Background: Athletes commonly consume insufficient fluid and electrolytes just prior to, or during training and competition. Unlike non-athletes or athletes who do not engage in frequent rigorous and prolonged training sessions, “hard trainers” may require additional sodium and better benefit from a hydration plan tailored to their individual physiology. The purpose of this randomized cross-over study was to determine whether a hydration plan based off of an athlete’s sweat rate and sodium loss improves anaerobic and neurocognitive performance during a moderate to hard training session as well as heart rate recovery from this session. Methods: Collegiate athletes who were injury free and could exercise at ≥ 75% of their maximum heart rate for a minimum of 45 min were recruited for this randomized, cross-over study. After completing a questionnaire assessing hydration habits, participants were randomized either to a prescription hydration plan (PHP), which considered sweat rate and sodium loss or instructed to follow their normal ad libitum hydration habits (NHP) during training. Attention and awareness, as well as lower body anaerobic power (standing long jump) were assessed immediately before and after a moderate to hard training session of ≥ 45 min. Heart rate recovery was also measured. After a washout period of 7 days, the PHP group repeated the training bout with their normal hydration routine, while the NHP group were provided with a PHP plan and were assessed as previously described. Results: Fifteen athletes from three different sports, aged 20 ± 0.85 years, participated in this study. Most participants reported feeling somewhat or very dehydrated after a typical training session. Compared to their NHP, participants following a PHP jumped 4.53 ± 3.80 in. farther, tracked moving objects 0.36 ± 0.60 m/second faster, and exhibited a faster heart rate recovery following a moderate to hard training session of 45–120 min in duration. Conclusion: A tailored hydration plan, based on an athlete’s fluid and sodium loss has the potential to improve anaerobic power, attention and awareness, and heart rate recovery time. Keywords: Sweat testing, Dehydration, Athletes, Prescription hydration plan, Standing long jump, Attention and awareness, Heart rate recovery Background exhaustion [2–6]. Additionally, inadequate replacement of Suboptimal hydration strategies during training and com- sodium, the predominant electrolyte lost through sweat, is petition are well known to reduce athletic performance thought to exacerbate the decline of these factors . Hy- through increased physiological stress [1–6]. Athletes who dration beverages that replace both fluid and electrolytes lose as little as 1–2% of their body mass through sweat lost through sweat have been employed over the last sev- loss exhibit an increase in heart rate, core temperature, eral decades, as evident with the widely available commer- muscle glycogen use, as well as a decrease in cardiac out- cial sports drink market. put, cognitive awareness, anaerobic power, and time to However, there is no one universal hydration strategy that athletes can utilize to mitigate dehydration-associated performance declines because each individual sweats at a * Correspondence: firstname.lastname@example.org different rate and loses a unique amount of sodium Department of Health Sciences, Merrimack College, O’Reilly Hall, Room 414, 315 Turnpike Street, North Andover, MA 01845, USA © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 2 of 10 through this sweat . In a convenience sample of 500 than 75% of their maximal heart rate for a minimum of athletes, Baker et al., determined fluid and sodium 45 min, were on one of the college’s sports teams, and pro- − 1 losses through training to range from 0.3–5.7 L. h vided informed consent. Informed consent was also re- − 1 − 1 and 18.2–70.8 mmol. L (418–1628 mg. L ) respect- quired by the participant’s head coach and the head ively . Based on these numbers, many commercially athletic trainer on campus. Because the training sessions available sports drinks do not supply enough sodium to utilized in this study consisted of already-scheduled team replace the amount lost through sweat for many athletes. training sessions, athletes were recruited from in-season This prompts the question of whether it is worthwhile to sports that were currently engaged in heavy sports-specific create a hydration plan tailored to the individual athlete or training sessions. Once recruited, participants underwent a if a more universal strategy is adequate. Compounded qualitative assessment for hydration habits and knowledge. with this, is past research, which has shown that athletes Participants were interviewed one-on-one by researchers seldom have a thorough understanding of what they to gauge hydration habits and knowledge pertaining to should be drinking, how much they should be drinking, or dehydration and overhydration. This subjective question- how often they should be drinking [10–12]. A study by naire consisted of a combination of open-response and Torres-McGehee and colleagues found that when 185 ath- multiple-choice questions. The full list of questions are letes were assessed on their knowledge of hydration and shown in the results section of this study. Following this, intake of micro and macronutrients, only 9% of them ex- participants were assessed for sweat loss, then randomized hibited adequate knowledge in these areas of nutrition to either a prescription hydration plan (PHP) or asked to . A more recent analysis by Abbey et al., showed simi- continue with their normal hydration habits (NHP). Partic- lar findings when collegiate athletes scored an average of ipants in each group underwent performance assessments 55% on a nutrition knowledge assessment . Research prior, during, and immediately after a moderate to hard has also indicated that a majority of athletes have a ten- training session (goal average heart rate ≥ 75% of max- dency to rely on a sense of thirst to inform them of when imum for at least 45 min in duration). Maximum heart rate they should be drinking fluids during training sessions was estimated with the formula, 207-(0.7 x age in years) and competitions. Unfortunately, when athletes rely on a . Heart rate (HR) was recorded remotely using the sense of thirst alone, they do not voluntarily drink enough Zephyr PSM Training System (Zephyr Technology fluid to prevent the occurrence of dehydration during Corporation, Annapolis, MD, US) . Mean and peak exercise [8, 11, 13]. This is exacerbated by the fact that a heart rate were recorded throughout the entire training majority of athletes begin training or competition in a session, including just prior to warm up, warm up, and somewhat dehydrated state [8, 11, 14]. Overall, the 15-min cool down. All measurements took place immedi- research indicates that the sports performance of many ately before, during, or after a sports-specific training ses- athletes are likely being hindered by substandard hydra- sion. For example, hockey players recruited for this study tion habits. underwent assessments during a full-pad, on ice, practice. In light of these findings, the purpose of this investiga- Similarly, Lacrosse players were assessed outdoors on the tion was to determine whether a prescribed hydration Lacrosse field during one of the teams harder practice ses- plan that considers both fluid and sodium loss, improves sions. Athletes were also weighed several times per week the athletic performance of collegiate athletes engaged in in the two weeks preceding the training session for deter- a variety of sports. Here, athletic performance is defined mining fluid loss (see “Sweat Assessment”)as wellasprior by several metrics: heart rate recovery, anaerobic power, to the NHP and PHP training sessions in order to deter- and attention and awareness following a moderate to hard mine weight stability. training session of at least 45-min in duration. We also The overall design of this study is shown in Fig. 1. sought to contribute to the findings of Torres-McGehee Each participant completed a training session with their et al. , Abbey et al. , and others [15, 16], by deter- NHP and PHP, separated by 7 days. mining what collegiate athletes are consuming during To determine the NHP for each participant, re- training and what their knowledge-base is regarding searchers observed the hydration habits of each athlete proper hydration. during at least one training session in addition to reviewing the results of the hydration survey noted earl- Methods ier. No instruction was provided to athletes with regards Study design to their NHP. Each participant was monitored during Fifteen collegiate athletes from Merrimack College their NHP training session for compliance, particularly (NCAA Division I (ice hockey) and II (all other sports)) those who were randomized to follow a PHP first. were recruited for this randomized, crossover study. Par- Researchers also controlled for pre-training hydration ticipants were eligible if they were between 18 and status by monitoring fluid consumption beginning at 24 years of age, injury-free, able to exercise at greater 60 min prior to the start of the sweat assessment, NHP, Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 3 of 10 Fig. 1 Randomized, cross-over study design to test the effectiveness of a prescription hydration plan on sports performance and PHP training sessions. All fluids consumed during the use of Pilogel® Iontophoretic Discs, placed in two elec- this study were kept at room temperature. trodes (red and black) that were strapped to the partici- pant’s forearm (Fig. 2). Activation of the sweat inducer Sweat assessment served to deliver enough pilocarpine for sweat gland Both fluid loss and sweat sodium (Na ) concentration stimulation (equivalent to 5 min of iontophoresis at 1.5 were assessed. Fluid loss from training was performed as milliamps). Following induction, a macroduct sweat col- described previously . Briefly, nude weight was taken lector was placed over the skin where the red electrode immediately prior to training. Fluid bottles (32 oz of was previously. The collector contained a blue dye that water or sports drink of choice (lemon-lime flavored allowed the researchers to observe the collection of sweat Gatorade®)) were measured out and provided to each by capillary action. Once enough sweat was collected, the participant. Participants were instructed to only drink [Na ] in each sample was assessed using a Sweat� Chek™ from his or her bottle and consumption of fluid was Conductivity Analyzer (ELITech Group, Model #3120) as closely monitored during the training session. Partici- described previously . pants were again weighed immediately afterwards (nude weight, surface sweat removed via towel dry). The time Prescription hydration plan (PHP) development of day, length of training session, temperature, and level of Fluid losses for each athlete (determined previously) − 1 humidity during the session were also recorded. For refer- were expressed in ounces. 15 min . This time measure- ence, all sweat assessments took place during the cooler ment was agreed upon by participants and coaches and months (November–March) within the New England re- represented a feasible fluid consumption plan during gion of the U.S. Fluid loss was determined from the training sessions. A range of fluid consumption per change in pre-training to post-training body mass and cor- 15 min was calculated by determining the minimum con- − 1 rected for fluid intake. Sweat rate was expressed in L. h sumption rate (enough to prevent mild dehydration or 2% by taking the total fluid loss and adjusting for the duration bodyweight loss ) and the maximum consumption rate of the training session. Relative sweat rate was expressed (fluid loss determined earlier, which is equated to main- − 1 − 1 + as ml. kg .hr. . To determine sweat [Na ], sweat was taining, but not exceeding pre-training bodyweight). For induced and collected from each participant using a example, if an 82 kg athlete with an absolute sweat rate of − 1 Macroduct® Sweat Collection System (ELITech Group, 1.4 L. h engaged in a 90 min training session, maximum Model #3700 SYS), according to the manufacturer’sin- fluid consumption was calculated as: 1.4 L × 1.5 h = 2.1 L structions [19, 20]. Briefly, sweat induction occurred via (71 oz) fluid lost / session. Convert to six 15 min drink Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 4 of 10 Fig. 2 Pilocarpine iontophoresis used for determining the sweat sodium concentration of each athlete intervals in a 90 min session = no more than 11.8 oz. con- were instructed to consume 8 oz of their prescribed sumed every 15 min. Minimum fluid consumption was beverage. calculated as follows: 82 kg × 2% = 1.64 kg (57.6 oz. equivalent) allowable sweat loss. 71 oz. lost / session – Neurotracker 57.6 oz. allowed / session = 13.4 oz. (at minimum) that Spatial awareness and attention was assessed by need to be made up via fluid consumption. 13.4 oz. / six 3-dimensional multiple object tracking (3D-MOT) cap- 15 min intervals = 2.2 oz. of fluid consumed every 15 min acity via the NeuroTracker™ system (CogniSens Athletic at minimum. This participant would then be advised to Inc., Montreal, Canada) as described previously [23, 24]. consume between 2 oz. to 12 oz. of fluid every 15 min of All testing was conducted in a quiet, dimly lit room with activity. The bottles used in this study were individually minimal outside distractions and consisted of three marked for quantity to delineate how much should be 10 min trials interspersed with five minute rest periods. consumed at each 15 min interval. More specifically, there During these assessments, participants wore 3D glasses would be two markings for each 15 min interval such as and were required to track designated objects on a “Min-15”, “Max-15”, “Min-30”,and “Max-30,” beginning screen as they moved in variable patterns and at subse- from the top of the bottle to the bottom. The exact vol- quently faster speeds. Each of the assessments began at umes would vary from athlete to athlete and each partici- a preliminary speed of 1.0 m per second. The degree of pant would be instructed to sip their bottle at each difficulty associated with the assessment progressively interval such that the fluid line was between the minimum increased with every correct answer provided by the par- and maximum. For athletes engaging in training sessions ticipants. In contrast, the level of difficulty associated that exceeded the fluid capacity of the bottle, multiple with the assessment progressively decreased with every similarly marked bottles would be provided. Researchers incorrect answer. The mean score of the three trials monitored fluid consumption throughout the training ses- (expressed as tracking speed in meters/second) was used. sion to gauge whether an athlete was on track with their Each participant performed the neurotracker assessments prescribed volume. The composition of fluid that each before and immediately after the training sessions. Changes participant consumed for the PHP was based upon what in spatial awareness and attention were illustrated by com- he or she regularly consumed (NHP fluid), supplemented paring pre-training with post-training scores. with a level of NaCl corresponding to the participant’s sweat sodium loss. This usually involved adding NaCl to Standing long jump 32 oz. of a commercially available sports drink or water To gauge lower body anaerobic power , three standing depending upon which beverage-type was normally con- long jump tests (SLJs) were performed before and after sumed by the individual. For example, if an athlete lost the NHP or PHP training sessions. The pre-training SLJs + − 1 + − 1 43.5 mmol Na .L (1000 mg Na .L ) of sweat and pre- immediately followed the neurotracker assessments, while ferred lemon-lime Gatorade G2™, which contains 480 mg the post-training SLJs preceded the neurotracker. Prior to sodium/32 oz , the researchers would add 520 mg completing the first of the three maximal SLJs, each NaCl to the beverage to create a solution that was isotonic participant completed two submaximal trials to be- relative to sweat sodium content. Lastly, 30 min prior come familiarized with the protocol. For the test it- to engaging in a PHP training session, participants self, participants were instructed to stand with their Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 5 of 10 feet should-width apart behind a starting line. On the Results command “ready, set, jump!” the participants executed the Fifteen NCAA Division I and II athletes from three differ- jump. Researchers measured each of the jumps from the ent sports participated in this study. Participant demo- participants’ rear-most heel and took the average of the graphics are shown in Table 1. Relative and absolute sweat − 1 − 1 − 1 three attempts in inches. rates were 1.3 ± 0.6 L� hr. and 18.8 ± 7.5 mL� kg � hr. − 1 respectively while sodium loss was 24.6 ± 7.1 mmol� L . The training sessions on average lasted 90 min (range of Statistical analysis 45–120 min) with participants exerting themselves at Wilcoxon Signed Rank test for paired samples was con- 78–79% of their maximum heart rate. Seven of the 15 par- ducted in order to determine if there was a significant ticipants engaged in 120-min training sessions, 6 engaged difference in the pre and post athletic performance mea- in 70 min sessions, and 2 engaged in 65 min and 45-min surements and when participants followed their normal training sessions respectively. The duration and structure hydration plans compared to when they followed their of the NHP and PHP training sessions did not differ for individualized prescription hydration plans. All data are each participant. All participants had practice in the after- presented as means ± SD except where otherwise speci- noon or evening. The time of day of the NHP and PHP ses- fied. SPSS 23 for Windows (IBM SPSS, Chicago, IL) was sions did not differ among any of the athletes in this study. used for all statistical analyses. GraphPad Prism® software The results of the fluid and hydration survey, includ- (version 6.07) was used for graphical displays. A value of ing the normal hydration habits of the participants in P < 0.05 was regarded as statistically significant. Where this study are shown in Table 2. Sixty percent of the par- statistically significant effects were observed, effect sizes ticipants in this study believed that their current hydra- (Cohen’s D) were determined by assessing the differences tion strategies were effective despite 40% reporting that between the two group means based on > 0.2 SD indicat- they feel very dehydrated during a training session. Most ing a small effect, > 0.5 a moderate effect, and > 0.8, a participants consumed water during training, as it was large effect . usually the only fluid available. Table 1 Baseline characteristics and exercise training of participants All NHP PHP Participants (N) 15 Female 9 Male 6 Age (years) 20 ± 0.85 Weight (kg) 70.9 ± 9.1 Sport Women’s Ice Hockey 6 Women’s Lacrosse 3 Men’s Lacrosse 3 Men’s Track & Field 3 Sweat Assessment −1 Absolute sweat rate (L� hr. ) 1.3 ± 0.6 −1 − 1 Relative sweat rate (mL� kg � hr. ) 18.8 ± 7.5 − 1 Sodium Loss (mmol� L ) 24.6 ± 7.1 Training Conditions Temperature (°C) 7.9 ± 4.3 Relative Humidity (%) 37 ± 4.0 Training Bout Training Duration (mins) 91.2 ± 28.1 91.3 ± 28.4 91.0 ± 28.8 Training Heart Rate (bpm) 152 ± 6 153 ± 6 151 ± 6 % of Max HR 79 ± 3 79 ± 3 78 ± 3 Numbers expressed are means ±SD, unless otherwise stated Training conditions did not significantly differ between sweat assessment session and NHP or PHP training sessions Does not include warm-up or cool down period Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 6 of 10 Table 2 Fluid and hydration survey results pre-training performance. Similarly, attention and aware- ness improved when participants followed a prescription Question Response (n) hydration plan. After training with their NHP, participants How often do you consider hydration Consider very much (6) before practice? on average experienced a non-significant reduction of Consider somewhat (7) − 1 0.11 ± 0.32 m� s in their ability to track moving objects Consider not often (2) compared with pre-training tracking speed (Fig. 3). In con- How often do you consume fluids Often / Every 15–30 min (7) trast, when following their PHP, participants significantly during practices/competitions? − 1 Somewhat Often / Every improved object tracking ability by 0.26 ± 0.40 m� s . 30–60 min (6) Rarely to Never (2) Between group differences (PHP effect) What type of hydration beverages Water (12) Heart rate recovery was faster post-training when partic- do you normally consume during Sports Drink (3) practices/competitions? ipants followed a PHP as compared with their respective normal hydration plans (Fig. 4). These differences were How much fluid do you usually More than 12 oz (2) consume during practices/competitions? significant at 10 min and 15 min post-training (Table 3). Less than 12 oz (5) Similarly, standing long jump performance as well as Less than 8 oz (6) attention and awareness was also improved. The effect Not Sure (2) size for both heart rate recovery (− 4.47 ± 6.71 bpm at Do you believe that your current Yes (9) 10 min, − 3.73 ± 6.58 bpm at 15 min) and standing long hydration strategies are effective? No (6) jump performance (4.53 ± 3.80 in.) was large. How dehydrated do you feel Very dehydrated (6) during practices/competitions? Somewhat dehydrated (7) Discussion Not dehydrated (2) This study investigated whether an individually tailored hydration plan improves performance outcomes for col- How often do you consider Consider very much (9) hydration after practice? legiate athletes engaged in seasonal sports. Participants Consider somewhat (5) were recruited from three sports (ice hockey, lacrosse, Consider not often (1) and track & field) as these sports were currently in sea- Where did you learn your current Parents (8) son and the athletes were engaged in consistent and hydration strategies from? Coaches (6) standardized training sessions. All athletes in this study Athletic Trainers (5) had practice in the afternoon or evening with the NHP and PHP sessions occurring at the same time of day for Nutritionist (5) each individual. A prescription hydration plan (PHP) Teammates (4) was created for each participant that was based on both Nutrition Class (3) fluid and sodium losses incurred during moderate to Other (3) hard training sessions lasting at least 45 min in duration. Do you believe that it is possible Yes (11) Athletes were instructed to drink at 15 min intervals at to overhydrate? No (4) a volume of fluid that prevents a 2% bodyweight loss as well as any weight gain. A maximum fluid consumption Do you believe that overhydration Impaires (13) improves or impairs athletic performance? level for each PHP was established as a precaution, given Improves (2) that overhydration is a well-known risk factor for Do you believe that thirst alone can Strongly agree (1) exercise-induced hyponatremia . However, the likeli- be a predictor of dehydration? Agree (6) hood of this occurring in this study was low given that Neutral (3) the athlete cohort in this study engaged in training ses- Disagree (3) sions lasting no more than 120 min . The fluid itself was isotonic relative to the athlete’s specific sweat so- Strongly disagree (2) dium concentration and was based off of fluids readily available to him or her. The results indicate that this ap- Within group differences (training effect) proach was effective in improving heart rate recovery, All participants in the study complied with their respective attention and awareness, and mitigating the loss in an- prescription hydration plans. Compared with pre-training aerobic power that occurred from the training session. performance, participants jumped 2.42 ± 2.29 in. shorter Compliance was high with the prescribed volume of after training when following their NHP (Fig. 3). In con- fluid well tolerated by the participants. While some ath- trast, when these participants followed a PHP, they letes did remark that they could taste the extra sodium, jumped 2.13 ± 3.15 in. farther post-training compared with this did not appear to affect the compliance to their Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 7 of 10 Fig. 3 Change in performance following a 45–120 min bout of moderate to hard training. * = P < 0.05, ** = P < 0.01 prescribed hydration protocol, even among those who composition of a beverage. The PHP intervention ma- required the most salt added to their beverage. nipulated only the fluid quantity and sodium consumed To our knowledge, this is the first investigation to look immediately before and during exercise. at whether an individually tailored hydration plan im- In all cases, the final [Na ] of the PHP beverages were proves athletic performance for collegiate athletes en- higher than any of the sports drinks available to our ath- gaged in a variety of sports. Previous work has shown letes (though most habitually consumed water during train- that hydration plans based purely on fluid loss hold ing). With the notable exception of endurance-focused promise . Bardis et al., examined whether consuming sports drinks, many commercially available beverages do water at regular intervals to offset fluid losses as com- not match the sodium loss rate of many individuals. This is pared with ad libitum fluid consumption improved the understandable as it is commercially untenable to create a performance of cyclists . The researchers found that sports drink unique to every individual’ssweat compos- power output was maintained throughout a training ses- ition. For the majority of individuals engaged in recre- sion consisting of three 5-km hill repeats, whereas when ational physical activity these drinks are more than these cyclists consumed water ad libitum, their power sufficient. For elite and amateur athletes looking for every output dropped with each successive repeat . Other possiblesafemethodtoimprove performance, theresults studies have examined the effects of isotonic beverages of this study support commercial sweat testing in order to on sports performance, yet often compare such bever- develop optimal hydration strategies. This may hold espe- ages to water [29–31]. This presents the obvious issue of cially true for athletes engaged in longer sporting events accounting for any carbohydrate effect as most commer- such as a marathon or Ironman triathlon, where the loss of cially available sports drinks are 6–10% carbohydrate so- fluid through sweat is substantial . Supplementation lutions mixed with several electrolytes, among them with higher sodium sports drinks or salt capsules may be sodium. In this study, because the specific beverage con- advisable for athletes engaged in prolonged exercise of 3 h sumed by each participant was held consistent between or more in order to maintain serum electrolyte concentra- the NHP and PHP training sessions, the results are not tions [33, 34]. Based on these studies and others, the longer confounded by factors such as the carbohydrate an event, the more critical it appears to be to have an ad- equate hydration plan in place that considers sweat rate and composition [1, 34]. In our study, most of the partici- pants engaged in training sessions lasting between 70 min to two hours and the benefits were apparent. Lastly, in line with previous work, we also found that while most athletes in this study felt that their current hydration strategies were effective, the majority of this cohort reported feeling dehydrated after a training ses- sion [10, 11, 15, 16]. The disconnect between ad libitum fluid consumption and hydration status during competi- tion is well documented [8, 11, 13, 15]. Studies have consistently shown that it is not uncommon for athletes to show up to a training session already dehydrated and consume inadequate fluid levels despite the ready avail- Fig. 4 Heart rate recovery after completing a training session with ability of water or sports drinks [8, 11, 14–16]. It cannot each hydration plan be definitively stated whether the athletes in our study Ayotte and Corcoran Journal of the International Society of Sports Nutrition (2018) 15:27 Page 8 of 10 Table 3 Effect of a prescription hydration plan on performance relative to an ad libitum hydration plan Variable Difference btw means 95% CI p-value Effect size (Cohen’sD) Standing Long Jump (in) 4.53 ± 3.80 2.43 – 6.64 < 0.0001 Large Attention and Awareness (m/s) 0.36 ± 0.60 0.03 – 0.70 0.0302 Small HR (5 min post) (bpm) −2.60 ± 6.82 −6.38 – 1.18 0.1838 NS Rec HR (10 min post) (bpm) −4.47 ± 6.71 −8.18 – −0.75 0.0087 Large Rec HR (15 min post) (bpm) −3.73 ± 6.58 −7.38 – −0.09 0.0139 Large Rec Differences are means ± SD were dehydrated at the beginning of practice. In this this study, sweat sodium concentrations were assessed at study, the researchers were present to monitor compli- the forearm. Previous research has indicated that meas- ance to the prescribed fluid volume, including the uring sodium from multiple body sites such as was done pre-practice consumption of the PHP beverage. While by Dziedzic et al., can lead to higher sweat sodium the PHP used in the present work was feasible to create values . Based on Dziedzic’s report, we determined and implement, ensuring compliance in day to day train- that this difference translates to adding roughly 200 mg ing may be challenging. In a study by Logan-Sprenger et more sodium per a 32-oz sports beverage than what was al., a third of all ice hockey players failed to hydrate ad- added to the 32 oz beverages in this study. We are un- equately during a game despite these fluids being readily clear on what impact this additional salt may have made available . Increasing hydration awareness along with concerning the performance outcomes used in this providing pre-marked bottles that state how much fluid study. From a practical standpoint, assessing the forearm should be consumed by set time periods, if feasible, may is often a more feasible approach to determining sweat be one approach to overcoming this issue. sodium concentrations than a whole-body approach. An- other limitation to this study is that it relied on body- Study limitations weight changes and fluid intake monitoring to gauge This study has several limitations. First, only one train- hydration status. This method is less precise than other ing session was utilized per hydration plan. Based on re- methods of hydration status such as a urine specific searcher observations, participant feedback, and input by gravity test (USG) . We were unable to conduct a coaches, there was little difference in the training ses- USG due to equipment limitations. We did note how- sions used for the NHP and PHP assessments with each ever, the bodyweight trends of all athletes in this study participant. It was important to control for the training over the two weeks preceding the pre-training body- sessions utilized as well as ensuring minimal fitness weight measurements (data not shown). There was no gains in between NHP and PHP sessions. Hence, we re- significant difference in these weights as compared with quired a “wash out” period of 7 days. The training ses- the pre-training bodyweights (taken during the NHP sions utilized in this study were already pre-scheduled so and/or PHP training sessions), indicating that each ath- as not to interfere with the practice plan that each coach lete was weight-stable. This however does not negate the designed for their athletes. For each sport at the college possibility that an athlete was dehydrated, euhydrated or where and when this study occurred, the number of hyperhydrated going into each training session. Further ideal sessions to test the PHP were limited. The fact that research should include tests such as USG so that hydra- multiple sports were used to test the PHP is both a tion status can be confidently determined. strength (broad applicability) and a limitation (non-spe- There are also several potential confounders that need cific). Given the team schedules and the timing of this to be addressed. Factors such as sleep quality, personal study during the winter/spring seasons in the New stress, medication use, menstrual cycle, and diet may England, USA area, it is unclear what affect a warmer, have affected the outcomes. We did not assess nor con- more humid climate may have had on the results. Given trol for the athlete’s environment outside of one hour that both the NHP and PHP training sessions were simi- from the training session. One main advantage of the lar in duration, intensity, mode of training, and climate, randomized, cross-over design utilized for this study is we postulate that these results will hold in warmer con- that each participant served as his or her own control, ditions. More so, given higher degrees of fluid loss with which presumably minimized the influence of any po- warmer, more humid climates, the benefits from the tential confounding covariates. Despite the strength of PHP observed in this study may even be amplified to a this design, future studies in hydration research may do certain degree. This is speculative however and future well to assess diet, stress level, and sleep quality as studies if feasible, should consider testing athletes over mentally, these factors can significantly impact athletic multiple training sessions per treatment. Additionally, in performance. 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Journal of the International Society of Sports Nutrition
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Published: Jun 4, 2018