Sweat Sodium Research Articles

No Relation Between Short-term Sodium Intake And Whole Body Sweat Sodium Concentration During Exercise-heat Stress

Research has been limited and mixed with regards to the effect of normal, short-term dietary sodium (Na) intake on sweat Na concentration ([Na]) and total sweat Na losses during exercise. PURPOSE: To determine the relation between dietary Na intake during exercise and up to 48-h before exercise on whole-body (WB) sweat [Na] and total sweat Na loss during 90 min of moderate-intensity cycling in the heat. METHODS: Forty-nine recreational athletes (34 men, 15 women; 34 ± 4 years; 75 ± 12 kg) cycled for 90 min at 78 ± 5% HRmax in the heat (320C, 25-50% RH). The WB washdown technique was used to collect sweat electrolytes during exercise and ion chromatography analysis was used to determine sweat [Na]. Total sweat Na loss was the product of WB sweat [Na] and WB sweat loss. Subjects were instructed to consume their normal diet before their trials. Upon arriving to the lab, each subject turned in a diet log, which included specific portion sizes and brand/type for all foods, fluids, and dietary supplements consumed in the previous 48 h. The investigators reviewed the diet logs for completeness with the subjects. Na intake was determined by Registered Dietitians using a computer based dietary analysis tool. Na intake during the trial was determined from the volume of 6% carbohydrate electrolyte (38 mmol/L Na) solution consumed ad libitum. Pearson correlation analysis was used to determine the relation between Na intake versus WB sweat [Na] and total sweat Na loss. Data are shown as mean ± SD. RESULTS: WB sweat [Na] was 41.1 ± 15.6 mmol/L and total sweat Na losses were 60.9 ± 35.3 mmol. Na intake during exercise, 24-h and 48-h before exercise were 32.4 ± 18.0 mmol, 188 ± 102 mmol, and 350 ± 159 mmol. There were no significant correlations between dietary Na intake and WB sweat [Na] (r = -0.002 to 0.02, p=0.90-0.99) or total sweat Na losses (r = 0.07 to 0.19, p=0.20-0.61) for any of the comparisons. CONCLUSION: There were no correlations between normal dietary Na intake during and up to 48 h before exercise versus WB sweat [Na] or total sweat Na losses. These results suggest that short-term Na intake does not play a significant role in explaining the inter-individual differences in WB sweat Na during exercise.

Assessment of dehydration, sweat rate, electrolyte loss through the field sweat test on athletes

Purpose The purpose of this study was to confirm and evaluate the assessment of dehydration, whole body sweat rate, sweat sodium · potassium concentration, and fluid intake during workout in college badminton and rugby athletes using the field sweat test. Methods 14 male badminton athletes and 17 male rugby athletes were measured during an usual training session in a typical environment. USG(urine specific gravity) was measured before the start of training. Whole body sweat rate, sweat sodium·potassium concentration, and fluid intake were measured during and post a session of training. Results USG higher than 1.023 in both groups, which was considered as dehydrated. Sweating rate were 1.037±0.315L/h for the badminton athletes and 1.987±0.386L/h for the rugby athletes. The concentration of sodium and potassium were 53.6±20.2mmol/L, 4.1±0.7mmol/L for badminton athletes, and 55.6±15.2mmol/L, 4.3±0.5mmol/L for rugby athletes, respectively. The loss of sodium and potassium were 1.02±0.48g, 0.08±0.02g for badminton athletes, and 1.95±0.52g, 0.15±0.03g for rugby athletes, respectively. Conclusions In this study, a standard protocol of field sweat test was suggested as a useful factor in evaluating athletes' hydration status and electrolyte loss during a routine in-door or out-door training session. And, it is expected to build reliable data to establish a standard hydration guideline for Korean athletes.

Sweat Characteristics in Individuals With Varying Susceptibilities of Exercise-Associated Muscle Cramps.

Szymanski, M, Miller, KC, O'Connor, P, Hildebrandt, L, and Umberger, L. Sweat characteristics in individuals with varying susceptibilities of exercise-associated muscle cramps. J Strength Cond Res 36(5): 1171-1176, 2022-Many medical professionals believe dehydration and electrolyte losses cause exercise-associated muscle cramping (EAMC). Unlike prior field studies, we compared sweat characteristics in crampers and noncrampers but accounted for numerous factors that affect sweat characteristics including initial hydration status, diet and fluid intake, exercise conditions, and environmental conditions. Sixteen women and 14 men (mean ± SD; age = 21 ± 2 year, body mass = 69.1 ± 11.6 kg, height = 171.4 ± 9.9 cm) self-reported either no EAMC history (n = 8), low EAMC history (n = 10), or high EAMC history (n = 12). We measured V̇o2max, and subjects recorded their diet. At least 3 days later, subjects ran at 70% of their V̇o2max for 30 minutes in the heat (39.9 ± 0.6° C, 36 ± 2% relative humidity). Dorsal forearm sweat was collected and analyzed for sweat sodium concentration ([Na+]sw), sweat potassium concentration ([K+]sw), and sweat chloride concentration ([Cl-]sw). Sweat rate (SWR) was estimated from body mass and normalized using body surface area (BSA). Dietary fluid, Na+, and K+ ingestion was estimated from a 3-day diet log. We observed no differences for any variable among the original 3 groups (p = 0.05-p = 0.73). Thus, we combined the high and low cramp groups and reanalyzed the data against the noncramping group. Again, there were no differences for [Na+]sw (p = 0.68), [K+]sw (p = 0.86), [Cl-]sw, (p = 0.69), SWR/BSA (p = 0.11), dietary Na+ (p = 0.14), dietary K+ (p = 0.66), and fluid intake (p = 0.28). Fluid and electrolyte losses may play a more minor role in EAMC genesis than previously thought.

Rapid Capture and Extraction of Sweat for Regional Rate and Cytokine Composition Analysis Using a Wearable Soft Microfluidic System

Rapid Capture and Extraction of Sweat for Regional Rate and Cytokine Composition Analysis Using a Wearable Soft Microfluidic System

A wearable sensor for the detection of sodium and potassium in human sweat during exercise

The SwEatch platform, a wearable sensor for sampling and measuring the concentration of electrolytes in human sweat in real time, has been improved in order to allow the sensing of two analytes. The solid contact ion-sensitive electrodes (ISEs) for the detection of Na+ and K+ have been developed in two alternative formulations, containing either poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(3-octylthiophene-2,5-diyl) (POT) as a conductive polymer transducing component. The solution-processable POT formulation simplifies the fabrication process, and sensor to sensor reproducibility has been improved via partial automation using an Opentron® automated pipetting robot. The resulting electrodes showed good sensitivity (52.4 ± 6.3 mV/decade (PEDOT) and 56.4 ± 2.2 mV/decade (POT) for Na+ ISEs, and 45.7 ± 7.4 mV/decade (PEDOT) and 54.3 ± 1.5 mV/decade (POT) for K+) and excellent selectivity towards potential interferents present in human sweat (H+, Na+, K+, Mg2+, Ca2+). The 3D printed SwEatch platform has been redesigned to incorporate a double, mirrored fluidic unit which is capable of drawing sweat from the skin through passive capillary action and bring it in contact with two independent electrodes. The potentiometric signal generated by the electrodes is measured by an integrated electronics board, digitised and transmitted via Bluetooth to a laptop. The results obtained from on-body trials on athletes during cycling show a relatively small increase in sodium (1.89 mM–2.97 mM) and potassium (3.31 mM–7.25 mM) concentrations during the exercise period of up to 90 min.

Effects of training intensity and environmental condition on the hydration status of elite football players

ABSTRACT Objective: To examine the effects of training intensity and environmental condition on the hydration status of Elite football players. Methods: Eleven elite football players completed three training sessions of varying intensity in cool (12°C) and warm (23°C) environments. Training demands was measured by Global Positioning System, sweat rate and sweat sodium concentration were measured using dermal patches and body mass change. Results: Warm condition increased sweat rate (0.9 ± 0.3 vs 1.7 ± 0.3 L.h-1, P<0.001), fluid intake (0.7 ± 0.1 vs 1.5 ± 0.2 L, P<0.001), total sodium loss (1405 ± 340 vs 2946 ± 958 mg, P<0.001) and total sweat loss (1.4 ± 0.5 vs 2.5 ± 0.4 L, P<0.001) compared to cool. Training intensity increased sweat sodium concentration (16.1 ± 6.6 vs 54.6 ± 22.2 mmol.L-1, P<0.001) and sodium loss (779 ± 231 vs 1405 ± 340 mg) in both environmental conditions. Total sweat loss and sodium loss were positively correlated with total distance covered (r=0.48, P=0.005 and r=0.4, P=0.023, respectively), meanwhile sodium loss was also positively correlated with the total number of high-intensity efforts (r=0.35, P=0.045). Conclusions: The results show that training load and environmental condition have a major impact on the hydration status of elite football players, hence hydration strategies should be developed accordingly.

Sweat Characteristics of Cramp-Prone and Cramp-Resistant Athletes.

Exercise-associated muscle cramps (EAMCs) are thought to be caused by dehydration and/or electrolyte losses. In this multicenter, cross-sectional study, the authors determined whether sweat rates (SRs), sweat electrolyte concentrations, or sweat electrolyte content differed in athletes with (i.e.,crampers) and without (i.e.,noncrampers) a history of EAMCs and whether these variables could predict EAMC-prone athletes. Male and female collegiate athletes (N = 350) from 11 sports with (n = 245) and without (n = 105) a self-reported history of EAMCs completed a typical exercise or conditioning session. SRs, calculated from body mass, and posterior forearm sweat were analyzed for sweat sodium concentration ([Na+]sw), sweat potassium concentration ([K+]sw), and sweat chloride concentration ([Cl-]sw). The authors used SRs and sweat electrolyte concentrations to calculate sweat electrolyte content lost. Within each gender, no differences in SRs (204 males, p = .92; 146 females, p = .24); [Na+]sw (191 males, p = .55; 126 females, p = .55); Na+sw content (191 males, p = .59; 126 females, p = .20); [K+]sw (192 males, p = .57; 126 females, p = .87); K+sw content (192 males, p = .49; 126 females, p = .03); [Cl-]sw (192 males, p = .94; 77 females, p = .57); and Cl-sw content (192 males, p = .55; 77 females, p = .34) occurred between crampers and noncrampers. Receiver operating characteristic curve analysis revealed that sweat electrolyte content and SRs were predictive of EAMC-prone athletes in American football (area under curve = 0.65-0.72, p ≤ .005), but not in any other sport. EAMCs may not be solely caused by fluid or electrolyte losses in most athletes. Fluid and electrolyte replacement may help American footballers. Clinicians should individualize fluid and electrolyte replacement and understand different etiologies for EAMCs.

Permanent tattooing has no impact on local sweat rate, sweat sodium concentration and skin temperature or prediction of whole-body sweat sodium concentration during moderate-intensity cycling in a warm environment.

This study investigated the impact of permanently tattooed skin on local sweat rate, sweat sodium concentration and skin temperature and determined whether tattoos alter the relationship between local and whole-body sweat sodium concentration. Thirteen tattooed men (27 ± 6years) completed a 1h (66 ± 4% of [Formula: see text]) cycling trial at 32°C, 35% relative humidity. Sweat rate and sweat sodium concentration were measured using the whole-body washdown and local absorbent patch techniques. Patches and skin-temperature probes were applied over the right/left thighs and tattooed/non-tattooed (contralateral) regions. Local sweat rates did not differ (p > 0.05) between the right (1.11 ± 0.38) and left (1.21 ± 0.37) thighs and the permanently tattooed (1.93 ± 0.82) and non-tattooed (1.72 ± 0.81mgcm-2min-1) regions. There were no differences in local sweat sodium concentration between the right (58.2 ± 19.4) and left (55.4 ± 20.3) thighs and the permanently tattooed (73.0 ± 22.9) and non-tattooed (70.2 ± 18.9mmolL-1) regions. Difference in local skin temperature between the right and left thighs (- 0.043) was similar to that between the permanently tattooed and non-tattooed (- 0.023°C) regions. Prediction of whole-body sweat sodium concentration for the permanently tattooed (41.0 ± 6.7) and the non-tattooed (40.2 ± 5.3mmolL-1) regions did not differ. Permanent tattoos do not alter local sweat rate, sweat sodium concentration or local skin temperature during moderate-intensity cycling exercise in a warm environment. Results from a patch placed over a tattooed surface correctly predicts whole-body sweat sodium concentration from an equation developed from a non-tattooed region.

Validity of a wearable sweat rate monitor and routine sweat analysis techniques using heat acclimation.

the aim of this study was to assess the validity of a novel wearable sweat rate monitor against an array of sweat analysis techniques which determine sudomotor function when exercising moderately under heat stress. Construct validity was determined utilising a 5-day short-term heat acclimation (STHA) intervention. Nineteen healthy individuals (age: 41±23 years, body mass: 74.0±12.2kg, height: 174.9±6.9cm) [male; n=15, female; n=4] completed nine trials over a three-week period, in a controlled chamber set to 35°C, 50% relative humidity for all sessions. The pre and post-trials were separated by five consecutive controlled hyperthermia HA sessions. Sweat analysis was compared from pre and post-trial, whereby whole body sweat rate (WBSR) was assessed via pre and post nude body mass. Local sweat rate (LSR) was determined via technical absorbent patches (TA) (weighed pre and post) and a novel wearable KuduSmart® (SMART) monitor which was placed on the left arm during the 30-min of exercise. Tegaderm patches, used to measure sweat sodium chloride conductivity (SC), and TA patches were placed on the back, chest and forearm for the 30-min cycling. Sudomotor function significantly adapted via STHA (p<0.05); demonstrated by a WBSR increase of 24%, LSR increase via the TA method (back: 26%, chest: 45% and arm: 48%) and LSR increase by the SMART monitor (35%). Finally, SC decreased (back: -21%, chest: -25% and arm: -24%, p<0.05). All sweat techniques were sensitive to sudomotor function adaptation following STHA, reinforcing their validity. The real time data given by the wearable KuduSmart® monitor provides coaches and athletes instant comparable sudomotor function feedback to traditional routinely used sweat analysis techniques.

A276 TOTAL PANCREATIC LIPOMATOSIS AND EXOCRINE PANCREATIC INSUFFICIENCY IN A PATIENT WITH CELIAC DISEASE: AN UNUSUAL ENTITY

Abstract Background Exocrine pancreatic insufficiency (EPI) is characterized by maldigestion and malabsorption of nutrients and is most commonly caused by diseases of the pancreatic parenchyma including chronic pancreatitis and cystic fibrosis (CF). However, EPI is also observed in other conditions including celiac disease (CD). Aims We report a case of EPI in a patient with CD found to have total fatty replacement of the pancreas. Methods A case report and review of the literature were performed. Results Case Report: A 42-year-old man with CD on gluten-free diet (GFD) presented with a two-year history of increasing bowel frequency (4–6 times daily) and steatorrhea. Quantitative fecal fat over 72 hours confirmed fecal fat excretion of 101g/day; N &amp;lt; 7g) and total stool weight of 3761g. Nadir weight was 67.6 kg. There was a dramatic response to pancreatic enzyme replacement therapy (PERT) with marked improvement in bowel habits and weight gain to 74.8 kg over half a year. There is no history of pancreatitis, abdominal pain or alcohol abuse. He does not smoke but drinks 1–2 units of alcohol per week at most. Family history is negative for pancreatitis and pancreatic malignancy. On examination, following PERT, the patient appeared well-developed and nourished. He did not have clinical features or biochemical evidence of fat-soluble vitamin deficiency following PERT. Anti-tTG was equivocal (7.6 U/mL; N &amp;lt; 7 U/mL). IgG subclasses were normal. Chromogranin was mildly elevated (100mcg/L; N &amp;lt; 94mcg/L), but gastrin (15ng/L) and 24-hour urine for 5-hydroxyindoleacetate [5-HIAA] (23umol/d) were normal. Endoscopic evaluations including upper endoscopy, colonoscopy, and capsule endoscopy demonstrated intact duodenal villous architecture without inflammation, no microscopic colitis, and no small bowel mucosal disease, respectively. CT of the abdomen revealed total fatty replacement of the pancreas with no pancreatic parenchyma (Figure 1). Sweat sodium test was positive (67 mmol/L, N &amp;lt; 60 mmol/L) but CFTR gene sequencing was negative. There was no evidence of diabetes, hyperlipidemia, hyperferritinemia, Cushing’s syndrome, or hepatic disease on biochemical investigations. Literature Review: Total pancreatic lipomatosis (TPL), or fatty replacement of the pancreas, is a rare cause of EPI which leads to maldigestion, malabsorption, and malnutrition. The pathogenesis of TPL is poorly understood but predisposing factors include obesity, diabetes mellitus, hyperlipidemia, malnutrition, Cushing’s syndrome, hemochromatosis, chronic pancreatitis and CF. EPI can also manifest in patients with CD due to active small bowel inflammation or chronic pancreatitis. Last but not least, there appears to be higher prevalence of CD in CF patients. Conclusions Persistent steatorrhea with weight loss despite GFD in patients with CD should prompt other considerations of EPI and trial of PERT. Funding Agencies None

The Impact of Dietary Sodium Intake on Sweat Sodium Concentration in Response to Endurance Exercise: A Systematic Review

The collection, processing, and analysis of sweat samples to determine sodium losses during endurance exercise is common amongst sports and exercise nutrition practitioners, and necessary for researchers investigating sodium losses and replacement strategies. Several factors influence sweat sodium concentration ([Na+]) that need to be controlled or considered when interpreting results. Dietary sodium intake in the days preceding exercise is one factor that may influence sweat [Na+]. A systematic review was undertaking using six databases (CINAHL, Embase, Medline Ovid, Scopus, SPORTDiscus, and Web of Science) to determine the impact of dietary sodium intake on sweat [Na+] in response to endurance exercise. Six papers met the inclusion criteria. They varied in the level of sodium intake (<196 to 9177 mg/d), intervention timeframe (3 to 42 days), exercise modality (cycling ergometry, treadmill walking and running), and sweat collection method (whole body washdown and regional patch techniques). Two studies showed significant differences in sweat [Na+] due to diet, two showed no significant difference, and two were not analysed statistically. No relationship was found across studies comparing the difference in sodium intake between interventions and sweat [Na+]. Several limitations were identified, including lack of validation of the intervention, collecting regional sweat samples from limited sites or averaging results across sites or collection days, and lack of statistical analysis. It is concluded that the impact of dietary sodium intake on sweat [Na+] in response to endurance exercise remains uncertain, however the review provides useful insights into the optimal study design for future research in this area.

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.

Prolonged Heat Acclimation and Aerobic Performance in Endurance Trained Athletes.

Heat acclimation (HA) involves physiological adaptations that directly promote exercise performance in hot environments. However, for endurance-athletes it is unclear if adaptations also improve aerobic capacity and performance in cool conditions, partly because previous randomized controlled trial (RCT) studies have been restricted to short intervention periods. Prolonged HA was therefore deployed in the present RCT study including 21 cyclists [38 ± 2 years, 184 ± 1 cm, 80.4 ± 1.7 kg, and maximal oxygen uptake (VO2max) of 58.1 ± 1.2 mL/min/kg; mean ± SE] allocated to either 5½ weeks of training in the heat [HEAT (n = 12)] or cool control [CON (n = 9)]. Training registration, familiarization to test procedures, determination of VO2max, blood volume and 15 km time trial (TT) performance were assessed in cool conditions (14°C) during a 2-week lead-in period, as well as immediately pre and post the intervention. Participants were instructed to maintain total training volume and complete habitual high intensity intervals in normal settings; but HEAT substituted part of cool training with 28 ± 2 sessions in the heat (1 h at 60% VO2max in 40°C; eliciting core temperatures above 39°C in all sessions), while CON completed all training in cool conditions. Acclimation for HEAT was verified by lower sweat sodium [Na+], reduced steady-state heart rate and improved submaximal exercise endurance in the heat. However, when tested in cool conditions both peak power output and VO2max remained unchanged for HEAT (pre 60.0 ± 1.5 vs. 59.8 ± 1.3 mL O2/min/kg). TT performance tested in 14°C was improved for HEAT and average power output increased from 298 ± 6 to 315 ± 6 W (P < 0.05), but a similar improvement was observed for CON (from 294 ± 11 to 311 ± 10 W). Based on the present findings, we conclude that training in the heat was not superior compared to normal (control) training for improving aerobic power or TT performance in cool conditions.

Devil in the detail of newborn screening for cystic fibrosis

The recognition that the sweat chloride concentration was elevated in people with cystic fibrosis (CF) was fundamental to its diagnosis and treatment.1 A sweat chloride >60 mmol/L was diagnostic of...

The Role of Volume Regulation and Thermoregulation in AKI during Marathon Running.

Marathon runners develop transient AKI with urine sediments and injury biomarkers suggesting nephron damage. To investigate the etiology, we examined volume and thermoregulatory responses as possible mechanisms in runners' AKI using a prospective cohort of runners in the 2017 Hartford Marathon. Vitals, blood, and urine samples were collected in 23 runners 1 day premarathon and immediately and 1 day postmarathon. We measured copeptin at each time point. Continuous core body temperature, sweat sodium, and volume were assessed during the race. The primary outcome of interest was AKI, defined by AKIN criteria. Runners ranged from 22 to 63 years old; 43% were men. Runners lost a median (range) of 2.34 (0.50-7.21) g of sodium and 2.47 (0.36-6.81) L of volume via sweat. After accounting for intake, they had a net negative sodium and volume balance at the end of the race. The majority of runners had increases in core body temperature to 38.4 (35.8-41)°C during the race from their baseline. Fifty-five percent of runners developed AKI, yet 74% had positive urine microscopy for acute tubular injury. Runners with more running experience and increased participation in prior marathons developed a rise in creatinine as compared with those with lesser experience. Sweat sodium losses were higher in runners with AKI versus non-AKI (median, 3.41 [interquartile range (IQR), 1.7-4.8] versus median, 1.4 [IQR, 0.97-2.8] g; P=0.06, respectively). Sweat volume losses were higher in runners with AKI versus non-AKI (median, 3.89 [IQR, 1.49-5.09] versus median, 1.66 [IQR, 0.72-2.84] L; P=0.03, respectively). Copeptin was significantly higher in runners with AKI versus those without (median, 79.9 [IQR, 25.2-104.4] versus median, 11.3 [IQR, 6.6-43.7]; P=0.02, respectively). Estimated temperature was not significantly different. All runners experienced a substantial rise in copeptin and body temperature along with salt and water loss due to sweating. Sodium and volume loss via sweat as well as plasma copeptin concentrations were associated with AKI in runners. This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_08_13_CJASNPodcast_19_09_.mp3.

Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial.

To determine the impact of altering dietary sodium intake for 3days preceding exercise on sweat sodium concentration [Na+], and cardiovascular and thermoregulatory variables. Fifteen male endurance athletes (runners n = 8, cyclists n = 7) consumed a low (LNa, 15mgkg-1day-1) or high (HNa, 100mgkg-1day-1) sodium diet, or their usual free-living diet [UDiet, 46 (37-56) mgkg-1day-1] for 3days in a double-blind, randomized cross-over design, collecting excreted urine (UNa) and refraining from exercise. On day 4, they completed 2h running at 55% [Formula: see text]O2max or cycling at 55% maximum aerobic power in Tamb 35°C. Pre- and post-exercise blood samples were collected, and sweat from five sites using absorbent patches along the exercise protocol. UNa on days 2-3 pre-exercise [mean (95% CI) LNa 16 (12-19) mgkg-1day-1, UDiet 46 (37-56) mgkg-1day-1, HNa 79 (72-85) mgkg-1day-1; p < 0.001] and pre-exercise aldosterone [LNa 240 (193-286) mgkg-1day-1, UDiet 170 (116-224) mg kg-1day-1, HNa 141 (111-171) mg kg-1day-1; p = 0.001] reflected sodium intake as expected. Pre-exercise total body water was greater following HNa compared to LNa (p < 0.05), but not UDiet. Estimated whole-body sweat [Na+] following UDiet was 10-11% higher than LNa and 10-12% lower than HNa (p < 0.001), and correlated with pre-exercise aldosterone (1st h r = - 0.568, 2nd h r = - 0.675; p < 0.01). Rectal temperature rose more quickly in LNa vs HNa (40-70min; p < 0.05), but was similar at the conclusion of exercise, and no significant differences in heart rate or perceived exertion were observed. Three day altered sodium intake influenced urinary sodium excretion and sweat [Na+], and the rise in rectal temperature, but had no effect on perceived exertion during moderate-intensity exercise in hot ambient conditions.

SHORT-TERM CHANGES IN DIETARY SODIUM INTAKE INFLUENCE SWEAT SODIUM CONCENTRATION AND MUSCLE SODIUM CONTENT IN HEALTHY SUBJECTS

Objective: There is increasing evidence that sodium can be stored in the skin and muscles without being osmotically active, yet whether acute changes in dietary sodium intake alter sweat and muscle sodium content has not been investigated previously. Design and method: In a cross-over design, we assessed muscle sodium content by 23Na magnetic resonance imaging (MRI) in 38 healthy normotensive volunteers (aged 33.5 ± 11.1 years, 76.3% female) after 5 days of high sodium diet (HS) (6 g of salt added to their normal diet) and 5 days of a low-sodium diet (LS). Women performed each study visit during the same phase of the menstrual cycle. In a sub-group of 18 participants (72.2% female) we conducted quantitative pilocarpine iontophoretic sweat collections and measured the sodium concentration in sweat. Office blood pressure, electrolytes, creatinine and circulating aldosterone levels were measured in all participants, and 24 h urine was collected Results: Under HS conditions urinary sodium excretion, muscle sodium content and sweat sodium concentration all increased significantly (see Figure). Muscle sodium content by MRI (rm = 0.47, p = 0.03) and sodium sweat concentration (rm = 0.72, p < 0.001) correlated positively with salt intake as estimated by 24-hour urine sodium excretion. Age, gender or the phase of the menstrual cycle did not influence muscle or sweat sodium concentrations or their changes. In contrast, plasma aldosterone levels were strongly and negatively associated with both muscle sodium content (rs = −0.42, p = 0.0001) and sweat sodium (rs = −0.52, p = 0.002). Sweat and muscle sodium content were not different in participants with a salt-sensitive blood pressure compared to non-sensitives. Conclusions: Muscle and sweat sodium concentrations are significantly higher under high salt conditions in healthy male and female subjects, suggesting that muscle and sweat play a role in the dietary sodium balance in humans.

Chloride and sodium ion concentrations in saliva and sweat as a method to diagnose cystic fibrosis

ObjectiveCystic fibrosis diagnosis is dependent on the chloride ion concentration in the sweat test (≥60mEq/mL – recognized as the gold standard indicator for cystic fibrosis diagnosis). Moreover, the salivary glands express the CFTR protein in the same manner as sweat glands. Given this context, the objective was to verify the correlation of saliva chloride concentration and sweat chloride concentration, and between saliva sodium concentration and sweat sodium concentration, in patients with cystic fibrosis and healthy control subjects, as a tool for cystic fibrosis diagnosis. MethodsThere were 160 subjects enrolled: 57/160 (35.70%) patients with cystic fibrosis and two known CFTR mutations and 103/160 (64.40%) healthy controls subjects. Saliva ion concentration was analyzed by ABL 835 Radiometer® equipment and, sweat chloride concentration and sweat sodium concentration, respectively, by manual titration using the mercurimetric procedure of Schales & Schales and flame photometry. Statistical analysis was performed by the chi‐squared test, the Mann–Whitney test, and Spearman's correlation. Alpha=0.05. ResultsPatients with cystic fibrosis showed higher values of sweat chloride concentration, sweat sodium concentration, saliva chloride concentration, and saliva sodium concentration than healthy controls subjects (p‐value<0.001). The correlation between saliva chloride concentration and sweat chloride concentration showed a positive Spearman's Rho (correlation coefficient)=0.475 (95% CI=0.346 to 0.587). Also, the correlation between saliva sodium concentration and sweat sodium concentration showed a positive Spearman's Rho=0.306 (95% CI=0.158 to 0.440). ConclusionsSaliva chloride concentration and saliva sodium concentration are candidates to be used in cystic fibrosis diagnosis, mainly in cases where it is difficult to achieve the correct sweat amount, and/or CFTR mutation screening is difficult, and/or reference methods for sweat test are unavailable to implement or are not easily accessible by the general population.

Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: An update and analysis by sport

ABSTRACTThe purpose of this study was to expand our previously published sweat normative data/analysis (n = 506) to establish sport-specific normative data for whole-body sweating rate (WBSR), sweat [Na+], and rate of sweat Na+ loss (RSSL). Data from 1303 athletes were compiled from observational testing (2000–2017) using a standardized absorbent sweat patch technique to determine local sweat [Na+] and normalized to whole-body sweat [Na+]. WBSR was determined from change in exercise body mass, corrected for food/fluid intake and urine/stool loss. RSSL was the product of sweat [Na+] and WBSR. There were significant differences between sports for WBSR, with highest losses in American football (1.51 ± 0.70 L/h), then endurance (1.28 ± 0.57 L/h), followed by basketball (0.95 ± 0.42 L/h), soccer (0.94 ± 0.38 L/h) and baseball (0.83 ± 0.34 L/h). For RSSL, American football (55.9 ± 36.8 mmol/h) and endurance (51.7 ± 27.8 mmol/h) were greater than soccer (34.6 ± 19.2 mmol/h), basketball (34.5 ± 21.2 mmol/h), and baseball (27.2 ± 14.7 mmol/h). After ANCOVA, significant between-sport differences in adjusted means for WBSR and RSSL remained. In summary, due to the significant sport-specific variation in WBSR and RSSL, American football and endurance have the greatest need for deliberate hydration strategies.Abbreviations: WBSR: whole body sweating rate; SR: sweating rate; Na+: sodium; RSSL: rate of sweat sodium loss

Tattoos do not affect exercise-induced localised sweat rate or sodium concentration

ObjectivesSkin tattoos have been shown to reduce localised sweat rate and increase sweat sodium concentration ([Na+]) when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. DesignUnblinded, within-participant control, single trial. MethodsTwenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4cm2 in size, ≥2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20min of intermittent cycling (4×5min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C; 64±6% RH). Resultant sweat was collected into absorbent patches applied at two pairs of contralateral skin sites (pair 1: Tattoo vs. Non-Tattoo; pair 2: Control 1 vs. Control 2 (both non-tattooed)), for determination of sweat rate and sweat [Na+]. Paired samples t-tests were used to determine differences between contralateral sites. ResultsTattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43mg·cm−2·min−1, respectively; p=0.693) nor sweat [Na+] (Median(IQR): 37(32–52) vs. 37(31–45) mM·L−1, respectively; p=0.827) differed. Control 1 vs. Control 2: Neither sweat rate (Mean±SD: 1.19±0.53 vs. 1.19±0.53mg·cm−2·min−1, respectively; p=0.917) nor sweat [Na+] (Median(IQR): 29(26–41) vs. 31(25–43)mM·L−1, respectively; p=0.147) differed. The non-significant differences for sweat rate and [Na+] between Tattoo vs. Non-Tattoo were inside the range of the within participant variability (sweat rate CVi=5.4%; sweat [Na+] CVi=4.4%). ConclusionsSkin tattoos do not appear to alter the rate or [Na+] of exercise-induced sweating. The influence of skin tattoos on localised sweat responses may have previously been over-estimated.