Intended Hydration Strategies and Knowledge of Exercise-Associated Hyponatraemia in Marathon Runners: A Questionnaire-Based Study

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1 Journl of Athletic Trining 2018;53(7): doi: / Ó by the Ntionl Athletic Triners Assocition, Inc Exertionl Het Illness Intended Hydrtion Strtegies nd Knowledge of Exercise-Associted Hypontremi in Mrthon Runners: A Questionnire-Bsed Study Thoms Leggett, MBChB*; Jonthn Willims, MSc*; Colm Dly, hd*; Courtney Kipps, MSc ; Richrd Twycross-Lewis, hd* *Centre for Sports nd Exercise Medicine, Queen Mry University of London, Englnd; Institute of Sport, Exercise nd Helth, University College London, Englnd Context: Exercise-ssocited hypontremi (EAH) is potentilly ftl condition tht cn be prevented by voiding excessive fluid intke. Running hs become more populr in recent yers, so it is importnt to ssess the sfety of runners hydrtion strtegies. Objective: (1) To explore the intended hydrtion strtegies of smple of mrthon runners before the 2014 London Mrthon, (2) to exmine their sources of informtion nd knowledge bout fluid intke nd their understnding of EAH, nd (3) to compre these findings with the results of similr study crried out before the 2010 London Mrthon. Design: Cross-sectionl study. Setting: The 2014 London Mrthon. tients or Other rticipnts: A totl of 298 runners (148 mles, 150 femles), 0.83% of ll rce finishers. Min Outcome Mesure(s): lnned frequency, type, nd volume of hydrtion; sources of informtion bout pproprite drinking; nd understnding of hypontremi were explored. Comprisons were mde with dt collected from smple of prticipnts t the 2010 London Mrthon. Dt relting to the 2014 cohort re presented in descriptive form. Comprisons of the 2010 nd 2014 cohorts were conducted using prmetric nd nonprmetric methods. Results: A totl of 48.7% of the 2014 cohort listed drinking to thirst s the most importnt fctor ffecting their hydrtion strtegy during the rce. This compred with 25.3% of runners from the 2010 cohort nd represented n increse (v 2 ¼ 29.1, ¼.001); 5.8% of the 2014 cohort plnned on drinking more thn 3.5 L, compred with 12% of the 2010 cohort (v 2 ¼ 4.310, ¼.038). Conclusions: The number of smpled individuls using thirst to guide hydrtion strtegies in the 2014 London Mrthon incresed from However, more thn hlf of the 2014 cohort ws not plnning to drink to thirst. Runners still need to be educted bout the risks of overdrinking s they continue to demonstrte lck of knowledge nd understnding. Key Words: physicl endurnce, fluid intke, thirst Key oints Since the 2010 London Mrthon, eduction led to improvements in runners intended fluid strtegies for the 2014 London Mrthon. Exercise-ssocited hypontremi remins mediclly significnt problem for mrthon runners. More runners currently hd sfer intended hydrtion strtegies, but distinct lck of understnding persisted. Therefore, further eduction of runners bout pproprite fluid intke is still required. Over the lst 2 decdes, mrthon running hs become n incresingly populr sport. 1,2 Exercisessocited hypontremi (EAH) is concerning nd serious medicl compliction in endurnce thletes. 3 Worldwide, number of mrthon deths due to EAH hve been recorded, including young runner in the 2007 London Mrthon; 15 runners in the 2003 London Mrthon were dmitted to the hospitl with EAH. 4 Exercise-ssocited hypontremi is defined s serum sodium concentrtion of less thn 135 mmol/l during or up to 24 hours fter prolonged physicl ctivity. 4 The min cuse is believed to be excessive fluid intke. 5,6 Alow serum sodium concentrtion cn be ssocited with rnge of signs nd symptoms, such s nuse, hedches, nd seizures. A sodium concentrtion of less thn 135 mmol/l will often not result in ny physicl signs or symptoms but my still led to the development of more serious, lifethretening complictions, such s pulmonry or cerebrl edem, unconsciousness, nd deth. Additionl risk fctors for EAH include inpproprite ntidiuretic hormone relese nd metbolism nd extreme environmentl conditions. 7 Studies crried out t the 2002 Boston Mrthon 8 nd the 2006 London Mrthon 4 indicted tht up to 13% of finishers hd symptomtic hypontremi; however, the point t which symptomtic thletes become symptomtic hs not been estblished. Guidnce hs vried over time s more reserch hs been undertken. revious suggestions were to bse hydrtion strtegies on the swet rte 9 ; the uthors of 2017 updte 10 dvised drinking to thirst nd using body weight to guide hydrtion. The use of thirst s guide to hydrtion strtegies ws widely recommended by 696 Volume 53 Number 7 July 2018

2 Tble 1. Vrible Chrcteristics of the Study Smples Dt 14 Dt Sttisticl Test Vlue Vlue Smple size No. declined to tke prt Men ge, y t ¼ Men 6 SD Finishing time, h t ¼ Femles 66 (30.4) 150 (50.3) U ¼ Mles 151 (69.6) 148 (49.7) First mrthon 117 (54) 162 (54.4) U ¼ Member of running club 56 (25.8) 83 (27.9) U ¼ Independent-smples t test or Mnn-Whitney U test. consensus sttements nd other publictions. 6,11 13 An erlier investigtion by members of our group 14 explored the hydrtion strtegies of 217 runners ttending registrtion for the 2010 London Mrthon (0.6% of the totl finishers 15 ). The runners lcked knowledge bout sfe drinking nd prevention of EAH on rce dy: 12% plnned to drink in excess of 3500 ml during the mrthon, volume tht could hve put them t significntly higher risk of developing EAH. 4,8,14 A totl of 55 runners (25.3%) plnned to drink ccording to their thirst. Only 35.5% hd bsic understnding of EAH. The London Mrthon, held in the spring over flt city course, is full 26.2-mi (42.2-km) mrthon. Wter bottles (250 ml) were vilble t 23 wter sttions situted t 1-mi (1.6-km) intervls from miles 3 to 25. In ddition, sttions t 5, 10, 15, 19, nd 23 miles distributed 380-mL schets of sports energy drinks (Lucozde Sport, Uxbridge, United Kingdom). Since 2010, efforts hve been mde to rise wreness of the risks of overdrinking nd EAH. Specific informtion is now provided in the prerce mteril, which is supplied to every runner. 16 We imed to explore the intended hydrtion strtegies of smple of mrthon runners before the 2014 London Mrthon, to exmine their sources of informtion nd knowledge bout fluid intke nd their understnding of EAH, nd to compre these findings with those of similr study crried out before the 2010 London Mrthon. METHODS rior ethicl pprovl for the study ws obtined from the Queen Mry University of London Reserch Ethics Committee. Any thlete scheduled to run in the 2014 London Mrthon ws eligible to be invited to tke prt t the event registrtion. Consistent with the 2010 reserch protocol, 14 every ninth runner ttending ws pproched t stggered intervls throughout the 4 registrtion dys nd invited to prticipte. Runners were given n informtion sheet outlining the study. They were excluded if they hd ny problems understnding the questionnire (ie, lnguge brriers or lerning difficulty). Those who greed to prticipte were given the study questionnire, which ws vlidted in 2010 (see the Appendix), 10 nd sked to complete it t the reserch sttion. The questionnire comprised the following sections: 1. Bckground demogrphics 2. Drinking strtegies 3. Sources of informtion bout fluid intke 4. Knowledge of EAH Sttisticl Anlysis We used SSS (version 21.0; IBM Corp, Armonk, NY) for nlysis. Dt from the questionnire were presented descriptively. Chi squred, independent t, nd Mnn- Whitney U tests were used to ssess the differences in proportions between dt collected in 2010 nd Findings relted to the sources of EAH knowledge were explored using descriptive sttisticl methods. A vlue of,.05 ws defined s sttisticlly significnt. RESULTS Smple Chrcteristics A totl of 315 runners were invited to be prt of the study (0.9% of ll finishers 17 ); 17 of these runners did not tke prt in the study due to lnguge brriers or lck of time. The finl smple ws 298 prticipnts (0.83% of ll finishers 17 ). Smple demogrphics re described in Tble 1. The men finishing time of the cohort ws hours versus 4.50 hours for ll the runners in the 2014 London Mrthon. 17 Consumption Volume Runners were sked to estimte the totl milliliters of fluid they plnned to consume over the course of the rce. Those plnning to drink more thn 3.5 L were deemed to be t incresed risk of EAH. This volume guideline is bsed on the findings of previous studies, which suggested higher risk of developing EAH, 4,8 nd ws used in the 2010 study. 14 The totl volume the runners plnned to drink during the rce is shown in the Figure. Overll, 241 (81%) of the 2014 prticipnts specified the volume they intended to consume. The medin (interqurtile rnge) volume these runners plnned to consume ws 1.0 ( ) L. Of these 241 runners, 14 (5.8%) plnned to drink more thn the 3.5-L threshold compred with 26 runners (12%) in the 2010 cohort (v 2 ¼ 4.310, ¼.038; Tble 2). Tble 2. Comprison of 2010 nd 2014 Dt for Rce Strtegies Vrible 2010 Dt Dt Sttisticl Test Vlue Vlue Hydrtion strtegy during rce? 208 (95.8) 277 (93) U ¼ Medin (interqurtile rnge) plnned volume consumption during rce, L 1.2 ( ) 1.0 ( ) t ¼ No. of runners intending to drink.3.5 L (%) 26 (12) 14 (5) Z ¼ Independent-smples t test, Mnn-Whitney U test, or Z rtio. Journl of Athletic Trining 697

3 Tble 3. Comprison of 2010 nd 2014 Dt for Frequency of Hydrtion Attempts Vrible Medin No. (Interqurtile Rnge) 2010 Dt Dt Figure. Volume of fluid (L) runners plnned to drink during the mrthon. The horizontl line represents the volume tht previous reserch hs shown my put runners t greter risk of hypontremi. Independent- Smples t Test Vlue Vlue lnned wtersttion visits 10 (5 24) 8 (4 11) lnned sportsschet sttion visits 4 (2 5) 3 (2 5) Wter bottle ¼ 250 ml, sports schets ¼ 380 ml. Eduction Absolute Knowledge. In 2014, 190 (63.8%) runners climed to hve herd of hypontremi. However, in response to the question exploring their knowledge of EAH, only 70 (40%) demonstrted bsic understnding, s qulified by the criteri in Tble 5. Runners Self-erceptions of Their Knowledge. In totl, 258 (86.6%) of the 2014 runners perceived tht they knew enough bout sfe drinking on mrthon dy. Sources of Knowledge A totl of 282 (94.6%) runners climed to hve either red or been told bout pproprite hydrtion strtegies on mrthon dy. Most hd gined their informtion from reding the officil prerce informtion mgzine (66.4%), tlking to running friends (40.4%), or reding other running mgzines (30.9%). Most runners hd identified more thn 1 source of informtion. All sources of informtion re shown in Tble 6. Frequency of Drinking Runners in the 2014 mrthon plnned to drink t medin of 8 (4 11) wter sttions compred with medin of 10 (5 24) sttions for the runners in the 2010 mrthon (t ¼ 3.353, ¼.001), indicting reduction in consumption frequency. Furthermore, medin of 3 (2 5) sttions dispensing sports drinks were intended stops for the 2014 runners compred with medin of 4 (2 5) for the 2010 runners (t ¼ 3.869, ¼.0001; Tble 3). Drinking to Thirst Thirst ws reported s the min fctor influencing the intended hydrtion strtegy by 145 (48.7%) runners in 2014, which ws more thn the 55 (25.3%) of runners in 2010 (v 2 ¼ , ¼.001; Tble 4). The proportions of femle nd mle runners who plnned on drinking to thirst differed (55% nd 43%, respectively; v 2 ¼ 4.365, ¼.037). We found no difference between the proportions of experienced nd nonexperienced runners (v 2 ¼ 0.256, ¼.613) plnning on drinking to thirst. DISCUSSION Exercise-ssocited hypontremi is multifctoril condition in which consumption of lrge mount of fluid is recognized risk fctor. 4,8,14 Consuming volume of 3.5 L hs been ssocited with higher risk of developing EAH. 4,8,14 Recent deths ttributed to EAH 4,18,19 hve highlighted the importnce of voiding overdrinking. Dt collected in 2014 showed tht 14 (5%) of the runners plnned to drink more thn 3.5 L during the rce. Compred with the previous dt from 2010, when 26 runners (12%) plnned to drink in this rnge, this decrese demonstrted chnge in runners behvior 4 yers lter. This is further highlighted by the reduction in the number of wter sttions from which the runners intended to drink during the rce. Both intentions correlted with 2 ssocited risk fctors for developing EAH. The current guidnce is for runner to guide fluid intke bsed on thirst. It ws importnt to exmine wht proportion of the runners plnned to use their own thirst Tble 4. Comprison of 2010 nd 2014 Dt for Those lnning to Drink to Thirst Independent- Vrible 2010 Dt Dt Smples t Test Vlue Vlue Drinking to thirst 55 (25.3) 145 (48.7) Volume 53 Number 7 July 2018

4 Tble 5. Comprison of 2010 nd 2014 Dt for Runners Knowledge of Exercise-Associted Hypontremi (EAH) Vrible 2010 Dt Dt Mnn- Whitney U Test Vlue Vlue Herd of EAH 141 (65) 190 (63.8) Bsic understnding of EAH 77 (37) 70 (40) Runners felt they knew enough 182 (83.9) 258 (86.6) Those who mentioned overdrinking, or dilution effects, etc, were deemed to hve bsic understnding of EAH. Understnding of EAH ws deemed bsic if their nswer in free text identified cuse such s drinking too much fluid or signs nd symptoms included words ssocited with mlise, collpse, or deth, s per the 2010 study. 14 s guidnce. In this study, 48.7% of runners listed drinking to thirst s the most importnt fctor ffecting their hydrtion strtegy throughout the rce. Although this ws n increse from 4 yers previously, more thn hlf of the runners in our smple were still not wre of current guidnce regrding thirst s the min indictor for hydrtion. This chnge suggests tht messges regrding hydrtion re beginning to rech lrger proportion of the running popultion. Rce inexperience is known risk fctor for EAH. 20,21 However, we noted no sttisticl difference observed between the numbers of experienced nd nonexperienced runners plnning on drinking to thirst. More rce experience does not lwys equte to better understnding of the science underlying conditions such s EAH. This ffirms the importnce of directing messges nd eduction bout this topic t runners of ll experience levels. We found tht 94.6% of runners hd red or been told bout hydrtion on mrthon dy, nd 86.6% perceived they knew enough bout drinking, which might imply tht similr proportion would pln to drink n pproprite nd sfe mount. Yet only 48% plnned on drinking to thirst nd only 40% of runners hd bsic understnding of EAH, indicting tht the messge to runners bout pproprite hydrtion nd EAH still requires further dissemintion. A totl of 66.4% of runners in our smple listed the officil prerce informtion mgzine s source of informtion regrding fluid intke. The 2014 officil mgzine contined more prominently plced, detiled, nd specific dvice bout pproprite nd sfe drinking, including the potentil hzrds of drinking too much nd EAH. The mgzine gve cler instructions to void drinking too much: Drinking too much cn be very dngerous nd led to hypontremi (wter intoxiction), fits [seizures], nd even deth. 16 Sent to ech runner s prt of the finl preprtion before the rce, the mgzine is the single most importnt London Mrthon eductionl resource. No other specificlly directed informtion is given to ll runners. Interestingly, the dt gthered on sources of informtion showed tht most runners consulted more thn 1 source, including wide rnge from mgzines to the Internet nd discussions with peers. This fct highlights how brodly informtion cn be distributed throughout community: runners in this cse. The messge bout sfe fluid intke nd EAH still needs to be reinforced, nd perhps more trgeted ttempts to dispense the informtion through the running community would ffect runners future behvior. The min limittions of this study were using questionnire nd predictive mesures nd compring them with biologicl fctors nd outcomes. Exercisessocited hypontremi is multifctoril biologicl process ffecting the dilution effects of fluids within the body. A 3.5-L volume ws used s guideline; however, it is not possible to sy tht this volume of wter should be used s definitive cutoff, s mny other fctors cn contribute to the development of EAH. The runners in the 2014 study hd difference of pproximtely 20 minutes in their verge finishing time, which my hve influenced the results. Although low percentge of totl finishers completed the questionnire, the numbers were comprble cross the 2010 nd 2014 studies; we invited every ninth runner to ensure n equl distribution of runners cross the signup dys t the mrthon. Results of the questionnires depended on the honesty of the respondents, nd ccurcy cnnot be determined; such recll bis is generl limittion when using questionnires. The questionnire ws the sme for both studies, nd it ws previously vlidted for the 2010 study, llowing vlid comprisons to be mde. The risks nd consequences of EAH re known, but mny runners remin unwre of how much they should drink. More eduction of runners is needed. Tble 6. Vrible 2014 Sources of Informtion for Runners About Fluid Intke on Mrthon Dy Compred With 2010 Dt 2010 Dt Dt Mnn-Whitney U Test Vlue Red or told bout drinking 202 (93.1) 282 (94.6) Virgin Money London Mrthon Mgzine 152 (70) 198 (66.4) Running friends 97 (44.7) 121 (40.4) Running mgzine 75 (34.6) 92 (30.9) Virgin Money London Mrthon Web site 57 (26.3) 71 (23.8) Running club 36 (16.6; 64% of club runners) 49 (16.4; 59% of club runners) Informtion from chrity 51 (23.5; 29.1% of chrity runners) 62 (20.8; 26.4% of chrity runners) Running coch 30 (13.8) 54 (18.1) Running book 23 (10.6) 46 (15.4) Other sources of informtion b 34 (15.7) 26 (8.7) Mostly Runner s World mgzine. b Minly Internet, socil medi, or helth professionl. Vlue Journl of Athletic Trining 699

5 As discussed erlier, informtion is slowly disseminting through the running community, but further improvement is still needed. The most frequently consulted source of informtion ws the prerce mgzine, nd this publiction should continue to be used to inform runners. erhps more trgeted pproch strting t the grssroots level would help to increse the understnding of this subject re mong the running community; recommendtions hve lredy been mde to brodly trget these thletes nd to focus on certin roles within running community. 10 CONCLUSIONS Exercise-ssocited hypontremi remins mediclly significnt problem for mrthon runners. Eduction hs led to certin improvements in runners intended fluid strtegies t the London Mrthon, with sttisticlly significnt reduction in the proportion of our cohort plnning to drink greter thn 3.5 L nd higher proportion of these runners now plnning on drinking to thirst, s recommended by the current medicl guidelines for endurnce thletes. Among our cohort, 94.6% felt they hd enough informtion nd 86.6% perceived they knew enough bout sfe hydrtion strtegies. However, only 48% of these runners intended to drink to thirst, indicting persistent nd distinct lck of understnding of the topic. More effective eduction of runners bout pproprite fluid intke nd EAH is required to further reduce the risk nd ultimtely the incidence of EAH. ACKNOWLEDGMENTS We thnk the prticipnts in this study, the mrthon officils who ssisted with logistics, nd the students from Queen Mry University of London. Appendix. Questionnire Continued on Next ge Mny thnks for tking prt in this questionnire. If you re not cler bout ny of the questions, plese feel free to sk the resercher. lese nswer the questions in order by putting tick in the box or writing n nswer on the line. Bckground informtion bout you s runner: 1) Is this your first mrthon? (nd if Yes, plese go to question 3) If this is not your first mrthon, how mny previous mrthons hve you run? (plese tick) or more mrthons 2) Wht is your fstest time? h min 3) Wht is your estimted finishing time? h min 4) Are you running on behlf of chrity? If Yes, which chrity? 5) Are you member of Running club? 6) Gender: Mle Femle 7) Age: y 8) How tll re you? 9) Wht is your weight? Informtion on drinking on mrthon dy: 10) Hve you red bout or been told bout drinking fluids on mrthon dy? (if No, plese go to question 11) If Yes, where hve you received this informtion from? (plese tick ll tht pply) London Mrthon mgzine London Mrthon Web site Running club Running coch Running friends Running mgzine (if so, which mgzine?) Running book (if so, which book?) From the chrity for which you re running Other sources of informtion (plese specify; eg, other online source, smrtphone pp, librry book etc) 700 Volume 53 Number 7 July 2018

6 Appendix. Continued From revious ge Before the mrthon: 11) Do you hve ny plns bout drinking in the morning before the strt of the mrthon? (if No, plese go to question 15) 12) If Yes, wht re you plnning to drink? 13) How much re you plnning to drink? 14) When re you plnning to drink this? During the mrthon: 15) Do you hve ny plns bout drinking during the rce? (if No, plese go to question 19) 16) If Yes, wht re you plnning to drink? 17) How much re you plnning to drink? 18) At wht stges of the rce re you plnning to drink? 19) Some people crry their own drinks from the strt of the rce do you intend to do tht? (if No, plese go to question 25) 20) If Yes, wht drink will you crry? 21) Wht volume will you crry? 22) Do you pln to drink wter provided in bottles t wter sttions during the rce? (if No, plese go to question 25) 23) If yes, t how mny wter sttions will you tke bottles of wter? 24) How much of ech bottle do you nticipte tht you will drink? A few sips Severl mouthfuls Hlf the bottle Most or ll of the bottle 25) Do you pln to drink the sports drink (Lucozde) provided t the drink sttions during the rce? (if No, plese go to question 28) 26) If Yes, t how mny drink sttions will you tke sports drink? 27) How much of ech pck do you nticipte tht you will drink? A few sips Severl mouthfuls Hlf the pck Most or ll of the pck 28) Wht is the volume of ech wter bottle given out on the course? (plese estimte if you don t know exctly) mls 29) Wht is the volume of ech pck of sports drinks given out on the course? (plese estimte if you don t know exctly) mls 30) Wht fctors my ffect how much you drink in order of importnce? (plese mrk 1 0 for the most importnt for you, 2 0 for the second, 3 0 for the third most importnt nd 4 0 for the lest importnt) My pln How thirsty I feel The temperture on rce dy Other (plese specify) 31) Hve you prctised drinking wter during your trining? 32) Hve you prctised drinking sports drink during your trining? After the mrthon: 33) Do you hve ny plns bout drinking in the 6 hours fter the mrthon? (if No, plese go to question 37) 34) If Yes, wht re you plnning to drink? 35) How much re you plnning to drink? 36) How often re you plnning to drink? Journl of Athletic Trining 701

7 Appendix. Continued From revious ge Informtion bout fluids: 37) Do you feel tht you know enough bout wht nd how much to drink on mrthon dy? If No, wht would help you to be better informed for future rces? 38) Hve you herd of the term hypontremi (low slt or sodium levels) If Yes, wht is your understnding of its cuses nd effects? 39) Do you hve ny other comments bout drinking fluids on mrthon dy? Mny thnks for completing this questionnire. lese return it to the resercher. The questionnire is reproduced in its originl form except tht underlined spces replced boxes for nswers. REFERENCES 1. Fredericson M, Misr AK. Epidemiology nd etiology of mrthon running injuries. Sports Med. 2007;37(4 5): Rsmussen CH, Nielsen RO, Juul MS, Rsmussen S. Weekly running volume nd risk of running-relted injuries mong mrthon runners. Int J Sports hys Ther. 2013;8(2): Speedy DB, Nokes TD, Schneider C. Exercise-ssocited hypontremi: review. Emerg Med (Fremntle). 2001;13(1): Kipps C, Shrm S, Tunstll edoe D. The incidence of exercisessocited hypontremi in the London Mrthon. Br J Sports Med. 2011;45(1): Drper SB, Mori KJ, Lloyd-Owen S, Nokes T. Overdrinkinginduced hypontremi in the 2007 London Mrthon. BMJ Cse Rep. 2009;2009. DOI: /bcr Nokes TD. Is drinking to thirst optimum? Ann Nutr Metb. 2010; 57(suppl 2): Nokes TD, Shrwood K, Speedy D, et l. Three independent biologicl mechnisms cuse exercise-ssocited hypontremi: evidence from 2, 135 weighed competitive thletic performnces. roc Ntl Acd Sci U S A. 2005;102(51): Almond CS, Shin AY, Fortescue EB, et l. Hypontremi mong runners in the Boston Mrthon. N Engl J Med. 2005;352(15): Convertino VA, Armstrong LE, Coyle EF, et l. Americn College of Sports Medicine position stnd. Exercise nd fluid replcement. Med Sci Sports Exerc. 1996;28(1):i vii. 10. Hew-Butler T, Loi V, ni A, Rosner MH. Exercise-ssocited hypontremi: 2017 updte. Front Med (Lusnne). 2017;4: Hew-Butler T, Ayus JC, Kipps C, et l. Sttement of the Second Interntionl Exercise-Associted Hypontremi Consensus Development Conference, New Zelnd, Clin J Sport Med. 2008; 18(2): Hew-Butler T, Almond C, Ayus JC, et l. Consensus sttement of the 1st Interntionl Exercise-Associted Hypontremi Consensus Development Conference, Cpe Town, South Afric, Clin J Sport Med. 2005;15(4): Hew-Butler T, Verblis JG, Nokes TD; Interntionl Mrthon Medicl Directors Assocition. Updted fluid recommendtion: position sttement from the Interntionl Mrthon Medicl Directors Assocition (IMMDA). Clin J Sport Med. 2006;16(4): Willims J, Tzortziou Brown V, Mllirs, erry M, Kipps C. Hydrtion strtegies of runners in the London Mrthon. Clin J Sport Med. 2012;22(2): London Mrthon Rce Results MrthonGuide.com Web site. Accessed April 11, Shrm S. London Mrthon medicl dvice. Virgin Money London Mrthon Web site. trining/stying-helthy/medicl-dvice. ublished April Accessed Februry 22, London Mrthon rce results MrthonGuide.com Web site. Accessed Februry 22, Grdner JW. Deth by wter intoxiction. Mil Med. 2002;167(5): Severc M, Orbn JC, Lepltois T, Ichi C. A ner-ftl cse of exercise-ssocited hypontremi. Am J Emerg Med. 2014;32(7): Chorley J, Cinc J, Divine J. Risk fctors for exercise-ssocited hypontremi in non-elite mrthon runners. Clin J Sport Med. 2007; 17(6): Hew TD, Chorley JN, Cinc JC, Divine JG. The incidence, risk fctors, nd clinicl mnifesttions of hypontremi in mrthon runners. Clin J Sport Med. 2003;13(1): Address correspondence to Jonthn Willims, MSc, Centre for Sports nd Exercise Medicine, Queen Mry University of London, 80 Slde Rod, ortished, Bristol BS20 6BH, London, Englnd. Address e-mil to jonthnwillims1066@gmil.com. 702 Volume 53 Number 7 July 2018