Golf is a popular sport for players of all ages and skill levels with more than 55 millions playing in over 30,000 golf courses around the world (8). Golf becomes increasingly popular among youth, especially female junior adolescents in Korea with major international championship victories of Korean female golfers. In sports competitions, there is inherent stress (26), defined as disturbing human homeostasis and resulting in psychophysiological changes in the human body (34). During golf competitions, stress might play an important role (7,28) because it requires steadiness, precision, and motor control for effective shot making for a relatively long duration (4 hours per round). However, most of research in stress response during competitions has been rather limited to elite adult male golfers (7,28). Individuals perceive competition differently; thus, stress response of junior golfers during competitions is needed to be identified to provide an individualized training program.
Exercise increases the concentration of stress hormones, including cortisol (2,3,20). Concentration of plasma cortisol is known to be elevated during (7,9,10,28) and before (32) sport competition because of physical exertion or anticipatory response. In elite male golfers, cortisol levels were elevated before and during a competition (7,28) compared to during practice. Furthermore, in elite male golfers, the cortisol level before a competition was reported to be higher than during and/or after the competition (7,28). Gender difference in cortisol responses to a sport competition has not been extensively investigated (28). To our knowledge, only one study reported that there was no significant difference in cortisol levels (24). The primary purpose of their study (24), however, was to examine the cortisol response to an intensified training in elite swimmers (8 male and 16 female), not to examine its sex-specific response. Gender mediates psychophysiological responses to stress (4). During a golf competition, stress responses of elite male and female junior golfers have not been examined yet. Thus, a cortisol response to a competition compared with practice in junior female golfers and male golfers may provide an insight of sex-specific stress response to the competition.
After prolonged, intense exercise, the immune system may be temporarily suppressed (33). In elite athletes, frequent upper respiratory tract infections are associated with suppression of salivary immunoglobulin A (IgA) levels (11). Immunoglobulin A is a predominant antibody contained in secretions of the mucosal immune system and acts primarily as a host defense against pathogenic microorganisms. The effect of exercise on IgA is still inconclusive. Immunoglobulin A levels are reported to be suppressed in response to a single prolonged, intense exercise (25,30), remain unchanged (31) or are increased in response to moderate-intensity exercise (6,35,37). In a golf competition, salivary IgA response has not been investigated, yet.
Although cortisol and IgA are often assessed using blood serum assays, salivary cortisol and IgA measurements are used in the field with ease of data collection and sample preparation. Furthermore, they are relatively stress free because of lack of venipuncture. Salivary cortisol and/or IgA levels have been used in various sports, such as soccer (1,13,37), swimming (11), rowing (29), rugby (27), tennis (31), and golf (7,28). Thus, in this study, cortisol and IgA levels were examined by saliva.
It is commonly known that immune and endocrine systems of the body interact with each other. Exercise is associated with a variety of hormonal and immunological changes (1,24) especially in a competition. However, there was no study to observe stress and immune response to a golf competition in elite junior athletes. Thus, the purpose of this study was to investigate the responses of salivary cortisol and Ig A during a golf competition compared with a practice round in various periods of golf game (rest, and before, during, and after rounds) in both elite male and female junior golfers. It was hypothesized that (a) salivary cortisol level would be elevated before and after rounds during a competition in both elite male and female junior golfers, and (b) salivary IgA level would be elevated after rounds during a competition in both elite male and female golfers.
Experimental Approach to the Problem
Both elite male (n = 6) and female (n = 6) junior golfers participated in this study to investigate their stress and immune responses during a competition. Salivary cortisol as a stress hormone and salivary IgA were measured in the field. This study was conducted under 2 game types, golf competition vs. practice rounds in early summer (May-June). Each game was performed on a separate day. In other words, a practice round was completed as the practice round only, with each team having 3-4 players without any coach intervention. A competition round was conducted on the first day of the competition in a national tournament, held by junior or senior high-school leagues in which college entrance points were granted. The practice round was played at the same time of the day and in the same location as the competition was played to eliminate any confounding variables, such as circadian variations of cortisol level.
All participants were familiarized for a salivary sample collection before the first data collection. Salivary collections were performed in 4 different occasions of golf game (rest, and before, during, and after a round) on 2 different days (competition and practice rounds) totaling 8 collections overall. For the rest values, saliva collection was conducted after dinner followed by getting enough rest on the day before a competition/a practice, and for the values of before a round was done 30 minutes before a competition/a practice. The values for during a round salivary collection was performed immediately after hole 9, and one for the after a round was done immediately after hole 18. Subjects were asked not to eat too much within the 1-hour period before the salivary collection, with no food intake permitted at all 15-20 minutes before the collection. They were also asked to wash out their mouths with fresh water 15 minutes before salivary collection. After the specimens were collected, they were placed in noncontaminated plastic tubes, correctly labeled with the subjects' names and dates, and then immediately frozen. Because at least 200 μl of saliva was required for a test to be conducted, at least 3 ml was collected for use after centrifugation.
The subjects of this study were 12 elite junior golfers-6 men and 6 women, respectively. Physical characteristics of subjects are as shown in Table 1. All the subjects were healthy with no known major diseases. All subjects were junior golfers enrolled at Korean middle junior and high school leagues. The Institutional Review Board approved the research. All the subjects and their guardian were fully informed of the purpose and risks of participating in this investigation, and signed informed consent documents before any testing.
Salivary cortisol and IgA assessments are used widely in sports because they are noninvasive and convenient ways (23,36) to examine stress and immune responses. Salivary cortisol has been used widely as an accurate and reliable method (16).
Cortisol was analyzed by the COBRA II Gamma counter (Packard, Meriden, CT, USA) by using Solid-phase radioimmunoassay (RIA) as the testing method. The test principle was as follows: The Coat-A-Cortisol procedure is a solid-phase RIA, wherein 125I-labeled cortisol competes for a fixed time with cortisol in the saliva sample for antibody sites. Because the antibody is immobilized to the wall of a polypropylene tube, simply decanting the supernatant suffices to terminate the competition and to isolate the antibody-bound fraction of the radiolabeled cortisol. Counting the tube in a gamma counter then yields a number, which converts by way of a calibration curve to a measure of the saliva cortisol present in the sample. Reference level of salivary cortisol is as follows: 8 am: 0.47-0.87 μg·dl−1, Noon: 0.18-0.36 μg·dl−1, 4 pm: 0.11-0.29 μg·dl−1, and Midnight: 0.04-0.15 μg·dl−1 (CARLCAM Pharmaceutical Co., Ltd., Seoul, Korea).
Immunoglobulin A (IgA) Analyses
Immunoglobulin A was analyzed by Kinetic microplate reader (Molecular device, Meno Park, CA, USA) by using enzyme immunoassay (EIA) as the testing method with the test principle as below: When induced for response by placing a standard reference material and the saliva sample in a tube with conjugated horseradish peroxidase and goat antihuman SIgA, a standard reference material and SIgA, from among the saliva, form an antibody conjugate. At this point in time, the uncombined free form is eliminated, whereas the conjugated substance shows the reaction of peroxidase enzymes from substrate tetramethylbenzidine material. The developed color is blue and is induced to a yellow color by the addition of a stopping agent. Color-developed plates measured SIgA levels in the specimen by reading the rate of absorbance at a wavelength of 450 nm. Reference level of salivary IgA is as follows: high level: 805.38 ± 56.32 μg·ml−1; moderate level: 336.03 ± 17.89 μg·ml−1; and low level: 91.08 ± 4.09 μg·ml−1 (Salivary SIgA Indirect EIA kit, Salimetrics, LLC, State College, PA, USA).
All statistical computations were performed using SPSS. The values were expressed as average ± SDs. Descriptive analyses were performed on physical characteristics of subjects. The levels of salivary cortisol and IgA were analyzed using repeated measures analysis of variance (game types × salivary collection times) for both male and female junior golfers. Contrast tests were conducted to investigate the significant difference in variants according to each saliva collection time in game types. The statistical significance level of all analysis was p < 0.05.
The number of subjects was estimated on the basis of power analysis on salivary cortisol (power: >0.80; effect size using Eta squared: >0.41) (17).
Figure 1 illustrates the average salivary cortisol levels on practice rounds and competitions among elite male (a) and female (b) junior golfers per saliva collection time. In male junior golfers, there was no interaction between game types and collection times (p = 0.143). The significant main effects, however, were found in both on game types (p = 0.009) and collection times (p < 0.001). Because results of contrast test, salivary cortisol was significantly different between rest and before rounds of golf (p = 0.029) in male junior golfers. All other contrast tests were not significant.
In female junior golfers, there was also no interaction between game types and collection times (p = 0.228). The significant main effect was found in collection times (p < 0.001), but it was not found in game types (p = 0.092). As results of contrast test, salivary cortisol was significantly different between rest and after rounds of golf (p = 0.016) in female junior golfers. All other contrast tests were not significant.
Salivary Immunoglobulin A
Figure 2 illustrates the average of salivary IgA on practice rounds and competitions among elite male (a) and female (b) junior golfers according to saliva collection time. In male junior golfers, salivary IgA showed no interaction between game types and collection times (p = 0.443). The significant main effects were found in both on game types (p = 0.019) and collection times (p = 0.018). Contrast test on collection times revealed no significant difference although salivary IgA tends to be different between before and during/after rounds of golf.
In female junior golfers, salivary IgA showed no interaction between game types and collection times (p = 0.439). No main effects were found in either game types (p = 0.152) or collection times (p = 0.090).
This was the first study to investigate the responses of salivary cortisol and IgA during a golf competition in elite male and female junior golfers. Our main findings were the salivary cortisol was significantly elevated in a golf competition compared with a practice round in male junior golfers, whereas it was not in female junior golfers. Salivary cortisol level was higher before the round than at rest for male junior golfers although it was higher after the round than at rest for female junior golfers. Our results suggest that salivary cortisol levels might have gender-specific response to a competition in junior golfers. In male junior golfers, salivary IgA was also significantly elevated during a golf competition compared with a practice round, whereas it was not in female junior golfers. Although there was no significant change in salivary IgA, it tended to be elevated after rounds. None of changes was found to be significant in salivary IgA for female junior golfers.
The study hypothesis for the cortisol was that salivary cortisol level would be elevated before and after rounds during a competition in both elite male and female junior golfers. However, no interaction between game types (practice vs. competition) and salivary collection times (in stability, before, during, and after rounds of golf) was found in the salivary cortisol levels for either male or female elite junior golfers. A significant main effect was found in game types for male but it was not found for female junior golfers. Also, salivary collection times were significant in both male and female junior golfers.
Cortisol is an essential hormone that performs important functions, such as energy metabolism and blood pressure control. However, where cortisol secretion becomes excessive, induced by excessive stress or anxiety, it can result in disproportionate metabolism rates or even life-threatening disease. In particular, cortisol is a hormone of great significance to athletes, because it can directly affect, for example, a golfer's performance, by atrophying their muscle protein. Therefore, this study suggests that a new concept in physical and psychological training programs might be incorporated with a golfer's stress hormone levels.
Male junior golfers exhibited higher concentrations of salivary cortisol during a competition than during practice rounds. Elevated salivary cortisol level during competition is presumed to be because of adrenocorticotropic hormone (ACTH), located in the hypothalamus, being stimulated to increase secretions of cortisol by the higher psychological and physical stress in competition. These results are similar to those found in a study that found higher heart rates and concentrations of cortisol among 15 professional golfers during competition than during practice (7,28).
Salivary cortisol levels of both male and female junior golfers were influenced by different time periods of golf game, whereas they exhibited different patterns. For male junior golfers, cortisol was higher before a round than at rest, whereas it was higher after rounds than at rest for female junior golfers. In male golfers, significantly elevated cortisol levels ‘before’ rounds might be gradually stabilized after anticipatory response (7). Female golfers exhibited their highest levels of cortisol production during competition, suggesting they easily become stressed or anxious as they played. In this study, female golfers showed a significant increase in salivary cortisol levels during rounds. Plasma cortisol has shown to be elevated during a long period of exercise with relatively low-intensity exercise (3). Golf is a low-intensity sport, but it does induce physical fatigue and psychological stress because it requires a long duration of exercise in excess of 4 hours. The cortisol response of male junior golfers exhibited similar responses to that in the study by Doan et al. (7), but the response of female junior golfers was different in this study. This might be affected by sex or age. To assure the gender-specific response of stress hormone, various stress hormones from junior and adult golfers including both men and women should be collected and analyzed.
The study hypothesis for the IgA was that salivary IgA level would be elevated after rounds during a competition in both elite male and female golfers. However, no interaction between game types (practice vs. competition) and salivary collection times (in stability, before, during, and after rounds of golf) was found in the salivary IgA levels for either male or female elite junior golfers. A significant main effect was found in game types for male but it was not found for female junior golfers. No main effect was found for salivary collection times in either male or female junior golfers.
Immune function is influenced by many factors, such as psychological stimulation, nutritional status, injury, and exercise. The reaction of immunocyte may differ depending on how homeostasis is controlled (21). It is suggested that psychological factors and psychoneuroimmunology might be associated with physical disease (5). Recently, the hypothalamic-pituitary-adrenal axis (HPA) axis and the neuroendocrine modulating circuit have been identified. It is argued that this finding suggests that the immune system is controlled by the neuroendocrine system, with the nervous system and the immune system being strongly associated with each other. In the study by Jemmott and others (15), who studied the relation between stress and IgA reaction, it was explained that the correlation between stress and IgA, in terms of the secretion rate of IgA, was significantly lower during stressful periods. A number of other researchers have also found that the level of salivary IgA decreases with higher levels of anxiety, when this anxiety is induced by psychological causes (12,15). On the other hand, there have also been reports that the IgA value has a positive correlation with active mood states (14,19). This suggests trends heading in differing directions.
Salivary IgA level was elevated in competition than on practice in male golfers (p = 0.019), but not in female golfers (p = 0.152). In male golfers, salivary IgA level was not significantly different among collection times although it tended to be elevated during and after a round. In female golfers, IgA showed no significant main effects on both game type and collection times. We found that in male golfers, salivary IgA level was decreased when salivary cortisol level was increased. These findings are similar to those of other studies (12,15,18). However, in the case of female golfers, the tendency was not found. IgA also appeared higher during the round, at the time of higher cortisol levels. To identify the relationship between stress and immune response, future study should be performed with an increased number of male and female golfers so that correlations of these variables would be estimated. The concentrations of IgA found in this study exhibited higher tendencies after rounds than in stability or before a round in competition, contrary to the previous studies implying decreased concentration levels of salivary IgA after exercise (11,39). However, a recent study that analyzed saliva collected during exercise (22,29) found similar results to this study, reporting increased concentrations of IgA. It was claimed that the level of IgA increased after training periods and competitive games among basketball players who were at both before and after puberty ages, suggesting conformity with the results found in this present study in terms of age range (38). It is thought that the level of IgA increased during and after rounds of golf as a way for golfers to cope with physical or psychological responses generated by exercise. Thus, golf is a low- to moderate-intensity physical exercise, which might be capable of enhancing immunological reactions.
For the future study, finding in this study should be examined over 4 days of the whole competition period to identify whether temporary increased phenomena is caused by dehydration, decreased plasma volume, and decreased salivary flow because cortisol and IgA might be affected by long-term golf competitions that induced psychophysiological factors among golfers. Furthermore, with the increased number of subjects, the correlation between stress response and performance needs to be investigated with a gender-specific approach.
Stress is an intrinsic factor in sports, especially in golf games. Identifying the physiological stress response during an actual golf competition might be important for athletes' conditioning and training for young athletes who do have few game experiences. Salivary collection used in this study is an easy way to be applied in the field for individualized training. Salivary cortisol and IgA levels were higher in competition than practice in male junior golfers, whereas they were similar in female junior golfers. In male golfers, cortisol was higher before rounds than at rest, but in female golfers, it was higher after rounds than at rest. Salivary cortisol and IgA measurements may be used to study the stress and immune responses during golf practice and competitions. Our results also suggest that sex might play a role on stress and immune responses during a game of golf.
We thank our subjects for their efforts.
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