Pre-exercise Hydration Status Research Articles

Effects of a Short-Term Heat Acclimation Protocol in Elite Amateur Boxers

Stone, BL, Ashley, JD, Skinner, RM, Polanco, JP, Walters, MT, Schilling, BK, and Kellawan, JM. Effects of a short-term heat acclimation protocol in elite amateur boxers. J Strength Cond Res 36(7): 1966-1971, 2022-Boxing requires proficient technical and tactical skills coupled with high levels of physiological capacity. Although heat and humidity negatively affect acute exercise performance, short-term exercise training in hot and humid environments can lead to physiological adaptations that enhance exercise performance in both hot and thermoneutral conditions. In highly trained endurance athletes, exercise-induced acclimation can occur in as little as 5 days (known as short-term heat acclimation [STHA]). However, the impact of a 5-day heat acclimation (5-DayHA) in combat athletes, such as elite amateur boxers, is unknown. The aim of the present investigation was to determine whether a 5-DayHA improves aerobic performance in a thermoneutral environment and causes positive physiological adaptations in elite boxers. Seven elite amateur boxers underwent a 5-DayHA protocol, consisting of 60-minute exercise sessions in an environmental chamber at 32 °C and 70% relative humidity. Repeat sprint test (RST) evaluated aerobic performance in a thermoneutral environment 24 hours before and after the 5-DayHA. Presession and postsession hydration status (urine specific gravity) and body mass were assessed. After a 5-DayHA period, boxers significantly improved RST performance (13 ± 7 to 19 ± 7 sprints, d = 0.92, p = 0.03) but not pre-exercise hydration status (1.02 ± 0.01 to 1.01 ± 0.01, d = 0.82, p = 0.07). Therefore, these findings suggest 5-DayHA enhances aerobic performance in elite-level amateur boxers and may provide a viable training option for elite combat athletes.

Modified Stroop task performance when wearing protective clothing in the heat: An evaluation of the maximum adaptability model

IntroductionThis exploratory study investigated whether performance in a behavioural inhibition task followed the shape proposed by the Maximum Adaptability Model during progressive exertional heat stress—that is, an initial improvement in cognitive performance is followed by a plateau, and subsequent decline once body temperature continues to rise unabated. MethodsSeventeen adult males walked on a treadmill at 4 km h−1 (1% grade) for up to 120 min, in three protective clothing ensembles, across three simulated environments. The simulated environments were equivalent to wet bulb globe temperatures 21, 30 and 37 °C. Cognitive function was assessed using a modified colour-word Stroop Task, with performance expressed as inverse efficiency scores in the simple (congruent) and more complex (incongruent) task conditions. The Stroop Task was completed before a trial, at termination, and every 30 min during walking, and core body temperature was continuously measured. Data were modelled using Bayesian penalised regression, with core body temperature included as a non-linear term (i.e., second degree polynomial). ResultsWe did not find any evidence that core body temperature had an effect on congruent or incongruent inverse efficiency scores, and no evidence that the relationship between these variables followed the shaped described by the Maximum Adaptability Model. There was, however, evidence that higher pre-exercise serum osmolality values were associated with slower congruent (β = 9.19) and incongruent (β = 8.67) inverse efficiency scores. The posterior probability that these effects were greater than zero was 0.971 and 0.952, respectively. ConclusionsIn young, fit men, performance in the behavioural inhibition task was unaffected by increases in body temperature up to 39 °C and did not follow the shape proposed by the Maximum Adaptability Model. A secondary finding of the study was that pre-exercise hydration status affected performance in the inhibition task. Future studies are needed to confirm this result.

An investigation of dietary intake, nutrition knowledge and hydration status of Gaelic Football players

PurposeTo assess the dietary intake, nutrition knowledge and hydration status of Irish Gaelic footballers.MethodOne hundred and sixty-eight male club/county level Irish Gaelic footballers (median [IQR]; age 23 years [20.0, 27.0]; height 1.79 m [1.74, 1.84]; body mass 78.0 kg [73.5, 84.8]) participated in this cross-sectional study. Dietary intake was assessed using a 4-day semi-quantitative food record, with the application of Goldberg cut-offs to define acceptable reporters (n = 62). Nutrition knowledge was assessed using the validated Nutrition for Sport Knowledge Questionnaire in a sub-group of athletes (n = 24), while hydration status was measured using urine specific gravity pre-exercise (USG) in 142 athletes.ResultsDietary analysis indicated an energy deficit at the group level (485 kcal [IQR 751,6]) (p < 0.001), with carbohydrate intakes (3.6 g/kg [IQR 3.0,4.1]) below current guidelines for athletes participating in one hour moderate intensity exercise per day (5–7 g/kg; p < 0.001). Average vitamin D (3.8 µg [IQR 1.8, 5.5]) and selenium intakes (54.2 µg [47.2, 76.7]) were significantly below the reference nutrient intakes (p < 0.001). A high proportion of individual athletes also had sub-optimal intakes for: vitamin D (95.2%), selenium (72.6%), vitamin A (38.7%), potassium (30.6%), zinc (25.8%), magnesium (19.4%) and calcium (12.9%). Nutrition knowledge was deemed poor (40.2 ± 12.4%), while pre-exercise hydration status (median USG 1.010 [IQR 1.005, 1.017]) was significantly below the cut-off to denote dehydration (1.020; p < 0.001).ConclusionsOur findings suggest that Irish Gaelic footballers have sub-optimal dietary practices and lack nutrition knowledge. Individualised nutrition support may benefit these athletes to meet their nutrition requirements, to support health and performance.

Sweat Loss and Fluid Intake of Female Varsity Ice Hockey Players During On-Ice Practices and Games.

Bigg, JL, Gamble, ASD, Vermeulen, TF, Bigg, LM, and Spriet, LL. Sweat loss and fluid intake of female varsity ice hockey players during on-ice practices and games. J Strength Cond Res 34(2): 389-395, 2020-Sweat losses of ∼1.5-2% body mass (BM) during exercise impairs athletic performance in stop and go sports such as ice hockey. The study examined the pre-exercise hydration status, sweat loss, fluid and carbohydrate (CHO) intake, and sodium balance of female hockey players. Twenty-four female varsity hockey players were tested during 2 practices and 4 games. Data analyses were performed using a level of significance of p ≤ 0.05. Over 70% of players arrived at the practices and ∼50% of players arrived at the game mildly dehydrated. Before the high- (P1) and low-intensity (P2) practices, players consumed an average of 0.19 ± 0.14 and 0.15 ± 0.13 L. Before the games, mean fluid intake was 0.39 ± 0.19 L. The sweat rate during P1 was significantly greater than P2 (p = 0.006), but there was no significant difference in total fluid intake between practices (p = 0.279). Consequently, the average BM loss for P1 was significantly greater than that for P2 (p = 0.016). Sweat loss during games was 1.01 ± 0.29 L and fluid intake was 0.70 ± 0.43 L, resulting in minimal BM losses (<1% BM for all players). CHO intake during games was 39.2 ± 22.8 g, with 19/20 players consuming CHO before or during the intermissions of the game. Sweat sodium losses were 0.64 ± 0.34 and 0.32 ± 0.18 g·h for P1 and P2, and 0.83 ± 0.38 g during the game. In conclusion, female ice hockey players replaced the fluid they lost through sweat during practices and games and maintained adequate hydration. Players also consumed adequate CHO during games from the CHO containing food and drinks provided.

Developing Information media as Dehydration Prevention Strategy In Indonesia Recreational Futsal Players

Background: Futsal as leisure time sport is very popular in Indonesia. However, this sport is characterized by high intensity which tends to cause dehydration.&#x0D; Aim: The aim of this study was to identify pre-exercise hydration status of recreational futsal players and develop information media to prevent dehydration in Indonesia recreational futsal players.&#x0D; Method: Descriptive cross-sectional study was implemented as part of preliminary study to get the picture of pre-exercise hydration status of recreational futsal players. Twenty seven male participants were recruited in this study (age 22 + 3.19 years old., weight 65.85 + 13.54 kg, height 1.69 + 0.08 m, BMI 22.73 + 3.08 kg/m2). Hydration status was checked by using urine strip test before they played futsal. Participants filled out short questionnaires to find out the information source of dehydration. Information media was created based on the result of this preliminary study to prevent dehydration. Additionally, media expert and sports medicine doctor also assessed the development of information media.&#x0D; Result: The preliminary study showed that 77.7% (n = 21) of the subjects suffered from dehydration before playing futsal. The short questionnaires result showed that most of the subjects received information about dehydration from television (52%) and internet (43%). The content and design of developed information media was considered valid by the experts.&#x0D; Conclusion: Our findings conclude that incidence of pre-exercise dehydration among recreational futsal players in Indonesia was high. Further study to evaluate the use of developed information media is needed to prevent the risk of dehydration during high intensity exercise.&#x0D; Bangladesh Journal of Medical Science Vol.19(1) 2020 p.122-128

Dehydration Impairs Executive Function Task in Middle‐Age and Older Adults Following Endurance Exercise

Dehydration attenuates exercise and cognitive function performance in younger adults, but less is known about the impact of dehydration on the aging population. Regular exercise serves as a robust prophylactic treatment to prevent age‐related decline in physical and cognitive function. However, middle‐age and older adults often display a blunted thirst perception, which places them at risk for dehydration and subsequently may reduce the cognitive health‐related benefits of exercise.PURPOSETo examine the impact that pre‐exercise hydration status has on executive function task following endurance exercise within a middle‐age and older adult cohort.METHODSThis field study was conducted at a mass participation cycling event in Wichita Falls, Texas (ambient temperature, 26°C mean, 30°C maximum; relative humidity, 75% mean, 93% maximum). Forty‐nine recreational cyclists (55±6 y, range 44–70y) were enrolled following informed consent and were retrospectively separated into 2 groups (euhydrated, EUH; dehydrated, DEH) based on pre‐exercise hydration status. Criteria for euhydration were consistent with sports medicine consensus guidelines (urine specific gravity &lt;1.020, Usg; urine color &lt; 4 units, Ucol). All cyclists were screened for mild cognitive impairment via the validated Mini‐Cog™ assessment (4±1). At baseline, participants were familiarized with the executive function pencil‐paper test (Trail Making A and B Tests, TMT) and anthropometric measurements were recorded. Cyclists completed the TMT prior to and immediately following the event. Ratings of perceived exertion (RPE) and total exercise time were determined at the finish line. Pre‐ and post‐TMT scores were compared via paired T‐test and Cohen d effect size were recorded. All the following data are presented as mean±SD.RESULTSGroups (EUH vs DEH) did not differ in age (55±5 vs 54±8 y) or body fat percentage (12.8±5.6 vs 14.5±5.1) (p&gt;0.05). Significant differences were note in both Usg (1.015±0.004 vs 1.023±0.002) and Ucol (3±1 vs 5±1) (p&lt;0.001). Post exercise RPE (15±2 vs 17±2), total event time (362±59 vs 359±51 min), and body mass loss ( −2.0%, EUH and DEH) were similar for both groups (p&gt;0.05). After the HHH 164‐km endurance cycling event, there was a significant improvement (i.e., faster completion time) in the TMT noted in the EUH group (pre vs post, 83±24 vs 71±18 s; p&lt;0.05) but not the DEH group (pre vs post, 86±26 vs 79±22 s). Further analysis showed the Cohen d effect sizes to be moderate (0.5) in the EUH and small (0.2) in the DEH group.CONCLUSIONIn this prospective study, dehydration negatively impacted an executive function task (TMT) in middle‐age and older adults following an acute bout of prolonged, moderate‐intensity endurance exercise. This suggests that older adults should adopt adequate drinking behaviors to reduce cognitive fatigue and potentially enhance the cognitive benefits of regular exercise participation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ad Libitum Fluid Intake Does Not Prevent Dehydration in Suboptimally Hydrated Young Soccer Players During a Training Session of a Summer Camp

There is a lack of studies concerning hydration status of young athletes exercising in the heat. To assess preexercise hydration status in young soccer players during a summer sports camp and to evaluate body- water balance after soccer training sessions. Initial hydration status was assessed in 107 young male soccer players (age 11-16 yr) during the 2nd day of the camp. Seventy-two athletes agreed to be monitored during 2 more training sessions (3rd and 5th days of the camp) to calculate dehydration via changes in body weight, while water drinking was allowed ad libitum. Hydration status was assessed via urine specific gravity (USG), urine color, and changes in total body weight. Mean environmental temperature and humidity were 27.2 ± 2 °C and 57% ± 9%, respectively. According to USG values, 95 of 107 of the players were hypohydrated (USG ≥ 1.020) before practice. The prevalence of dehydration observed was maintained on both days, with 95.8% and 97.2% of the players being dehydrated after the training sessions on the 3rd and 5th days, respectively. Despite fluid availability, 54 of the 66 (81.8%) dehydrated players reduced their body weight (-0.35 ± 0.04 kg) as a response to training, while 74.6% (47 out of the 63) further reduced their body weight (-0.22 ± 0.03 kg) after training on the 5th day. Approximately 90% of the young soccer players who began exercising under warm weather conditions were hypohydrated, while drinking ad libitum during practice did not prevent further dehydration in already dehydrated players.

Age related decreases in thermoregulation and cardiovascular function in horses

Older horses have an increased risk of hyperthermia due to impaired cardiovascular function. While many studies have investigated thermoregulation in horses during exercise, none have investigated the effects of ageing. To test the hypothesis that there is a difference in thermoregulation during exercise and plasma volume (PV) in young and old horses. Study 1: 6 young (Y, 7.7 ± 0.5 years) and 5 old (O, 26.0 ± 0.8 years) unfit Standardbred mares (507 ± 11 kg, mean ± s.e.) ran on a treadmill (6% grade, velocity calculated to generate a work rate of 1625 watts) until core temperature reached 40 °C. Core (CT), skin (ST), rectal temperature (RT) and heart rate (HR) were measured every min until 10 min post exertion. Packed cell volume (HCT), lactate (LA) and plasma protein (TP) were measured in blood samples collected before, at 40 °C and every 5 min until 10 min post exercise. Sweat loss was estimated using bodyweight. Study 2: Plasma volume was measured in 26 young (8.2 ± 0.7 years) and 8 old (26.6 ± 0.7 years) Standardbred mares (515 ± 12 kg) using Evans Blue dye. Pre-exercise blood (rBV) and red cell (rRCV) volumes were calculated using PV and HCT. Data analysis utilised repeated measures ANOVA and t tests and data are expressed as mean ± s.e. Old horses reached 40 °C faster (998 ± 113 vs. 1925 ± 259 s; P < 0.05) with a greater HR at 40 °C (184 ± 6 vs. 140 ± 5 beats/min; P < 0.05) and greater sweat losses (P < 0.05). Heart rate did not differ (P > 0.05) post exercise. Age did not alter (P > 0.05) CT, ST, RT, LA, HCT or TP. Plasma volume was greater in Y vs. O horses (P < 0.05, 28.5 ± 1.4 vs. 24.1 ± 1.6 l) as was rBV (41.3 ± 2.0 vs. 35.3 ± 2.3 l) and rRCV (13.3 ± 0.6 vs. 11.1 ± 0.8 l). Ageing compromises the ability to handle the combined demand of exercise and thermoregulation in part due to decreased absolute pre-exercise PV.

Dehydration and rehydration in competative sport

Dehydration, if sufficiently severe, impairs both physical and mental performance, and performance decrements are greater in hot environments and in long-lasting exercise. Athletes should begin exercise well hydrated and should drink during exercise to limit water and salt deficits. Many athletes are dehydrated to some degree when they begin exercise. During exercise, most drink less than their sweat losses, some drink too much and a few develop hyponatraemia. Athletes should learn to assess their hydration needs and develop a personalized hydration strategy that takes account of exercise, environment and individual needs. Pre-exercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity or osmolality. Changes in hydration status during exercise can be estimated from the change in body mass: sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples. An appropriate, individualized drinking strategy will take account of pre-exercise hydration status and of fluid, electrolyte and substrate needs before, during and after a period of exercise.

Development of hydration strategies to optimize performance for athletes in high‐intensity sports and in sports with repeated intense efforts

Hypohydration - if sufficiently severe - adversely affects athletic performance and poses a risk to health. Strength and power events are generally less affected than endurance events, but performance in team sports that involve repeated intense efforts will be impaired. Mild hypohydration is not harmful, but many athletes begin exercise already hypohydrated. Athletes are encouraged to begin exercise well hydrated and - where opportunities exist - to consume fluid during exercise to limit water and salt deficits. In high-intensity efforts, there is no need, and may be no opportunity, to drink during competition. Most team sports players do not drink enough to match sweat losses, but some drink too much and a few may develop hyponatremia because of excessive fluid intake. Athletes should assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment and individual needs. Pre-exercise hydration status can be assessed from urine markers. Short-term changes in hydration can be estimated from the change in body mass. Sweat salt losses can be determined by collection and analysis of sweat samples. An appropriate drinking strategy will take account of pre-exercise hydration status and of fluid, electrolyte and substrate needs before, during and after exercise.

Development of Individual Hydration Strategies for Athletes

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.

Initial Hydration Status and Fluid Balance during Recreational Exercise in Physically Active Adults

Athletes typically fail to consume sufficient fluids during exercise to replace losses, whilst many arrive for exercise already dehydrated. However, very little is known about the pre-exercise hydration status and fluid balance of recreational exercisers, which may influence exercise adherence and overall wellbeing. PURPOSE: To investigate initial hydration status and fluid balance during recreational exercise in physically active adults. METHODS: Fifty-two physically active adult male (n = 31) and female (n = 21) subjects aged 36 ± 12 years (mean ± SD); body mass 80.7 ± 15.9 kg; volunteered to participate at a fitness centre. Urine samples were collected upon arrival. Nude body mass was recorded before and after exercise. Subjects performed a freely chosen gymnasium-based exercise session in mean ambient conditions of 21 oC and 55% relative humidity, with ad libitum access to water. Sweat loss was estimated from the change in body mass after correction for fluid intake and urinary losses. RESULTS: Mean ± SD (range) exercise duration was 64 ± 22 mins (15 - 125 mins). Pre-exercise urine osmolality was 698 ± 288 mOsmol.kg-1 (166 - 1245 mOsmol.kg-1) and was not different for gender (p = 0.915). Urine osmolality was above 900 mOsmol. kg-1 (used as a threshold for dehydration) in 38% of participants; 32% of males and 43% of females. The change in body mass during exercise was −0.51 ± 0.32 kg (−1.30 - 0.25 kg) and was greater in males than females (−0.59 ±0.35 vs. −0.39 ± 0.23 kg; p< 0.05). This was equivalent to a percentage change in pre-exercise body mass of-0.62 ± 0.2% (−1.63 - 0.40%) which was not different for gender (p = 0.258). Sweat loss was 794 ± 391 ml (50 - 1656 ml) and was greater in males than females (938 ± 390 vs. 556 ± 264 ml; p < 0.01), whilst fluid intake was 390 ± 298 ml (0 - 1610 ml) and was also greater in males than females (468 ± 329 vs. 275 ± 200 ml; p < 0.05). CONCLUSION: Although there was large inter-individual variability, male and female recreational exercisers generally became modestly dehydrated during a typical exercise session, as insufficient fluid was consumed to replace sweat losses. Furthermore, for many adults this was superimposed on existing dehydration because a large proportion of participants arrived to take part in exercise in a dehydrated state.

Urine specific gravity in exercisers prior to physical training

Urine specific gravity (USG) is used as an index of hydration status. Many studies have used USG to estimate pre-exercise hydration in athletes. However, very little is known about the pre-exercise hydration status of recreational exercisers. The purpose of the present study was to measure the pre-exercise USG in a large sample of recreational exercisers who attended 2 different fitness centers in the United States. In addition, we wanted to determine if factors such as time of day, geographic location, and gender influenced USG. We tested 166 subjects in Chicago and 163 subjects in Los Angeles. Subjects completed a survey on their typical training regimen and fluid-replacement habits, and thereafter voided and delivered a urine sample to the investigators prior to beginning exercise. Samples were measured on site for USG using a hand-held refractometer. The mean (SD) USG was 1.018 (+/- 0.007) for all subjects. Males had a higher average USG (1.020 +/- 0.007) when compared with females (1.017 +/- 0.008; p = 0.001). Despite differences in climate, no difference in mean USG occurred based on location or time of day. Based on standards used for athletes (USG > or = 1.020), 46% of the exercisers were likely to be dehydrated.

Effect of Hydration State on Testosterone and Cortisol Responses to Training-Intensity Exercise in Collegiate Runners

Exercise intensity powerfully influences testosterone, cortisol, and testosterone : cortisol ratio (T:C) responses to endurance exercise. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to endurance exercise and training. This study examined the effect of running intensity on testosterone, cortisol, and T : C when exercise was initiated in a hypohydrated state. Nine male collegiate runners (age = 20 +/- 0 y, height = 178 +/- 2 cm, mass = 67.0 +/- 1.8 kg, body fat % = 9.8 +/- 0.7 %, V.O2max = 65.7 +/- 1.1 ml.kg (-1).min (-1)) completed four 10-min treadmill runs differing in pre-exercise hydration status (euhydrated, or hypohydrated by 5 % of body mass) and exercise intensity (70 % or 85 % V.O2max). Body mass, urine osmolality, and urine-specific gravity documented fluid balance; blood samples drawn pre-, immediately post-, and 20 min post-exercise were analyzed for testosterone, cortisol, and T : C. Except for heart rate measured during the 70 % V.O2max trials, heart rate, V.O2, and plasma lactate were similar between euhydrated and hypohydrated conditions for a given intensity, suggesting hypohydration did not measurably increase the physiological stress of the exercise bouts. Furthermore, hydration state had no measurable effect on testosterone concentrations before, during, or after exercise at either intensity. Regardless of exercise intensity, cortisol concentrations were greater during hypohydration than euhydration pre-exercise and 20 min post-exercise. Additionally, T : C was significantly lower 20 min post-exercise at 70 % V.O2max when subjects were initially hypohydrated (T : C = 0.055) versus euhydrated (T : C = 0.072). These findings suggest that depending on exercise intensity, T : C may be altered by hydration state, therefore influencing the balance between anabolism and catabolism in response to running exercise performed at typical training intensities.