertical jump and medicine ball throws assessments. Multiple trials were completed to reduce the influence of a learning effect, and the order of performance tests were randomized using a counterbalanced design. Additionally, subjects were instructed to refrain from high intensity physical activity 48 hours before each testing session and eat according to their normal diet.

Subjects

Forty-eight male subjects volunteered to participate in the study (age: 20.1 ± 3.2 years, height: 1.76m ± 0.07 m, mass: 72.8 ± 7.8 kg, handicap: 5.8 ± 2.2). Subject prerequisites involved a minimum of 2 years golf playing experience with single figure handicap classifications. Upon commencement of the study, participants were in the early stages of the golf season, free from injury, had no quantifiable strength training experience, no prior experience of the performance tests, and were only involved in golf practice and competitions. Informed consent was gained before participation, and ethical approval was granted by the University Research Ethics Committee in accordance with the Declaration of Helsinki.

Procedures

Anthropometry Protocol. Height (cm) was recorded using a Seca (274, Seca, Milan, Italy) measurement platform. Weight (kg) was recorded using calibrated Seca (786 Culta, Seca, Milan, Italy) scales. Total arm length was measured in a standing position with the elbow fully extended with anatomical reference points, the greater tuberosity of the humerus and ulnar styloid.

Golf Drive Performance

Club head speed was measured using a flight scope (Kudu Launch Monitor, Stellenbosch, South Africa) placed one metre behind the ball in set up position. Subjects performed a standardized warm up including dynamic stretching and 5 practice shots. Subsequently, 3 recorded drives were completed separated by 60-second rest periods with instructions to swing maximally as has been suggested previously (12). The highest of the 3 swing speed values was used to report CHS values. Subjects were blinded of their results to ensure no subsequent changes in technique. The same driver (Callaway Diablo, Callaway, USA) and make of golf ball (Titleist Pro-V1, Titleist, USA) was used throughout.

Performance Testing

Vertical Jumps. The highest of 3 maximal attempts of a CMJ, SJ, right leg countermovement jump (RLCMJ), and left leg countermovement jump (LLCMJ) were recorded, and used for subsequent analysis. Participants were instructed to jump as high as possible, avoid bending knees whilst airborne, and to keep hands in contact with hips throughout the test. The CMJ, RLCMJ, and LLCMJ involved lowering into a quarter squat followed immediately by an explosive concentric contraction. Performance of the SJ involved lowering the hips until the thighs were parallel to the floor followed by a 4-second isometric pause and subsequent explosive concentric only jump with no countermovement. Trials were repeated if a visible countermovement was used. All jumps were measured using a contact mat (Kinetic Measurement System, Optimal Kinetics, Moorestown, NJ, USA), with peak power calculated using previous recommendations (23). Recent support for this approach highlighted strong correlations to peak power measured against force plate data (r = 0.96 and 0.95) for the CMJ and SJ, respectively (9).

Medicine Ball Seated Throw. A 45° angle incline bench was used to facilitate the optimal trajectory and ensure standardization (6). Subjects used a 3-kg medicine ball (Jordan Fitness, Cambridgeshire, United Kingdom), performing a warm-up throw followed by 3 recorded attempts, with the best distance reported. For each trial, the ready position was assumed with the subject placing the ball against their chest, and it was held statically for 4 seconds. Instructions were to throw maximally using a concentric only motion. Subjects had to maintain their back and head in contact with the bench ensuring their feet remained on the floor. This test has previously been deemed a reliable method of assessment, with the intraclass correlation coefficient (ICC) reported at 0.92 (3).

Medicine Ball Rotational Throw. Using a 3-kg medicine ball (Jordan Fitness), subjects assumed a golf stance and rotated away in a backswing type action followed by an immediate rotation toward the target as in a golf swing, aiming for maximal distance. Feet were required to remain in contact with the floor, although the rear heel was allowed to rise in the follow through action promoting triple extension of the ankle knee and hip as would be present in the golf swing. Three tests were recorded with the best score reported. This test has been performed previously with the ICC reported at (r = 0.89) (11).

For both the medicine ball seated throw (MBST) and MBRT, a measuring tape was placed on the floor with the near end anchored under the frame of the bench. To ensure accuracy of measurement, the throwing area was covered in sand, and this was reraked before each test. Additionally, a predetermined landing width was marked out (1.5 m) on each side for which the ball must land in to be classified as a legitimate throw.

Statistical Analysis

Descriptive statistics (mean ± SD) were calculated for anthropometric data, CHS, and all physical performance tests. The strength and direction of the relationships between variables were initially examined using a Pearson correlation coefficient, with magnitudes of correlations based on a previously reported scale (4). After this, all variables were entered into a multiple stepwise regression analyses to identify the main determinants of CHS. The assumption of independent errors was tested using the Durbin-Watson test, whereas multicollinearity was tested using both tolerance and variance inflation factor collinearity diagnostics. The level of significance for all tests was set at alpha level P ≤ 0.05. Descriptive statistics were computed along with a multiple stepwise regression analysis via SPSS® V.18 for Windows.

Results

Within-test reliability for CHS and all other performance tests were calculated using ICC and are displayed in Table 1. Based on previous research (13), the ICCs reported were deemed acceptable (r = 0.7–0.9) for all variables.

T1-9
Table 1:
ICC for the CHS and performance testing.

Descriptive statistics and correlations between CHS, anthropometrics, and the range of field tests conducted are shown in Table 2.

T2-9
Table 2:
Descriptive statistics and correlations between CHS, anthropometrics, and field tests.

Significant correlations were reported between CHS and MBRT (r = 0.63; p < 0.01), MBST (r = 0.67; p < 0.01), CMJ peak power (r = 0.54; p < 0.01) and SJPP (r = 0.53; p < 0.01). Although the relationships between other performance measures and CHS were predominantly significant, the correlations were deemed weak (r = < 0.3) to moderate (r = 0.3–0.5). From the multiple regression analysis, the MBST and SJ height were the greatest predictors of CHS, explaining 49% of the variance. For the model reported, there was no evidence of multicollinearity as suggested by acceptable values for tolerance (>0.1) and variance inflation factor (<10).

Discussion

The results of this study demonstrate that a wide range of strength and power performance measures are significantly correlated with CHS. In particular, concentric only actions including SJ and seated MBST; moderate correlations were also evident with CMJ and MBRT; and low-level significant correlations reported with anthropometrics and RLCMJ. As such, strength and power development may positively impact golf CHS.

Due to the current lack of evidence in golf with regard to valid and reliable field-based measures of physical performance, strength and conditioning practitioners are faced with a challenge as to how they should effectively assess athletic abilities. The current study reported high reliability in the range of field tests used and statistical significance with CHS in all performance measures apart from LLCMJ. By comparison, lower levels of reliability have been reported in previous work (31) and a range of other studies assessing physical relationships with CHS did not report reliability statistics for the physical performance tests (12, 16). Additionally, the MBRT used in the current study displayed high reliability (ICC = 0.90), and this is comparable to other work using the same test (11).

The current study highlighted that SJ and MBST explained the highest variance (R2 = 49%) in CHS. This is in contrast with previous research that suggests the stretch shortening cycle (SSC) is the major muscle action contributing to the golf swing (14). The SSC has previously been classified into either fast or slow actions dependent on contraction times (<250 or >250 ms) and angular joint displacements (24). The current study identified strong relationships between CHS and performance tests requiring largely concentric muscle actions. Therefore, the golf swing may not reflect fast SSC activity, which is dependent on large contributions from stretch reflex properties and elastic energy reutilization (2), but rather slow SSC activity, which takes advantage of an increased time for cross-bridge formation (29). This notion is supported by research that has reported the time from downswing to impact as approximately 290 ms for male professional players (18). Speculatively, this may suggest that the backswing merely allows increases in force production through the eccentric action, providing an increase in impulse (force × time), compared with a downswing without a prestretch (20).

The significance of the SJ reported in the current study highlights the importance of lower limb concentric strength to initiate a powerful downswing. Interestingly, Nesbit and Serrano (19) noted that lower handicap players worked at slower rates initially in the downswing and were then faster through impact than less skilled players. As such, better players may generate more force initially as evidenced by the slower speeds (due to the force or velocity relationship) and greater total work done. Additionally, the lower body has been shown to initiate the downswing, whereas the upper body and club continue the backswing (10). This generates what has been referred to as the “X-factor stretch” (21), increasing the eccentric action, subsequently generating increases in muscular force.

Another finding of this study was that the highest correlation to CHS and greatest explanation of variance was the MBST, a concentric only chest dominant movement. Previous research has examined the impact of chest strength on CHS (11) and noted that increased chest strength was a significant indicator of CHS (r = 0.69). This is supported by the fact that the pectoralis major is highly active in the acceleration phase of the downswing (15). However, it should be noted that the golf swing involves a sequential utilization of the kinetic chain to produce force, commencing from the ground, moving up to the distal segments during the downswing (10). This is further evident in a range of other sports involving high levels of trunk rotation such as boxing (9) and baseball (26), in which a definite synchronization between leg, trunk, and arm actions plays a major role in increasing the force of a strike. Therefore; upper body dominant strategies may not be suitable for optimizing CHS. Further to this, the force generation sequence up the kinetic chain has also been identified (30) with mastery in the shot put involving a shift from the shoulder to the leg muscles. In the current study, the subjects were physically untrained, and as such may have over utilized upper body mechanics with less contribution from the legs and hips.

Future research may wish to investigate correlations of various physical performance tests with CHS in physically trained golfers to assess if there is an increased relationship of leg power and a transition from upper body dominance as has been seen in other rotational-based sports. Additionally, field-testing with different age ranges, specifically looking at youth populations, could be implemented to assess relationships during different periods of growth and maturation.

Practical Applications

The range of field tests utilized in this study namely: SJ, CMJ, medicine ball seated chest throw, and standing rotational throw displayed high reliability statistics and moderate correlations with CHS in single figure handicap golfers. This has implications for performance, as increases in CHS relate positively to reductions in handicap via increased driving distances (8). Strength and Conditioning coaches may also accurately and efficiently assess the physical abilities of their golf athletes using the aforementioned field tests as part of a primary assessment and then periodically to highlight the effectiveness of subsequent training interventions. Based on the results of this study, concentric dominant movements may be more effective in assessing the magnitude of CHS due to the association between MBST, SJ, and CHS.

Acknowledgments

The authors would like to thank the staff at Merrist Wood College and Golf club for their cooperation and assistance in providing the subjects and golf facilities to perform this research. No funding or endorsement was provided for the current research.

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Keywords:

field testing; golf; strength and power; driving performance

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