SIMILAR HORMONAL STRESS AND TISSUE DAMAGE IN RESPONSE TO NATIONAL COLLEGIATE ATHLETIC ASSOCIATION DIVISION I FOOTBALL GAMES PLAYED IN TWO CONSECUTIVE SEASONS ADAM J. STERCZALA, SHAWN D. FLANAGAN, DAVID P. LOONEY, DAVID R. HOOPER, TUNDE K. SZIVAK, BRETT A. COMSTOCK, WILLIAM H. DUPONT, GERARD J. MARTIN, JEFF S. VOLEK, CARL M. MARESH, AND WILLIAM J. KRAEMER Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut ABSTRACT Sterczala, AJ, Flanagan, SD, Looney, DP, Hooper, DR, Szivak, TK, Comstock, BA, DuPont, WH, Martin, GJ, Volek, JS, Maresh, CM, and Kraemer, WJ. Similar hormonal stress and tissue damage in response to National Collegiate Athletic Association Division I football games played in two consecutive seasons. J Strength Cond Res 28(11): 3234–3238, 2014—The recovery process from a college football game has been studied, yet the stability of such findings year to year in the same players remains unclear. The purpose of this study was to examine the same players’ biochemical recovery process in 2 consecutive seasons to a National Collegiate Athletic Association (NCAA) Division I football game. Ten starting players volunteered to participate in the study in each of the 2 seasons. Players performed a periodized heavy resistance training program over the entire year for each season. Fasted resting blood samples were obtained at similar times the Friday before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). In both seasons, serum creatine kinase (CK) concentrations increased significantly from T1 to T2, and returned to T1 values at T3. When we compared seasons, CK values did not differ at any time point. Myoglobin demonstrated similar patterns and results. Testosterone and cortisol values were similar at all time points and did not differ by season as no significant differences were observed for the resting hormonal concentrations. The results of this study indicate that yearly programs should maintain a periodized progressive program, which seeks to increase physical potential of players while providing a protective
Address correspondence to William J. Kraemer, [email protected]. 28(11)/3234–3238 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
3234
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effect on skeletal muscle and stabilization of hormonal status in response to both game and season stressors.
KEY WORDS myoglobin, creatine kinase, testosterone, cortisol, American football, resistance training INTRODUCTION
T
he high impact collisions and repetitive contact inherent to sports such as American football and rugby provide an additional stress not commonly encountered in other forms of physical activity. Consequently, numerous studies have investigated the physiological impact of such high contact sports. Such studies have consistently found postgame increases in the indirect markers of muscle damage, creatine kinase (CK), and myoglobin (8,11–14,19,20), and postgame CK levels have been correlated with the number of high impact collisions sustained (13,19,20). Surprisingly, however, the elevated CK values are lower than those observed after noncontact activities such as soccer, basketball, endurance training, and resistance exercise protocols performing heavy eccentric loads or short rest periods (1,10,15,21). Season-long studies have shown that CK values increase dramatically but briefly at the onset of the competitive season, then decrease for the remainder of the season (9,12). The combined findings of the acute and season-long studies have led sport scientists to suggest that attenuated muscle damage may result from “contact adaptation” (9,11,12). Contact adaptation has been defined as the tissue’s adaptive resistance to blunt force trauma and was theorized to contribute to reductions in acute CK and myoglobin responses to competition, despite slow accumulations in these biomarkers over the course of a football season (9). Another distinct possibility is that heavy resistance exercise, as commonly performed throughout a collegiate football career, exerts a protective effect against acute skeletal muscle damage (2–4,16,21). Although the acute effects of damaging competitive events
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
the
TM
Journal of Strength and Conditioning Research have been reasonably well characterized, the potential for periodized heavy resistance training programs to mitigate such effects has only recently gained attention. We had previously reported that starters on a National Collegiate Athletic Association (NCAA) Division I football team experienced significant increases in CK and myoglobin 18–20 hours after the ninth game of the season, which returned to baseline 40–42 hours after (11). Creatine kinase and myoglobin increases were apparent after the game, but these responses were attenuated when compared with values reported in the previously mentioned research. In line with previous contact sport research, we suggested that this observation could reflect contact adaptation or the protective effects of the eccentric component of the repetition loads used with resistance exercise. Testosterone and cortisol were measured due to their roles in the extent of skeletal muscle damage incurred and the subsequent repair (5). Additionally, these hormones can provide insights on psychological state. Testosterone increases have been associated with aggressive behavior and may be related to the will to win (18). Consequently, greater postmatch testosterone increases have been observed after wrestling and rugby wins (6,7). Cortisol is indicative of psychological and physical stress. One and 2 days after the game, neither hormone differed significantly from pregame values, which indicated minimal disruption to the metabolic or psychological state of players. Although the acute and season-long effects of football have been examined (8,9,11,12), there is little information on how measures of skeletal muscle damage change from year to year, with maturation, additional game experience, and further physical training. Based on our previous speculation that the attenuated muscle damage was due in part to the team’s strength and conditioning practices and “contact adaptation,” an additional year of these protective effects may be expected to produce further reductions in muscle damage. Given that individual characteristics of games and players can affect the amount of muscle damage, a follow-up study using the same players in similar competitive games allows for a more accurate assessment of season-to-season muscle damage changes. Thus, the purpose of this follow-up investigation was to determine whether an additional year of physical training and game play experience affected muscle damage in the same players under similar previous strength and conditioning programs and competitive game conditions.
METHODS
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Fortuitously, the game conditions were similar in both years. Additionally, only starters from the previous game were selected for this within-group follow-up investigation. We again measured CK and myoglobin to determine whether the additional training and experience would further reduce skeletal muscle damage caused by a football game. Testosterone and cortisol were measured to provide insight into the metabolic status of the players and their psychological states and level of stress. Subjects
Ten NCAA Division I American football players from the previous season volunteered for the study (age 21.1 6 2 years; body mass 110.2 6 9.1 kg; height, 192.1 6 8.7 cm). There were 3 offensive lineman, 2 defensive linemen, 2 offensive backs, and 3 linebackers; all were starters in both seasons. As in the previous season, all players participated in an individualized, periodized, off-season, summer, and inseason strength and conditioning programs in both years. Though the players may have acquired minor injuries over the course of the season, none had been diagnosed with injuries that limited or prevented participation in the game. The Institutional Review Board of University of Connecticut approved the study and each player signed an informed consent document to participate in the investigation. Procedures
In both years, fasted resting blood samples were obtained at similar times the Friday before (T1), 18–20 hours after (T2), and 42–44 hours (T3) after the ninth game of the season. The practice schedule during the week leading up to the game was similar. Additionally, similar resistance training programs were used both years as the same strength and conditioning staff members were identical for each year. Briefly, players participated in in-season, off-season, and summer training, based on multijoint exercises, heavy loading, multiple sets, and a mix of linear and nonlinear periodization. Exercise intensity was adjusted to account for increases in strength, but the workout structures and relative intensity of training were consistent. Again, the programs were supervised by the same strength and conditioning staff. A key factor was the use of heavy and very heavy resistance concentric/eccentric repetition loads (e.g., 90–100% of the concentric 1 repetition maximum) during different workouts and training cycles, which provided the known protective effects against damage in skeletal muscle (2). More detailed descriptions of the practice schedule and resistance training program can be found in the earlier investigation (11).
Experimental Approach to the Problem
Blood Collection/Biochemical Assay Analyses
To determine whether an additional year of physical training and game play experience would further attenuate muscle damage sustained in an NCAA Division I football game, we replicated the experimental procedures of our previous investigation as closely as possible. Blood samples were obtained before and after the ninth game in both seasons.
Before blood collection, each subject quietly rested in the supine position to equate body position dynamics. A resting 10-ml blood sample was obtained from an antecubital vein in the forearm using a vacutainer and tube containing SST Gel and Clot Activator. Blood was allowed to clot at room temperature and then centrifuged at 3,000 rpm at 48 C for VOLUME 28 | NUMBER 11 | NOVEMBER 2014 |
3235
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Biochemical Stress of American Football Games
Figure 1. Creatine kinase responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18– 20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. *T2 . T1 and T3 in both seasons.
Figure 3. Testosterone responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. No significant differences were observed between seasons or time points.
20 minutes. Samples were aliquoted into different sample tubes and frozen at 2808 C for subsequent analyses. The same assays and instrumentation were used for blood samples from each season. Serum CK and lactate dehydrogenase concentrations were determined using a colorimetric enzyme-immunoassay procedure with the use of a spectrophotometer and commercially available enzymatic kit (Sigma Diagnostics, St. Louis, MO, USA). Myoglobin concentrations were determined using a double antibody liquid phase 125I radioimmunoassay with a sensitivity of 6.25 ng$ml21 (Alpco Diagnostics, Windham, NH, USA). The intra-assay and interassay variances for CK and myoglobin were less than 15 and 5% for each year’s analysis, respectively. Serum testosterone and cortisol were determined in duplicate using a 125I solid phase radioimmunoassay (Diagnostic Systems Laboratories Inc., Webster, TX, USA). Values were determined using a gamma counter and online data-reduction system. The
intra-assay and interassay variances for testosterone and cortisol were less than 7 and 5% for each year, respectively.
The data are presented as mean 6 SD. All data sets met the assumptions for linear statistics. A 2-way (2 season 3 3 time
Figure 2. Myoglobin responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. *T2 . T1 and T3 in both seasons.
Figure 4. Cortisol responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. No significant differences were observed between seasons or time points.
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Game Conditions
Each game was the ninth of the season, played at home, in a highly competitive environment. The first game began at 3:30 PM in approximately 15.58 C weather, with 91 offensive and 66 defensive plays. The second game began at 7:15 PM in approximately 108 C weather, with 60 offensive and 87 defensive plays. In total, there were 157 and 147 plays for games 1 and 2, respectively, with subjects participating in an average of 61 6 9.2 and 59 6 8.5, respectively. Both games resulted in wins over divisional opponents, which further contributed to the similarity of competitive environments. Statistical Analyses
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
the
TM
Journal of Strength and Conditioning Research points) analysis of variance with repeated measures was used to analyze the data. When a significant F-value was observed, pairwise comparisons were made using Fisher’s least significant difference post hoc test. The alpha level for this study was p # 0.05.
RESULTS In both seasons, serum CK concentrations increased significantly from T1 to T2, and returned to T1 values at T3 (Figure 1). When we compared seasons, CK values did not differ at any time point. Myoglobin values also increased from T1 to T2 and returned to initial values by T3, with no difference between years at any time point (Figure 2). Testosterone values were similar at all time points and did not change from Years 1 to 2 (Figure 3). Similarly, cortisol values did not significantly deviate from resting values. Similar values were also observed when seasons were compared (Figure 4).
DISCUSSION Interestingly, we observed nearly identical physiological responses to 2 football games in back-to-back seasons. The similar response, despite an additional year of physical training and game play experience seemingly indicates a limit to the potential prophylactic mechanisms responsible for the attenuated muscle damage observed in previous football studies. The reduced muscle damage observed in this investigation is in line with previous research. Discrepancies in CK and myoglobin concentrations can be attributed to different sampling time points. Immediately after an NCAA Division III football game, Hoffman et al. (8) observed greater myoglobin concentrations and a reduced CK response. After a rugby match, myoglobin peaked 45 minutes after, whereas CK did not peak until 24 hours later (19). The study of Hoffman et al. (8) likely observed near peak myoglobin concentrations while conversely we observed peak CK concentrations. In a longitudinal investigation that examined changes in physiological responses to football games over the course of a season, we reported significantly lower resting CK values than those reported here (12). This difference likely reflected the inclusion of non-starters, who experienced less playing time, and correspondingly lower CK values. We suggested that reductions in CK and myoglobin were a result of contact adaptation, which corresponded with the findings of Hoffman et al. (9), where a spike in CK was observed during training camp, followed by reductions as the season progressed. Similar CK and myoglobin concentrations after the ninth game indicate that if present, contact adaptations already occurred at this point in the season. In addition, the team’s resistance training program likely contributed to reduced muscle damage. Compared with CK levels observed after other forms of physical activity, CK values of football players 18–20 hours after the game were
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relatively low. Furthermore, CK was rapidly cleared from the blood, as pregame values were reestablished 42–44 hours later. This finding is in agreement with previous research, where eccentric exercise resulted in an increased rate of skeletal muscle repair in response to subsequent exercise (2–4,16). Further evidence in NCAA Division I football players was provided by Smoot et al. (17), as higher participation rates in an off-season conditioning program were associated with lower average CK values during training camp. Our results indicate that there may be a limit to the protective effects of contact adaptation and resistance training against the physiological stress of the blunt trauma and physical exertion in football. Unchanged cortisol and testosterone resting values are consistent with previous research, where differences were not observed immediately after a football game or over the course of the season (9,11,12). Testosterone may be unaffected by a football game or change more acutely during or directly after a football game. Future work using intragame sampling would provide additional insights into the psychophysiological effects of a football game. Elevated cortisol is observed after sport competition, and values typically return to baseline within 1–4 hours. It was surprising to observe high values (close to the normal upper limit) at all time points. These findings may indicate the presence of accumulated stress rather than an acute response the conditions present during a game. The physiological demands of football play vary by position and may impact the amount of muscle damage incurred during a game. Additionally, investigation of rugby play has correlated CK concentrations with the number of high impact collisions (13). Therefore, investigation of the role that position plays on the number of high impact collisions and amount of muscle damage sustained is warranted. In summary, we present evidence to suggest that an additional year of practice and resistance training does not confer additional prophylactic benefits against the physiological stress of a football game. However, the moderate amount of tissue damage observed and the absence of adrenal cortical hyperactivity both support the positive effects of continued resistance training over 2 seasons. Our results also support previous observations of an attenuated response to football when compared with other forms of exercise, which may reflect the protective effects of resistance training and contact adaptation.
PRACTICAL APPLICATIONS This study extended our understanding of the importance of periodized heavy resistance training on the stabilization of damage markers and anabolic and catabolic hormonal signal response patterns in players who participated in 2 years of training and practice. The ability of such training to limit the extent of skeletal muscle tissue damage and negative hormonal signaling focuses the challenges of the game on other injury and sudden death factors (e.g., concussion, heat VOLUME 28 | NUMBER 11 | NOVEMBER 2014 |
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Biochemical Stress of American Football Games stress). Thus, yearly programs should maintain a periodized progressive program that seeks to increase the physical potential of players, elicit protective adaptations in skeletal muscle, and stabilize the hormonal response to acute and seasonal football stress.
ACKNOWLEDGMENTS We would like to thank all of the many UCONN research groups who have contributed to our understanding of the stresses related to the game of American football and to the medical and research staff members who have provided support. We thank the former strength and conditioning staff members and the former football coaching staffs for their beliefs in forwarding the science of this sport. This study was supported by internal research funds and does not represent any endorsement by the National Strength and Conditioning Association.
REFERENCES 1. Ascensao, A, Rebelo, A, Oliveira, E, Marques, F, Pereira, L, and Magalhaes, J. Biochemical impact of a soccer match—Analysis of oxidative stress and muscle damage markers throughout recovery. Clin Biochem 41: 841–851, 2008.
Kang, J, and Kraemer, WJ. Performance, biochemical, and endocrine changes during a competitive football game. Med Sci Sports Exerc 34: 1845–1853, 2002. 10. Kostopoulos, N, Fatouros, IG, Siatitsas, I, Baltopoulos, P, Kambas, A, Jamurtas, AZ, and Fotinakis, P. Intense basketball-simulated exercise induces muscle damage in men with elevated anterior compartment pressure. J Strength Cond Res 18: 451–458, 2004. 11. Kraemer, WJ, Looney, DP, Martin, GJ, Ratamess, NA, Vingren, JL, French, DN, Hatfield, DL, Fragala, MS, Spiering, BA, Howard, RL, Cortis, C, Szivak, TK, Comstock, BA, Dunn-Lewis, C, Hooper, DR, Flanagan, SD, Volek, JS, Anderson, JM, Maresh, CM, and Fleck, SJ. Changes in creatine kinase and cortisol in National Collegiate Athletic Association Division I American football players during a season. J Strength Cond Res 27: 434–441, 2013. 12. Kraemer, WJ, Spiering, BA, Volek, JS, Martin, GJ, Howard, RL, Ratamess, NA, Hatfield, DL, Vingren, JL, Ho, JY, Fragala, MS, Thomas, GA, French, DN, Anderson, JM, Ha¨kkinen, K, and Maresh, CM. Recovery from a national collegiate athletic association division I football game: Muscle damage and hormonal status. J Strength Cond Res 23: 2–10, 2009. 13. McLellan, CP, Lovell, DI, and Gass, GC. Biochemical and endocrine responses to impact and collision during elite Rugby League match play. J Strength Cond Res 25: 1553–1562, 2011. 14. McLellan, CP, Lovell, DI, and Gass, GC. Markers of postmatch fatigue in professional Rugby League players. J Strength Cond Res 25: 1030–1039, 2011.
2. Chen, TC, Chen, HL, Pearce, AJ, and Nosaka, K. Attenuation of eccentric exercise-induced muscle damage by preconditioning exercises. Med Sci Sports Exerc 44: 2090–2098, 2012.
15. Nieman, DC, Luo, B, Dreau, D, Henson, DA, Shanely, RA, Dew, D, and Meaney, MP. Immune and inflammation responses to a 3-day period of intensified running versus cycling. Brain Behav Immun 39: 180–185, 2014.
3. Clarkson, PM, Nosaka, K, and Braun, B. Muscle function after exercise-induced muscle damage and rapid adaptation. Med Sci Sports Exerc 24: 512–520, 1992.
16. Nosaka, K and Clarkson, PM. Influence of previous concentric exercise on eccentric exercise-induced muscle damage. J Sports Sci 15: 477–483, 1997.
4. Clarkson, PM and Tremblay, I. Exercise-induced muscle damage, repair, and adaptation in humans. J Appl Physiol (1985) 65: 1–6, 1988.
17. Smoot, MK, Cavanaugh, JE, Amendola, A, West, DR, and Herwaldt, LA. Creatine kinase levels during Preseason camp in national collegiate athletic association division-I football Athletes. Clin J Sport Med 24: 438–440, 2014.
5. Deschenes, MR, Kraemer, WJ, Maresh, CM, and Crivello, JF. Exercise-induced hormonal changes and their effects upon skeletal muscle tissue. Sports Med 12: 80–93, 1991. 6. Fry, AC, Schilling, BK, Fleck, SJ, and Kraemer, WJ. Relationships between competitive wrestling success and neuroendocrine responses. J Strength Cond Res 25: 40–45, 2011. 7. Gaviglio, CM, Crewther, BT, Kilduff, LP, Stokes, KA, and Cook, CJ. Relationship between pre-game Free testosterone concentrations and outcome in Rugby Union. Int J Sports Physiol Perform 9: 324–331, 2014. 8. Hoffman, JR, Kang, J, Ratamess, NA, and Faigenbaum, AD. Biochemical and hormonal responses during an intercollegiate football season. Med Sci Sports Exerc 37: 1237–1241, 2005. 9. Hoffman, JR, Maresh, CM, Newton, RU, Rubin, MR, French, DN, Volek, JS, Sutherland, J, Robertson, M, Gomez, AL, Ratamess, NA,
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18. Suay, F, Salvador, A, Gonzalez-Bono, E, Sanchis, C, Martinez, M, Martinez-Sanchis, S, Simon, VM, and Montoro, JB. Effects of competition and its outcome on serum testosterone, cortisol and prolactin. Psychoneuroendocrinology 24: 551–566, 1999. 19. Takarada, Y. Evaluation of muscle damage after a rugby match with special reference to tackle plays. Br J Sports Med 37: 416–419, 2003. 20. Twist, C, Waldron, M, Highton, J, Burt, D, and Daniels, M. Neuromuscular, biochemical and perceptual post-match fatigue in professional rugby league forwards and backs. J Sports Sci 30: 359– 367, 2012. 21. Vincent, HK and Vincent, KR. The effect of training status on the serum creatine kinase response, soreness and muscle function following resistance exercise. Int J Sports Med 18: 431–437, 1997.
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Address correspondence to William J. Kraemer, [email protected]. 28(11)/3234–3238 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
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effect on skeletal muscle and stabilization of hormonal status in response to both game and season stressors.
KEY WORDS myoglobin, creatine kinase, testosterone, cortisol, American football, resistance training INTRODUCTION
T
he high impact collisions and repetitive contact inherent to sports such as American football and rugby provide an additional stress not commonly encountered in other forms of physical activity. Consequently, numerous studies have investigated the physiological impact of such high contact sports. Such studies have consistently found postgame increases in the indirect markers of muscle damage, creatine kinase (CK), and myoglobin (8,11–14,19,20), and postgame CK levels have been correlated with the number of high impact collisions sustained (13,19,20). Surprisingly, however, the elevated CK values are lower than those observed after noncontact activities such as soccer, basketball, endurance training, and resistance exercise protocols performing heavy eccentric loads or short rest periods (1,10,15,21). Season-long studies have shown that CK values increase dramatically but briefly at the onset of the competitive season, then decrease for the remainder of the season (9,12). The combined findings of the acute and season-long studies have led sport scientists to suggest that attenuated muscle damage may result from “contact adaptation” (9,11,12). Contact adaptation has been defined as the tissue’s adaptive resistance to blunt force trauma and was theorized to contribute to reductions in acute CK and myoglobin responses to competition, despite slow accumulations in these biomarkers over the course of a football season (9). Another distinct possibility is that heavy resistance exercise, as commonly performed throughout a collegiate football career, exerts a protective effect against acute skeletal muscle damage (2–4,16,21). Although the acute effects of damaging competitive events
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
the
TM
Journal of Strength and Conditioning Research have been reasonably well characterized, the potential for periodized heavy resistance training programs to mitigate such effects has only recently gained attention. We had previously reported that starters on a National Collegiate Athletic Association (NCAA) Division I football team experienced significant increases in CK and myoglobin 18–20 hours after the ninth game of the season, which returned to baseline 40–42 hours after (11). Creatine kinase and myoglobin increases were apparent after the game, but these responses were attenuated when compared with values reported in the previously mentioned research. In line with previous contact sport research, we suggested that this observation could reflect contact adaptation or the protective effects of the eccentric component of the repetition loads used with resistance exercise. Testosterone and cortisol were measured due to their roles in the extent of skeletal muscle damage incurred and the subsequent repair (5). Additionally, these hormones can provide insights on psychological state. Testosterone increases have been associated with aggressive behavior and may be related to the will to win (18). Consequently, greater postmatch testosterone increases have been observed after wrestling and rugby wins (6,7). Cortisol is indicative of psychological and physical stress. One and 2 days after the game, neither hormone differed significantly from pregame values, which indicated minimal disruption to the metabolic or psychological state of players. Although the acute and season-long effects of football have been examined (8,9,11,12), there is little information on how measures of skeletal muscle damage change from year to year, with maturation, additional game experience, and further physical training. Based on our previous speculation that the attenuated muscle damage was due in part to the team’s strength and conditioning practices and “contact adaptation,” an additional year of these protective effects may be expected to produce further reductions in muscle damage. Given that individual characteristics of games and players can affect the amount of muscle damage, a follow-up study using the same players in similar competitive games allows for a more accurate assessment of season-to-season muscle damage changes. Thus, the purpose of this follow-up investigation was to determine whether an additional year of physical training and game play experience affected muscle damage in the same players under similar previous strength and conditioning programs and competitive game conditions.
METHODS
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Fortuitously, the game conditions were similar in both years. Additionally, only starters from the previous game were selected for this within-group follow-up investigation. We again measured CK and myoglobin to determine whether the additional training and experience would further reduce skeletal muscle damage caused by a football game. Testosterone and cortisol were measured to provide insight into the metabolic status of the players and their psychological states and level of stress. Subjects
Ten NCAA Division I American football players from the previous season volunteered for the study (age 21.1 6 2 years; body mass 110.2 6 9.1 kg; height, 192.1 6 8.7 cm). There were 3 offensive lineman, 2 defensive linemen, 2 offensive backs, and 3 linebackers; all were starters in both seasons. As in the previous season, all players participated in an individualized, periodized, off-season, summer, and inseason strength and conditioning programs in both years. Though the players may have acquired minor injuries over the course of the season, none had been diagnosed with injuries that limited or prevented participation in the game. The Institutional Review Board of University of Connecticut approved the study and each player signed an informed consent document to participate in the investigation. Procedures
In both years, fasted resting blood samples were obtained at similar times the Friday before (T1), 18–20 hours after (T2), and 42–44 hours (T3) after the ninth game of the season. The practice schedule during the week leading up to the game was similar. Additionally, similar resistance training programs were used both years as the same strength and conditioning staff members were identical for each year. Briefly, players participated in in-season, off-season, and summer training, based on multijoint exercises, heavy loading, multiple sets, and a mix of linear and nonlinear periodization. Exercise intensity was adjusted to account for increases in strength, but the workout structures and relative intensity of training were consistent. Again, the programs were supervised by the same strength and conditioning staff. A key factor was the use of heavy and very heavy resistance concentric/eccentric repetition loads (e.g., 90–100% of the concentric 1 repetition maximum) during different workouts and training cycles, which provided the known protective effects against damage in skeletal muscle (2). More detailed descriptions of the practice schedule and resistance training program can be found in the earlier investigation (11).
Experimental Approach to the Problem
Blood Collection/Biochemical Assay Analyses
To determine whether an additional year of physical training and game play experience would further attenuate muscle damage sustained in an NCAA Division I football game, we replicated the experimental procedures of our previous investigation as closely as possible. Blood samples were obtained before and after the ninth game in both seasons.
Before blood collection, each subject quietly rested in the supine position to equate body position dynamics. A resting 10-ml blood sample was obtained from an antecubital vein in the forearm using a vacutainer and tube containing SST Gel and Clot Activator. Blood was allowed to clot at room temperature and then centrifuged at 3,000 rpm at 48 C for VOLUME 28 | NUMBER 11 | NOVEMBER 2014 |
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Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Biochemical Stress of American Football Games
Figure 1. Creatine kinase responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18– 20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. *T2 . T1 and T3 in both seasons.
Figure 3. Testosterone responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. No significant differences were observed between seasons or time points.
20 minutes. Samples were aliquoted into different sample tubes and frozen at 2808 C for subsequent analyses. The same assays and instrumentation were used for blood samples from each season. Serum CK and lactate dehydrogenase concentrations were determined using a colorimetric enzyme-immunoassay procedure with the use of a spectrophotometer and commercially available enzymatic kit (Sigma Diagnostics, St. Louis, MO, USA). Myoglobin concentrations were determined using a double antibody liquid phase 125I radioimmunoassay with a sensitivity of 6.25 ng$ml21 (Alpco Diagnostics, Windham, NH, USA). The intra-assay and interassay variances for CK and myoglobin were less than 15 and 5% for each year’s analysis, respectively. Serum testosterone and cortisol were determined in duplicate using a 125I solid phase radioimmunoassay (Diagnostic Systems Laboratories Inc., Webster, TX, USA). Values were determined using a gamma counter and online data-reduction system. The
intra-assay and interassay variances for testosterone and cortisol were less than 7 and 5% for each year, respectively.
The data are presented as mean 6 SD. All data sets met the assumptions for linear statistics. A 2-way (2 season 3 3 time
Figure 2. Myoglobin responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. *T2 . T1 and T3 in both seasons.
Figure 4. Cortisol responses to a football game in Years 1 and 2. The concentrations were measured the day before the game (T1), 18–20 hours after the game (T2), and 42–44 hours after the game (T3). Data are presented as mean 6 SD. No significant differences were observed between seasons or time points.
3236
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Game Conditions
Each game was the ninth of the season, played at home, in a highly competitive environment. The first game began at 3:30 PM in approximately 15.58 C weather, with 91 offensive and 66 defensive plays. The second game began at 7:15 PM in approximately 108 C weather, with 60 offensive and 87 defensive plays. In total, there were 157 and 147 plays for games 1 and 2, respectively, with subjects participating in an average of 61 6 9.2 and 59 6 8.5, respectively. Both games resulted in wins over divisional opponents, which further contributed to the similarity of competitive environments. Statistical Analyses
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
the
TM
Journal of Strength and Conditioning Research points) analysis of variance with repeated measures was used to analyze the data. When a significant F-value was observed, pairwise comparisons were made using Fisher’s least significant difference post hoc test. The alpha level for this study was p # 0.05.
RESULTS In both seasons, serum CK concentrations increased significantly from T1 to T2, and returned to T1 values at T3 (Figure 1). When we compared seasons, CK values did not differ at any time point. Myoglobin values also increased from T1 to T2 and returned to initial values by T3, with no difference between years at any time point (Figure 2). Testosterone values were similar at all time points and did not change from Years 1 to 2 (Figure 3). Similarly, cortisol values did not significantly deviate from resting values. Similar values were also observed when seasons were compared (Figure 4).
DISCUSSION Interestingly, we observed nearly identical physiological responses to 2 football games in back-to-back seasons. The similar response, despite an additional year of physical training and game play experience seemingly indicates a limit to the potential prophylactic mechanisms responsible for the attenuated muscle damage observed in previous football studies. The reduced muscle damage observed in this investigation is in line with previous research. Discrepancies in CK and myoglobin concentrations can be attributed to different sampling time points. Immediately after an NCAA Division III football game, Hoffman et al. (8) observed greater myoglobin concentrations and a reduced CK response. After a rugby match, myoglobin peaked 45 minutes after, whereas CK did not peak until 24 hours later (19). The study of Hoffman et al. (8) likely observed near peak myoglobin concentrations while conversely we observed peak CK concentrations. In a longitudinal investigation that examined changes in physiological responses to football games over the course of a season, we reported significantly lower resting CK values than those reported here (12). This difference likely reflected the inclusion of non-starters, who experienced less playing time, and correspondingly lower CK values. We suggested that reductions in CK and myoglobin were a result of contact adaptation, which corresponded with the findings of Hoffman et al. (9), where a spike in CK was observed during training camp, followed by reductions as the season progressed. Similar CK and myoglobin concentrations after the ninth game indicate that if present, contact adaptations already occurred at this point in the season. In addition, the team’s resistance training program likely contributed to reduced muscle damage. Compared with CK levels observed after other forms of physical activity, CK values of football players 18–20 hours after the game were
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relatively low. Furthermore, CK was rapidly cleared from the blood, as pregame values were reestablished 42–44 hours later. This finding is in agreement with previous research, where eccentric exercise resulted in an increased rate of skeletal muscle repair in response to subsequent exercise (2–4,16). Further evidence in NCAA Division I football players was provided by Smoot et al. (17), as higher participation rates in an off-season conditioning program were associated with lower average CK values during training camp. Our results indicate that there may be a limit to the protective effects of contact adaptation and resistance training against the physiological stress of the blunt trauma and physical exertion in football. Unchanged cortisol and testosterone resting values are consistent with previous research, where differences were not observed immediately after a football game or over the course of the season (9,11,12). Testosterone may be unaffected by a football game or change more acutely during or directly after a football game. Future work using intragame sampling would provide additional insights into the psychophysiological effects of a football game. Elevated cortisol is observed after sport competition, and values typically return to baseline within 1–4 hours. It was surprising to observe high values (close to the normal upper limit) at all time points. These findings may indicate the presence of accumulated stress rather than an acute response the conditions present during a game. The physiological demands of football play vary by position and may impact the amount of muscle damage incurred during a game. Additionally, investigation of rugby play has correlated CK concentrations with the number of high impact collisions (13). Therefore, investigation of the role that position plays on the number of high impact collisions and amount of muscle damage sustained is warranted. In summary, we present evidence to suggest that an additional year of practice and resistance training does not confer additional prophylactic benefits against the physiological stress of a football game. However, the moderate amount of tissue damage observed and the absence of adrenal cortical hyperactivity both support the positive effects of continued resistance training over 2 seasons. Our results also support previous observations of an attenuated response to football when compared with other forms of exercise, which may reflect the protective effects of resistance training and contact adaptation.
PRACTICAL APPLICATIONS This study extended our understanding of the importance of periodized heavy resistance training on the stabilization of damage markers and anabolic and catabolic hormonal signal response patterns in players who participated in 2 years of training and practice. The ability of such training to limit the extent of skeletal muscle tissue damage and negative hormonal signaling focuses the challenges of the game on other injury and sudden death factors (e.g., concussion, heat VOLUME 28 | NUMBER 11 | NOVEMBER 2014 |
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Biochemical Stress of American Football Games stress). Thus, yearly programs should maintain a periodized progressive program that seeks to increase the physical potential of players, elicit protective adaptations in skeletal muscle, and stabilize the hormonal response to acute and seasonal football stress.
ACKNOWLEDGMENTS We would like to thank all of the many UCONN research groups who have contributed to our understanding of the stresses related to the game of American football and to the medical and research staff members who have provided support. We thank the former strength and conditioning staff members and the former football coaching staffs for their beliefs in forwarding the science of this sport. This study was supported by internal research funds and does not represent any endorsement by the National Strength and Conditioning Association.
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