Loock, Henriëtte V. MSc; Grace, Jeanne M. PhD; Semple, Stuart J. MTech, PhD
The golf swing is one of the most difficult and complex yet intriguing sport motions (11). Although researchers have only recently begun to document the value of sufficient and specific core training in certain sports, especially golf (25), the importance of core muscle development for the golf swing cannot be underestimated, as well as the application thereof (25). The term core commonly refers to the midsection of the body and thus involves many structures that form the “center” of the body, an area that is also known as the “torso” or the “power zone” (12,25). The core is the cornerstone of all athletic movements, and therefore, the training of these muscles should form the basis of every prescribed exercise program (12). According to Edell (12), all movements are generated from the core and transferred to the extremities. Strengthening the core muscles thus provides, among other benefits, improved performance through increased strength, power, speed, agility, and quickness and through improved balance (1,12,20). These parameters (power, speed, agility, quickness, and balance) have previously been used in strength and conditioning programs. Therefore, the importance of incorporating core training in any athletic/sports program is inevitable because these previously mentioned parameters (strength, power, speed, agility and quickness) are fundamental in most, if not all, sport types.
Golf players with core dysfunction may present with weak intra-abdominal muscles compared with those participating in regular core training (26,39,43) and therefore be at risk for injuries, back pain, and/or back problems (10,12,20,27,38,39,42). Previous research has found that a significant number of golf players often suffer from injuries to the hips and lower back, possibly because of the repetitive external and internal rotation (IR) of the hip that occurs during the swing motion (14). Similar findings were reported by Evans and Oldreive (13), Bulbulian and Seaman (4), Horton et al. (21), Grimshaw et al. (17), and Lindsay and Horton (28). Furthermore, the majority of golf players presenting with lower back pain had little abdominal activation and also presented with weak core muscles (20,27,38). Clearly, adequate core strength is vital for golf players, regardless of their level of participation, age, or gender. This point is further emphasized by Cheetham et al. (7) demonstrating that the development of club head speed is initiated from the legs and hips with a rapid rotation of the pelvis, followed by progressively faster rotations of the upper body as the point of impact nears (7). For these rapid actions to occur in time and with the necessary strength, to perform a high-quality golf swing, the body is relying a great amount on the muscles comprised in the core region.
Aforementioned strength can be obtained through specific golf exercises. Exercises specific to golf training focusing on increased core strength improved the trunk-pelvic rotation relation, ball speed, and carry distance by approximately 6% in a group of recreational golf players (36,44); this study has yet to be repeated on elite golf players. The present viewpoint regarding the golf swing emphasizes an increase in trunk coiling throughout the backswing. Hypothetically, this leads to augmented downswing impulse and, subsequently, to improved ball speed and carry distance (36). To perform an advanced golf swing, the body, to a large degree, relies upon the core system, including adequate back strength, to provide the necessary support, strength, and balance (27). Although forces are produced from the ground-up along the kinetic chain, the core system plays a crucial role in the production and transference of force. The golf player's core muscle group must be physically powerful enough to produce adequate upper trunk flexion force to resist the extension (8). According to some reviewers (3), only 2 muscle groups are of absolute necessity during the golf swing, and without sufficient strengthening of these specific muscles, the golf player will not be able to effectively execute a comfortable, “high-quality” golf swing. These 2 muscle groups are as follows: the gluteus muscle group and the abdominal muscle group (3). These 2 muscle groups have also been popular focus points in previous strength and conditioning training programs for golf players (3).
However, examples of the application of scientific core muscle training to elite golf players are scarce (25), and although core training seems to be an increasingly important aspect of golf training, no literature portraying the activation/activity of the various individual core muscles within each specific phase of the golf swing is available. For the strength and conditioning coach, the lack of literature around the specific core muscles activated within the different phases of the golf swing provides little assistance for programming guidance. A structured review of the available literature on the specific core muscles at work within the different phases of the golf swing can help identify valuable information regarding golf-specific core training, intervention programs, and/or specific muscle rehabilitation programs as well as information regarding the correction of golf swing errors (3). The aim of this article is to evaluate the available literature, highlighting the different core muscles and core muscle groups used within each phase of the golf swing. This information will edify the available material for the strength and conditioning specialist regarding the core muscle group, highlighting what is known about strength and conditioning in the different phases of the golf swing as well as areas where research is needed.
LITERATURE SEARCH STRATEGY
A literature search was conducted during March 2012 using MEDLINE (1990–2012), CINAHL Plus with Full Text (1990–2012), and SPORTDiscus with Full Text (1990–2012) as well as JSTOR + SABINET, SCOPUS, and ERIC through EBSCO Publishing. Search terms included controlled vocabulary from these databases (MeSH terms: “core muscles,” “golf biomechanics,” “golf swing,” “golf performance,” “golf kinetics”; CINAHL headings: “core muscles,” “golf biomechanics,” “golf swing,” “golf performance,” “golf kinetics”). All terms from the controlled vocabularies were exploded and searched as major concepts when available.
Controlled vocabulary search terms and text words were combined with the Boolean operator “OR” to capture all relevant articles pertaining to a closed concept. Similarly, the controlled vocabulary search terms and text words were combined with the Boolean operator “AND” to identify articles that would be used for screening for inclusion. In addition, scanning of reference lists was performed from the retrieved studies to identify any articles that may have been missed from the literature search.
Relevant articles were screened using abstracts and citations. Articles were included if they met the following criteria: the primary focus was the reporting of active core muscles within the different phases of the golf swing; was published in a peer-reviewed journal; was, at a minimum, a case report experimental design; and was written in English. Articles were excluded if they did not meet the above criteria.
In total, the search resulted in the retrieval of 150 articles (1990–2012), of which 91 articles failed to report a primary focus on the core muscles throughout the various stages of the golf swing. Out of the remaining articles, 16 were accepted for review; 11 of these were randomized control studies, whereas the remaining 5 were observation studies. The remaining 43 articles did not deal directly with the question of core muscles.
Table 1 is a summary of the randomized control studies that were examined for this review article, including their main findings. Observational studies were excluded from Table 1. However, the observational studies (6,9,15,23) were included in Table 2, and among these, 2 articles providing a review of a number of different case studies are, in their method of analyzing muscle activity, marked as “review.”
Table 2 provides a breakdown of all the different core muscles analyzed during various phases of the golf swing. Many of these researchers emphasize the importance of core muscles but tend to focus on the transverse abdominus and multifidus as specific core muscles and/or the pelvis and torso as a general muscle group of importance during specific phases of the golf swing. The abdominus and multifidus muscle groups have received great attention in previous strength and conditioning intervention programs for golf players (3). Fewer studies have focused on the oblique muscles within the golf swing or on the active muscle groups supporting the scapula during certain phases of the golf swing (6,24). Very little data are available on the specific core muscles within each specific phase of the golf swing. In most case studies, only the backswing and downswing have been examined. Different examining methods are used by researchers to analyze muscle contraction during the golf swing including both electromyography (EMG) (36) and motion capture measurement (photography, film, video, optical, magnetic, and inertial motion), which is also known as “motion analyzer” (37).
Although there are specific core muscles that are more active during certain stages of the golf swing, the swing itself may in fact differ between golf players. This is indicative of the extent to which the employment of certain core muscles, within a given phase of the swing, can also differ (29). However, this difference is not expected to amount to a considerable variation in the golf swing (29). Studies of the involvement of certain core muscles in specific phases of the golf swing can therefore still be regarded as applicable to the general golfing population (29). The literature also revealed the consistency with which golf players, especially professional golf players (31), perform their swing regardless of whether the swing was performed with an iron or a driver (31). Given that some core muscles are more active than others during certain stages of the golf swing provides valuable information in terms of applying specific strength and conditioning training programs to the golf player to focus on these specific core muscles to be able to achieve the fullest action from these muscles when needed. The literature drew further attention to important aspects that can affect the involvement of the core muscles within the specific phases or stages of the golf swing.
CORE MUSCLE INVOLVEMENT WITHIN THE DIFFERENT PHASES OF THE GOLF SWING
The entire golf swing
The execution of the golf swing involves precise bodily awareness and the well-coordinated exertion of the various muscle groups that participate in the swing. Fundamentally, 4 phases of a golf swing (backswing, downswing, impact, and follow-through) have been identified. The entire golf swing involves all 4 phases in sequential manner. This swing is referred to as the “modern” golf swing, which is opposed to the “classic” golf swing. The “modern” golf swing focuses on an “X-factor,” producing more powerful and further reaching shots (8,19,36) and has essentially replaced the “classic” swing, which involves rotation of both the upper trunk and of the pelvis. During the “modern” swing, the golf player's shoulders are turned further away than the hips in relation to the target (36). The consequent breakup of the hip-shoulder configuration at the maximal height of the swing has been termed the “X-factor” (16,22,33,34).
The primary phases of the golf swing, as determined by club head position, occur in the following order: the backswing, the downswing, the moment of impact, and follow-through (6,31,35). The ideal model for a golf swing starts with a backswing with a clockwise pelvic and trunk rotation, assuming right-handed golf player (31). The downswing is initiated by the reversal of pelvic rotation followed by a reversal of the trunk rotation. Impact refers to the moment of contact between the head of the shaft and the golf ball. Finally, the follow-through phase signifies the last part of the golf swing, where a “follow-through” motion is present.
The ideal golf swing can further be explained as a movement that starts in the pelvis, followed by the motion of the trunk, the arms, and finally of the golf club (38). Because the start of the golf swing is initiated by the pelvis, the strength of the muscles incorporated in the pelvis region is essential. These muscles fall under the core muscle group, and many of the pelvis muscles include external oblique, internal oblique, rectus abdominus, and gluteus muscle group. Followed by the pelvis movement is the movement trunk rotation. The trunk region comprises most of the core muscles. Many of the trunk muscles include rhomboids, trapezius, supraspinatus, infraspinatus, latissimus dorsi, and erector spinae. These muscles are important focus points for the strength and conditioning coach to create the ideal golf swing. As mentioned earlier, very little research has identified the specific active muscles involved during these phases. Rather, the available research constructs a summary of the global muscle groups at work during the complete swing. In essence, it is suggested that the major muscle groups from the arms (biceps muscle group, triceps muscle group, deltoid muscle group), shoulders (rhomboids, trapezius, supraspinatus, infraspinatus), back (latissimus dorsi, erector spinae), and hips (external oblique, internal oblique, rectus abdominus, gluteus muscle group) are the primary muscles involved throughout the complete golf swing (6) (Table 1). The golf swing is further explained as follows (assuming a right-handed golf player): the golf player begins with the left upper extremity in glenohumeral flexion, adduction, and external rotation (ER) and moves into extension, abduction, and IR (9). The right upper extremity moves from glenohumeral flexion, abduction, and ER and moves into extension, adduction, and IR (9). The first step is to have the golf player keep the elbow of the lead arm in extension at the address position of glenohumeral flexion, adduction, and ER (9). The golf player begins the movement by adducting the right shoulder, while the left shoulder follows. This initial motion against resistance is associated with the activation of the right lateral trunk flexors and glenohumeral flexion. Lateral bending activates the quadratus lumborum, latissimus dorsi, and abdominal oblique muscle (9). The lateral bending is an important part of the swing because it generates the necessary force and momentum to accurately place the ball as far as possible and as fast as possible (9). In other words, accuracy, distance, and speed are the parameters gaining advantage from a corrective lateral bending (9). Therefore, the proper conditioning of the quadrates lumborum, latissimus dorsi, and abdominal oblique muscles are of high importance, so that these muscles will be enabled to repetitively perform this lateral bending with the necessary strength.
During the golf swing, the spine rotates synchronously with the shoulder girdle, whereas the pelvic girdle only rotates to 45° because of the relative immobility of the lower half of the thoracic spine (23). The shoulder turn is completed (to 90° or more) by the differential rotation of the upper thoracic spine, pivoting about the upper cervical spine. The hip joints provide a pathway for the transmission of forces between the pelvis and lower extremities (23). The maximal height of the swing is an important element because it marks the finalization of all preparation for the comparatively brisk downswing (3,8). Therefore, the body of the golf player should be enabled to reach such a height during a backswing. Conditioning of the muscles of the spine will allow enough flexibility for the spine to reach desired height during backswing and still provide enough strength for a sharp, forceful downswing.
The pelvis and related pelvic core muscle are contracted throughout the 4 stages of the golf swing. This region is regarded as a vital muscle group that provides the golf player with the necessary support to effectively execute a high-standard golf swing. These muscles do provide not only a primary drive throughout the complete golf swing but also the effectiveness of core muscle activation in each phase can influence the following phase's efficiency (31). For example, peak pelvic-shoulder rotation during the backswing can determine the efficacy of the downswing which, in turn, can have a direct influence on the impact and distance of the shot (31). However, this is applicable only to consistent golf players. In the event of inconsistent golf players, the unpredictable technique can influence the efficiency of the following phase, over and above the influence that the unpredictable technique initially has on pelvic and related pelvic muscle activation (31). As each phase of the golf swing influences the next phase, it is therefore important that each phase is properly executed. Applying strength and conditioning exercise programs, specifically to the core muscles initiating the golf swing, is consequently a fundamental start to understanding the activation of the different muscles of the different phases of the golf swing.
A kinematic sequence of the golf swing, with the model representing ideal muscle activation during each phase of the golf swing, has been designed (7) (Figure). According to this kinematic sequence, the golf player initiates the golf swing with his arms (as the position of the club head is the first section of the sequence), after which the sternum (trunk/torso) and then the hips (from address position 0.91 seconds elapse until the backswing) are activated. At the transition phase, between the backswing and the downswing, no muscle movement occurs within any of the major muscle groups in the body. The transition phase is very fast (0.2 seconds (7)). Up until this point, all the movements have been in acceleration. The hips (pelvis and pelvic-related muscles) are the primary initiators of the downswing and are followed by the sternum (trunk/torso), arms, and the club head. At impact, all body parts are decelerating in this specific order (Figure). For the acceleration phase, high-standard conditioning of relevant muscles is necessary to execute strength while accelerating. The muscles from the hips are in reality fully contracted for 0.91 seconds. In this time frame, precise and accurate movements must take place, which relies almost only on the level of strength of the applicable muscles during that specific stage.
Figure. Kinematic se...Image Tools
The hip flexors and extensors, in terms of muscle activation, are less active during the golf swing. However, one study (41) suggests that the basic trunk movement, which includes trunk forward tilt and lateral flexion, is just as essential in the golf swing as in the trunk rotation and lateral bending movement. Therefore, the study suggests incorporating hip flexor and extensor strengthening together with abdominal and trunk extensor strengthening into golf-specific training programs (8). There is nevertheless, to date, no published literature that examines the level of hip flexor and hip extensor contraction/activation throughout the different phases of the golf swing. More recently, many studies have emphasized the rotation, specifically in the transverse plane, of the pelvis and of the trunk (46). The trunk and shoulder muscles, including the scapulothoracic muscles, are highlighted as important stabilizers, which, during the golf swing, generate beneficial interaction torques (46). These interaction torques are necessary for the final outcome of the golf swing. These interaction torques require strength generated from the applicable areas to take place effectively.
The backswing is the first part of the golf swing. Researchers differ with regard to which muscle group is the primary mover/initiator of the backswing. Some state that the pelvic muscles initiate the backswing, followed by the musculature of the upper torso, whereas others (3,31,36) suggest that the backswing begins with the concurrent rotation of the trunk and the arms; the club moving away from the address position, with pelvic rotation following almost instantaneously. Research also indicates that backswing, the duration of which averages 800–1000 milliseconds, is considered to be of minor importance in comparison to downswing (6). Generally, it is agreed that the upper torso core muscle group is highly activated during the backswing, regardless of whether the prime movement is initiated by the torso or by the pelvis (6,31,35,36) (Table 3). These muscles include the pectoralis, deltoid, trapezius, and rhomboid muscle groups and, to a smaller extent, the upper extremity muscles in the arms.
EMG studies have established the activity of the muscles of the trunk, namely, the erector spinae, abdominal oblique, rectus abdominis, latissimus dorsi, and gluteus, throughout the backswing (3,36) (Table 4). Moreover, during this phase, the stretched trunk muscles may facilitate a greater concentric action, encouraging greater force generation and contributing to a more powerful ball strike. Henceforward, applying strength and conditioning training programs to the aforementioned muscle groups will result in greater concentric action required for optimal golf swing.
The turning motion of the body to correctly place the head of the shaft at both the maximal height of the backswing and within the end position is drawn from the hips and spine (29). Even though the backswing is regarded as less important than other phases of the golf swing (6), it is still an essential action, preparing the golf player's body for the actual shot. Ineffectiveness during the backswing can have detrimental effects in the downswing, which can ultimately have a negative effect on shot performance. Bearing this in mind, it can be argued that all phases of the golf swing are equally important. Little data are available on the precise core muscles involved during the backswing.
The downswing is the phase that follows after the backswing until just before impact. The downswing is considered to be the most vital component of the complete golf swing and may predict the outcome of swing performance. The pelvis and related pelvic core muscles continue to lead the upper torso throughout the downswing, primarily generating force (3,6,23,31,35) (Table 4). These muscles include the gluteus, quadriceps, and hamstring muscle group; internal and external hip rotators; hip abductors and adductors; and the lower abdominals and the internal and external obliques. The downswing is initiated by the rotation of the pelvis, which moves toward the position of impact. This is rapidly followed by rotation of the trunk and that of the arms and the club (3,36) (Figure). This rapid rotation requires high levels of strength to be able to precisely perform the action. Focusing on the trunk muscles in terms of strength and conditioning is therefore essential. In this phase, the pelvis and the pelvic-related muscles are the primary movement initiators. The specific muscle group within the pelvic region that generally initiates this movement is the oblique group; the rest of the movement in this phase being supported by the rectus abdominus, gluteus, and quadriceps muscle groups. This information is also vital to the golf player in assisting him/her in understanding which muscles are required to contract more than other muscles in the downswing to help the golf player focusing on contracting these muscles during the downswing to promote this rapid rotation movement.
The downswing is of greater value than the backswing with regard to the performance outcome of the swing (6) and is rapidly executed, generally within approximately 300 milliseconds. This is in agreement with another research study suggesting that the second phase of the swing continues for 230–130 milliseconds before impact (35).
Analyzing bilateral muscle activity patterns in 8 different muscles of the shoulder (an analysis of both the leading and trail arms) during the golf swing reveals that while golf does not require an extremely demanding arm action (41), it does, however, entail highly synchronized rotator cuff muscle activity so as to protect the shoulder complex, especially during the downswing (29). These findings agree with research that also considered the activity of the scapular muscles in the upper back region (levator scapulae, rhomboid, trapezius, serratus anterior) throughout the golf swing (24). These data indicate that the upper, middle, and lower trapezius muscles work collectively, assisting in the retraction of the scapula throughout different sections of the swing. The primary activation of the trailing arm occurs in the context of the backswing, whereas that of the leading upper extremities occurs on the downswing. Also, with regard to the lead side, both the levator scapulae and the rhomboids play a key role in elevating and retracting the scapula during the downswing. A breakdown of the different phases of the golf swing and the specific core muscles active during each phase was, however, not performed during these studies.
Further research considered muscle movement in the erector spinae, gluteus maximus, and abdominals (oblique/rectus), establishing that all core muscles are active throughout the accelerative downswing (47). The trailing abdominal obliques demonstrated the greatest relative activity within this muscle group. Two researchers (41,47) have however found a higher relative contribution from the leading internal oblique as compared with the trailing external oblique on the downswing with both muscles contracting before the club reached the top of the backswing. High levels of bilateral erector spinae activity on the downswing are thought to help stabilize the spine during the powerful trunk flexion and rotation forces produced by the abdominal muscles (41,47). Similar results found that the leading hip generates considerably higher IR speed during the downswing, in comparison to that of the trailing hip that rotates externally. That is to say that the IR speed of the leading hip exceeds the ER speed of the trailing hip (15). No further data are available investigating specific core muscles during the downswing.
Impact is the phase that takes place immediately after the downswing, before follow-through. At impact, the upper torso is relatively parallel to the intended line of flight and rotates beyond the pelvis during follow-through. Impact is much shorter in duration (40–60 milliseconds) than any other phase of the golf swing. Even when measuring less experienced golf players, who generate more modest peak velocities, the duration of the impact phase does not differ when compared with that of experienced golf players (6). The oblique muscles are active throughout all segments of the golf swing because they are the primary driver of torso rotation (torso rotation occurs in the backswing, the downswing, and the follow-through) but are especially active during impact. In addition, these muscles need to control the motion of the swing (8). Very little data is available on the specific core muscles active during the impact phase. This may be the result of the short impact duration; however, with this information, it still remains essential that the core muscles—focusing mainly on the oblique muscle groups, during the impact phase—should be conditioned enough to evoke proper strength to maintain bodily balance and stability within this short phase to lead to a desired outcome.
Follow-through is the concluding phase of the golf swing. In the final phase, muscular activity predominantly occurs around the shoulders and the spine, with the pectoral, abdominal, and anterior deltoid muscles also involved (40,41) (Tables 3 and 4). The infraspinatus and supraspinatus on the left side of a right-handed golf player are predominantly active during the follow-through, whereas the activity of the subscapularis is “observable” throughout the forwardswing and impact. It can thus be concluded that not only are these muscles critical in assuring the stability of the shoulders throughout the golf swing but also their importance persists throughout the follow-through (6). Literature on the follow-through with regard to the different core muscles active in this phase is limited. A possible reason for this may be that the downswing receives the greatest attention as the most important segment of the golf swing in which the timing and activation of different muscles can have a definite result on the outcome of the ball strike and which consequently affects the quality of the swing.
Tables 3 and 4 provide a summary of the percentage of the contraction/activation of the active muscles throughout certain phases of the golf swing. Assuming the muscle contraction to be that of a right-handed golf player, the tables differentiate between the leading (left) and trailing (right) side's muscle contribution for each phase within the upper body (Table 3) and the lower body (Table 4) (3).
CORE MUSCLE INVOLVEMENT WITH REGARD TO HANDICAP AND/OR SKILL DIFFERENCE BETWEEN GOLF PLAYERS
The golf swing is a unique movement that requires substantial coordination and powerful muscle contractions. During professional practice sessions and competitions, these potent movements are repeated several hundred times, resulting in the formation of and dissipation of considerable stress throughout various body structures (29). Conversely, recreational golf players are far less exposed to these stressors, and consequently, their core muscle groups will be predictably less active and thus less conditioned (3). However, this does not imply that professional golf players use “different” core muscles than recreational golf players throughout the different phases of the golf swing motion. This should in fact encourage recreational/amateur golf players to focus more on the conditioning of the weaker muscle groups.
The biomechanical factors that may influence the golf swing of 10 professional and 5 amateur male golf players using 3-dimensional kinematics and kinetics have been examined (31). Both the professional and the amateur groups relied on the same muscles for initiating and for supporting movements during most phases of the golf swing. Nevertheless, it is important to keep in mind that the purpose of this study was not to determine which individual muscles were activated throughout the specific phases of the golf swing; rather the goal was to determine other biomechanical factors such as muscle patterns throughout the entire golf swing.
Although the duration of each phase of the golf swing between amateur and professional golf players does not differ substantially (6), the skill of certain golf players may nevertheless differ by either lengthening or shortening the degree of the backswing (29). Furthermore, results (29) showed that while shortening the backswing by approximately 20% corresponded to a decrease in trunk muscle activation levels; this had no effect on stroke accuracy and no significant reduction in club head velocity (29).
The activity patterns of the core muscles, specifically the erector spinae and abdominal obliques, have been investigated in recreational (nonprofessional) golf players (41). The results showed that for the majority of the swing, oblique muscle activity was fairly high and constant, correlating with that of professional golf players (41). The pattern of muscle activity within the gluteus maximus, gluteus medius, adductor magnus, biceps femoris, semimembranosus, and vastus lateralis of professional golf players are associated with powerful contractions of the hip extensors and hip abductors (2). Similarly, right-handed golf players playing off a low handicap exhibit significantly larger right hip abduction and adduction, together with left hip abduction, and right and left trunk rotation strength when compared with golf players playing off middle or high handicaps (44). Also, players with a zero handicap show increased hip, trunk, and shoulder strength than their less proficient counterparts. Unfortunately, no results are available regarding trunk muscle activation within specific phases of the golf swing. Furthermore, during the complete golf swing, significantly higher right shoulder ER, right shoulder IR, and ER of the left shoulder has been recorded in low-handicap golf players as compared with high-handicap golf players (44). Research further indicates that highly skilled golf players, who are able to produce faster club head speed and a greater “X-factor” stretch have more pronounced shoulder and spinal strength, particularly of the rotator cuff (44). It must be noted that these results are applicable to the entire golf swing and not specifically to certain phases thereof. However, this information emphasizes the degree to which focus should be placed on the hip extensors and hip abductors—both muscle groups within the core muscle group. These core muscles consist of the gluteus maximus, the gluteus medius, the adductor magnus, the biceps femoris, the semimembranosus, and the vastus lateralis. Referring to the aim of this current study, it is valuable to learn that the activation of the aforementioned muscles are predominant throughout the golf swing, and therefore, applying strength and conditioning programs specifically to these muscles and/or muscle groups will result in desired golf outcomes.
A kinematic study of Professional Golfer's Association tour professionals, using a motion analyzer, showed that approximately 70% of professional golf players initiate the downswing from their pelvis (37). This is very important, linking to earlier observations that concluded, that the pelvis and pelvis-related muscles are also responsible for a rapid movement followed by progressively faster rotations of the upper body as the point of impact nears (7). This consequently places more emphasis on the pelvis muscle group (as part of the core muscle group) to provide the golfer's body with sufficient strength to perform such actions. Likewise, a number of studies relating to muscle-firing patterns of golf players' scapular (24), hip and knee (2), and trunk muscles (47) proposed that this sequential activation occurs in experienced golf players. Similarly, an analysis of a professional golf player's swing using an EMG found that the downswing motion was instigated by the muscles of the golf player's lower extremities, followed by the activation of the muscles of his upper extremities (37). Further studies have shown that in an experienced group of golf players, pelvic rotation was reduced after the backswing, whereas their torso showed continuous motion (37). In amateur golf players, reasonably and constantly high activity was recorded in the oblique muscles during of the swing (37). However, no distinction was made between internal or external abdominal oblique muscles, nor were any phases of the golf swing highlighted. It has been proposed that the main difference between professional and recreational golf players, regarding muscle activation throughout the different phases of the golf swing, can be ascribed to the conditioned state of the gluteus muscle group and the abdominal muscle group (3). This suggests that professional golf players' abdominal and gluteus muscle groups are more conditioned (3); therefore, less skilled golf players should focus on developing abdominal and gluteus strength and aim to improve the conditioning status of these muscle groups. Given the available data, it is evident that slight differences in technique and/or muscle activation patterns, between professional and amateur players, may occur. Nevertheless, regardless of their level of participation, golf players tend to rely on the same muscle groups throughout different phases of the golf swing. Data pertaining to the specific muscles at work within individual swing phases is however not fully available.
OTHER ASPECTS RELATED TO THE GOLF SWING
Core muscle involvement and weight transfer
To date, no studies examining the differences in core muscle activity during specific phases of a “late swing” and “early swing” brought on by weight transfer are available. Nevertheless, the sequence of actions that take place during the swing is determined by how the body is positioned at setup. Every effective swing begins in placing the golf player in an advantageous position, which enables him to perform a repeatable, skillful movement. Although it is unlikely that one setup posture is ideal for all golf players, the athletic posture adopted by many professionals (3,29), namely, a stable starting point (determined by appearance), allows efficiency of motion, particularly around the trunk region, ensuring that the golf player uses the same muscle groups for each phase to complete the swing (29).
The shortage of studies concentrated on muscle activation in “late swings” and “early swings” as a result of weight transfer may be because of the fact that weight transfer is an automatic factor of the golf swing and not a consciously initiated deliberate change (3).
Documentation has shown that golf players who experience fatigue will unwillingly alter their approach to the golf swing (44). This is important for the strength and conditioning specialist to be aware of when working with golf players who may be exposed to fatigue and to avoid misinterpretation of “weak” core muscles. In such situations, the body compensates in using muscles it would normally not rely on during certain phases of the golf swing (6,44). Fatigue can be caused by a number of factors including inadequate fitness levels and poor muscle conditioning. The explosive changes in direction that require alternation in force production necessitate the contraction of core muscles and other muscle groups at precise points in the golf swing. The most active of these muscle groups are located in the torso, shoulder, and hip (pectoral, deltoid, rhomboids, lower back, abdominal, internal and external obliques, and gluteus) (8,23,36,44,45). During fatigue onset, muscle groups of the upper extremities have been shown to rearrange their patterns of activity, thereby combating the overloading of specific muscles and minimizing fatigue (45). Such reorganization of muscle contraction patterns may compensate for exhaustion during the entire movement. Regardless of this, such mechanisms may actually modify the coordinated patterns of movement necessary for an effective golf swing. The participation of added muscle(s) or muscle groups to counterbalance fatigue may have a negative effect on swing mechanics, and considering the relatively small margin of error involved in the achievement of an accurate impact, even relatively low fatigue levels may call the ultimate success of the movement into question (45). Therefore, it should be the aim of the strength and conditioning coach to reduce the effects of fatigue on a golf player, by incorporating strength and endurance to the muscle groups prone to experience fatigue.
Golf swing biomechanics have recently received substantially greater attention in the literature (5,7,17,18,21,22,29,30,32,34). There is, however, very little research available on the activity of specific core muscles throughout different stages of the golf swing. Rather, studies identify a general number of muscle groups as important during the entire golf swing.
Although the abdomen and lower back are considered to be the “power zones” and are thus understood to be the regions that play a fundamental role in power production during the golf swing, this review established that there is relatively little information detailing which specific core muscles and core muscle groups are used in each phase of the golf swing.
In the results and discussion, meaningful attention was given to the role of certain core muscle groups within each section of the golf swing. Even though these findings have merit, numerous studies conclude that the success of the entire golf swing is furthermore dependent not only on the effectiveness of each muscle group in each phase but also on synergism, that is, the flow of the entire swing considered as a single unit (6,9,36).
Various trunk muscles are active throughout the swing to provide dynamic stability while simultaneously contributing to swing velocity. Further muscles reported to be active for the full duration of the golf swing are the contralateral external obliques and ipsilateral internal obliques, whereas the erector spinae, rectus abdominis, quadratus lumborum, transverse abdominis, and multifidus provide stability (6,9,36). These stability muscles are crucial when acknowledging the application of strength and conditioning.
The differing methodological approaches of the examined studies must be taken into consideration. Additional research should concentrate on the association between muscle activation in the torso, upper extremity, and lower extremity and during the execution of the swing to identify how the kinematic progression of the swing is affected by these variables. Further research should also include information on muscle contraction patterns throughout the specific phases of the golf swing, both between males and females; between different age groups; and between “late” and “early swings.” Very little data examining core muscle activation throughout the different phases of the golf swing with regard to age and gender is available. A factor that this review did not cover is the shift in muscle contraction or change in muscle activation during the swing because of injury; this too should be incorporated in future studies.
From the studied literature, the importance for golf players to develop improved muscle strength, especially core muscle strength (abdominal, lower back, and gluteus) is imperative to enhance each phase of the golf swing's outcome. Conditioning of the referred muscles and muscle groups deliver other benefits like lower handicap levels (3), muscle endurance (45), and less fatigue within a game (45).
The golf swing may seem like a momentum-type movement, where in reality it includes very precise bodily movement as a result of rapid, exact, and powerful muscle contraction from specific core muscles. The strength and conditioning specialist can incorporate specific core muscle training focusing on specific phases of the golf swing to enhance performance. When conducting a strength and conditioning training program for the golf player, the basic knowledge of the biomechanics of each phase of the golf swing and the available literature assists in identifying areas of need of the golf player, as well as areas of need for further research.
Golf has evolved from a leisure time activity to a competitive and elite sport where the biomechanical aspects that comprise the golf swing are now imperative. The golf swing is a fascinating and complex motion requiring skilled movements and specific muscle contraction to be executed supremely. Because of the rapid and precise technical demands of the golf swing, specific core muscle strength and conditioning is important. The scientific research on the biomechanics of the golf swing is growing, yet unfortunately, much of the research around the activation of specific core muscles during the different phases of the golf swing is limited. Because of this, the strength and conditioning professional looking to improve the performance of a golf player has limited resources on which to call upon for programming information. A literature search of from 1990 to 2012 was conducted. The purpose of this article is to equip the strength and conditioning specialist with the basic knowledge of the different core muscles activated during the specific phases of the golf swing, by portraying the existing research to apply specific performance enhancing strength and conditioning exercises for the golf player.
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