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Medicine & Science in Sports & Exercise:
doi: 10.1249/01.mss.0000433618.51426.13

A-43 Free Communication/Poster - Sodium Supplementation/Hydration/Cooling

Free Access

May 29, 2013, 7:30 AM - 12:30 PM

Room: Hall C

304 Board #156 May 29, 9:30 AM - 11:00 AM

Sodium Consumption Induces Hyperhydration But Does Not Change Plasma Volume Or Exercise Heart Rate Response

Joshua R. Huot, david M. morris, adam jetton, Scott collier, FACSM, alan utter, FACSM. Appalachian State University, Boone, NC.

(No relationships reported)

Hyperhydration prior to exercise (HPE) in the heat has been shown to improve endurance exercise performance. Possible mechanisms for this ergogenic effect include increases in plasma volume (PV) and improvement in cardiac function.

PURPOSE: to measure the PV and heart rate (HR) responses to HPE and exercise in a hot environment.

METHODS: Nine male subjects (27 ± 4 yrs, 73 ± 9 kg) completed an exercise test to exhaustion on an electronically braked ergometer to determine VO2 max power output (PMAX). Subjects returned on 3 occasions receiving one of three treatments: 60 mg/kg bm NaCl, (NA), an equal volume of placebo (PL), or no treatment (NT) followed by a 2-hr hydration period in which they consumed water ad-libitum (HP). Immediately following HP, subjects began a 1-hr dehydration ride (DR) at 50% of PMAX at a temperature of 30° C. Nude body mass and blood samples were obtained

prior to and immediately following HP, and upon completion of the 1-hr ride. Blood samples were analyzed for PV and changes in NBM were used to calculate hydration status. HR was obtained at minutes 5 and 50 of the 1-hr ride. Data were analyzed using

one-way ANOVAs.

RESULTS: NA induced a significantly greater rate of HPE (1.1 ± 0.5%) than did PL (0.3 ± 0.4%, P = 0.03) and NT (-0.01 ± 0.6%, P = 0.003) and resulted in lower levels of dehydration following DR (0.7 ± 0.6%) compared to PL (1.3 ± 0.7%, P = 0.045), and NT (1.6 ± 0.4%. P = 0.004). Changes in PV after HP in NA (1.3 ± 5.2%) were not significantly different from PL (-4.4 ± 9.3, P = 0.51) or NT (-1.1 ± 9.5%, P = 0.91). No significant difference in PV following DR were seen between NA (-7.0 ± 8.4%,) and PL (-10.1 ± 6.3%, P = 0.47) or NT (-8.7 ± 10.2%, P = 0.98). No significant differences were observed between treatments with regards to HR at 5 min of exercise (NA = 136 ± 12 bpm, PL = 135 ± 10 bpm, NT = 136 ± 12 bpm, all P > 0.22), HR at 50 min of exercise (NA = 151 ± 13 bpm, PL = 151 ± 11 bpm, NT = 155 ± 12 bpm, all P > 0.86), or increase in HR from 5 to 50 min of exercise (NA = 15 ± 8 bpm, PL = 16 ± 8 bpm, NT = 19 ± 4 bpm, all P > 0.48).

CONCLUSION: Although sodium consumption promoted hyperhydration, the increase in body water did not significantly affect plasma volume or exercising heart rates when compared to no treatment or consumption of placebo.

Financial support received from ASU URC and

305 Board #157 May 29, 9:30 AM - 11:00 AM

Sodium Supplementation and Hydration Habits of Ironman Triathletes

Luke N. Belval1, Douglas J. Casa, FACSM1, Rebecca L. Stearns1, Evan C. Johnson1, Brittanie M. Volk1, William M. Adams1, Tracey A. Viola2. 1University of Connecticut, Storrs, CT. 2Lake Placid Health Center, Lake Placid, NY.

(No relationships reported)

An Ironman triathlon challenges both an athlete’s fitness and nutrition practices. Sodium supplementation (SS) is commonly advocated for cramp prevention and sweat-associated sodium loss during training and competition. However, gaps between research findings and real world practice may exist.

PURPOSE: To investigate Ironman triathletes’ 1) SS practices, 2) hydration habits, and 3) perceptions on the efficacy and performance benefits of both.

METHODS: 161 triathletes were surveyed from the 2012 Ironman World Championships in Kona, HI (IMWC, n=60) and the 2012 Ironman Lake Placid in Lake Placid, NY (IMLP, n=101). Participants had 7.1 ± 6.2 years of experience at Ironman or Half-Ironman distance triathlons. Survey questions targeted hydration and sodium intakes during training and competition. In addition perceived effect of SS in relation to cramping and performance were examined.

RESULTS: 72.3% reported changing their drinking habits based on duration of exercise or environmental conditions. 62.7% reported currently taking sodium supplements either during training or racing. 49.0% replied as being “salty sweaters.” Overall, independent of current use, 32.9% responded as having been advised by a coach or medical professional to consume sodium supplements. There were no differences between IMLP and IMWC for changing drinking habits (p=0.787), sodium supplement use (p=0.580), coach or medical advice for SS (p=0.454) or “salty sweaters” (p=0.140). 9.3% reported previous exercise-associated illnesses related to hydration or heat stress. 80% of those who reported these illnesses change their drinking habits based on duration of exercise or environmental conditions, while 53.3% take sodium supplements. Overall, 83.1% either agreed or somewhat agreed with the statement “Sport drinks prevent cramps.” 77.2% either agreed or somewhat agreed with the statement “SS prevents cramps.” 69.1% either agreed or somewhat agreed with the statement “SS improves performance.”

CONCLUSION: SS is a common practice for Ironman triathletes and many believe that this reduces incidence of cramps and improves performance. The majority of triathletes also believe that hydration practices should incorporate sport drinks to prevent cramps.

Supported by Timex, Inc.

306 Board #158 May 29, 9:30 AM - 11:00 AM

Effects Of Sodium Ingestion On Voluntary Water Consumption, Hydration, And Exercise Performance In The Heat

David Morris, Josh Huot, Adam Jetton, Scott Collier, FACSM, Alan Utter, FACSM. Appalachian State University, boone, NC.

(No relationships reported)

Co-consumption of sodium and water prior to exercise tempers dehydration and improves exercise performance in the heat. While this strategy is effective in controlled environments, promoting fluid consumption in unsupervised, non-thirsty individuals is difficult. Thirst can be induced with sodium ingestion via the vasopressin response.

PURPOSE: We sought to determine the effects of sodium ingestion on ad-libitum, pre-exercise fluid consumption, hydration, and subsequent exercise performance in the heat.

METHODS: Nine male subjects (27 ± 4 yrs, 73 ± 9 kg) completed an exercise test to exhaustion on an electronically braked ergometer (EBE) to determine VO2 max power output (PMAX). Subjects returned on 3 occasions receiving one of three treatments: 60 mg/kg bm NaCl, (NA), an equal volume of placebo (PL), or no treatment (NT) followed by a 2-hr hydration period in which they consumed water ad-libitum (HP). Immediately following HP, subjects began a 1-hr ride at 50% of PMAX, followed immediately by a 200 kJ time trial (TT), both performed on the EBE. Ambient

temperature during these periods was 30° C. Fluid consumption and urinary output during HP were measured and used to calculate fluid retention. Nude body mass was measured prior to and at the end of the HP and immediately following the 50% PMAX and TT to determine hydration status. Elapsed time to complete TT was used as a performance measure. Data were analyzed using one-way repeated measures ANOVA.

RESULTS: Subjects consumed significantly more water during HP in NA (1380 ± 581 mL) compared to PL (815 ± 483 mL, P = 0.05) and NT (782 ± 454 mL, P = 0.02). Fluid retained at the end of HP was significantly greater in NA (821 ± 367 mL) compared to PL (244 ± 402 mL, P = 0.004) and NT (148 ± 289 mL, P < 0.001). Dehydration rate at the end of the 50% PMAX ride was significantly lower in NA (0.7 ± 0.6%) compared to PL (1.3 ± 0.7%, P = 0.045) and NT (1.6 ± 0.4%. P = 0.004). The TT was completed significantly faster in NA (773 ± 158 s) compared to PL (851 ± 156 s, P = 0.004) and NT (872 ± 190 s, P = 0.006). No significant differences were detected between PL and NT for any of the variables.

CONCLUSION: The results suggest that acute sodium ingestion can enhance voluntary fluid consumption leading to hyperhydration and improved exercise performance in the heat. Financial support received from ASU URC and

307 Board #159 May 29, 9:30 AM - 11:00 AM

Comparison Of Thirst-Driven vs. Programmed Fluid Intake On Half-Marathon Running Performance In Highly-trained Distance Runners

Tommy Dion, Audrey Asselin, Eric DB Goulet. University of Sherbrooke, Sherbrooke, QC, Canada.

(No relationships reported)

A meta-analysis (Goulet, BJSM, 2011) has demonstrated that 1) exercise-induced dehydration (EID) of up to 4% bodyweight (BW) does not impair cycling time-trial (TT) performance and; 2) drinking to thirst optimizes endurance performance (EP). It has long been believed that EID ≥2% BW impairs EP/endurance capacity (Cheuvront et al., CSMR, 2003). No studies have yet tested the impact of EID upon running TT performance.

PURPOSE: To compare the effects of thirst-driven (TD) vs. programmed fluid intake (PFI) on half-marathon running performance.

METHODS: Following a familiarization trial, 7 highly-trained distance runners (age: 27 ± 8 yrs; weight: 71 ± 3 kg; height: 177 ± 4 cm; VO2peak: 69 ± 4 ml/kg/min) underwent, in a randomized, crossover fashion, 2, 21.1 km running TTs on a motorized treadmill (30°C, 45% RH, facing wind speed adjusted according to running speed) while consuming 3 energy gels (every 6 km) and either drinking water 1) according to thirst sensation (TD) or; 2) to maintain BW loss at 1% (PFI).

RESULTS: Subjects were well- and equally-hydrated at their arrival at the laboratory before each experimental trial (urine specific gravity, TD: 1.013 ± 0.008 g/ml; PFI: 1.019 ± 0.009 g/ml, P=0.23). In both trials, volunteers’ total water intakes (TD: 500 ± 251 ml; PFI: 2128 ± 189 ml, P<0.01) were less than their sweat (TD: 2679 ± 232 ml; PFI: 2827 ± 246 ml, P=0.13) and urine (TD: 62 ± 61 ml; PFI: 88 ± 43 ml, P=0.24) losses, thereby producing an EID level of 3.1 ± 0.5% BW (TD) (range: 2.5-3.6% BW) vs. 1.1 ± 0.4% BW (PFI) (range: 0.4-1.6% BW) (P<0.01). Mean rectal temperature (TD: 39.6 ± 0.6°C; PFI: 39.2 ± 0.5°C, P=0.01), perceived exertion (TD: 13.9 ± 1.2; PFI: 13.5 ± 1.0, P=0.05) and perceived thirst (TD: 4.7 ± 0.9; PFI: 3.2 ± 1.4, P<0.01), but not heart rate (TD: 163 ± 15 bpm; PFI: 159 ± 13 bpm, P=0.18), were significantly different between trials. Half-marathon performance times (TD: 88 min 45 s ± 4 min 2 s; PFI: 87 min 46 s ± 5 min 4 s, P=0.43) and running paces (TD: 4 min 19 s ± 20 s/km; PFI: 4 min 15 s ± 24 s/km, P=0.43) were not significantly different between groups. There was no correlation between the changes in EID levels and TT performance times (P=0.84).

CONCLUSION: These results suggest that, under a 30°C ambient temperature, both thirst-driven and programmed fluid intake optimize half-marathon running performance in highly-trained distance runners.

308 Board #160 May 29, 9:30 AM - 11:00 AM

Effects of 75 Versus 150% Fluid Replacement on Subsequent Morning Hydration Status and 10-km Running Performance

Brett A. Davis1, Lauren K. Thigpen2, Jared H. Hornsby3, Mary C. Stevenson2, Pattie L. Riethmaier4, James M. Green, FACSM2, Eric K. O’Neal2. 1Middle Tennessee State University, Murfreesboro, TN. 2University of North Alabama, Florence, AL. 3University of Alabama, Tuscaloosa, AL. 4Old Dominion University, Norfolk, VA.

(No relationships reported)

PURPOSE: To examine the effects of reasonable but low fluid replacement volume (75% of sweat losses) compared to replacement of 150% of sweat losses as suggested by ACSM guidelines between running bouts on 10-km running performance.

METHODS: Well-trained, heat acclimated runners (n = 13; age = 37 ± 12 y; VO2max = 63.3 ± 4.5 ml/kg/min) completed a 75 min run of moderate intensity by completing multiple laps on a challenging 5-km outdoor road course on two separate hot summer evenings (WBGT = ∼27 °C). Following the run and in a counter-balanced crossover design, participants replaced 75% (1637 ± 372 mL) or 150% (3099 ± 850 mL) of their sweat losses with a combination of water, sport beverage, and orange juice. Participants also consumed a standardized dinner and breakfast provided by the investigators. Early the following morning, runners completed a 10-km time trial by completing two laps on the same course utilized the previous evening (WBGT = ∼23 °C). Urine voids were collected between runs and urine specific gravity (USG) was assessed pre-run.

RESULTS: High and low fluid replacement volumes resulted in a significant difference (P = 0.02) in pre-run body mass (75% = 69.6 ± 9.2; 150% = 70.1 ± 9.3 kg) and USG (75% = 1.026 ± 0.005; 150% = 1.014 ± 0.007; P < 0.001). Average heart rates (168 ± 14 vs. 168 ± 12 beats per minute) and intestinal temperatures were not significantly different (P > 0.05) between treatments (75%: pre-run = 37.10 ± 0.43 vs. 37.08 ± 0.25; post-run = 39.08 ± 0.52 vs. 150%: 39.00 ± 0.70 °C). Despite finishing 2.9 ± 2.5% faster (75% = 47.28 ± 6.64; 150% = 45.93 ± 6.04 min; P = 0.001), mean session rating of perceived exertion was lower (P = 0.02) for 150% (7.5 ± 1.3) versus 75% (8.4 ± 0.9) trials.

CONCLUSIONS: Fluid replacement equaling 75% of sweat loss was intended to mimic beverage intake of a reluctant drinker and was found to be inadequate to maintain optimal running performance and resulted in unfavorable perceptual measures. However, copious urine production and reported difficulties in consuming fluid volumes equivalent to 150% of sweat losses suggests an alternate fluid intake prescription below 150% may be ideal and practical, as well as more easily tolerated, particularly for heavy sweaters.

309 Board #161 May 29, 9:30 AM - 11:00 AM

Rehydration With Lemon Tea, Carbohydrate-electrolyte Beverage And Water After Exercise-induced Dehydration Under Hot Environment

Hiu Fai, Steven Tsoi, Siu Kuen, Robert Ng. The Chinese University of Hong Kong, Hong Kong, China.

(No relationships reported)

Adequate fluid restoration after exercise is particular important so as to reduce the risk of exercise-induced dehydration (EID).

PURPOSE: This study compared the effectiveness of packed lemon tea (LT) with carbohydrate-electrolyte drink (CE) and distilled water (DW) on whole-body fluid restoration for a 4-hour recovery period (REC) after moderate EID under hot environment.

METHODS: Ten recreationally active male subjects (mean age: 23.1 ± 1.6 yr; body weight (BW): 75.1 ± 8.6 kg; VO2max: 46.2 ± 4.1 mL/kg/min; HRmax : 196 ± 4 beats/min) underwent 3 main trials. In each trial, they ran on treadmill for 60-min at 60% HRmax under hot condition of 29.1 ± 0.8oC and 71 ± 4% relative humidity. After exercise, the subjects stayed at the same thermal condition for 4-hour REC where one of the drinks (LT, CE and DW) was randomly assigned for ingestion. No other food was allowed during REC. Six equal portions of the given drinks representing 150% of BW loss were taken at 30, 60, 90, 120, 150, and 180 min of REC. Blood samples were taken at pre and post exercise. Both blood samples and urine outputs were also collected at 30 min intervals throughout REC. Abdominal discomfort (AD) and stomach fullness (SF) were assessed 5 min prior to each blood sample collection.

RESULTS: After the 60-min run, subjects lost ∼2.0% of their BW in all trials with no significant difference found (p > 0.05). At the end of REC, all subjects were in slightly hypohydration with net fluid balance being the lowest for DW (p < 0.05), despite no significant difference was found in total volume of drinks consumed (p > 0.05). For the 2% BW loss, percent rehydration was similar for LT (84.8 ± 5.6%) and CE (85.4 ±7.0%), but significantly lower for DW (72.5 ± 11.6%) (p < 0.05). Similarly, percent of drinks retained in body was similar for LT (56.5 ± 3.7%) and CE (60.4 ± 6.2%), but significantly lower for DW (48.3 ± 7.8%) (p < 0.05). Cumulative urine volumes for DW (649 ± 177 mL) was significantly higher than LT (433 ± 101 mL) and CE (471 ± 81 mL) at the end of REC (p < 0.05). Plasma volume recovery was completed for all trials with LT (8.5 ± 11.2%) and CE (6.5 ± 5.8%) being higher than DW (0.2 ± 7.7%) during REC (p < 0.05). No significant difference was found in AD and SF among trials.

CONCLUSION: LT is better than DW, and as effective as CE for rehydration following an EID with 2% BW loss under hot environment.

310 Board #162 May 29, 9:30 AM - 11:00 AM

Hydration Efficacy Of A Hyperoxygenated Nutritionally Enhanced Beverage In Experienced Runners

Allan J. Sommer, Alexandria L. Ianni, Jeffrey A. Conkle, Kevin E. Schill, Eric T. Trexler, Brian C. Focht, FACSM, Steven T. Devor, FACSM. The Ohio State University, Columbus, OH.

(No relationships reported)

Exercising in hot and humid environmental conditions produces high sweat rates and may lead to significant dehydration and decline in athletic performance. Hyperoxygenated beverages have been on the market for several years claiming hydration and health benefits and even enhanced athletic performance. The addition of vitamins and minerals increases osmolality, which may result in physiological responses that could enhance hydration status. To date, no research has provided evidence to support the claims, nor demonstrated any negative side effects, from drinking a hyperoxygenated beverage enhanced with vitamins and trace minerals.

PURPOSE: When compared with water, our objective was to determine if a commercially available hyperoxygenated beverage (O2water), would limit dehydration when consumed during a sub-maximal running bout in hot and humid conditions.

METHODS: Experienced male runners (Mean age= 30.3 years, VO2 = 65.9 VO2 ml/kg/min, height = 1.72 m, body mass = 73.3 kg, and percent body fat = 11.3%) completed two 45-minute runs at 70% of their pre-determined VO2max in a temperature and humidity controlled environmental chamber. Conditions were set to 30° C and 50% humidity. Subjects were randomly provided either O2water or water during their first run, and were permitted to consume ad libitum. For the second run, subjects were prescribed the same volume they consumed in the first run of the alternate beverage. Hydration status was determined via plasma osmolality pre-run and 30, 60, and 90 minutes post-run. Pre- and post-run nude body weight was used to measure sweat rate and fluid retention.

RESULTS: Average sweat rate and fluid consumption for subjects was 890.3 mL and 613.5 mL, respectively. Post urination body weight indicated greater fluid retention (180g), when consuming O2water versus water. Pre-run osmolality averaged 283.2 mOsm/kg. When subjects consumed water, post-run plasma osmolality increased 0.67%, 0.67%, and 0.82% at 30, 60, and 90 minutes, respectively. Conversely, when subjects consumed O2water, plasma osmolality decreased 0.7% and 0.15% at 30 and 60 minutes, and increased 0.12% at 90-minutes post-run.

CONCLUSION: Compared with water, O2water may limit dehydration for experienced male runners in hot humid conditions Research supported by private funds provided by O2water.

311 Board #163 May 29, 9:30 AM - 11:00 AM

Prescribed Hydration Improves Cycling Performance in the Heat

Costas N. Bardis1, Konstantinos S. Danias1, Eleni Samara1, Lili Karagiorgou1, Giorgos Stais1, Eleutheria Axioti1, Labros S. Sidossis2, Stavros A. kavouras, FACSM3. 1Harokopio University, Athens, Greece. 2University of Texas Medical Branch, Galveston, TX. 3University of Arkansas, Fayetteville, AR.

(No relationships reported)

Drinking ad-libitum during exercise leads to involuntary dehydration ranging from -1 to -3% of body weight.

PURPOSE:To study the effect of prescribed protocol matching fluid losses on repeated hill cycling performance during circuit course in the heat (31.6±0.5 °C).

METHODS:Ten elite, heat-acclimated, male endurance cyclists (30±5 y, 76.5±7.2 kg, 1.81±0.07 m, VO2max: 61.3±5.2 mlmin-1kg-1, body fat: 10.5±3.3%, Powermax: 392±33 W) performed a cycling circuit on a laboratory ergometer. The circuit consisted of 3 sets of 5 km at 50% of max power output and 5 km of hill (3%) race pace cycling. Subjects rode the performance test on two separate occasions and in counterbalance mode while drinking water Ad-Libitum (AD; as they wished) or following a Prescribed Drinking (PD; drinking every 1 km to match fluid losses). To design the PD subjects also performed a familiarization trial. Cyclists started the 1st 5 km climbing race pace bout either in PD trial at 0% loss or in AD trial by -0.3±0.3% of body weight. Post-exercise body weight was for PD: -0.5±0.3% vs. AD: -1.8±0.7%.

RESULTS:Time to completion for the 3rd bout of the 5km race hill cycling was shorter in PD (10.0±0.8 min) than in the AD trial (10.5±0.9 min), by 5.1±4.8% ; (P<0.05). Tc, Tsk, and Tb immediately after the last hill climbing were greater in the AD than in the PD trial; (P<0.05). Overall, sweat sensitivity during the circuit course was lower in the AD (88±40 g×°C-1×min-1) than in the PD trial (165±66 g×°C-1×min-1), P=0.026).

CONCLUSIONS:The data suggested that the individual hydration protocol improved cycling performance during the circuit repeated hilly course in the heat, as opposed to ad libitum drinking, leading to a small degree of dehydration (<-2%bw).

312 Board #164 May 29, 9:30 AM - 11:00 AM

The Role of Glucose and Non-Glucose Containing Beverages on Rehydration

Matthew R. Feeback, Lynn S. Kakos, Keith Burns, Nick Haught, Corey Peacock, Brandon Pollock, Michael Rebold, Yongsuk Seo, John Gunstad, Ellen L. Glickman, FACSM. Kent State University, Kent, OH.

(No relationships reported)

PURPOSE: Glucose and electrolyte containing beverages during prolonged exercise in the heat help to maintain glucose, electrolyte, thermoregulation and plasma homeostasis. Current literature supports the relationship between strenuous exercise, dehydration and hypoglycemia. Therefore the purpose of the current investigation is to examine the effects of a glucose and non-glucose, electrolyte based drinks on rehydration and physiological markers after exercise in a 37° C for ninety minutes.

METHODS: Ten males between the ages of 18 to 25 volunteered for participation in the current investigation. Participants were asked to exercise on a cycle ergometer in a 37° C, 50% humidity environment inducing dehydration of 2% of the participant’s body weight. The physiological markers of rectal and skin temperature, blood glucose and VO2 were measured directly after the completion of the exercise bout (“dehydrated” time point). At the completion of the protracted exercise, subjects were administered either a glucose or non-glucose containing electrolyte based sports drink ad libitum for thirty minutes. Post rehydration process, the same physiological markers will be measured as the rehydration time point; rectal and core temperature, blood glucose and VO2, this time point will be considered as “rehydrated”.

RESULTS: Data demonstrated no significant differences on any recorded physiological marker between the two conditions at the “dehydrated” time point. Participants consumed equal amounts of the glucose (987.5 ml) and non-glucose containing (990 ml.) beverages in the rehydration stage of the protocol. After consuming the beverage, significant differences in the two trials emerged for blood glucose (p=0.009) and VO2 (p=0.013) at the “rehydrated” time point but not for rectal (p=0.218) or skin temperature (p=0.525).

CONCLUSION: This data suggest that the ingestion of a beverage containing glucose during rehydration is not needed to maintain thermoregulation after prolonged exercise in the heat.

313 Board #165 May 29, 9:30 AM - 11:00 AM

Evaluating Gastro-Intestinal Symptoms Experienced in Athletes During the Lake Placid Ironman Triathlon

Deanna M. Dempsey, Laura J. Kunces, FACSM, Douglas J. Casa, FACSM, Rebecca L. Stearns, Julie K. DeMartini, Kelly D. Pagnotta, Amy L. McKenzie, Jenna M. Apicella. University of Connecticut, Manchester, CT.

(No relationships reported)

Many athletes experience a variety of gastro-intestinal (GI) symptoms during an Ironman triathlon. Proper hydration reduces the risk of heat illness, however little is known in regards to its effect on upper abdominal symptoms (UAS) and lower abdominal symptoms (LAS) experienced during a race.

PURPOSE: To examine the relationships between hydration status, performance, and severity of UAS and LAS experienced during an Ironman triathlon.

METHODS: Subjects (29 men, 7 women) competed in the Lake Placid Ironman triathlon (Mean±SD: age: 39±7yr; height: 174±10cm; weight: 71.8±9.8kg; body fat: 15.3±5.5%). A GI symptom questionnaire, comprised of 10-point Likert scales, was completed immediately post race. Average total symptom severity (ALL), UAS severity, and LAS severity was calculated. Pre- and post-race urine specific gravity (Usg) and body mass were measured. Percent body mass loss (%BML) was calculated. Spearman’s rho correlations compared symptoms experienced during the race with hydration status and finish time. Groups were organized by post-race hydration status: most hydrated (MOST Usg≤1.022), moderately hydrated (MOD Usg 1.023-1.029), and least hydrated (LEAST Usg ≥ 1.030) to compare symptom severity.

RESULTS: Average severity of UAS and LAS were 2±3 and 1±2, respectively. When organized by hydration status: MOST, MOD, and LEAST average UAS severity were 2±2, 2±3, and 3±2, respectively. Average LAS severity for MOST, MOD, and LEAST were all 1±1. Average ALL severity for MOST, MOD, and LEAST were all 2±1. Symptom severity among MOST, MOD, and LEAST were not significantly different. The most severe and frequently reported symptom was Stomach pain/cramping (3±3), experienced by 81% of subjects. Finish time (13.16±1.35hrs) was not significantly correlated with UAS or LAS. Percent body mass loss (-3.1±1.6%) was significantly correlated (r2=0.14, p=0.024) with ALL symptoms (2±2), Nausea (r2=0.11, p=0.046), and Vomiting (r2=0.17, p=0.013).

CONCLUSION: Given the duration of the event, the 3% post race BML and Usg indicates subjects consumed amounts of fluid necessary for such an event and successfully attenuated moderate %BMLs. GI symptoms were experienced in all post-race hydration groups. Despite this, reported GI symptoms were mild and not correlated with finish time.

314 Board #166 May 29, 9:30 AM - 11:00 AM

Exercise-associated Hyponatremia And Hydration Status In 161-km Ultramarathoners In Northern California

Kristin Stuempfle, FACSM1, Tamara Hew-Butler, FACSM2, Martin Hoffman, FACSM3. 1Gettysburg College, Gettysburg, PA. 2Oakland University, Rochester, MI. 3University of California Davis Medical Center and Sacramento VA Medical Center, Sacramento, CA.

(No relationships reported)

PURPOSE: This work combines and reanalyzes five years of exercise-associated hyponatremia (EAH) research at 161-km ultramarathons in northern California with primary purposes to define the relationship between post-race blood sodium concentration ([Na+]) and change in body weight, examine the interactions among EAH incidence, ambient temperature and hydration state, and explore the effect of hydration status on performance.

METHODS: Pre-race and post-race body weight and finish time data were obtained on 887 finishers, and post-race [Na+] was also obtained on a subset of 669 finishers.

RESULTS: EAH incidence was 15.1% overall (range 4.6- 51.0% by year) and had a significant positive relationship with ambient temperature. Of the runners with EAH, 23.8% were classified as overhydrated (weight change ≥0), 40.6% were euhydrated (weight change <0 to -3%), and 35.6% were dehydrated (weight change <-3%) at the finish. There was a weak significant relationship (r=0.17, p<0.0001) between post-race [Na+] and change in body weight such that a lower [Na+] was more common with increased weight loss. Considering all finishers examined, 18.5% were dehydrated and 34.9% were overhydrated at the finish. There was a weak significant relationship (r=0.092, p=0.006) between change in body weight and performance in that faster runners tended to lose more weight. Top finishers varied in body weight change from ∼1% gain to ∼6% loss.

CONCLUSION: EAH incidence can be high in 161-km ultramarathons in northern California. In this environment, EAH is more common with dehydration than overhydration and is more common in hotter ambient temperature conditions. Because weight loss >3% does not appear to have an adverse effect on performance, excessive sodium supplementation and aggressive fluid ingestion beyond the dictates of thirst are ill-advised.

315 Board #167 May 29, 9:30 AM - 11:00 AM

Core Cooling Rates Are Not Affected By Delays In Treatment In Hyperthermic Individuals

Mark J. Carlson1, Brian J. Friesen1, Douglas J. Casa, FACSM2, Glen P. Kenny1. 1University of Ottawa, Ottawa, ON, Canada. 2University of Connecticut, Storrs, CT.

(No relationships reported)

The incidence rate of exertional heat stroke (EHS) continues to rise in both recreational and occupational populations. The most important component of EHS care is the rapid cooling that should take place as soon as possible after the incident occurs. Victims of EHS in whom treatment is delayed have higher rates of multi-organ failure, longer hospitalizations and a greater number of fatalities. Death related to EHS is preventable, through immediate treatment via cold-water immersion (CWI). To date little is known about the influence of delays in treatment on core cooling rate in EHS.

PURPOSE: To examine the effects of a delay in treatment on cardiovascular and thermal responses prior to, during, and following CWI treatment in individuals rendered hyperthermic during exercise in the heat.

METHODS: Eight males ran on a treadmill in the heat (40°C, 20% relative humidity) wearing an impermeable rain suit until rectal temperature (Tre) reached 40.0°C (∼45 min). Participants were seated in the heat for either a short (S, 5 min), moderate (M, 20 min) or prolonged (P, 40 min) delay, and were subsequently immersed in a circulated ice water bath regulated at 2°C until Tre returned to 37.5°C. Heart rate and Tre were measured continuously while blood pressure was measured every 5 min during the delay and at 2 min intervals during immersion.

RESULTS: There were no differences in Tre immediately prior to immersion among conditions (S: 40.08 ± 0.32; M: 39.81 ± 0.40; P: 39.57 ± 0.29°C). Core cooling rates during cold water immersion were similar among all conditions (S: 0.20 ± 0.04; M: 0.18 ± 0.07; P: 0.17 ± 0.04 °Cmin-1) and were paralleled by similar immersion times (S: 13.09 ± 3.42; M: 13.69 ± 4.25: P: 13.00 ±3.70 min). Mean arterial pressure was similar among conditions post exercise (S: 81 ± 16; M: 81 ± 12; P: 82 ± 12 mmHg) and following each delay period (S: 75 ± 7; M: 73 ± 6; P: 70 ± 5 mmHg).

CONCLUSION: We show that delays in treatment of hyperthermic individuals results in severe cardiovascular and thermal strain. Despite delays in treatment extending up to 40 min for individuals with hyperthermia, CWI is an effective and safe treatment modality. The project was supported by NSERC Discovery grant RGPIN-298159-2009.

316 Board #168 May 29, 9:30 AM - 11:00 AM

Combined Effect Of Hyperhydration And Pre-Cooling On Endurance Cycling Performance In Hot And Humid Conditions

Claire Potter1, David Hughes1, Adam Sharples1, Ben Davies1, Natalie Dixon1, James Tuttle1, Alexis Mauger2, Paul Castle1, Bryna Chrismas1, Lars McNaughton, FACSM3, Lee Taylor1. 1The University of Bedfordshire, Bedford, United Kingdom. 2University of Kent, Kent, United Kingdom. 3Edgehill University, Ormskirk, United Kingdom. (Sponsor: Lars McNaughton, FACSM)

(No relationships reported)

Thermoregulatory interventional strategies can acquiesce some of the decrement seen during endurance performance in the heat, delaying increases in core temperature (Tc). Hyperhydration (HH) has been shown to increase evaporative sweat loss, thus potentially enhance thermoregulation. Pre-cooling (PC) reduces starting temperatures (Tc, skin(Tsk)) increasing latent body heat capacity. To the authors knowledge no research has combined both strategies.

PURPOSE: To determine whether 10 mile cycling time trial (10 mile TT) performance in the heat can be improved by the combined strategies of HH and PC by reducing the negative thermoregulatory response to exercising in such an environment. Additionally, the cellular response, Hsp72 mRNA relative expression (Hsp72) pre and post the exercise was assessed.

METHODS: 5 recreationally active males reported to the laboratory to perform four 10 mile TT (30°C: 50% RH) on separate weeks with randomised conditions of; hyperhydration (HH), pre-cooling (PC), both (HH+PC) or none (C). HH was administered through a glycerol solution and PC via cold water immersion (12 ± 2°C for 20 min). Glycerol or placebo was administered in all trials; with HH being determined by plasma volume levels through capillary blood sampling. The strategies effectiveness was assessed via performance (10 mile completion time). Typical physiological (HR, blood lactate) and thermoregulatory (Tc, Tsk) measures were recorded throughout. Body mass and urine osmolality were monitored pre and post exercise. Venous blood samples were obtained at rest (pre any intervention), pre and immediately post exercise to assess HSP72 within leukocytes using qRT-PCR. Two-way ANOVA with repeated measures were used.

RESULTS: PC performance time (32:44 ± 1:03 mins) was significantly quicker by 6.1% than C, 4.1% than HH and 2.4% than PC+HH (F1, 4=2879, P<0.001). Tc increase from pre to post 10 mile TT was significantly less for PC and PC+HH (0.1 ±0.4°C & 0.4 ±0.1°C) than C and HH (1±0.2°C & 1± 0.1°C) (P<0.001). There was no significant difference between pre and post exercise Hsp72 levels across the 4 conditions (F3, 24 = 1.428, P = .259).

CONCLUSION: PC, irrelevant of whether HH was present or not; elicited enhanced endurance performance in hot and humid environments.

317 Board #169 May 29, 9:30 AM - 11:00 AM

Body Surface Area-to-Lean Body Mass Ratio and Whole-Body Cooling Following Exercise-Induced Hyperthermia

Brian J. Friesen, Mike R. Carter, Martin P. Poirier, Glen P. Kenny. University Of Ottawa, Ottawa, ON, Canada.

(No relationships reported)

Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada. Current guidelines for the cooling of exertional heat stroke victims do not consider biophysical differences which could affect treatment time. In fact, it has been suggested that body surface area-to-lean body mass ratio (AD/LBM) may be a key factor influencing core temperature cooling rates during cold water immersion following exercise-induced hyperthermia.

PURPOSE: We therefore examined the influence of AD/LBM on rectal temperature (Tre) cooling rates during cold water immersion (2°C) following exercise-induced hyperthermia.

METHODS: Twenty male participants were divided into a High (315.57 ± 7.91 cm2/kg) or Low (275.58 ± 8.59 cm2/kg) AD/LBM group. Participants ran on a treadmill in the heat (40°C, 20% relative humidity) wearing an impermeable rain suit until Tre reached 40.0°C (∼45 min). Following exercise and a 5-min transition period, participants were immersed to the nipples (arms out of the water) in a circulated ice water bath regulated at 2°C until Tre returned to 37.5°C. Rectal temperature was measured continuously.

RESULTS: Immersion time was greater for Low compared to High (19.6 ± 7.7 vs. 11.1 ± 5.4 min, p = 0.01). Furthermore, the rate of Tre cooling was greater for High compared to Low (0.27 ± 0.10 vs. 0.16 ± 0.10°C/min, p = 0.02).

CONCLUSION: The current results suggest that individuals with a low body surface area-to-lean body mass ratio take longer to cool during cold water immersion following exercise-induced hyperthermia. Future work is therefore necessary to examine whether guidelines for the treatment of exertional heat stroke victims should consider biophysical differences between individuals. Supported by NSERC Discovery grant RGPIN-298159-2009.

© 2013 American College of Sports Medicine


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