Dancaster, CP

Whereat, SJ

English

AJOL - African Journals Online

-6 Februarie 1971 S.·A. MEDIESE TYDSKRIF 147FLUID AND ELECTROLYTE BALANCE DURING THE COMRADES MARATHON*c. P. DANCASTER, M.D., B.Sc. (RAND), M.R.C.P. (EDIN.) AND S. J. WHEREAT, M.B., B.S. ( EW SOUTH WALES),Department of Medicine, Grey's Hospital, Pietermaritzbu rgHeat exhaustion and even death have followed marathonrunning. At the end of the dramatic 1908 Olympic Mara-thon-run in London on a hot humid day-Dorando,dazed by the heat and exhausted, entered the stadium first,ran in the wrong direction, collapsed twice and was in asemi-coma for two days. During the 1912 Olympic Mara-thon in Stockholm, again run on a hot humid day, Lazarocollapsed after running 19 miles and died the next day.In the Paris Olympics five runners in the 10 000 metreswere hospitalized with heat-stroke following the event, andin the 1960 Rome Olympics three Danish cyclists developedheat-stroke in the lOO-km road race.The danger of inadequate water intake during marathonrunning has been stressed by Wyndham and Strydom'who showed that the rise in temperature in runners wasdirectly related to their water deficit and reached 105°Fafter a 20-mile marathon. These cases of heat-stroke in theOlympics were no doubt due to deficient fluid intake.The Comrades Marathon is a particularly gruelling event.It is run over 54 miles-twice the distance of the OlympicMarathon-and over a period of 6 - 11 hours. We wereparticularly interested in the sweat loss during this period,how competitors compensated for it and what effect it hadon the urea and electrolytes. The 1970 Comrades Marathonwas run from Durban to Pietermaritzburg.MATERIAL AND METHODSThirty-one runners were randomly selected from Pieter-maritzburg competitors. They were aged 19 - 51 years;some were novices, while others were experienced runners,and their training schedules varied from many months to afew weeks.They were examined and a blood sample was takenduring the week before the race and again at the com-pletion of the race, or as soon as possible after they hadstopped running. The organizers kindly provided a tent atthe finishing line and although we were able to examinesome patients immediately they crossed the finishing line,there was a delay of 5 - 10 minutes in seeing some com-petitors, and occasionally longer. There were two in-accuracies regarding the weighing of competitors: (a) thescale available was only sensitive to changes of t Ib and'Date received: 29 October 1970.(b) the competitors were not weighed immediately beforethe race (at 6 a.m. in Durban).Each competitor was given a questionnaire and agreedto keep a careful record of the quantity of fluid consumedduring the race and during a 24-hour period starting at thebeginning of the race. He was given separate containers tocollect urine passed during the race and for the 24-hourperiod referred to. He was asked to record any difficultiesexperienced, i.e. vomiting, diarrhoea and mental confusion.Co-operation was extremely good, but we had to excludesome competitors in the final analysis of fluid balance.The common faults were (a) having to pass urine duringthe race when the assistant with the container was notavailable, (b) in the excitement of the moment a spillageof urine from the containers, and (c) occasionally thevolume of fluid drunk during the race was not sufficientlywell recorded. Adequate records during the race itself wereobtained in 24 of these runners, and a fairly accurate 24-hour balance was obtained in 17 runners.In calculating the fluid consumed after the race, volumeswere calculated on the following basis: a bottle of beer =340 ml (all one type); Coca Cola (one size) = 300 ml;and a glass or cup of fluid = 200 m!.Blood was taken immediately after the race. Particularimportance was attached to analysing all blood samples onthe same afternoon and evening that the race was run.Sodium, chloride, potassium, urea and packed cell volumeswere estimated using standard techniques.'"RESULTSSweat Loss during the Race (Tables I -Ill)Eight runners with an average weight of 160 Ib (72'6 kg)lost more than 9 litres in sweat. Eleven whose averageweight was 144 Ib (65'4 kg) lost between 6t and 8 litresand five whose average weight was 133 Ib (60,4 kg) lostless than 6 litres. There was no correlation between thetime taken to complete the race or the age of the runnerand the sweat loss.Fluid Intake during the Race (Tables I - Ill)Two competitors drank 9t litres. Other competitorsdrank between 2 and 5t litres except for the competitorwho finished in the fourth place whose total intake wassix small nips of lemonade.rABLE I. SWEAT LOSS/FLUID I.ITAKE DURING RACERunner Swear loss Intake Water deficit Water deficit WeighT AgeNo. (m{) (m!) (m/) % (lb) (years) Time17 12800 9600 3200 4'3 162 19 9 hours6 10800 7200 3600 4·1 190 36 11 hours5 10400 9600 900 1·5 131 23 7 hours.n 10300 5800 4500 66 149 19 11 hours9 9700 7200 2750 4·3 142 2234 9300 4 ROO 4500 6·0 165 182 9200 4800 4500 5·2 190 35 9t hours16 9000 4500 4500 6-4 153 39Average 10300 160148 S.A. MEDICAL JOURNAL 6 February 1971TABLE n. SWEAT LOSS 6 600 - 7 800 IDlRunner Sweat loss Intake Water deficit Water deficit Weight AgeNo. (ml) (ml) (ml) % (lb) (years) Time7 7000 4200 2750 4·6 134 51 7t hours10 7800 3 300 4500 7'1 140 4912 7300 1800 5500 7·5 160 - 45 8+ hours13 6900 3000 3600 4·7 170 41 8'\' hours14 6500 4200 2300 3-7 135 29 8f hours21 7400 1860 5500 8·2 148 52 7i- hours22 7700 3600 4100 6'3 144 32 8 hours23 7200 4000 3200 5-0 142 38 8i- hours29 7100 3500 3600 5·0 148 43 8t hours30 7200 4500 2700 4-0 150 22 7i- hours31 6600 3000 3600 6'6 120 38 S hoursAverage 7700 144TABLE Ill. SWEAT LOSS UNDER 6 000 IDlRunner Sweat loss Intake Water deficit Water deficit Weight AgeNo. (ml) (m I) (ml) % (lb) (years) Time3 4300 200 4100 6·9 130 31 6 hours25 5000 1800 3200 5·3 133 25 8 hours26 5000 4500 500 0·6 159 23 9 h;:Jurs11 5400 2400 3200 6·0 119 34 lOt hours4 5750 3000 2750 4·9 126 36 8 hoursAverage 5100 133Water Deficit during the Race (Tables I - Ill)Those whose sweat loss was the greatest had the best in-takes. All of those who sweat loss exceeded 9 litres drankmore than 4t litres, but in spite of this the negativebalances were alarming. Water deficits of up to 5t litreswere recorded! In fact only two out of twenty-fourrunners had a water deficit of less than 1 litre or under3'1'0. One of these lost 10 litres as sweat, but drank 91' litresduring the race. Nearly half the runners (10 out of 24)had a water deficit greater than 6% of their weight. Onlythree runners had a water deficit of less than 4%.Rectal TemperaturesThe recording of rectal temperatures immediately afterthe race proved very difficul-t practically. Ten patients hadrectal temperatures taken within 5 minutes of the com-pletion of the race. One had a temperature of 99°F (hiswater deficit was not measured), the remainder had arectal temperature of 101 - 102°F. All had a water deficitof over 4%. The two with the greatest water deficits (8'2%and 7·1 %) had temperatures of 102° and 101°F respectively.24-hour Fluid Balance from Commencement of Race(Table N)Only 2 runners were in positive balance 24 hours afterthe race. One of these had a water deficit of 4t litres duringthe race, but made this up by drinking 6t litres over the24 hours.IntakeTABLE IV. FLUID BALANCE oVER 24 HOURS (ml)OutputRunner During From end of Sweat 24-hourNo. race race to 24 h Total loss Urine* Total balance2 4800 6500 11 300 9200 630 (100) 9830 +157026 5000 1440 6440 5000 1 180 (440) 6180 + 2605 9600 2440 12040 10400 1 700 ( 90) 12100 607 4200 2400 6600 6950 320 ( -) 7270 - 67030 4500 2640 7140 7200 720 (205) 7920 - 78014 42aO 1920 6120 6500 440 ( 70) 6940 - 8206 7200 3400 10600 10 800 1600 ( -) 12400 -180025 1800 1900 3700 5000 570 ( -) 5570 -187034 4800 3040 7840 9300 860 (200) 10160 -23203 200 2570 2950 4300 1850 ( -) 5385 -243533 5800 2720 8520 10 300 680 ( -) 10980 -246029 3500 1700 5200 7100. 780 ( 60) 7880 -26804 3000 800 3800 ';750 810 ( -) 6560 -276017 9600 1400 -il000 12800 1 200 (150) 14000 -300010 3300 2000 5300 7800' 560 ( -) 8360 -306021 1860 4000 5860 7360 1880 ( -) 9240 -338016 4500 800 5900 9000 610 (130) 9610 -3710*Figures in parenthesis represent volume of urine passed during the race.groups drank an average of 2'5 litres after the race. Therewere, however, two notable exceptions, competitors Nos. 3and 21 whose intake during the race was only 0·2 litres and1-8 litres, and yet they passed good 24-hour volumes-1·0 litres and 1·8 litres respectively.Packed Cell Volume, Urea and EleCTrolytes (Table V)There were moderate increases in the packed cell volumeafter the race in most competitors, although in 6 out of 27it was actually lower after the race and in 2 it was un-changed. In only 7 competitors was the packed cell volumeincreased by 5% or more. There was no relation betweenthe water deficit and rise in packed cell volume.The mean blood urea among 34 competitors was 27·1mgj 100 ml before the race (range 21 - 33 mgj 100 ml).After the race 30 of these competitors had a mean bloodurea of 41·7 mgj 100 ml (range 30 - 60 mgj 100 ml). Therewas no good correlation between the extent of blood urearises and the water deficit.The potassium levels rose from a mean of 4 mEqflitrebefore the race to 46 mEq j litre after the race. In only5 of 24 competitors did the post-race elevation exceedI mEqjlitre. The extent of the ri e in potassium was not149137140130~.;::.'<:140141138132132140137137139134137139137143132134140137136132139142137140134139140.,~..,CQ134137135130136137141132135136134134151143137135132134137141126134139139!3fi136137137D8134137136138140136Sodium(mEq j litre)101100991009910395979510710110210210399991039510210599103105969810210598103104~~CQ102105lOO106102102103969599981001041001031021021021051009595104104107-1059910310799100102101106101Chloride(mEq j liTre)0·503().,1-30·7061·00·60·41·40·6....:.~Cl0·70·60·50·20·81·10·20·8lA0·5-0'30·70·90·54·64·35·54'14·84·54·34·24·84·74·64·74·0.....,.;:,'<:5-l4·63·74·34'34·05·04·25-D4·55·25-35-94·04A4·63·9Potassium(mEq j liTre)38 11 4·460 27 4·040 331 10 3-836 11 4·142 937 8 4·234 244 12 3·949 26 4·330 9 4·458 36 3-944 11 5·437 19 4·343 17 3·750 24 3·748 22 3-444 22 3·935 12 3-937 8 4-l37 849 2246 13 4033 5 4030 -1 3·737 9 3·554 23 4·04·050 23 4·044 16 3·734 12 363·74·23-941·7 14·6 4·0Urea(mgj 100 ml)TABLE V. BLOOD TESTS2733372125332932322321223322262626222329292733283128312227282223272727'1S.-A. MEDIESE TYDSKRIF+2+8+5-1+1+5-6+2-1+1+5+1+6+1+5+2+1+3+1+6-4-2,1+1-I554947PCV~---'<:44474950484842474848494647514540464843454644504643424844474340464541474350474944414645434943444744484748474448444646550055004500450045004500450041004 lOO360036003600360032003200320032002750275027502700230090050036132931251117?~_.J4973014526181518192024272832Means1221103334216226 Februarie 1971Four others had a negative balance of under 1 litre at. the end of this time. The remaining eleven (64'70) who had24-hour balanct';s showed a negative balance at the endof that time of between 1 800 ml and 3 710 m!. Four stillshowed a negative balance in excess of 3 litres at the endof 24 hours.Urine Output orer 2.f. HoursDuring the race itself a satisfactory record of urinepassed was obtained in 26 runners, 10 of whom passed nourine at all. The others passed small amounts, the totalvolume varying from 40 ml to 440 m!. The 24-hour urinevolume varied from 320 ml to 1880 ml-6 out of 17 (35~0)passed over 1 litre. Eight runners (47"0) had a 24-hour out-put of less than 740 ml but in only two competitors wasthe 24-hour output less than 500 m!.The volume of fluid consumed during the race seemedto have more of a bearing on the total 24-hour urinevolume than the amount consumed after the race. Incomparing six competitors who passed I litre in 24 hoursto eight who passed under 750 ml, the average fluid con-sumed during the race was 5·6 litres in those passing over1 litre and 4-1 litres in those passing under 750 m!. Both150 S.A. MEDICAL JOURNALTABLE VI. AVERAGE FLUID REQUIREMENTS BASED ON WEIGHT6 February 1971Above 160 Ib (5 runners): average 175 Ib (79'45 kg)140 - 160 Ib (11 runners): average 149 Ib (68 kg)UnJer 14LJ 10 (~ runners): average 12~ Ib ()o'j2 kg)A verage sweat loss(m/)9800780063503% deficit ofweight (m/)228020401640A verage fluidrequirements (m/)752057604710related to water deficit or rise in blood urea. Rises in ureaand potassium after the race occurred in all competitorsexcept two: the blood urea fell from 31 mg/IOO ml to30 mg/ 100 ml in competitor No. 1 and potassium fell from4·3 mEqjlitre to 4·0 mEq/ litre in competitor No. 25.There was no consistent pattern in sodium and chloridelevels before and after the race-in some competitors levelswere higher after the race and in others they were lower.The mean chloride level remained at 101 mEqjlitre beforeand after the race, and the mean sodium level was alsovirtually the same (136 mEqjlitre before the event and137 mEq/ litre afterwards).DISCUSSIONAs would be expected in a I ace of this nature, sweat losseswere very high. One-third of these runners lost more than9 litres during the race. This is more than double themaximum sweat loss experienced in a 20-mile sugarmarathon.' The runner's weight is the most importantfactor determining the volume of sweat lost. It is theheavier man who loses most sweat. The time taken tocomplete the race did not affect the volume of sweat lostnor did the age of the competitor.Water deficits in these runners were very high and it wassurprising that none showed evidence of heat exhaustionor higher rectal temperatures. Only two runners reallyadequately replaced fluid loss and in the majority thewater deficits reached dangerous proportions (above 7%in 3 runners). Fortunately the race was run on an un-usually cool day which contributed towards the lowerrectal temperatures, but runners and their assistants arestill unaware of the risks involved in not adequately re-placing sweat loss. Wyndham and Strydom' stressed thatif the water deficits exceed 3 % of the body's weight rectaltemperatures rise, and if the water deficit exceeds 4% itmay rise excessively.In spite of these alarming water deficits we were relievedthat no competitors developed severe oliguria or uraemia.Urine volumes after the race were surprisingly good-onlytwo excreted less than 500 ml over 24 hours and the highestblood urea recorded after the race was 60 mg/100 ml.The mean elevation in potassium after the race was only0·6 mEq /litre, which was very much lower than found byMcKechnie et al. after the 1965 marathon: None of thesecompetitors had alarming potassium levels-the highestrecorded was 5·5 mEq/litre.In estimating the average fluid requirement a runnershould consume roughly between 5 and 8 litres, dependingBOEKE ONTVANGThe Natllre of Childhood Autism. 2nd ed. By G. O'Gorman,FR.C.P., D.P.M. Pp. vii + 163. Illustrated. R4.80. Lon-don: Butterworth. 1970.on his weight (Table VI), to maintain the water deficit at3%. The increased requirements of the heavier runners isstriking. However, there are individual variations, e.g. oneof the runners who only lost 5 litres as sweat weighed159 lb, whereas one who lost over 10 litres weighed 131 lb.It would therefore be preferable for each runner to weighhimself in kilograms on a sensitive balance immediatelybefore and after a long training run (approximately 50miles). The difference should be expressed in grammes andto this figure the volume of water consumed during therun (in ml) is added. The volume of fluid a runner shoulddrink should be at least three-quarters of the total (ex-pressed in m]) and in the heavier runners (over 150 Ib)four-fifths of the total. It is easier not to include any urinepassed as the volume is so small. It is quite practical todrink over 9 litres in the Comrades Marathon-one runnerdid this over 7 hours and another in 9 hours. Taking 300 ml(half a pint or a large cup) every twenty minutes asrecommended by Wyndham, would result in just over 8litres in 9-!- hours, and as he stresses this should start rightfrom the beginning of a race.SUMMARYThe fluid balance was recorded in 24 runners during theComrades Marathon, and in 17 of these it was extended over24 hours. The sweat loss during the race ranged from 4·3 to12·8 litres. There was a relation between the weight of therunner and the sweat loss, the heavier runners losing most.Neither the age of the runner nor the time taken was relatedto the sweat loss.The fluid intake during the race was totally inadequatein all but 2 of the 24 competitors, and in the majoritythe water deficit assumed dangerous proportions. Despite goodfluid intakes after the race only 2 runners had completelycompensated for their fluid loss at the end of 24 hours, andthe water deficit was still in excess of 1 litre in the majority(64%). In spite of ,the severe water deficits rectal temperaturesof ov~r 102 OF were not recorded. and elevations of urea andpotassium were only moderate.The lighter runners (under 140 Ib) should consume 5 litres offluid during the race and the heavier runners (over 160 Ib)should take about 8 litres (roughly a large cupful every twentyminutes).We should like to thank Dr E. Naude and Mr S. Sydenhamfor the blood urea and electrolyte estimations.REFERENCESI. Wyndham. C. H. and S!rydom, N. B. (1969): S. Afr. Med. J .. 43. 893.2. Varley. H. (1967): Practical Clinical Biochemistry, 4th ed., p. 493.London: \Villiam Heinemann Medical Books.3. King. E. J. and Wooton, I. D. P. (1964): Microanalysis in MedicalBiochemistry. 4th ed .. p. 66. London: J. & A. Churchill.4. Lynch. M. J.. Raphael. S. S.. Melior, L. D .. Spare, P. D. andInwood, M. J. (1969): Medical Laboratory Techniques and ClinicalPathology. p. 109. Philadelphia: W. B. Saunders.5. McKechnie, J. K., Leary, W. P. and Jouber!, S. M. (1967): S. Air.Med. J, 4~, 722.BOOKS RECEIVEDPrincitJles of Biolo/?ical Control. By D. F. Horrobin. M.A.,D.Phil.. B.M., B.Ch. Pp. x + 70. Illustrated. 15s Od. Ayles-hury: Medical & Technical Publishing. 1970. Obtainablefrom Cotton & Hardie (Ply) Ltd, Pinelands, Cape.

Fluid and electrolyte balance during the comrades marathon

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