Golf has traditionally been a sport where players focused on the tactical, technical, and mental aspects of the game rather than muscular strength and power. Many players even refrained from strength training based on the reasoning that it would hinder flexibility (11). This view has recently changed with the increase in physical conditioning in many of the top golf professionals and an increased emphasis at the collegiate level (5,8). As logic based on these trends would seem to dictate, players today are driving the ball further than in past years. With the primary function of the full swing being able to drive the ball as far as possible with accuracy, control, and consistency, physical conditioning of golfers has now become a significant aspect of the game (8,16).
Club head speed (CHS) is an important variable in golf affecting the distance the ball is hit, and CHS at ball contact has been shown to correlate strongly with handicap (9). Therefore, CHS represents a variable that strength and conditioning practitioners may wish to increase in golfers. As such, identifying potential conditioning exercises related to CHS that could be used to improve performance as well as provide field tests for golfers would be useful for practitioners.
It has been reported in several studies that much of the body's musculature is active during the golf swing (3,7,10,13,14,16,18,19,22). Clearly, the muscular forces applied through the limb segments to the club were found to have a profound effect on CHS (8). Strengthening the active muscles may allow the golfer to perform more mechanical work on the club during the swing, therefore creating a higher CHS at ball contact. Indeed, it has been reported that CHS is significantly increased after a period of resistance training (8,11,21). Previous researchers have identified that there is a summation of segmental forces during a golf swing that contributes to CHS, with the musculature of the shoulder, elbow, and wrist joints contributing a greater amount of work on the club than the spine and hip musculature (4,17). Despite this, Doan et al. (6) have reported that the relationship between strength of the chest musculature was not significantly correlated with CHS in intercollegiate golfers. Chest strength was assessed using the bench press, a relatively nonspecific movement to the golf swing, rather than a rotational movement that more closely mimics the action of the golf swing. The specificity of the movement used to assess the relationship between muscular strength and CHS is likely to be an important factor, and this has implications for the exercises selected during a resistance training program.
In addition to the strength of the muscles activated during a golf swing, the power of the active musculature of the trunk is also likely to be an important factor affecting CHS. High muscular power will allow more mechanical work to be done on the club during the swing per unit time, thus increasing CHS. Investigators have reported that the rotational power of the core musculature was significantly correlated to CHS in low handicapped golfers (6,23). However, both Doan et al. (6) and Yoon (23) used tests requiring complex equipment that may preclude the use of these tests by many practitioners. Although some authors have used field tests such as the vertical jump to measure power output in golfers (23), as previously noted, the contribution of the hip musculature to the work done on the club during the golf swing is relatively small (4,17). This likely explains the small relationships previously reported between power output in a vertical jump and CHS (23). In contrast, a test for power that is specific to the golf swing such as the hip toss would appear to provide a more valid field test of power for golfers.
It is possible that flexibility may also affect CHS. Specifically, greater flexibility about the joints may allow more mechanical work to be performed on the club during the swing, therefore increasing the CHS at ball contact. Despite this, Doan et al. (6) did not find a significant relationship between CHS and trunk rotational flexibility in a group of male and female golfers.
The importance of each of the aforementioned muscular variables to the CHS in golfers has significant implications for strength and conditioning practitioners charged with designing training programs. An advanced knowledge of the importance of these muscular variables may allow for more efficient use of training time for the athlete, as well as a more effective training and testing regimens. Therefore, the purpose of this study was to investigate the relationship of trunk flexibility, total body rotational power, and chest strength to CHS in experienced male golfers.
Experimental Approach to the Problem
A correlational study was designed to assess the magnitude of the relationships between the flexibility of the core, total body rotational power, and the strength of the chest to CHS in male golfers. All subjects were tested for flexibility, power, and strength in a variety of assessments, the results of which were subsequently correlated with their CHS to ascertain the magnitude of the relationships.
Fifteen male golfers agreed to participate in this study. The demographic and anthropometric data for the subjects are shown in Table 1. Fourteen subjects were right-handed and 1 was left-handed. Each subject reported a handicap of 8 or less. A limit of 8 or less was set for a handicap to minimize the variability in the mechanics of the swing. All subjects reported that they had practiced golf within the past 12 months, and each subject was free of musculoskeletal injury for the previous 12 months. Testing was conducted between February and March. Only 6 subjects reported having participated in golf within the 4 months before the testing period, and none were currently engaging in any type of physical fitness program to increase flexibility, power, or strength. Each subject was informed about the study and signed a consent form approved by the Institutional Review Board of East Stroudsburg University. All subjects were then given an orientation regarding the assessments and participated in practice trials of the assessments with feedback before testing.
Subjects performed a standardized warm-up that consisted of a 5-minute light cardiovascular warm-up on a cycle ergometer, 1 minute of arm circles (30 seconds forward and 30 seconds backward), and two 30-second golf-specific dynamic stretches derived from Simpson and Kaspriske (20). Subsequent to the warm-up, the subjects took 5 light golf practice swings. The 14 right-handed subjects then hit 5 practice wiffle golf balls with a Cleveland TA5 five iron. The 1 left-handed subject hit the wiffle balls with a Titleist 731PM five iron.
Club Head Speed
A Swing Mate (Beltronics, Inc., Mississauga, Ontario, Canada) was used to measure CHS in m·s−1. The device was placed 1 m behind the ball during each swing and the subjects were instructed to swing maximally during each trial. The subjects were blinded to the speed of the swings to ensure that the subject did not alter their swing technique. Five trials were performed with 30-second rest between each trial. The mean of all swing speed readings was used in the subsequent analysis to improve the reliability of the measure (2). In our laboratory, the interclass correlation coefficient (ICC) and coefficient of variation (CV) for this method are 0.95 and 2.0%, respectively.
Rotational Trunk Flexibility
A trunk rotation resistance training machine (Streamline, Inc., East Stroudsburg, PA) was used to assess the rotational flexibility of the trunk. Subjects sat in the trunk rotation machine and, with the weight stack removed, they were instructed to turn as far as possible in the direction of their backswing without allowing the chest pad to leave the center of their chest. An initial mark was made on the circular rotating pulley disk on the top of the machine aligned with the front edge of the machine. This marked where the subjects started the movement. A second mark was made on the rotating disk where the subject ended their turn. The distance between the 2 marks was measured. This distance was then converted to degrees using the formula (p/r) × (180/π), where p is equal to the distance measured along the arc of the rotating disk on the trunk rotation machine and r is equal to the radius of the rotating disk.
Total Body Rotational Power
The distance thrown of a 3-kg medicine ball during a hip toss movement was used as an index of total body rotational power. This movement was chosen because it was deemed specific to the golf swing and involves the musculature of the shoulders, core, and legs. Subjects were instructed to take a golf stance while holding the medicine ball and to mimic a golf backswing until the ball reached hip height. Subjects were then instructed to mimic a golf downswing and release the ball at hip height in what would represent their follow through. The subject's feet were required to stay planted on the floor during the turn in the direction of the backswing, although their rear heal was allowed to come off the floor during the forward throw to mimic a golf swing. Subjects were instructed to throw the ball on a flat trajectory along a tape measure that was placed on the ground. The distance the medicine ball traveled through the air was measured in meters. Subjects performed 5 tosses with 2-minute rest between trials, and the mean of the longest 3 tosses was used in the subsequent analysis to improve the reliability of the measure (2). A volleyball was used for practice trials of the hip toss before the medicine ball trials. In our laboratory, the ICC and CV for this method are 0.89 and 4.1%, respectively.
To measure chest strength, defined as load lifted in kilograms, a pec deck machine was used (Streamline, Inc.). Subjects performed an 8-repetition maximum (RM) because it has been suggested that no less than an 8-RM should be performed on single-joint exercises (1). The 8-RM was determined using a modified version of the protocol developed by Baechle et al. (1) for a 1-RM. Seat height was adjusted for each subject to ensure that a 90° angle was formed at the elbow with the upper arm being parallel to the ground at the starting position. Subjects were instructed to keep their backs against the seat and their elbows against the elbow pad during the entire exercise. A trial was considered acceptable if the subject was able to touch the elbow pads in front of their body on each repetition. Each subject was monitored throughout each trial to ensure that proper form was employed. Trials where the subject employed improper technique were disqualified as a legitimate trial. Each subject's 8-RM was determined within 5 trials using this protocol.
All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS for Windows, version 12.0, SPSS Inc., Chicago, IL). Measures of central tendency and spread of the data were represented as means and SDs. Pearson product moment correlations were used to evaluate the relationship between CHS and rotational trunk flexibility, total body rotational power, strength of the chest, and strength of the core. Coefficients of determination were also calculated and expressed as a percentage (R2 × 100). Partial correlations were used to control for the effect of handicap on the observed relationships between the variables.
Table 2 shows the means and SDs of the dependent variables (CHS, trunk flexibility, total body rotational power, and chest strength).
Table 3 displays the results calculated for the bivariate correlations between the various flexibility, power and strength measures, and CHS, as well as the associated confidence intervals. Chest strength had the highest correlation with CHS (r = 0.69, p ≤ 0.05) with total body rotational power demonstrating the next highest correlation with CHS (r = 0.54, p ≤ 0.05). The chest strength values explained 47% of the variance in the CHS values, whereas total body rotational power explained 29%. Trunk flexibility was not significantly correlated with CHS in these male golfers (p > 0.05). As shown in Table 3, the relationships did not change substantially when the effect of handicap was controlled for.
The purpose of this study was to investigate the relationship of trunk flexibility, total body rotational power, and chest strength to CHS in experienced male golfers. It was found that strength of the chest in the pec deck motion and total body rotational power measured in a hip toss correlated significantly with CHS in these male golfers. Jobe et al. (13) demonstrated that the pectoralis major muscle was very active during the acceleration phase of the downswing during the golf swing, further supporting the importance of chest strength in the pec deck motion. The large correlation between the strength of the chest and CHS recorded in the present study further highlights the importance of improving the strength of the chest musculature during training to improve CHS, although further longitudinal research is required to substantiate any proposed improvements.
Yoon (23) investigated the relationship of muscular power with CHS and found that rotational core power measured from a trunk rotation machine was the most strongly correlated of the power assessments measured. The strength of the relationship reported in the present study was similar to that reported by Yoon (23) (r = 0.54 and 0.63, respectively). The hip toss movement used in the present study involved the leg and arm musculature without specifically isolating the muscles of the core. It was proposed that this movement would be similar to the golf swing. Doan et al. (6) utilized a modified hip toss that stabilized the legs as a measure of core power by digitizing the medicine ball traveling through the air to find the speed of the release. Their assessment yielded an r value of 0.86 for the relationship between rotational core power and swing speed. Despite the strong relationship reported, the test employed by Doan et al. (6) required the use of complex digitizing equipment, precluding the use of this test for many practitioners. The present measure of total body rotational power, as assessed through a hip toss movement, represents an easy to administer field test that practitioners could use effectively.
Despite the different strength of the relationships demonstrated between measures of rotational power and CHS reported by Doan et al. (6), Yoon (23), and the present study, they all showed significant correlations. This implies that rotational power should be a high priority when conditioning golfers. Future research should concentrate on investigating the effects of training methods to improve rotational power on CHS.
Rotational trunk flexibility did not show a statistically significant relationship with CHS, which may indicate that the players with high swing speeds and low flexibility were still able to swing the club over a great enough distance to generate maximum speed. This finding is in agreement with that of Doan et al. (6) who used golfers of a similar standard to those in the present study. Hume et al. (12) demonstrated that the ability of a player to maximize the distance the shoulder girdle rotated compared with the hips only showed a strong correlation to driving distance with PGA tour players. Only a very low correlation was reported for the top senior and amateur players. The finding of the present study would seem to concur with that of Hume et al. (12). However, increasing rotational trunk flexibility may help to minimize the potential for injury of this area. Lindsay et al. (15) and Pink et al. (19) have stated that rotational flexibility of the trunk is important due to the amount of strain and the range of motion that this area goes through during the swing, as well as the number of times that this motion is repeated during a round of golf.
Several studies have shown that total body training can increase CHS (6,8,11,21). The findings of this study indicate that exercises such as the pec deck and hip toss could be added in a total body golf training program to help increase CHS. The results of this study do not suggest that golfers should focus merely on the pec deck or hip toss movements, rather these constitute exercises that may be beneficial in a total body workout to increase CHS. Similarly, these exercises provide appropriate field tests for practitioners when assessing the strength and power of golfers.
The results of the present study indicate that there are strong relationships between the strength of the chest musculature, total body rotational power, and CHS in male golfers. It is possible that by including exercises to strengthen the chest musculature and increase core power in a rotational manner to the training program of male golfers, CHS may be increased. These exercises may also provide useful field tests that practitioners could use to assess the strength and power of their golfers.
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