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Relationships Between Competitive Wrestling Success and Neuroendocrine Responses

Fry, Andrew C1; Schilling, Brian K2; Fleck, Steven J3; Kraemer, William J4

Journal of Strength and Conditioning Research: January 2011 - Volume 25 - Issue 1 - p 40-45
doi: 10.1519/JSC.0b013e3181fef62f
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Fry, AC, Schilling, BK, Fleck, SJ, and Kraemer, WJ. Relationships between competitive wrestling success and neuroendocrine responses J Strength Cond Res 25(1): 40-45, 2011-Previous research on wrestling suggests winning wrestlers will have a greater increase in testosterone (Tes) than losing wrestlers, although the physiological mechanism is unknown. To determine the role of the sympathetic nervous system in this phenomenon, 12 male wrestlers from an National Collegiate Athletic Association Division I program wrestled 5 matches over a 2-day period. Serum samples were collected pre (Pre) and immediately postmatch (Post) for the determination of Tes, cortisol (Cort), Tes/Cort, and epinephrine (Epi). The subjects had a combined record of 34 wins, 31 losses, and 4 ties. Testosterone increased (p < 0.05) for both winners and losers, but the increase was greater for winners (X ± SE; nmol·L−1; winners, pre = 16.4 ± 1.2, post = 23.2 ± 1.5; losers, pre = 14.8 ± 1.0, post = 19.4 ± 1.2). Cortisol and Epi increased similarly for both winners and losers, whereas the Tes/Cort ratio was unaltered at any time. Relative changes in the Epi response (%Δ) for losers were correlated to %ΔTes (r = 0.91), whereas winners did not exhibit similar relationships (r = 0.09). These data suggest that winning wrestlers may use a different regulatory mechanism for their acute Tes responses than losers who appear to depend on sympathetic regulation. Additionally, these data from humans support the biosocial theory of status and the challenge hypothesis developed for competing males in other species.

1Applied Physiology Laboratory, Department of Health, Sport and Exercise Sciences, University of Kansas, Lawrence, Kansas; 2Human Performance Laboratories, Department of Health and Sport Sciences, The University of Memphis, Memphis, Tennessee; 3Sport Science Department, Colorado College, Colorado Springs, Colorado; and 4Human Performance Laboratory, Department of Kinesiology, The University of Connecticut, Storrs, Connecticut

Address correspondence to Dr. Andrew C. Fry, acfry@ku.edu.

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Introduction

Considerable research is available concerning the physiological role of the acute testosterone (Tes) response during various types of physical activity in humans. Although Tes undoubtedly influences numerous physiological systems, it also appears to play a role in the psychophysiological responses to competitive conditions. Previous research (6,12) on male wrestlers indicated that the victorious wrestler had greater increases of Tes postmatch than the losing wrestler did, but these results are not consistent (26). This relationship has been supported in other events such as tennis (24), in nonphysical contests such as chess (23), and even in games of chance such as those that involve a coin toss (25). The mechanisms responsible for these responses, however, have not been determined. The stress of competition may be a factor in the Tes response (19) because the stimulatory influence of catecholamines on Tes has been noted previously (11,29).

In addition to Tes, cortisol (Cort) has been suggested as a performance indicator in human competition, including wrestling (12), weightlifting (26), and judo competition (30). It has been suggested that better athletes will have higher psychological anxiety, resulting in increased Cort concentrations. These athletes, however, are able to better control the outward physiological effects of competitive stress (13). Additionally, the level of competition influences Cort levels, with increased Cort at more important competitions (13,26). Furthermore, the ratio of Tes/Cort may emphasize the anabolic vs. catabolic response to winning or losing (26) and appears to indicate training stresses (15).

One way to examine the relationship between Tes and dominance in humans is in the context of sporting events, and in the case of this investigation, the combative sport of wrestling. Study of aggressive behavior in animals provides much relevant research. The biosocial theory of status provides an interesting context for interpreting the human sport physiology in response to winning and losing (22). This suggests that face-to-face aggressive encounters provide an opportunity to exhibit dominant behavior and that there is a feedback mechanism between Tes and aggressiveness when establishing dominance. Additionally, the challenge hypothesis as presented by Wingfield et al. (33) suggests that Tes levels are a critical factor when males of a species are aggressively confronted over territory, breeding mates, access to food, or other types of intrusions. These reports also suggest that whether human sport participants or animal survival encounters, winners of contests will have increased Tes, thus facilitating further confrontations. On the other hand, the loser will have an opposite effect, possibly preventing the loser from participating in future competition that could lead to a dangerous situation. Therefore, the purposes of this study were to (a) reexamine the relationships of Tes, Cort, and epinephrine (Epi) responses to winning or losing a freestyle wrestling match and (b) to examine one possible regulating mechanism, the role of sympathetic regulation of these responses.

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Methods

Experimental Approach to the Problem

Competitive collegiate wrestlers from a prior study who participated in a series of 5 freestyle wrestling matches over 2 days were classified as winners or losers for each match (21). Blood-borne variables were collected pre and post each match. A 2 nonrandom groups (winner and losers) pre-post design was used to determine differences in the endocrine variables for the winners and losers. Correlation coefficients determined possible regulating mechanisms.

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Subjects

Twelve men were recruited from a major American university varsity wrestling team to serve as subjects in this investigation. This particular squad had been highly successful during the preceding season, finishing third in the NCAA Division I Wrestling Championships. The experimental period was initiated 3-4 weeks after the national championships, which allowed for a recovery period. Subjects were representative of all Olympic freestyle weight classifications, with the exception of the heavyweight division. All subjects were currently freestyle wrestlers competing in national and international competitions. Subject characteristics were as follows (mean ± SE): age = 19.3 ± 1.2 years; height = 1.76 ± 0.02 m; weight = 75.3 ± 2.5 kg; body fat = 7.3 ± 0.7%. Subjects were informed of the potential experimental risks and gave their written informed consent to participate in this study, which was approved by the university's Institutional Review Board for the use of human subjects. Additionally, all subjects were screened by the team physician before participating in the study.

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Procedures

The 2-day wrestling tournament consisted of 5 freestyle matches (3 matches on day 1 and 2 matches on day 2). Each match was a 5-minute Olympic freestyle match that was formally refereed and scored. If a fall were to occur, the wrestlers would start again on their feet until the full 5-minute match was wrestled; however, no falls occurred. To create a demanding, competitive environment, each match was contested with an opponent of similar skills and training background and within the same weight class (i.e., wrestle-off competition) to simulate competition. Because each wrestler was competing for a starting position in his weight class, competition within the individuals in that weight class created both the physical and psychological stress of an actual competition. Testing was performed prematch and again postmatch for each of the matches wrestled. Matches on day 1 were wrestled at 10:00, 14:00, and 18:00 hours, and on day 2 at 10:00 and 19:00 hours to simulate the winner's bracket for an actual tournament.

Blood samples were collected via venipuncture from an antecubital arm vein by using a 20-mL disposable syringe equipped with a 20-gauge disposable needle. Subjects were seated in a semirecumbent position in a chair for all blood collections. Whole blood was removed from the 20-mL syringe and used for microcapillary analysis of hematocrit. Hematocrit was analyzed in triplicate using standard microcapillary techniques, and hemoglobin was analyzed in triplicate using a cyanmethemoglobin method (Sigma Chemical CO., St. Louis, MO, USA). Percent changes in plasma volume were then calculated using these variables according to the methods of Dill and Costill (10). Ten milliliters of blood was transferred to a plain Vacutainer® tube (Baxter, McGraw Park, IL, USA) and allowed to clot at room temperature and subsequently centrifuged at 1,500g for 15 minutes. The resulting serum was placed into separate 1.5-mL microcentrifuge tubes frozen at −88°C for later analysis of Tes and Cort. Three milliliters of blood was also transferred to a Vacutainer® tube containing ethylenediaminetetra acetic acid (EDTA) and mixed by gentle inversion. One millilter of this sample was transferred to a 1.5-mL microcentrifuge tune and frozen at −88°C for later analysis of hemoglobin. Seven milliliters of the syringe sample was transferred to a Vacutainer® containing sodium heparin to prevent clotting, mixed by gentle swirling, and placed in an ice bath for 5 minutes, then spun in a refrigerated centrifuge (4°C) for 15 minutes at 1,850 rpm. The resulting supernatant was then transferred to 1.5-mL microcentrifuge tubes and frozen at −88°C for later analysis of plasma Epi.

For analysis of plasma catecholamines, a 1-ml plasma sample was used for a preliminary aluminum oxide extraction procedure. Subsequently, high performance liquid chromatography (Waters, Division of Millipore Corp., Milford, MA, USA), which uses an M-45 solvent system and a 460-electrochemical detector with data integration system, was used for determination of Epi. Internal standards were used for each sample, and the analytical procedures followed have been previously described (14).

Serum Tes and Cort were determined in duplicate using 125I solid phase double-antibody radioimmunoassays (RIAs) (DSL-4100 [Tes], DSL-2000 [Cort], Diagnostic Systems Laboratory, Webster, TX, USA). Determinations of different serum immunoreactivity values were made using an LKB gamma counter (Turku, Finland) and an on-line data reduction system. All intra and interassay variances were <4% (Tes) and 7% (Cort), respectively. The Tes RIA had a detection limit sensitivity of 0.17 nmol·L−1 and the Cort RIA had a detection limit of 3.04 nmol·L−1. Primary antibodies for both assays were antirabbit polyclonal, whereas secondary antibodies were goat antirabbit globulin. No samples were thawed until analyzed, thus avoiding freeze-thaw artifact. All samples for a specific biochemical assay were decoded only after analyses were completed (i.e., blind analysis procedure).

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Statistical Analyses

The data were analyzed using a 2 × 2 (group [winners, losers] × time [pre, post]) mixed-model analysis of variance (X ± SE). The % change (%Δ) in scores was calculated pre-post for Tes, Cort, Epi, and Tes/Cort. Pearson product-moment correlations were determined between relative changes (%Δ) for Epi and Tes, Cort or Tes/Cort. Significance for all analyses was p ≤ 0.05. All cases were treated as independent, even though each wrestler accounts for more than one case (7).

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Results

Postmatch Tes values were significantly higher than those of prematch measures for both winners and losers. However, Tes concentrations of wrestlers after winning a match were significantly greater than those of losing wrestlers (Figure 1). Cortisol and Epi values postmatch were also significantly higher than prematch measures although no differences were observed between winners and losers (Figures 2 and 3). Plasma volume shifts for each match were as follows: match 1 = −10.0%, match 2 = −7.0%, match 3 = −9.1%, match 4 = −8.5%, and match 5 = −7.0%. As such, changes in circulating concentrations for Tes and Cort cannot be explained exclusively by the plasma volume shifts. There was no significant difference between pre and postmatch values for the Tes/Cort ratio (Figure 4). Correlations between %ΔEpi and either %ΔTes or %ΔTes/Cort ratios indicated that only losers exhibited significant correlations. No significant correlations for the winning wrestlers were observed (Table 1).

Table 1

Table 1

Figure 1

Figure 1

Figure 2

Figure 2

Figure 3

Figure 3

Figure 4

Figure 4

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Discussion

Similar to previous findings (6,12), our data showed a significant difference in Tes responses between winning and losing wrestlers. There was a significant difference for both groups from pre to post; however, the victorious wrestlers showed greater Tes increases than that of their opponents. This Tes difference could be because of the positive mood associated with winning, as has been shown in physical (7,12,24) and nonphysical (23-25) competitions. Testosterone responses may also be related to the motivation to win (30), although this was not measured in this study. Although the combatants in this investigation were familiar with one another, it is likely that there was a certain degree of anticipation of who the winner would be because they were relatively evenly matched, and because they were often competing for a position on the team. If it holds that the Tes increase seen in winners is related to mood or self-appraisal of performance (7,18,24), we can presume that the winner was satisfied with his performance. It has also been suggested that changes in social status may foster a hormonal response (25). If so, then the role of winning a contest may be to alter the status of the wrestler, thus contributing to an enhanced elevation of Tes. Subsequently, in sports where repeated contests occur over a short period of time (e.g., wrestling tournament), the Tes response to one match will likely affect the hormonal profile for a subsequent match (7). Therefore, the effects of winning or losing may be cumulative in such a setting.

Cortisol was not significantly different between winners and losers, contrary to previous findings (26,30). It is likely that the physiological stimulus (i.e., energy availability) may have been a predominant contributor to the Cort response, and as such, resulted in no differences between winners and losers. Within the scope of the present study, Cort does not seem to be a performance indicator. Likewise, there was no pre-post change in the Tes/Cort ratio for either winners or losers.

Concerning the catecholamine response, there was no difference in Epi between winners and losers. Circulating levels of Epi for the losing wrestlers suggest serum Tes concentrations could be under sympathetic regulation based on high correlations of r = 0.912 and r = 0.733 for %ΔTes or %ΔTes/Cort with %ΔEpi, respectively. Conversely, winning wrestlers showed no significant correlations for these comparisons, suggesting that the winners may have used a different regulatory mechanism for their Tes response to victory. Although luteinizing hormone is the primary trophic hormone for Tes in men, it is unlikely that differences in luteinizing hormone were responsible for the greater Tes postmatch in the winners because of the approximately 15-minute lag time for luteinizing hormone to produce actual increases in circulating Tes. The duration of the wrestling matches was not long enough to permit luteinizing hormone to be a major contributor. Increases in Tes have been observed in shooting competitions where the physical demands are considerably different (19), with no concomitant increase in luteinizing hormone. This increase could be caused by an increase in testicular blood flow (8), a decreased hepatic clearance (20), or increased sympathetic activity (11).

Although not the same as winning and losing, data exist supporting the role of Tes in aggressive behavior. In humans, greater Tes has been associated with greater sport-specific aggressiveness in competing judo athletes (27). Although athletic settings for humans are not identical to violent aggression, it has been suggested that sports research provides an excellent opportunity to assess aggression, success, and hormonal responses (27). It should be noted, however, that it has been suggested that team sports may present a different hormonal response to winning or losing (18).

The role of Tes on aggressive behavior has been closely studied with animal models. Testosterone appears to contribute to aggression, particularly when combined with prior competitive experiences (3,4) and with food or water deprivation (1,4). This response appears to be augmented with supraphysiological levels of Tes (2,3) and is apparent in both males and females (2,3,5). In this study, all the subjects were somewhat food and water deprived because they had undergone a 5-7% body weight loss the previous week to qualify for their appropriate wrestling weight classes (21). How large a factor such a weight loss was is beyond the scope of this study. Although the biosocial theory of status indicates an important role for Tes when establishing social status (22), this general concept has been examined from the perspective of aggressive encounters among males of a species when establishing territories, accessing food, and courting breeding mates (33). Although successful males of polygamous species exhibit consistently higher levels of circulating Tes, males of monogamous species appear to selectively increase Tes as needed for aggressive encounters. The monogamous males exhibit what appears to be a more efficient system. Numerous data exist supporting the challenge hypothesis throughout the animal kingdom. Relationships between aggressiveness and dominance with Tes and sympathetic activity are apparent for male lizards (31,32) and rats (28). On the other hand, high levels of Tes are not always required for supporting aggressive behavior, suggesting other factors contribute to the physiology of aggression (9). In comparison, the wrestlers in this study possess many characteristics similar to what is seen in monogamous males in other animal species. Previous human research also indicates that Tes and sympathetic activity is critical for aggressive behavior. Although aggressive encounters in the animal kingdom are typically related to survival, the wrestling encounters examined in this study may present an excellent example of survival of the athlete within the construct of competitive sport performance.

Review of data from this study suggests a theoretical paradigm for regulation of Tes in competing wrestlers (see Figures 5 and 6). The relationships reported in Table 1 allow us to calculate coefficients of determination (r2), thus estimating how much of the competition-induced changes in Tes may be accounted for by sympathetic activity (i.e., Epi). Testosterone responses for the losing wrestlers appear to be under primarily sympathetic regulation (%ΔTes & %ΔEpi, r2 = 0.83). On the contrary, sympathetic activity appears to have little to do with Tes responses for winning wrestlers (r2 = 0.01). Apparently, a different mechanism is responsible for this enhanced Tes response. Possible candidates for this regulation include psychological factors such as perceptions of winning, changes in status, and mood alterations (25). It is important to note here that this paradigm is based on correlational data, which does not infer causality. As such, it is theoretical at this stage, and further research is necessary to clarify these regulatory mechanisms.

Figure 5

Figure 5

Figure 6

Figure 6

In summary, winning wrestlers had higher Tes values postcompetition than losers did as has been previously reported (12). Cortisol and Epi were not different between groups, indicating no difference in stress or physical exertion. Epinephrine responses to competition were strongly correlated with Tes responses in the losers. These relationships were not present in the winners, indicating different mechanisms in Tes regulation in these groups.

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Practical Applications

Undoubtedly, success in the sport of wrestling is highly dependent on factors such as physical mastery of wrestling skills, physiological preparation, and mental skills training. What has not been fully appreciated is the critical role of establishing social dominance in this sport. These data clearly indicate that winning and losing wrestlers use different physiological mechanisms for the acute endocrine response to competition. Based on data from the animal kingdom, winning wrestlers appear to establish a mechanism conducive to future success and long-term survival as a wrestler. In summary, the ability to foster an aggressive demeanor and a social dominance on the wrestling mat may be highly dependent on previous success and the accompanying physiological responses and adaptations. As such, scheduling of appropriate opponents may be critical for establishing an enhanced wrestling social dominance to facilitate future success.

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Acknowledgments

The authors would like to thank Rich Lorenzo, John Fritz, and John Yankanich for their gracious assistance with the design and implementation of this study. Additionally, we would like to thank N. Travis Triplett, Scott E. Gordon, L. Perry Koziris, and Steven J. Fleck for assistance with the data collection. This study was funded by a grant from the US Olympic Committee.

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    Keywords:

    testosterone; cortisol; epinephrine; sympathetic nervous system; aggression; biosocial theory of status; challenge hypothesis

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