Hormonal and neuromuscular responses during a singles match in male professional tennis players

RESEARCH ARTICLE Hormonal and neuromuscular responses during a singles match in male professional tennis players Álvaro López-Samanes1,2☯, Jesús G. Pallarés1,3☯, Alberto Pérez-López4☯, Ricardo MoraRodrı́guez1☯, Juan F. Ortega1☯* 1 Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Toledo, Spain, 2 School of Physiotherapy, Faculty of Health Sciences, Francisco de Vitoria University, Madrid, Spain, 3 Faculty of Sports Sciences, University of Murcia, Murcia, Spain, 4 Departament of Medicine and Medical Specialties and Department of Biomedical Sciences. Faculty of Medicine and Health Science, University of Alcala, Madrid, Spain a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: López-Samanes Á, G. Pallarés J, PérezLópez A, Mora-Rodrı́guez R, Ortega JF (2018) Hormonal and neuromuscular responses during a singles match in male professional tennis players. PLoS ONE 13(4): e0195242. https://doi.org/ 10.1371/journal.pone.0195242 Editor: Alejandro Lucı́a, Universidad Europea de Madrid, SPAIN Received: November 23, 2017 Accepted: March 19, 2018 Published: April 6, 2018 Copyright: © 2018 López-Samanes et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ☯ These authors contributed equally to this work. * Abstract We sought to measure the response of cortisol concentrations around a professional tennis match and its association with hydration status and neuromuscular performance. Nine professional male tennis players were tested in a rest day, and 2-week after, during the first match of a professional tournament played in a clay-court. Salivary concentrations of cortisol (SalCC) were measured in a resting day (9:00 am and 8:00 pm), at the match day (9:00 am and 8:00 pm) and immediately before and after the match. Hydration status was assessed before the match (urine specific gravity; USG) while fluid turnover was tracked during the match. Finally, counter movement jump (CMJ) and handgrip isometric strength (HS) were measured before and after the match. SalCC, either in the morning (P = 0.161) and afternoon (P = 0.683) was similar in rest and match days. However, SalCC increased after the match (P = 0.033). Participants started the match hypohydrated (USG = 1.026 ±0.002) and during the match lost 1.0±0.3% of body weight despite 1.035±0.124 L/h of fluid ingested. CMJ and HS did not change post-match (P = 0.210 and P = 0.881, respectively). Correlations between the elevations in SalCC and dehydration (% BW loss) during the match were significant (r = -0.632; P = 0.034). Professional male tennis players did not show an anticipatory increase in SalCC the day of the match and neither signs of neuromuscular fatigue after it. During the match, the mild dehydration (i.e., <1.5%) was associated with the increases in cortisol levels which suggests that dehydration may be an added stress to be considered. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: The author(s) received no specific funding for this work. Introduction Competing interests: The authors have declared that no competing interests exist. Tennis is an intermittent sport played around the world by more than 83 millions of people, including over 4000 elite junior tennis players currently ranked by the nternational Tennis PLOS ONE | https://doi.org/10.1371/journal.pone.0195242 April 6, 2018 1 / 13 Salivary cortisol concentrations around a professional tennis match Federation[1] During a tennis match, players execute high-intensity actions characterized by short bouts of high intensity exercise (4–10 seconds), which are composed by accelerations/ decelerations, strokes and change-of-direction (COD) interspersed with periods of low-moderate intensity or rest (short break between points (10–20 seconds) and moderate rest between games and sets (90–120 seconds), with match duration between 1–5 hours[2, 3]. Demands of a tennis match may produce decrease in neuromuscular performance as a consequence of alterations in the mechanisms involved in muscle activation. Decrease in neuromuscular performance has been studied in several exercise/sports modalities using a relatively simple and feasible test, the counter-movement jump (CMJ)[4]. When neuromuscular performance decreases, it is denominated as neuromuscular fatigue (NMF). Research conducted during tennis national tournaments [5] and simulated tennis matches [6] have identified NMF by decrements either in the rate of force development [5] or the maximal voluntary contraction[6]. Moreover, the response of stress hormones like cortisol has been shown to be significantly increased during a tennis match[7, 8]. Professional tennis tournaments (i.e. ATP, Challengers and Futures) are scheduled around the world with a tight calendar which implies competition almost every week of the year. Hence, for professional players the physiological challenge of prolonged and frequent trips adds to the neuromuscular and physiological demands during the competition[9]. To minimize and control the incidence of these demands and to ensure adequate recovery between matches and tournaments tennis players are commonly advised to use nutritional supplements during the season [10, 11] as well as to adequate their behavioral/chronobiological patterns (e.g. sleep-hygiene, training at the schedule of competitions) and recovery strategies (coldwater immersion, compression garments) to maximize performance)[9, 12]. Several methods of assessing exercise-related physiological stress have been proposed, being the determination of the circulating levels of hormones (i.e., testosterone and cortisol concentrations [13] and the use of psychological questionnaires (e.g., CSAI-2R[14]) the most frequently used. Therefore, serum cortisol concentration has been used as physiological stress marker in individual[15] and team sports (e.g., soccer)[16]. Historically, cortisol concentrations have been determined from blood samples, however, the determination of cortisol in other body fluids, such as saliva, have been recently adopted since it is a non-invasive technique[17], and the results are highly correlated to serum cortisol concentration (r = 0.620, P<0.001;[18]). Thus, cortisol concentrations measured in blood or saliva are valid methods to measure physiological stress in tennis. Nonetheless, the effects of a tennis match in cortisol levels have only been described in amateur players but, to our knowledge, not in professional male tennis players competing in a professional tennis tournament (i.e., Futures). It has been reported that extreme elevations of serum cortisol concentration may interfere with decision making which could in turn affect performance[19]. In amateur tennis players, Filaire et (...truncated)