What Sports Related Risk is Associated With Thirst

What Sports Related Risk is Associated With Thirst.

  • Journal List
  • Nutrients
  • v.xi(11); 2019 Nov
  • PMC6893511

2019 Nov; 11(11): 2689.

The Utility of Thirst as a Measure out of Hydration Status Following Exercise-Induced Dehydration

William Chiliad. Adams

aneSection of Kinesiology, University of N Carolina at Greensboro, 1408 Walker Artery, 237L Coleman Building, Greensboro, NC 27412, Usa

Lesley W. Vandermark

twoDepartment of Health, Human Functioning, & Recreation, Academy of Arkansas, HPER 310D, Fayetteville, AR 72701, United states of america

Luke N. Belval

threeEstablish for Exercise and Environmental Medicine, Texas Health Presbyterian Infirmary Dallas and University of Texas Southwestern Medical Center, 7232 Greenville Ave, Dallas, TX 75231, USA

Douglas J. Casa

fourKorey Stringer Institute, Man Operation Laboratory, Department of Kinesiology, Academy of Connecticut, 2095 Hillside Rd, Unit 1110, Storrs, CT 06269, Us

Received 2019 Sep 20; Accepted 2019 Nov i.


The purpose of this study was to examine the perception of thirst as a marker of hydration status following prolonged do in the estrus. Twelve men (mean ± SD; historic period, 23 ± four y; body mass, 81.iv ± 9.9 kg; meridian, 182 ± 9 cm; torso fat, fourteen.three% ± 4.7%) completed two 180 min bouts of exercise on a motorized treadmill in a hot environs (35.2 ± 0.6 °C; RH, 30.0 ± 5.four%), followed by a lx min recovery menstruum. Participants completed a euhydrated (EUH) and hypohydrated (HYPO) trial. During recovery, participants were randomly assigned to either fluid replacement (EUHFL
and HYPOFL; 10 min ad libitum consumption) or no fluid replacement (EUHNF
and HYPONF). Thirst was measured using both a ix-point scale and separate visual analog scales. The per centum of trunk mass loss (%BML) was significantly greater immediately post exercise in HYPO (HYPOFL, three.0% ± ane.two%; HYPONF, ii.6% ± 0.6%) compared to EUH (EUHFL, 0.2% ± 0.seven%; EUHNF, 0.six% ± 0.5%) trials (p
< 0.001). Following recovery, there were no differences in %BML betwixt HYPOFL
> 0.05) or between EUHFL
> 0.05). First at minute 5 during the recovery menses, thirst perception was significantly greater in HYPONF
< 0.05). A 10 min, advert libitum consumption of fluid post do when hypohydrated (%BML > 2%), negated differences in perception of thirst between euhydrated and hypohydrated trials. These results stand for a limitation in the utility of thirst in guiding hydration practices.


fluid replacement, hypohydration, assessment, perception, exercise

i. Introduction

The complexities surrounding the turnover of body water complicates any single measure of hydration status qualifying as a standard for assessment [1]. Methods for assessing hydration condition utilize urinary and hematologic measures, amid others; nevertheless, these methods are not without limitations regarding accurateness and applicability in all settings [1,2,3,iv]. Furthermore, many of these assessment methods require expensive laboratory instrumentation and/or expertise in these techniques, limiting real-world applicability for all persons.

Thirst, defined equally a desire to consume fluids every bit a consequence of a trunk water deficit, is a subjective perception controlled by both neuroendocrine responses to maintain fluid homeostasis [5,6,7] and psychosocial influences [eight]. The physiological onset of thirst, occurring with fluid losses of a magnitude of i–2% body mass loss [6,9] is influenced by hyperosmolality, hormonal responses (arginine vasopressin (AVP) and angiotensin II (Ang II)), and peripheral osmoreceptors [10,11,12], but is highly variable within individuals [5]. In addition, not-homeostatic influences, such as beverage taste, availability, individual drinking habits, and timing with meals, dictate daily fluid intake [eight].

Current recommendations advocate for using thirst to guide hydration practices during exercise to reduce the risk of exertional hyponatremia [xiii]; nonetheless, recommendations by the American College of Sports Medicine [14] and the National Able-bodied Trainers’ Association [15] encourage individualized replacement of fluid losses to foreclose dehydration-mediated loss of >two% of body mass during practise. Evidence suggests that relying solely on thirst as a means of replacing fluid losses during exercise, peculiarly in hot environmental conditions, may prevent the full restoration of trunk h2o losses, leading to involuntary dehydration [half-dozen]. Armstrong et al. [16] has suggested that thirst may provide an cheap means of assessing hydration condition upon waking in the morning, just differences in thirst perception were negated following the consumption of a bolus of fluid, despite hypohydration equaling 2% body mass loss. Similar findings were observed when advertizing libitum consumption of water was allowed following high intensity intermittent exercise; however, torso water deficits were simply 1.3% of body mass [17].

An cess of thirst’due south tracking of hydration condition has previously been performed during exercise and at balance. Still, few studies have investigated the efficacy of thirst as a potential marker of hydration status when a bolus of water was provided following exercise-induced dehydration upon a magnitude of ~3% trunk mass loss. Therefore, the purpose of this written report was to examine the perception of thirst as a marker of hydration condition post-obit prolonged exercise in the heat. It was hypothesized that when a bolus of fluid was consumed following practise-induced dehydration, thirst awareness would be attenuated despite a sustained level of dehydration in a higher place the threshold (~ii% body mass loss from aridity) in which thirst is nowadays.

2. Materials and Methods

ii.one. Design

Participants completed 2 testing sessions in a randomized, counter-counterbalanced style. We randomly assigned participants to testing sessions, designed to manipulate participants’ hydration states post-obit exercise: euhydrated (EUH) and hypohydrated (HYPO). The EUH trial consisted of a euhydrated inflow to the laboratory, followed by minimal fluid losses throughout the duration of practice dictated past participant’s individual fluid needs. The HYPO trial was designed to reach a state of hypohydration of roughly 3% body mass loss and was achieved via 14 h fluid restriction prior to arrival to the laboratory and throughout the tour of exercise. Following practise, participants completed a 60 min bout of recovery in the heat, where they were randomly allocated to either a fluid replacement grouping or fluid restriction group. All do sessions occurred at the aforementioned time of day, ±1 h, and were separated by a minimum of 72 h to minimize the circadian variability of the physiological variables of interest and allow for appropriate recovery from the previous sessions, respectively. Do and recovery took place in a climate-controlled environmental chamber (Model 200, Minus-Eleven, Inc., Malden, MA, The states) with weather condition being: ambience temperature, 35.ii ± 0.6 °C; RH, 30.0% ± 5.4%; wet bulb earth temperature, 26.6 ± 1.i °C. Additionally, all exercise sessions took place during the winter months in Connecticut, United states to ensure that none of the participants were heat acclimated.

two.2. Participants

Twelve recreationally active men between the ages of 18 and 35 volunteered to participate in this study (mean ± SD; age, 23 ± four y; body mass, 81.4 ± ix.nine kg; tiptop, 182 ± 9 cm; body fat, 14.3% ± 4.vii%). All participants reported exercising a minimum of 4–5 d·wk−1
for at to the lowest degree 30 min per session. Participants were excluded if they reported any chronic health problems, such every bit cardiovascular, metabolic, or respiratory disease; electric current illness or musculoskeletal injury; or a previous history of exertional estrus illness within the final 3 y. Participants provided written and informed consent to participate in this study, which was canonical by the University of Connecticut’s Institutional Review Lath (protocol number: H15-154) and in accordance with the Proclamation of Helsinki.

2.3. Procedures

Familiarization Session.
Prior to the exercise sessions, participants completed a familiarization session for them to go acquainted with the laboratory and testing procedures. The familiarization session was scheduled as close to the scheduled testing session times equally possible, to ensure minimal variability in reference hydration values due to cyclic rhythm. To ensure participants arrived euhydrated, they were asked to consume 500 mL of water prior to going to bed the night before and upon waking in the morning. Hydration status was measured upon arrival to the laboratory using urine specific gravity (USG
≤ 1.020) (refractometer, model A300CL; Atago Inc., Tokyo, Japan) and urine color (UCOL
≤ 4) via urine color nautical chart [18]. Participants arriving to the laboratory for the EUH trial with a USG
> 1.020 were instructed to consume an additional 500 mL of fluid prior to the start of exercise. Participants arriving to the laboratory for the HYPO trial with a USG
> 1.020 were not provided fluid, equally the purpose of the HYPO trial was to induce a country of hypohydration prior to the start of exercise.

Each participant’s height was measured using a standard stadiometer and their body fat was calculated via 3-site skinfold measurements of the chest, belly, and thigh using calibrated calipers (Lange Skinfold Caliper; Beta Engineering science Inc., Santa Cruz, CA, USA) [nineteen]. Participants were instructed on the insertion of the rectal thermometer (Model 401, Measurement Specialties, Hampton, VA, United states of america), which was used for the monitoring of body temperature during the do sessions. They were too familiarized to the perceptual scales that they were asked almost during the practice sessions: the thirst perception (Thursday) and thirst sensation scales (TSS), described below.

Each participant’south sweat charge per unit was measured to determine their fluid needs during the EUH practise trial. A nude body mass (NBM) was measured to the nearest 0.1 kg using a calibrated scale (Defender 5000, OHAUS, Parsippany, NJ, USA) before entering the environmental chamber. Upon inbound the chamber, they stood for 15 min to get equilibrated to the environmental conditions prior to practise. Exercise consisted of walking on a motorized treadmill at a speed ranging from 5.6 to 6.4 km·h−ane
at a 2% gradient for a total of thirty min. Participants were instructed to set a speed equivalent to a “fast walk” that they would be able to sustain for up to three h. The speed selected during the familiarization session remained the same for both practice sessions. Following exercise, participants provided another NBM to determine sweat rate by assessing body mass change. Body water losses were used to quantify the prescribed fluid replacement during exercise of the EUH trial; 0.001 kg equaled 1 mL.

Testing Sessions.
For all testing sessions, participants were instructed to acquit their normal daily routine (east.chiliad., exercise, nutrient and fluid intake), then as to non deviate from their private norm. Participants were asked to eat an additional 500 mL of water the night prior and the morn of the EUH trial to ensure a land of euhydration. For the HYPO trial, participants were asked to restrict fluid intake (including fluid heavy foods) for 14 h prior to their inflow to the laboratory. Participants were scheduled for the same time of solar day for each of their trials to minimize any furnishings of circadian rhythms on physiologic office.

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Upon arrival to the laboratory for the EUH and HYPO trials, we obtained the following measures; NBM, USG, and UCOL. Post-obit a 15 min equilibration in the environmental sleeping accommodation, pre-exercise (PREEX) measures of rectal temperature (TREC), heart rate (HR) (Race Trainer, Timex Group Usa, Middlebury, CT, USA), body mass, TH, and TSS were obtained. A blood sample, with participants in a seated position, was also drawn at this time for the assessment of serum osmolality prior to exercise. Participants then began exercise, consisting of six 30 min bouts of exercise, each involving a 25 min walk at the speed at which participants performed the sweat rate assessment examination, followed by a five min residual. During the five min rest period, participants stepped off the treadmill, removed their shoes and t-shirt, toweled off as much as possible and provided a body mass mensurate to rail body mass loss over the course of exercise. Earlier commencing the next tour of exercise, TREC, HR, RPE, and TH were measured. During the EUH trial, participants consumed equal boluses of water during each 25 min do tour at a volume matching their calculated sweat rate for that time period. During the HYPO trial, participants were restricted from h2o throughout exercise.

Post-obit the 3 h bout of exercise, participants stepped off the treadmill, provided trunk mass, TREC, Hr, TH, and TSS post-exercise (POSTEX) measures, and sat in a chair to begin a 60 min period of recovery. During recovery, participants were randomly assigned to one of two recovery conditions; fluid replacement (FL; EUHFL
and HYPOFL) or no fluid replacement (NF; EUHNF
and HYPONF). Participants remained in the same recovery group for both trials. For EUHFL
conditions, participants were given a bolus of water equaling their full trunk mass losses that occurred during exercise. The participants were allotted 10 min to consume the h2o and were permitted to consume the water ad libitum. Subsequently ten min, any remaining water was taken from the participants and they remained in a seated position for the next 50 min. Post-obit the completion of the recovery portion of the trial, TREC
and 60 minutes were measured and Th and TSS were assessed for a post-recovery (POSTREC) time point. Prior to exiting the environmental chamber, a POSTREC
claret sample was obtained for assessment of serum osmolality. Participants and so exited the environmental sleeping room and provided final NBM, USG, and UCOL

two.four. Thirst Assessment

TH was measured using nine-point (1–9) Likert scale that provided verbal anchors of 1, “Not Thirsty at All”; iii, “A Lilliputian Thirsty”; five, “Moderately Thirsty”; vii, “Very Thirsty”; and ix, “Very, Very Thirsty” [20]. Participants were asked, “How thirsty are you right at present?” when shown the calibration, and they provided a numerical answer based on their perceived feeling of thirst.

The 2d mensurate of thirst assessment, TSS, was measured using a 100 mm visual analog scale, for which participants were asked, “How thirsty practice you experience correct now?” (not at all thirsty–very thirsty); “How pleasant would information technology exist to drink some water correct at present?” (very unpleasant–very pleasant); “How dry does your oral cavity experience right now?” (not at all dry out–very dry); “How would you depict the gustation in your rima oris?” (normal–very unpleasant); “How full does your tum experience right at present?” (non at all full–very full); “How sick to your stomach do you experience right now?” (not at all sick–very sick) [21,22]. All six visual analog scales were on ane piece of paper and each 100 mm line was anchored using the same words/phrases in parentheses above. Participants were asked to mark on each line their responses to each question.

2.5. Hematological Measures

Five milliliters of claret was drawn from an antecubital vein into a collection tube without condiment (BD Vacutainer, Becton Dickinson Company, Franklin Lakes, NJ, USA) and immune to clot at room temperature. Samples were and so centrifuged at 3000 rpm at 4 °C and assessed in triplicate for serum osmolality using the freezing point depression method (Model 3320, Advanced Instruments, Norwood, MA, USA).

2.6. Statistical Analysis

All statistical analyses were performed using SPSS Statistical Software version 21 (IBM Corporation, Armonk, NY, USA). Tests for normality were conducted using the Shapiro–Wilk tests with whatsoever not-unremarkably distributed data being analyzed past the appropriate not-parametric tests. All values are presented as means ± standard deviations unless otherwise noted. In add-on, comparisons between variables are presented as mean differences (Physician) and 95% confidence intervals (95%CI). Effect size (ES) was also calculated using Cohen’due south d, for which d = 0.2 was considered a small effect, d = 0.5 was considered a medium upshot, and d = 0.8 was considered a large result. A priori power analysis (G*Ability 3.1, Düsseldorf, DE) computing an F examination for repeated measures ANOVA with inside–between interaction for two groups (NF and FL) across 20 timepoints with an alpha level of 0.05, ability of 0.8, and a medium effect size of d = 0.five yielded a total sample size of 8. A sample size of 12 (n
= 6 were each assigned to each of NF and FL groups) was used to ensure a ability of >0.8.

Three-way (condition × trial × time) repeated-measures ANOVAs were used to appraise differences in dependent variables (Thursday, TSS, body mass, serum osmolality, 60 minutes, and TREC) betwixt weather condition (FL and NF), trials (EUH and HYPO), across time. With significant iii-way interactions, follow-upward postal service hoc testing utilizing appropriate two-way ANOVAs were utilized. Significance was fix a priori at
< 0.05.

Post hoc power analysis comparing Th (comparison of pooled means during recovery) yielded a power-accomplished of β = 0.997, confirming that the sample size selected was appropriate for the assay. Mail service hoc power analysis comparing the TSS measures of thirstiness, pleasantness, dryness, gustatory modality, fullness, and sickness yielded power measures of β = 0.579, β = 0.338, β = 0.516, β = 0.415, β = 0.453, and β = 0.435, respectively.

3. Results

Figure aneA depicts the modify in TH throughout practise and recovery and
Effigy 1B depicts the delta change (recovery–do) in pooled means for TH. There was a meaning three-manner interaction for Th between EUHFL, EUHNF, HYPOFL, and HYPONF
= 0.015). Follow-up testing revealed that, during recovery, mean Th was significantly greater in HYPONF
than EUHFL
< 0.001, ES = vi.44), EUHNF
< 0.001, ES = 5.05), and HYPOFL
= 0.002, ES = 3.70) (Figure aneA).

(A) Thirst perception throughout practice and post-exercise recovery and (B) delta alter (recovery–do) of pooled ways in thirst perception (Th) by trial × condition. # indicates a pregnant difference between HYPOFL
< 0.05. EUHFL
= minimized fluid losses during exercise and remaining losses replaced during recovery; EUHNF
= minimized fluid losses during exercise and did not supervene upon losses during recovery; HYPOFL
= fluid restricted during exercise and losses replaced during recovery; HYPONF
= fluid restricted during exercise and losses not replaced during recovery.

Figure 2
portrays the dissever measures assessed in TSS at the PREEX, PostEX, and POSTREC
fourth dimension point. In that location were no significant differences in feelings of thirstiness (p
= 0.052), pleasantness toward drinking water (p
= 0.211), dryness in the mouth (p
= 0.072), sense of taste in the mouth (p
= 0.12), fullness (p
= 0.099), and sickness (p
= 0.145) between trial, recovery condition, and time; still, information technology can exist observed that feelings of thirstiness and dryness in the rima oris trended toward significance in this 3-way interaction. Despite no significant iii-way interactions, there were significant trial × time interactions for thirstiness (p
= 0.004), pleasantness in the mouth (p
= 0.034), dryness in the mouth (p
= 0.002), and fullness (p
= 0.034). Specifically, thirstiness was significantly greater at POSTEX
(ES = v.81) and POSTREC
(ES = iii.48) in the HYPO trial (POSTEX, 69.5 ± ix.0; POSTREC, 51.ix ± xiv.1) than EUH trial (MailEX, 23.1 ± 6.eight; POSTREC, 15.5 ± 4.4). Pleasantness in the mouth was significantly greater (greater unpleasant feeling) at PostEX
(ES = 8.01) and POSTREC
(ES = three.95) in the HYPO trial (PostEX, 84.ix ± v.9; Postal serviceREC, 67.3 ± 10.6) than in the EUH trial (Mail serviceEX, 36.4 ± 6.2; POSTREC, 32.1 ± 6.8). Dryness in the rima oris was significantly greater at POSTEX
(ES = 6.48) and POSTREC
(ES = 3.eighteen) in the HYPO trial (MailEX, 70.3 ± 5.9; POSTREC, 60.6 ± 12.three) than in the EUH trial (PostEX, 26.2 ± 7.half-dozen; PostREC, 29.two ± six.6). Lastly, participants experienced significantly greater fullness at Postal serviceEX
(ES = 2.93) in the EUH trial (39.5 ± 9.0) compared to the HYPO trial (sixteen.9 ± six.1).

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Object name is nutrients-11-02689-g002.jpg

Perceptions of (A) thirstiness, (B) dryness, (C) pleasantness, (D) fullness, (Due east) taste, and (F) sickness in EUHFL
groups. * indicates a significant divergence between the HYPO trial (HYPOFL
and HYPONF) and EUH trial (EUHFL
and EUHNF);
< 0.05. EUHFL
= minimized fluid losses during exercise and remaining losses replaced during recovery; EUHNF
= minimized fluid losses during exercise and did not supersede losses during recovery; HYPOFL
= fluid restricted during practice and losses replaced during recovery; HYPONF
= fluid restricted during exercise and losses not replaced during recovery.

The hypohydrated trials (HYPOFL
and HYPONF) resulted in significantly greater levels of aridity at PostEX
than the euhydrated trials (EUHFL
and EUHNF), every bit measured by the pct of body mass loss (%BML) (p
< 0.001) (Table 1). Fluid replacement after practice did not influence %BML betwixt HYPO trials (HYPOFL, 2.1% ± ane.1%; HYPONF, ii.half-dozen% ± 0.6%) or EUH trials (EUHFL, 0.ii% ± 0.seven%; EUHNF, 0.half-dozen% ± 0.5%) at POSTREC, respectively (p
= 0.330) (Table 1). Serological and urinary hydration measures are shown in
Table 2. Changes in TREC
= 0.052) and HR (p
= 0.067) trended toward statistical significance (Figure 3).

Table 1

Body mass changes past status.

Condition PREEX
Mass (kg)
Mass (kg)
%BML (%)
Mass (kg)
%BML (%)
Fluid Consumed (mL)
% BML Replaced (%)
EUHFL 77.0 ± 10.ix 76.8 ± 10.2 0.ii ± 0.7 76.9 ± 11.1 0.2 ± 0.7 337.five ± 48.three 57.four ± 13.2
EUHNF 85.ix ± 6.iii 85.4 ± 6.7 0.6 ± 0.seven 85.four ± 6.3 0.6 ± 0.5 0 ± 0 0 ± 0
HYPOFL 76.4 ± 11.3 74.1 ± eleven.0 3.0 ± 1.two
74.eight ± 11.iv 2.1 ± 1.1
1100.0 ± 155.0 55.3 ± xv.6
HYPONF 86.4 ± half-dozen.five 84.i ± half-dozen.1 2.6 ± 0.6
84.one ± 6.5 2.6 ± 0.6
0 ± 0 0 ± 0

Tabular array 2

Serological and urinary hydration variables.

Variable Condition PREEX Mail serviceREC
Serum Osmolality (mOsm·kg−1) EUHFL 295 ± ii 296 ± three
EUHNF 290 ± 5 291 ± 5
HYPOFL 296 ± 8 310 ± 6
HYPONF 294 ± 3 304 ± 3
Urine Specific Gravity (AU) EUHFL 1.012 ± 0.009 ane.009 ± 0.004
EUHNF 1.018 ± 0.005 i.017 ± 0.007
HYPOFL one.014 ± 0.008 1.017 ± 0.004
HYPONF 1.021 ± 0.007 1.020 ± 0.005

iv. Give-and-take

This study evaluated the use of thirst as a marker of hydration following exercise-induced dehydration. Subjective sensations of thirst (Thursday and TSS) were significantly elevated immediately following an practice bout that induced a level of hypohydration of ii.viii% ± 0.9% body mass loss (combined hateful of HYPOFL
groups). Our hypothesis was supported in that when HYPOFL
was permitted to swallow water advertisement libitum during the initial ten min of a 60 min bout of recovery following practise, subjective feelings of thirst (TH) were minimized throughout and at the completion of recovery to levels similar to the EUHFL
groups, despite %BML remaining >2% (Figure 1A). Measures of thirstiness and dryness in the oral cavity, as measured by TSS, approached statistical significance (p
= 0.052 and
= 0.072, respectively), with HYPOFL
exhibiting a reduction in thirst and dryness in the mouth following threescore min of recovery (Figure 2).

The role of oropharyngeal receptors in attenuating thirst has been extensively studied in both human [11,17,23,24,25,26] and animal models [27,28,29,30]. Figaro and Mack [eleven] showed that oropharyngeal receptors played an firsthand role in inhibiting thirst, and thus, fluid intake, without influencing plasma osmolality when fluid was extracted immediately from the tum subsequently consumption. In addition, Mears et al. [17] establish that thirst, which was stimulated by a rising in serum osmolality following a bout of loftier intensity interval exercise, apace declined upon the consumption of fluid immediately after exercise. Thirst as well remained elevated when fluid consumption was delayed for 30 min or prohibited at any point during recovery, despite a decline in serum osmolality. Our findings support these results and the function that oropharyngeal receptors play in reducing the thirst awareness, despite a sustained elevation of serum osmolality, in that the sensation of thirst was immediately reduced in HYPOFL
in one case fluid was permitted and remained at levels similar to EUHFL
(Figure 1A and
Figure two), despite a sustained superlative in serum osmolality levels compared to baseline (+14 mOsm·kg−ane). This is evident in
Effigy 1B, where the delta change of pooled means for TH between recovery and do shows a negative delta change for EUHFL, EUHNF, and HYPOFL
compared to HYPONF; this figure shows that sensations of thirst for the former conditions are lower across the recovery menstruation on average than what appeared during exercise.

Interestingly, unlike the piece of work by Figaro and Mack [xi] and Mears et al. [17], we did not see a decline in serum osmolality when advertizing libitum fluid intake was permitted. We postulate that this may be due to the total volume of water consumed. In the Figaro and Mack [eleven] and Mears et al. [17] studies, participants replaced ~67–86% and 63–82% of the water lost during practice, respectively. In our study, participants in HYPOFL
only replaced ~55% of what they lost, which may have influenced the amount of water absorbed into the vasculature during recovery. As we did non measure serum osmolality immediately post-obit exercise or throughout the recovery portion of the trial, nor did we mensurate the amount of fluid absorbed from the gastrointestinal tract during recovery, we are unable to develop a farther rationale as to why we did not detect a change in serum osmolality. We postulate that the full volume of water consumed during the initial 10 min of recovery was not big enough to result in a alter in serum osmolality.

The office of 1’s mouth’southward country may be an important factor when considering fluid replacement following practice eliciting levels of dehydration that exceed 2% BML, a level of dehydration that has been shown to adversely impact physiological function [31,32,33,34] and exercise performance [4,35,36,37]. Our findings, in support of prior literature [10,21,26], show that individuals will take a reduced drive for consuming fluids once sensations of thirst, dryness in the mouth, and unpleasantness in the oral fissure are rectified and prior to completing fluid replacement; this incomplete fluid replacement has commonly been termed “involuntary” or “voluntary” dehydration [6,38]. Specifically, in our written report, thirst, mouth dryness, and ratings of unpleasantness in the mouth in HYPOFL
were lower at POSTREC
(Figure 3), despite a level of hypohydration of two.1% ± 1.ane%, a level of body mass loss where thirst is typically induced [six,9]. Despite not being statistically meaning, thirst (p
= 0.052) and dryness in the mouth (p
= 0.072) exhibited a large effect for HYPONF
when compared to HYPOFL
(ES = 7.15 and 6.iii, respectively), EUHFL
(ES = vii.49 and 6.02, respectively), and EUHNF
(ES = v.6 and v.61, respectively) conditions.

Nosotros observed that within the first 10 min of recovery, participants in HYPOFL
consumed approximately 55% of total fluid losses incurred during practice, which is consistent with prior literature [11,17]. It must be noted, even so, that nosotros but permitted participants ten min to swallow water, which may have prevented additional consumption to offset fluid losses. Interestingly, Evans et al. [39] assessed advertizing libitum intake of fluids at 15 min increments for 2 h post-obit exercise; their findings testify that after 15 min of ad libitum fluid consumption, roughly 25–30% of fluid losses were replaced. Speculating every bit to the reason for this discrepancy, knowledge from the participants of how long they had access to fluid in the electric current report may have prompted them to consume more fluid than they would have if allotted more fourth dimension overall to consume fluids. Despite this, we believe that if our participants were permitted to eat water throughout the entire 60 min recovery period, they would non fully supplant fluid losses. Work by Maughan et al. [twoscore,41,42] and Shirreffs et al. [43,44] advise that post-obit exercise, especially when in that location is limited time before the side by side bout, a strategic approach to rapid rehydration based on private losses must be utilized to optimize the potential for rehydration. Relying solely on thirst alone would not exist advisable in this scenario, peculiarly if fluid losses exceed ~3% of body mass, every bit shown in our study.

To contextualize the aforementioned into real-world context, assuasive participants to consume fluids during the first x min of a post-do recovery period, may mimic what could occur in a sport. For example, sports such as soccer and rugby, require athletes to perform continuous practice, with the elite levels of these sports preventing the number of substitutions permitted; this could create a scenario in which athletes enter the half-fourth dimension portion of a competition (typically x–15 min in length) hypohydrated to ~2% BML, specially if competition is being performed in hot conditions. If provided ad libitum admission to fluids, based on our findings, these athletes would swallow fluids to quench their thirst, and if only using thirst equally a measure of preparedness for the second half of contest, would enter the latter half of the event hypohydrated to a level that may event in marked operation deficits. While our written report did non examine whether thirst would remain adulterate if a second bout of exercise ensued based on the aforementioned example, our findings would back up the recommendation that individualized fluid replacement strategies are optimal for minimizing the extent of fluid losses during practise.

This study is not without limitations. We only tested male person participants in this study, which may not be generalizable to females, specially given the physiological changes that occur during the menstrual bicycle that may influence hydration state and thirst [45]. Furthermore, we just permitted participants to consume water ad libitum for a 10 min cake of fourth dimension immediately postal service exercise. Without permitting advertisement libitum consumption of water for the entire duration of post-practise recovery, we were unable to make up one’s mind if fluid consumption would take continued to further correct fluid losses. Additionally, given the influence of increasing the osmolarity of the fluid that is being consumed and the attenuation in the turn down of thirst, we are unable to make a conclusion of how the osmolarity of fluid following exercise-induced hypohydration may have further augmented the replacement of fluids. Evans et al. [39] institute no difference of advertizement libitum fluid ingested when comparison hypertonic ten%, ii%, and 0% glucose solutions; however, since an equal concentration of sodium was included in each beverage, it is unknown if differences would have been establish if evidently water was also ingested. Furthermore, the thirst scales utilized, Th [20] and TSS [21,22], have not been validated to date; there is no existing evidence that has compared changes in plasma osmolality to the thirst scales utilized for this study. While this prevents us from making conclusions based on perceptual scales validated against physiological measures, in utilizing a randomized cross-over pattern where participants completed both a euhydrated and hypohydrated trial under the same environmental atmospheric condition and exercise stress, nosotros feel that the inside-person changes in the thirst scales tested allows for consistency in these measures. Our mail hoc power analysis revealed that nosotros were underpowered for the TSS measures, which may explain why we observed non-significant findings for thirstiness, dryness in the mouth, pleasantness in the oral fissure, and fullness. Lastly, by not utilizing an exercise duration and/or intensity that may mimic various settings (athletic, occupational, and military settings) we are not able to make conclusive statements surrounding the use of thirst in guiding fluid replacement following the cessation of exercise.

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five. Conclusions

In conclusion, our findings point that when a bolus of fluid is provided immediately following exercise-induced aridity, the sensation of thirst rapidly declines to levels observed in euhydrated individuals for up to 60 min post-obit practice, despite a level of dehydration exceeding 2% torso mass loss. The prolonged inhibition of thirst when less fluid was consumed than total h2o losses may prevent 1’s ability to rehydrate chop-chop following prolonged exercise. These findings back up the recommendation that individuals may benefit from knowing their fluid needs and that fluid replacement should be individualized based on fluid losses and subsequent fluid need. Hereafter enquiry should consider examining the types of fluids consumed and allowing participants swallow fluids advertisement libitum at their discretion following practice-induced aridity. This would further expand on the utility of thirst as a tool to guide fluid replacement following exercise-induced dehydration and provide for more refined, data-informed recommendations existence derived.


The authors would like to give thanks Rachel Vanscoy, MS, ATC, Sarah Attanasio, MS, ATC, and Elizabeth 50. Adams, for their assistance with this study.

Writer Contributions

W.M.A., 50.W.V. and D.J.C. conceptualized the design and methodology of this report. Westward.One thousand.A., L.W.V., and L.N.B. were responsible for the data curation. W.M.A. was responsible for the initial analysis and writing of the original draft of this manuscript. L.W.V., L.N.B., and D.J.C. were responsible for critically reviewing and revising the manuscript. W.M.A., L.W.V., Fifty.N.B., and D.J.C. provided last blessing of the manuscript prior to submission.


This study was funded in part by Nothing, Inc.

Conflicts of Interest

The authors declare no conflicts of interest for the submitted piece of work. In improver, the sponsor had no function in the pattern, execution, interpretation, or writing of the report.


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What Sports Related Risk is Associated With Thirst

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