Assessing hydration status and reported beverage intake in the workplace

The aim was to examine the hydration status of adults working in different jobs at the beginning and end of a shift and their reported water intake. One hundred and fifty-six subjects (89 males, 67 females) were recruited from workplaces within the local area (students, teachers, security, office, firefighters, catering). A urine sample was obtained at the start and end of the shift and was analyzed for osmolality (Uosm), specific gravity (USG), and sodium and potassium concentrations. Euhydration was considered Uosm <700 mOsmol/kg or USG <1.020. At the end of the shift, subjects were asked to report all water intake from beverages during the shift. Females had lower Uosm than males at the start (656 [range, 85-970] vs 738 [range, 164-1090] mOsmol/kg) and end (461 [range, 105-1014] vs 642 [range, 130-1056] mOsmol/kg; P <.05) of their working day. Fifty-two percent of individuals who appeared hypohydrated at the start of the shift were also hypohydrated at the end. Reported water intake from beverages was greater in males compared with females (1.2 [range, 0.0-3.3] vs 0.7 [range, 0.0-2.0] L, respectively; P <.0001). In conclusion, a large proportion of subjects exhibited urine values indicating hypohydration, and many remained in a state of hypohydration at the end of the shift

Voluntary water intake during and following moderate exercise in the cold

Exercising in cold environments results in water losses, yet examination of resultant voluntary water intake has focussed on warm conditions. The purpose of the study was to assess voluntary water intake during and following exercise in a cold compared to a warm environment. Ten healthy males (22±2 years, 67.8±7.0 kg, 1.77±0.06 m, V˙O2peak 60.5±8.9 ml.kg-1.min-1) completed two trials (7-8d). In each trial subjects sat for 30 minutes before cycling at 70% V˙O2peak (162±27W) for 60 minutes in 25.0±0.1°C, 50.8±1.5% relative humidity (RH) (warm) or 0.4±1.0°C, 68.8±7.5% RH (cold). Subjects then sat for 120 minutes at 22.2±1.2°C, 50.5±8.0% RH. Ad libitum drinking was allowed during the exercise and recovery periods. Urine volume, body mass, serum osmolality and sensations of thirst were measured at baseline, post-exercise and after 60 and 120 minutes of the recovery period. Sweat loss was greater in the warm trial (0.96±0.18 l v 0.48±0.15 l) (p0.05). Ad libitum water intake adjusted so that similar body mass losses occurred in both trials. In the cold there appeared to a blunted thirst response

The effects of high-intensity intermittent exercise compared with continuous exercise on voluntary water ingestion

Water intake occurs following a period of high intensity intermittent exercise (HIIE) due to sensations of thirst yet this does not always appear to be caused by body water losses. Thus, the aim was to assess voluntary water intake following HIIE. Ten healthy males (22±2y, 75.6±6.9kg, V˙O2peak 57.3±11.4ml.kg-1.min-1) (mean±SD) completed two trials (7-14d apart). Subjects sat for 30min then completed an exercise period involving 2min of rest followed by 1min at 100%V˙O2peak repeated for 60min (HIIE) or 60min continuously at 33%V˙O2peak (LO). Subjects then sat for 60min and were allowed ad libitum water intake. Body mass was measured at start and end of trials. Serum osmolality, blood lactate and sodium concentrations, sensations of thirst and mouth dryness were measured at baseline, post-exercise and after 5, 15, 30 and 60min of recovery. Vasopressin concentration was measured at baseline, post-exercise, 5 and 30min. Body mass loss over the whole trial was similar (HIIE: 0.77±0.50; LO: 0.85±0.55%) (p=0.124). Sweat lost during exercise (0.78±0.22 v 0.66±0.26 l) and voluntary water intake during recovery (0.416±0.299 v 0.294±0.295 l) (p<0.05) were greater in HIIE. Serum osmolality (297±3 v 288±4mOsmol.kg-1), blood lactate (8.5±2.7 v 0.7±0.4mmol.l-1), serum sodium (146±1 v 143±1mmol.l-1) and vasopressin (9.91±3.36 v 4.43±0.86pg.ml-1) concentrations were higher after HIIE (p<0.05) and thirst (84±7 v 60±21) and mouth dryness (87±7 v 64±23) also tended to be higher (p=0.060). Greater voluntary water intake after HIIE was mainly caused by increased sweat loss and the consequences of increased serum osmolality mainly resulting from higher blood lactate concentrations

Electrolyte supplementation during severe energy restriction increases exercise capacity in the heat

PURPOSE. This study examined the effects of sodium chloride and potassium chloride supplementation during 48-h severe energy restriction on exercise capacity in the heat. METHODS. Nine males completed three 48-h trials: adequate energy intake (100 % requirement), adequate electrolyte intake (CON); restricted energy intake (33 % requirement), adequate electrolyte intake (ER-E); and restricted energy intake (33 % requirement), restricted electrolyte intake (ER-P). At 48 h, cycling exercise capacity at 60 % V˙V˙O2 peak was determined in the heat (35.2 °C; 61.5 % relative humidity). RESULTS. Body mass loss during the 48 h was greater during ER-P [2.16 (0.36) kg] than ER-E [1.43 (0.47) kg; P < 0.01] and CON [0.39 (0.68) kg; P < 0.001], as well as greater during ER-E than CON (P < 0.01). Plasma volume decreased during ER-P (P < 0.001), but not ER-E or CON. Exercise capacity was greater during CON [73.6 (13.5) min] and ER-E [67.0 (17.2) min] than ER-P [56.5 (13.1) min; P < 0.01], but was not different between CON and ER-E (P = 0.237). Heart rate during exercise was lower during CON and ER-E than ER-P (P < 0.05). CONCLUSIONS. These results demonstrate that supplementation of sodium chloride and potassium chloride during energy restriction attenuated the reduction in exercise capacity that occurred with energy restriction alone. Supplementation maintained plasma volume at pre-trial levels and consequently prevented the increased heart rate observed with energy restriction alone. These results suggest that water and electrolyte imbalances associated with dietary energy and electrolyte restriction might contribute to reduced exercise capacity in the heat

Thirst responses following high intensity intermittent exercise when access to ad libitum water intake was permitted, not permitted or delayed

An increase in subjective feelings of thirst and ad libitum drinking caused by an increase in serum osmolality have been observed following high intensity intermittent exercise (HIIE) compared to continuous exercise. The increase in serum osmolality is closely linked to the rise in blood lactate and serum sodium concentrations. However, during an ensuing recovery period after HIIE when serum osmolality will decrease, the resultant effect on sensations of thirst and subsequent water intake is unclear. Therefore the aim of the study was to assess the sensations of thirst and subsequent effect on ad libitum water consumption when water intake was immediately allowed, delayed or prevented following a period of HIIE.Twelve males (26 ± 4 years, 80.1 ± 9.3 kg, 1.81 ± 0.05 m, V̇O2peak 60.1 ± 8.9 ml.kg(-1).min(-1)) participated in three randomised trials undertaken 7-14 days apart. Participants rested for 30 min then completed a 60 min HIIE exercise period (20 x 1 min at 100% V̇O2peak with 2 min rest) followed by 60 min of recovery, during which ad libitum water intake was provided immediately (W), delayed until the final 30 min (W30) or not permitted (NW). Body mass was measured at the start and end of the trial. Blood lactate and serum sodium concentrations serum osmolality and sensation of thirst were measured at baseline, immediately post-exercise and during the recovery.Body mass loss was different between all trials (W: 0.25 ± 0.45, W30: 0.49 ± 0.37, NW: 1.29 ± 0.37%; p0.05). Serum osmolality (299 ± 6 v 298 ± 5 vs. 298 ± 3 mOsmol.kg(-1)), blood lactate (7.1 ± 1.1 vs. 7.2 ± 1.1 v 7.1 ± 1.2 mmol.l(-1)) and serum sodium concentrations (142 ± 2 vs. 145 ± 2 v 145 ± 2 mmol.l(-1)) peaked post-exercise (W vs. W30 vs. NW; p0.05).Sensations of thirst were increased following HIIE and remained until satiated by water intake. This was despite the likely primary stimulus, serum osmolality, decreasing during the recovery period following a post-exercise peak. A combined effect of reduction in blood lactate and serum sodium concentrations, restoration of plasma volume and water intake contributed to the similar decrease in serum osmolality observed throughout the trials

Fluid Needs for Training, Competition, and Recovery in Track-and-Field Athletes

The 2019 International Amateur Athletics Federation Track-and-Field World Championships will take place in Qatar in the Middle East. The 2020 Summer Olympics will take place in Tokyo, Japan. It is quite likely that these events may set the record for hottest competitions in the recorded history of both the Track-and-Field World Championships and Olympic Games. Given the extreme heat in which track-and-field athletes will need to train and compete for these games, the importance of hydration is amplified more than in previous years. The diverse nature of track-and-field events, training programs, and individuality of athletes taking part inevitably means that fluid needs will be highly variable. Track-and-field events can be classified as low, moderate, or high risk for dehydration based on typical training and competition scenarios, fluid availability, and anticipated sweat losses. This paper reviews the risks of dehydration and potential consequences to performance in track-and-field events. The authors also discuss strategies for mitigating the risk of dehydration

Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration

Hypohydration, or a body water deficit, is a common occurrence in athletes and recreational exercisers following the completion of an exercise session. For those who will undertake a further exercise session that day, it is important to replace water losses to avoid beginning the next exercise session hypohydrated and the potential detrimental effects on performance that this may lead to. The aim of this review is to provide an overview of the research related to factors that may affect post-exercise rehydration. Research in this area has focused on the volume of fluid to be ingested, the rate of fluid ingestion and on fluid composition. Volume replacement during recovery should exceed that lost during exercise to allow for ongoing water loss however ingestion of large volumes of plain water results in a prompt diuresis, effectively preventing longer term maintenance of water balance. Addition of sodium to a rehydration solution is beneficial for maintenance of fluid balance due to its effect on extracellular fluid osmolality and volume. The addition of macronutrients, such as carbohydrate and protein, can promote maintenance of hydration by influencing absorption and distribution of ingested water which, in turn, effects extracellular fluid osmolality and volume. Alcohol is commonly consumed in the post-exercise period and may influence post-exercise rehydration as will the co-ingestion of food. Future research in this area should focus on providing information related to optimal rates of fluid ingestion, advisable solutions to ingest during different duration recovery periods and confirmation of mechanistic explanations for the observations outlined

Muscle cramping during exercise : causes, solutions and questions remaining

Muscle cramp is a temporary but intense and painful involuntary contraction of skeletal muscle that can occur in many different situations. The causes of, and cures for, the cramps that occur during or soon after exercise remain uncertain, although there is evidence that some cases may be associated with disturbances of water and salt balance, while others appear to involve sustained abnormal spinal reflex activity secondary to fatigue of the affected muscles. Evidence in favour of a role for dyshydration comes largely from medical records obtained in large industrial settings, although it is supported by one large-scale intervention trial and by field trials involving small numbers of athletes. Cramp is notoriously unpredictable, making laboratory studies difficult, but experimental models involving electrical stimulation or intense voluntary contractions of small muscles held in a shortened position can induce cramp in many, although not all, individuals. These studies show that dehydration has no effect on the stimulation frequency required to initiate cramping and confirm a role for spinal pathways, but their relevance to the spontaneous cramps that occur during exercise is questionable. There is a long history of folk remedies for treatment or prevention of cramps; some may reduce the likelihood of some forms of cramping and reduce its intensity and duration, but none are consistently effective. It seems likely that there are different types of cramp that are initiated by different mechanisms; if this is the case, the search for a single strategy for prevention or treatment is unlikely to succeed.Publisher PDFPeer reviewe

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients