The World Cup. These three words are arguably the most popular in the world – well, maybe it’s “I love you”, but “The World Cup” is probably a close second. Every four years, the most elite national soccer teams assemble to partake in a tournament viewed by billions worldwide. It’s an event of immense magnitude, immeasurable spectacle, and the highest stakes in sports. This year, the FIFA Women’s World Cup is being hosted by France, with multiple games in Paris! Seeing as I live in the United States, where we haven’t yet fully embraced the beautiful game, it is a rare occurrence to attend high level soccer matches; so, a few days ago, when our class had the unbelievable experience of attending a group-stage match in the 2019 Women’s World Cup between the United States of America and Chile, I was over-the-moon excited.
The game did not disappoint, the United States dominated Chile, especially in the first half where they scored three goals, including a super-strike from veteran Carli Lloyd. However, despite the beat down imposed upon the Chileans, the atmosphere remained lively. Thunderous chants of “Chi-Chi-Chi Le-Le-Le, ¡Viva Chile!” clashed with shouts of “USA! USA! USA!” for the entire 90 minutes, and with every goal scored by the United States women, the thrill of ensuing victory became more intensely expressed on the players’ faces.
While the triumphant screams, hugs between teammates, and big smiles made their emotions evident on the surface, a more complicated biological phenomenon was occurring inside the bodies of the athletes. In a recent study published in 2015, Drs. Kathleen Casto and David Edwards examined how levels of certain hormones fluctuated during different stages of competition in female soccer players (Casto and Edward, 2015). Competition, at its heart, is a contest for social status driven by a desire to be superior to an opponent (Casto and Edwards, 2015). This desire seems to be heavily linked with the neuroendocrine system – a physiological system in which the central nervous system regulates hormone production (Martin, 2001) – and with three hormones in particular: testosterone, cortisol, and estradiol (Casto and Edward, 2015). Both testosterone (Carré and Olmstead, 2015) and estradiol (Stanton and Schultheiss, 2007) are related with dominance motivation and aggressive behavior, while cortisol is related with stress (Dickerson and Kemeny, 2004).
This study, conducted by Emory University researchers, analyzed salivary levels of testosterone, cortisol, and estradiol from the Emory University varsity women’s soccer team in five conditions: a baseline condition (three days before a match), before warming up for a match, shortly before the beginning of the match, immediately after the match, and 30 minutes after the match (Casto and Edwards, 2015). In addition to comparing hormone levels during different parts of the match, levels during both a home game and an away game were analyzed to investigate whether playing in front of an opposing crowd influenced hormone levels (Casto and Edwards, 2015).
When analyzing testosterone levels, the researchers found no significant difference between the athlete’s baseline levels and their levels before warming up (Casto and Edwards, 2015). However, testosterone levels after completing a warm-up rose 22% from levels before the warm-up (p<0.001) during a home game and 32% (p<0.001) during an away game (Casto and Edwards, 2015). Immediately following the conclusion of the game, testosterone levels were 19% (p=0.046) higher than during warm-ups at a home game and 18% (p=0.003) higher during an away game (Casto and Edwards, 2015). 30 minutes after the game’s conclusion, testosterone levels dropped 16% for a home game (p<0.001) and 26% for an away game(p<0.001) (Casto and Edwards, 2015).
Like testosterone levels, cortisol levels also displayed variation during different stages of competition. However, whereas testosterone levels continuously rose from before a warm-up to immediately after competition, cortisol levels were significantly elevated prior to warming up but did not significantly change after a warm-up (Casto and Edwards, 2015). Cortisol levels peaked immediately after the end of the match, where they were elevated 142% (p=0.001) after a warm-up during a home game and 131% after an away game (p=0.002) (Casto and Edwards, 2015). 30 minutes after a match’s end there were no significant changes in cortisol levels (Casto and Edwards, 2015). I, for one, find this cortisol data especially surprising because, when I used to play sports, I remember feeling the most stressed immediately before a game, not during it, and, as cortisol is a stress hormone, I would have expected cortisol levels to be at their peak immediately preceding a game. Estradiol also fluctuated throughout stages of competition, as its levels significantly increased both before and during a warmup (Casto and Edwards, 2015). However, immediately after competition, estradiol levels significantly decreased and did not show any significant changes 30 minutes after the game (Casto and Edwards, 2015).
Interestingly, when this study statistically compared hormone levels during a home game to those during an away game, there were no statistical differences (Casto and Edwards, 2015). Maybe home-field advantage is not that big of a deal after all. Perhaps most surprising to me about this study though, was that the data did not show any significant differences in hormone levels when either winning or losing (Casto and Edwards, 2015). Another measurement I think the study could have taken for a potentially more in-depth analysis is hormone levels at half-time. At half-time, players can rest for a few minutes to catch their breath, but, while resting, are getting coached by the manager to make adjustments in preparation for the second half. Even though the players’ bodies are resting, their brains are still working hard in anticipation of the rest of the game, so it would be pertinent to study hormone levels at half-time.
Ultimately, the research by Casto and Edwards brings to light some fascinating and surprising conclusions about the neuroendocrine system’s activity during physical competition. Now that I’ve learned a bit more about hormone fluctuation in athletes, I wonder how hormone levels in fans, such as myself, would change while watching a match.
Carré, J., & Olmstead, N. (2015). Social neuroendocrinology of human aggression: Examining the role of competition-induced testosterone dynamics. Neuroscience, 286, 171-186. doi:10.1016/j.neuroscience.2014.11.029
Casto, K. V., & Edwards, D. A. (2015). Before, During, and After: How Phases of Competition Differentially Affect Testosterone, Cortisol, and Estradiol Levels in Women Athletes. Adaptive Human Behavior and Physiology, 2(1), 11-25. doi:10.1007/s40750-015-0028-2
Martin, J. V. (2001). Neuroendocrinology. In N. J. Smelser & P. B. Baltes (Eds.), International encyclopedia of the social and behavioral sciences (pp. 10585-10588). Retrieved from https://doi.org/10.1016/B0-08-043076-7/03420-3
Stanton, S. J., & Schultheiss, O. C. (2007). Basal and dynamic relationships between implicit power motivation and estradiol in women. Hormones and Behavior, 52(5), 571-580. doi:10.1016/j.yhbeh.2007.07.002