1 Journal of trength and Conditioning Research, 2004, 18(1), National trength & Conditioning Association CHANGE IN EXERCIE PERFORMANCE AND HORMONAL CONCENTRATIO OVER A BIG TEN OCCER EAON IN TARTER AND NOTARTER WILLIAM J. KRAEMER, 1 DUNCAN N. FRENCH, 1 NIGEL J. PAXTON, 2 KEIJO HÄKKINEN, 3 JEFF. VOLEK, 1 WAYNE J. EBATIANELLI, 2 MARGOT PUTUKIAN, 2 ROBERT U. NEWTON, 5 MARTYN R. RUBIN, 1 ANA L. GÓMEZ, 1 JAON D. VECOVI, 1 NICHOLA A. RATAME, 1 TEVEN J. FLECK, 4 J. MICHAEL LYNCH, 2 AND HOWARD G. KNUTTGEN 2 1 Human Performance Laboratory, Department of Kinesiology, The University of Connecticut, torrs, Connecticut 06269; 2 Center for ports Medicine/Laboratory for ports Medicine, Pennsylvania tate University, University Park, Pennsylvania 16802; 3 Department of Biology of Physical Activity, The University of Jyväskylä, Jyväskylä, Finland; 4 Department of port cience, Colorado College, Colorado prings, Colorado 80903; 5 chool of Biomedical and Exercise and port cience, Edith Cowan University, Joondalup, Australia. ABTRACT. Kraemer, W.J., D.N. French, N. Paxton, K. Häkkinen, J.. Volek, W.J. ebastianelli, M. Putukian, R.U. Newton, M.R. Rubin, A.L. Gómez, J. Vescovi, N.A. Ratamess,.J. Fleck, J.M. Lynch, and H.G. Knuttgen. Changes in exercise performance and hormonal concentrations over a Big Ten soccer season in starters and nonstarters. J. trength Cond. Res. 18(1): As a consequence of the physiological demands experienced during a competitive soccer season, the antagonistic relationship between anabolic and catabolic processes can affect performance. Twenty-five male collegiate soccer players were studied throughout a season (11 weeks) to investigate the effects of long-term training and competition. ubjects were grouped as starters (; n 11) and nonstarters (; n 14). Measures of physical performance, body composition, and hormonal concentrations (testosterone [T] and cortisol [C]) were assessed preseason () and 5 times throughout the season (T2 ). tarters and participated in 83.06% and 16.95% of total game time, respectively. Nonstarters had a significant increase ( 1.6%) in body fat at compared to. Isokinetic strength of the knee extensors (1.05 rad sec 1 ) significantly decreased in both ( 12%) and ( 10%; p 0.05) at. ignificant decrements in sprint speed ( 4.3%) and vertical jump ( 13.8%) were found at T5 in only. Though within normal ranges ( nmol L 1 ), concentrations of T at were low for both groups, but increased significantly by. Concentrations of C were elevated in both groups, with concentrations at the high end of the normal range (normal range nmol L 1 )atand T4 in and T4 in, with both groups remaining elevated at. Data indicate that players entering the season with low circulating concentrations of T and elevated levels of C can experience reductions in performance during a season, with performance decrements exacerbated in starters over nonstarters. occer players should therefore have a planned program of conditioning that does not result in an acute overtraining phenomenon prior to preseason (e.g., young players trying to get in shape quickly in the 6 to 8 weeks in the summer prior to reporting for preseason camp). The detrimental effects of inappropriate training do not appear to be unloaded during the season and catabolic activities can predominate. KEY WORD. testosterone, cortisol, overtraining, conditioning, training, football INTRODUCTION occer has been characterized as a high intensity sport that combines intermittent bouts of anaerobic and aerobic exercise (6, 12). During the course of a competitive soccer season, player s bodies are continuously subjected to a variety of psychological and physical stresses from both practice and competition (4, 6). As a consequence of the physiological demands placed on players, conditioning programs for soccer require that aerobic capacity, strength, power, speed, and speed endurance be developed as fundamental components of physical conditioning. Consequently, the goal of soccer practice and physical conditioning is to provide a stimulus for soccer-specific adaptations that will result in improved athletic performance (7). The maintenance or improvement in performance standards is not, however, solely determined by appropriate conditioning. The ability of bodily systems (e.g., neuromuscular system, endocrine system) to recover and regenerate following composite stresses including strenuous activity, psychological stress of practice and competition, etc., can also influence physical performance. Of particular importance to force development is the manner in which muscles respond and remodel following exercise stressors, (i.e., practice, conditioning, or competition). When a player is both training and competing, the dynamic homeostatic balance created between anabolic (building) and catabolic (breakdown) processes within the muscle can ultimately influence muscular force characteristics and, therefore, affect the quality of a player s performance (8). The effects of soccer training on immune function (22), muscular strength (19, 20), the hormonal responses to a single game (17), and long-term training (3 5) have previously been reported. Yet few data exist to track hormonal responses over the course of a competitive season. Indeed, biological and quantitative assessments are now a common practice used for the evaluation of physiological responses to many sport competitions and training programs. A wide variety of biochemical, hematological, and physiological markers have been used for the longterm monitoring of athletes (9). In particular, cortisol and testosterone have been identified as reliable markers of training stress (2, 21, 10, 11, 18). Reflective of this study, Carli et. al (4) have demonstrated that during the course of a competitive soccer season basal levels of both cortisol and testosterone can become significantly elevated. Based on such data, we hypothesized that increases in testosterone and cortisol would occur over the course of the sea- 121
2 122 KRAEMER, FRENCH, PAXTON ET AL. son. However, the potentially greater competitive responsibilities being placed on the actual starters in a sport, and the differential physiological and performance effects related to starter () or nonstarter () status have not been clarified in prior soccer research. Thus, it was not apparent how hormonal changes would temporally track in and over the course of a National Collegiate Athletic Association (NCAA) Division I Big Ten Conference season. While the use of biochemical markers for long-term monitoring of exercise stress is widespread, the relationship between hormonal concentrations and physical performance standards during the course of a competitive season remains unclear. If the physical demands of practice, conditioning, and competition are too great, it might be hypothesized that catabolic activities will predominate. If, however, the body is able to successfully cope with the demands, anabolic metabolism can help to maintain or improve performance over the course of the season (9). Nevertheless many factors impact this delicate metabolic balance, including conditioning activities, practice schedules, academic demands, psychological stressors, and competition, each contributing to the overall physiological status of a player. The purpose of this study was to investigate the physiological and performance changes that take place over a Big Ten season in college soccer players. In other words, we wanted to determine how these players adapted to the effects of conditioning, practice, and high level competition over an entire season. We were specifically interested in determining whether differences existed between and on a collegiate soccer team. METHOD Experimental Approach to the Problem We utilized a collegiate soccer team in the United tates of America who were as a team ranked in the top 10. Their competition included the national champion and top contenders in NCAA Division I soccer. We monitored the team throughout an 11-week competitive season consisting of 19 games using a longitudinal study design. Measures of physical performance (isokinetic and isometric strength, sprint speed, vertical jump), body composition (body density, percent body fat), and hormonal concentrations (testosterone, cortisol) were assessed 6 times during the course of the season. Baseline testing was performed 1 week before the first competitive game (), 4 assessments were made during the season (i.e., weeks 3, 7, 8, and 9; T2-T5), and a further assessment was made 1 week following the end of the competitive period () to determine if any dramatic recovery occurred. In all cases, a minimum of 7 days separated test administration. Throughout tracking players continued to participate in regular team practices (i.e., speed, agility, and speed endurance conditioning; simulated game play) and an inseason strength and conditioning program performed twice per week. All workouts were supervised by team coaches. The in-season strength-training program targeted the major muscle groups (i.e., legs, back, chest) and consisted of varied workouts with exercises focusing on muscular power development (e.g., jump squats, back squats, power cleans, bench throws) using loads of up to 75 85% of 1 repetition maximum (1RM). It should be noted that prior to players completed a preseason heavy strength development phase, with training loads at 90 95% 1RM, but endurance run/sprint interval training was based on individual preferences which we hypothesize led to a potential acute overtraining stressor due to the desire by each player to quickly gain cardiovascular fitness for the start of the preseason practice. Between and the mean weekly amount of combined training was 10 h wk 1. ubjects did not adjust their diets or lifestyles significantly during the course of the season. ubjects NCAA Division I male soccer players at Pennsylvania tate University volunteered to participate in the 11- week tracking study designed to examine physiological responses to a competitive Big Ten soccer season. Prior to commencing the study, players underwent physical examination by the team physician, and each was cleared of any medical or endocrine disorders that might confound or limit their ability to participate fully in the investigation. The study was approved by the institutional review board for use of human subjects, and all players gave their written informed consent to participate. At the conclusion of study, the 25 subjects fit the criteria of the study and completed the season without confounding injury. Those subjects were assigned to 1 of 2 groups, (n 11) or (n 14) based on the amount of game time each played during the season. tarters and participated in 83.06% and 16.95% of total game time, respectively. None of the subjects were injured to the extent to limit practice or playing time or confound the study by injury. The physical characteristics (mean D) of the and, respectively, were: age, and years; height, and cm; body mass, and kg; body fat, and %. Physical Performance Testing All subjects had prior familiarization with all of the testing protocols to insure a stable baseline. Upon reporting to the laboratory, subjects performed a standardized warm-up. ubmaximal cycling was carried out at 60 W against a load of 0.5 kg for 5 minutes, followed by light stretching. Concentric strength of the knee flexors and extensors was determined at 1.05 rad sec 1 and 5.25 rad sec 1 using a Cybex isokinetic dynamometer (Lumex Corp., Ronkonkoma, NY). Each player was given a series of submaximal practice trials prior to each testing velocity. ubjects were seated in an upright position and secured around the chest and thigh. The test limb (dominant leg) was positioned and secured to the dynamometers lever arm according to the manufacturer s guidelines, just proximal to the medial malleolus. All positions were noted and documented to assure reliability of testing conditions. Upon instruction, subjects performed 3 continuous maximal effort contractions (extension/flexion) throughout the complete range of motion. imilar encouragement was given to each player by the investigator team. The highest torque produced during each of the assessments was recorded and the data was used to represent the maximal isokinetic strength for that velocity. In addition, angle-specific torque was evaluated at 60 knee extension and knee flexion, and 45 knee extension and knee flexion at each velocity. Tests of different contractile velocities were assigned in a balanced, random order, and 2- to 3-minutes rest separated trials.
3 PHYIOLOGICAL REPOE TO A COMPETITIVE OCCER EAON 123 Isometric strength of the knee extensors was also assessed for the dominant limb of the players. Again, the Cybex isokinetic dynamometer was used for this testing protocol. The positioning of the test limb was carried out in an identical manner to that previously discussed. Assessments of isometric strength were performed at a constant position of 45 of knee flexion. Upon command, subjects were instructed to kick out maximally against the lever arm in an attempt to exert maximal force as quickly as possible. An investigator terminated each trial when a positive rise in force tracing ceased to be observed. Each trial had an average duration of between 4 and 6 seconds using a rapid force production effort protocol for the test. Three trials with a minimum of 2 minutes rest between were performed with the highest of the 3 recordings obtained and defined as the player s maximal isometric force. Maximal vertical jump height was measured using a Vertec vertical jump measurement device (ports Imports, Columbus, OH). Prior to testing, each subject s standing vertical reach was determined. Care was taken to make sure the standing reach was accurately determined with regard to limb stretch. ubjects were then given 3 trials to jump for maximum height, with 2 to 3 minutes rest separating trials. The highest jump of the 3 trials was recorded. Determination of maximal vertical jump height was calculated by subtracting the standing reach from the jump height. print speed was assessed over 18.3 meters (20 yards) and 36.7 meters (40 yards) on a synthetic grass (Astro- Turf) surface which was used for all testing. print times were recorded manually in the field using handheld digital stopwatches with the same timers used for each test. Timers were assigned to a specific set of subjects and were used for each test to assure test-to-test reliability. The timers were placed at both the 18.3 meter (20 yard) and 36.7 meter (40 yard) marks so that both times could be recorded during a single trial. ubjects performed 3 trials, with the fastest time recorded serving as the measure of maximal speed. Body Composition Body composition was determined from 7 skinfolds taken using a Lange skinfold caliper (Country Technology, Gays Mills, WI). The 7 sites used were the triceps, subscapula, suprailiac, thigh, midaxilla, abdomen, and chest. Measures were consistently recorded on the right side of the subject s body. Bone density was calculated using the methods of Jackson-Pollock (13) and percent fat determined using the iri equation (25). Three skinfold measures were taken at each site and a variance of less than 5% was used as an acceptable criterion for measurement. The same experienced technician performed all measurements throughout the study period. Body mass was measured to the nearest 0.5 kg using an electronic scale (American Business Equipment Company, Inc., New Holland, PA). Hormonal Analyses A resting blood sample of 10 ml was obtained from the antecubital vein in the arm following a 12-hour overnight fast. amples were collected at the same time of the morning ( hours) for each player s visit in order to control for circadian variances. Whole blood was allowed to clot at room temperature, following which it was FIGURE 1. Changes in percent body fat during the course of an 11-week competitive soccer season. Values are means E and represent the percent body fat recorded for nonstarters (white) and starters (black). * p 0.05 from. centrifuged at 3200 rpm (4 C) for 20 minutes. The resultant serum was removed and stored at 80 C until subsequent analysis. erum concentrations of testosterone and cortisol were determined in duplicate using a 125 I solid phase radioimmunoassay (Diagnostic ystems Laboratories, Inc., Webster, TX). Immunoreactivity values were determined using a gamma counter and on-line data reduction system (Model 1272, Pharmacia LKB Nuclear, Inc., Gaithersburg, MD). The intra- and interassay variances for testosterone were less than 3.45% and 7.02%, respectively. The intra- and interassay variances for cortisol were less than 4.44% and 5.66%, respectively. tatistical Analyses A one-tailed t-test was used to compare active game time in order to determine starters from nonstarters, which proved to be significantly different (i.e., again, and participated in 83.06% and 16.95% of total game time, respectively). A two way analysis of variance (ANOVA) with repeated measures was used to determine the pairwise differences between starters and nonstarters where appropriate. When a significant F value was achieved, appropriate Tukey posthoc tests procedures were used to locate the difference between the means. Test-retest reliabilities for the experimental tests demonstrated intraclass correlations of R Linear regression analyses were performed to examine the bivariate relationships between hormonal and performance variables. In all cases, the level of significance was set at p REULT Measures of body composition indicated that a change in percent body fat occurred only in nonstarters during the season (Figure 1). A significant increase of 1.6% was found at compared to preseason levels (). This increase in body fat was identified as having occurred during the latter half of the season, with no significant changes found between and midseason (). No significant changes in percent body fat were observed at any time during the season for starters. In both groups, isokinetic leg strength decreased over time when measured at 1.05 rad sec 1 (Table 1). had a decreased peak torque ( 10%) of the knee extensors at ( Nm) that was significantly smaller when compared to the corresponding assessment ( Nm). also demonstrated a decrement during the
4 124 KRAEMER, FRENCH, PAXTON ET AL. TABLE 1. Changes in isokinetic knee extension and flexion strength during the course of an 11-week competitive soccer season. Group Test Extension * * * Torque (Nm) Flexion ** ** Values are means E and represent isokinetic strength recorded at 1.05 rad sec 1 for nonstarters () and starters (). * p 0.05 from. ** p 0.05 from corresponding group. knee extension, with significant reductions in peak torque found at both ( 11%) and ( 12%) compared to ( Nm and Nm vs Nm, respectively). No changes in peak torque of the knee flexors were found in either of the groups during the tracking period; however, there were significant differences between and at (, Nm;, Nm) and (, Nm;, Nm). Comparisons of angle-specific isokinetic strength at 60 of knee extension were significantly decreased ( 19%) in the nonstarters at ( Nm vs Nm) (Table 2). In, significant decreases in angle-specific peak torque of the knee flexors were observed at for both 45 (17%; Nm vs Nm) and 60 ( 9%; vs ). Players classified as also demonstrated significantly greater angle-specific isokinetic torque for knee flexion at 45 than at. No significant changes in isokinetic leg strength at 5.25 rad sec 1 for knee extension or knee flexion were FIGURE 2. Changes in 20-yard sprint times during the course of an 11-week competitive soccer season. nonstarters; starters. Values are means E and represent the sprint times recorded for (white) and (black). * p 0.05 from. found in either group. Furthermore, there were no significant differences between the 2 groups at any point during the tracking period. Both groups did, however, show significant increases during the isokinetic knee flexion at 60 at compared to ( and vs and for and respectively; Table 3). Measures of isometric strength showed no significant changes during the season for either group. Furthermore, no significant differences were observed in isometric strength measures between the 2 experimental groups ( and ). Nonstarters showed no change across time for the 18.3-meter (20-yard) sprint. A significant difference in sprint speed was found in the group, with the times at T5 significantly longer than (Figure 2). Neither group demonstrated any changes in times for the 36.7-meter TABLE 2. Group Changes in angle-specific isokinetic knee strength during the course of an 11-week competitive soccer season. Test Angle-specific torque at 1.05 rad sec 1 (Nm) Ext 60 Ext 45 Flex 60 Flex * * ** * Values are means E and represent isokinetic strength recorded at 1.05 rad sec 1 for nonstarters () and starters (). * p 0.05 from. ** p 0.05 from corresponding group. TABLE 3. Group Changes in angle specific isokinetic knee strength during the course of an 11-week competitive soccer season. Test Angle-specific torque at 5.25 rad sec 1 (Nm) Ext 60 Ext 45 Flex 60 Flex * * Values are means E and represent isokinetic strength recorded at 5.25 rad sec 1 for nonstarters () and starters (). * p 0.05 from.
5 PHYIOLOGICAL REPOE TO A COMPETITIVE OCCER EAON 125 FIGURE 3. Changes in vertical jump height during the course of an 11-week competitive soccer season. nonstarters; starters. Values are means E and represent the height jumped for (white) and (black). * p 0.05 from and ; $ p 0.05 difference to corresponding group. FIGURE 5. Changes in resting concentrations of serum cortisol during the course of an 11-week competitive soccer season. nonstarters; starters. Values are means E and represent the circulating concentrations for (white) and (black). * p 0.05 from T2,, T5; $ p 0.05 difference to corresponding group. FIGURE 4. Changes in resting concentrations of serum testosterone during the course of an 11-week competitive soccer season. nonstarters; starters. Values are means E and represent the circulating concentrations for (white) and (black). * p 0.05 from T2; ** p 0.05 from. $ p 0.05 difference to corresponding group. (40-yard) sprint, nor were there any differences between groups. ignificant changes in vertical jump performance were observed only in the starters group. A significant decrease in jump height was found at T5 when compared to the baseline scores recorded at (Figure 3). No changes were observed at any time for the. At T5, also had a significantly higher vertical jump height when compared to. In both the and groups, changes in circulating concentrations of plasma testosterone were found during the season. ignificant increases in testosterone concentrations were observed for both groups (Figure 4). At, the demonstrated significantly higher ( 23%) concentrations compared to the values recorded at T2 (18.2 nmol/l vs nmol/l). In a similar manner, testosterone concentrations for the group at were significantly higher ( 29%) when compared to baseline values recoded at (17.2 nmol/l vs nmol/l). Differences between groups were only recorded at, with the having significantly higher concentrations of circulating testosterone compared to the group. When correlations between testosterone levels and performance characteristics were carried out, a significant relationship was found in the between testosterone and vertical jump FIGURE 6. Changes in the testosterone to cortisol ratio (T/C ratio) during the course of an 11-week competitive soccer season. nonstarters; starters. Values are means E and represent the T/C ratio for (white) and (black). * p 0.05 from and T4. performance at T5 (r 0.77). In those players categorized as, significant correlations were found between testosterone concentrations and knee flexion at 1.05 rad sec 1 for (r 0.58), knee flexion at 5.25 rad sec 1 for (r 0.55) and (r 0.61), and peak isometric torque at (r 0.64) and (r 0.71). At, plasma cortisol concentrations were significantly higher in compared to. This concentration was above normal ranges ( nmol L 1 ). There were no significant changes in plasma cortisol concentrations during the course of the season, with the exception of, who experienced a significant increase in cortisol concentrations at T4 only (Figure 5). The only significant correlations between cortisol concentrations and physical performance were found in the, with vertical jump at T2 (r 0.64) and (r 0.59), 20-yard sprint at T2 (r 0.78), 40-yard sprint at T2 (r 0.57), and 1.05 rad sec 1 for knee extension at (r 0.58) having a relationship to cortisol concentrations. No correlations between cortisol concentrations and physical performance were found in the players designated as. The testosterone/cortisol ratio (T/C ratio) was found to change during the season in the. ignificant elevations in the T/C ratio were observed at when compared to the values calculated for and T4 (Figure 6). Again, no significant changes were demonstrated during the season in those
6 126 KRAEMER, FRENCH, PAXTON ET AL. players recognized as. tarters did, however, show that the serum T/C ratio had a significant correlation to the vertical jump performances assessed at T5 (r 0.65). Nonstarters were found to have a significant correlation between the T/C ratio and both the 20-yard sprint at T2 (r 0.56) and the peak isometric torque recorded at (r 0.61). DICUION Temporal responses to training and competition may mediate general performance decrements during the course of the 11-week soccer season. Both and experienced reductions in exercise performance that were highlighted in the latter stages of the competitive period (i.e., ; near playoffs and tournaments). Though more pronounced in the starters, performance reductions were observed in all players, indicating that performance adaptations may be independent of total match play. tarters were found to have significant reductions in both sprint speed ( 4.3%) and vertical jump height ( 13.8%) compared to preseason values (). Decreases in the peak isokinetic torque (1.05 rad sec 1 ) of the thigh musculature were found in both ( 12%) and ( 10%) at the end of the season. Nonstarters were also observed to have a significant increase in body fat of 1.6%, a change not reflected in the. In association with the changes in exercise performance, changes in circulating concentrations of testosterone and cortisol were also tracked throughout the season. Though within the normal range of nmol L 1 reported in the literature (23), initial serum testosterone concentrations for all players (, 14.9 nmol L 1 ;, nmol L 1 ) were considered somewhat low following preseason conditioning (). These concentrations were found to increase significantly by to 18.2 nmol L 1 and 17.2 nmol L 1 for and, respectively. In contrasting fashion to the trends observed for testosterone, initial cortisol concentrations were considered elevated ( nmol L 1 ) in compared to the normal resting range of nmol L 1, and above normal ranges in ( nmol L 1 ). Furthermore, circulating concentrations of cortisol remained elevated throughout the 11- week season without any significant reductions in circulating concentrations. ince both testosterone and cortisol have been identified as reliable markers of training stress (1, 10, 11, 18, 18, 21), these data indicate that for much of the season (-T5) catabolic processes (i.e., elevated cortisol, reduced testosterone) may have predominated. This assumption is supported by the low testosterone/cortisol ratio, previously referred to by Häkkinen et al. (10, 11), which suggests catabolic metabolism was foremost throughout the majority of the season. Interestingly the catabolic environment that was apparently already initiated in the preseason was not obviated over the course of the season. Bosco et al. (3) have previously reported basal concentrations of both testosterone and cortisol to be maintained within normal recognized ranges for a group of professional male soccer players. Celani and Grandi (5) examined the testosterone responses of trained nonprofessional soccer players over 12 weeks, and after an initial 30- day rest period these investigators also observed that basal concentrations of testosterone were within normal ranges. The present data indicate basal concentrations of testosterone were within normal ranges, however, circulating concentrations were considered low for the predominance of the season with demonstrating lower values at the beginning of the preseason, which may be due to acute overtraining related to endurance overtraining. Only at did basal concentrations of testosterone significantly increase, with and responding similarly. This recovery appears to reflect a dramatic reduction in total stress related to the season. erum cortisol concentrations were found to remain elevated throughout the entire season, with having basal levels at the higher end of normal ranges and above normal values ( nmol L 1 ). Carli et al. (4) indicate that serum testosterone and cortisol increase during a soccer season, however, the current study suggests that concentrations of these training stress markers following off-season and preseason conditioning may affect both the anabolic and catabolic responses to the competitive season. These changes may be exclusive to the training approach of collegiate soccer, in which players try to get into shape quickly during the summer break prior to a very rigorous preseason practice schedule in August. In addition, if such high concentrations are created prior to preseason training camp, our data indicates that no abatement of this adrenal-cortical stress occurs in the circulating concentrations over the season. Both and are exposed to the same conditioning and soccer training stress and competition is only one part of the total stress equation, which is obviously greater in. However, it appears that practice and conditioning stress may also be important to the physiological recovery as were not devoid of hypopituitary-adrenal-testicular maladaptations over the season. The dramatic increase in testosterone observed in both and at T-6 represents a potential rebound of physiological function with stress reduction. As corroborated in studies by Kraemer et al. (14) and Aldercrentz et al. (1), sprint running increases circulating concentrations of cortisol and decrease concentrations of plasma testosterone. Categorized as high-intensity intermittent exercise, soccer has been identified as a sport that has a prevalence of repeated bouts of maximal effort sprints (6). Florini (8) previously reported the antagonistic relationship between anabolic and catabolic hormones, and indicates that a decrease in plasma testosterone coupled with the catabolic state that accompanies elevated cortisol levels can result in reduced physical performance standards. Elevated cortisol concentrations lead to increased binding at the glucocorticoid receptor, and have been shown to result in reduced protein synthesis and concomitant losses in muscular force and functional performance (13). An elevation in testosterone concentrations can assist in balancing these catabolic effects; however decreased testosterone concentrations do not provide adequate or optimal anabolic stimulation to offset the catabolic effects consequent to chronically elevated cortisol levels (e.g., protein catabolism, immune suppression, in attempt to preserve glycogen concentrations in muscle). This was the case observed in this tracking study over the season. An increased catabolic environment within the muscles may have contributed to the observed diminished knee extensor strength. Discussed previously, a catabolic state can lead to diminished force production due to losses of contractile proteins or neural transmitters typically stimulated by testosterone interactions and such mechanisms would result in potential decreases in isokinetic strength (8). This has been supported in work by Häkki-
7 PHYIOLOGICAL REPOE TO A COMPETITIVE OCCER EAON 127 nen et al. (10, 11) who have shown significant decreases in testosterone with heavy weight lifting, and correlative decreases between maximal strength and power and the testosterone/cortisol ratio. The decreased ability to produce force may manifest itself as concomitant performance reductions in speed, vertical jump height, and strength. The data from our investigation indicates that had low levels of circulating testosterone and what may be considered elevated levels of cortisol. This may have created a state that may be due to the greater amount of physical stress evoked during the significantly higher amount of game time. The earlier onset of decrements in knee extension strength in (at ) vs. (at ) may reflect this dramatic influence of the catabolic dominance. Increased muscle catabolism may also be a possible explanation as to why experienced significantly greater peak torque for knee flexion at 1.05 rad sec 1 at and compared to, but then demonstrated no difference in knee flexion strength at. The fact that neither group showed increases in isokinetic or isometric strength during the season with soccer training is consistent with the findings of Öberg et al. (19). However, with the use of an in-season conditioning program, one might have expected strength gains but sport practice and competition apparently overrode any gains from anabolic exercise in the weight room and points to the importance of sport coaching decisions related to practice stress and total work planned for different phases (e.g., amount of scrimmage time in practice) of the season. It is not readily apparent why elevated cortisol concentrations and decreased testosterone concentrations (i.e., low T/C ratio) would only affect slow-velocity high-force contractions and not highvelocity low-force contractions. Kuzon et al. (16) have indicated that soccer is not only a high intensity exercise, but also provides a significant oxidative stimulus that may have a greater impact on Type I fibers. ince slow velocity muscle actions have a greater contribution of Type I motor units, any negative effects on Type I (slow twitch fibers) would be reflected in slow velocity isokinetic testing and help explain our results (15). For this reason, overuse or overtraining of endurance-related soccer practice drills and conditioning activities may be more detrimental to Type I fibers and the slow twitch motor units that contribute to slow velocity force production. As the players in the present study entered the competitive soccer season with low values for testosterone and what can be considered elevated levels of circulating cortisol, it appears that preseason training played a critical role in determining the metabolic status of the players as they entered the competitive period. Data indicate that players entering the season in apparent catabolic state experienced reductions in performance throughout the season, with performance decrements exacerbated in compared to. It is plausible that intensive training prior to the start of the season, combined with continued high intensity training during both practice and competition, contributed to chronically elevated cortisol concentrations and suppressed concentrations of testosterone. uch physiological conditions may have contributed to the subsequent decrements in muscle force production, supporting the findings of previous research (8). From these data, we suggest that monitoring players prior to preseason conditioning during the summer could be a necessary next step in gaining a more complete understanding of the changes that occur during the course of a competitive soccer season. As most sport seasons are now extending to year-round training, a full year of study may be needed to fully document changes in collegiate soccer players to a competitive season. Furthermore, greater attention may need to be paid to the exact structure of the cardiovascular endurance training in relationship to strength-related conditioning during the summer. PRACTICAL APPLICATIO During the course of a competitive season, collegiate soccer players are exposed to a variety of physical and psychological stresses from practice, conditioning, and competition. The ability of the players to recover following such activities can ultimately affect the quality of performance for ensuing physical activity. This study has indicated that the nature in which players enter a season can have significant effects on physical performance tests over the season. Without appropriate rest and recovery, intensive preseason conditioning can be found to decrease circulating levels of testosterone while simultaneously increasing concentrations of the catabolic hormone cortisol. With the continued high intensity stress experienced throughout the season, the consequence of entering the competitive period in this nature is reflected as a chronic catabolic environment for the neuromuscular system. uch a catabolic physiological status results in significant losses in muscular force that are manifested as decreases in speed, vertical jump height, and strength. The latter stages of a season may well be regarded as critical in determining the fortunes of a team, as it is during this period that play-offs and tournaments are contested. Present data indicate that both and are susceptible to decrements in performance capabilities if entering the season with catabolic processes predominating. Assessment of the circulating concentrations of testosterone and cortisol represent a possible means of monitoring the stress of training and competition, therefore providing a means of avoiding the performance decrements associated with the rigors of practice, conditioning, and competition. port practice schedules may need to be more carefully considered by head coaches who may not appreciate the impact of their practice decisions on their players physiological status. trength and conditioning professionals need to monitor such changes and help to educate sport coaches as to the potentially negative physiological impact of high scrimmage and total work practices over the entire season. uch interfaces with strength and conditioning professionals and sport coaches will be the new frontier for strength coaches as part of the total performance and sports medicine teams. REFERENCE 1. ALDERCRENTZ, H., M. HARKONEN, K.KUOPPAALMI,H.NAVERI, I. HUHTANIEMI, H. TIKKANEN, K. REME, A. 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