REHYDRATION WITH SODIUM-ENRICHED COCONUT WATER AFTER EXERCISE-INDUCED DEHYDRATION

Transcription

1 REHYDRATION WITH SODIUM-ENRICHED COCONUT WATER AFTER EXERCISE-INDUCED DEHYDRATION I Ismil 1,3, R Singh 1 nd RG Sirisinghe 2 1 Sports Science Unit, 2 Deprtment of Physiology, School of Medicl Sciences, Universiti Sins Mlysi, Kubng Kerin, Kelntn; 3 Deprtment of Physicl Eduction nd Helth, Sultn Mizn Techers Trining Institute, Besut, Terenggnu, Mlysi Abstrct. This crossover study ssessed the effectiveness of plin wter (PW), sports drink (SD), fresh young coconut wter (CW) nd sodium-enriched fresh young coconut wter (SCW) on whole body rehydrtion (R) nd plsm volume (PV) restortion fter exercise-induced dehydrtion. Ten helthy mle subjects rn t 65% of VO 2mx in n environmentl temperture of 32.06±0.02ºC with reltive humidity (rh) of 53.32±0.17% for 90 minutes to lose 3% body weight (BW). During the 2-hour rehydrtion period, subjects drnk, in rndomized order, PW, SD, CW or SCW equivlent to 120% of BW lost in three boluses representing 50, 40 nd 30% of the fluid lost t 0, 30, nd 60 minutes, respectively. In ll trils subjects were still somewht dehydrted even fter the 2-hour rehydrtion period. Indexes of percent rehydrtion with PW, SD, CW nd SCW were 58±2, 68±2, 65±2 nd 69±1%, respectively, with significntly better rehydrtion with SD nd SCW. The rehydrtion indexes for SD nd SCW were significntly lower thn PW (p<0.01). PV ws restored to euhydrtion levels fter 2 hours of rehydrtion with SD, CW nd SCW but not with PW. The plsm glucose concentrtion were significntly higher when SD, CW nd SCW were ingested. SCW ws similr in sweetness to CW nd SD but cused less nuse nd stomch upset compred to SD nd PW. In conclusion, ingesting SCW ws s good s ingesting commercil sports drink for whole body rehydrtion fter exercise-induced dehydrtion but with better fluid tolernce. INTRODUCTION Correspondence: Prof Rbindrjeet Singh, Ntionl Institute of Sports, Ntionl Sports Council of Mlysi, Bukit Jlil, Kul Lumpur, Mlysi. Tel: ; Fx: E-mil: rbindrjeet@nsc.gov.my Rpid nd complete restortion of fluid blnce fter exercise is n importnt prt of the recovery process nd becomes even more importnt in hot humid conditions when repeted bouts of exercise hve to be performed. Hevy sweting during exercise, especilly in het, cn cuse body fluid losses in excess of 1 liter per hour (Costill, 1977). Following dehydrtion individuls must ingest sufficient fluids to recover from their dehydrted stte. The choice of drink fter exercise differs depending on the individul nd the circumstnces. Replcement of substrte in ddition to wter nd electrolytes is concern fter exercise in preprtion for further exercise or competition. Exercise performnce is impired when n individul is dehydrted by s little s 2% of body weight (Murry, 1998), nd losses in excess of 2.5% of body weight cn decrese the cpcity for high intensity work by bout 15% for exercise lsting 7 minutes (Mughn nd Leiper, 1995). The decrese in plsm volume which ccompnies dehydrtion my be of prticulr importnce in influencing work cpcity. Blood flow to the muscles must be mintined t high level to supply oxygen nd substrtes, but high blood flow to the skin is lso necessry to convert het to the Vol 38 No. 4 July

2 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH body surfce where it cn be dissipted (Mughn,1999). When the mbient temperture is high nd blood volume hs been decresed by swet loss during prolonged exercise, there my be difficulty in meeting the requirements for high blood flow to both these tissues. In this sitution, skin blood flow is likely to be compromized, llowing centrl venous pressure nd muscle blood flow to be mintined but reducing het loss nd cusing core body temperture to rise (Rowell, 1986). Rehydrtion fter exercise requires replcement of electrolytes, primrily sodium, lost in swet (Costill et l, 1976; Mughn et l, 1994; Mughn nd Leiper, 1995; Shireffs et l, 1996; Ry et l, 1998). Ingestion of plin wter results in rpid fll in plsm sodium concentrtion nd in plsm osmollity (Mughn, 1999; Nose et l, 1988). These chnges hve the effect of reducing the stimulus to drink (thirst) nd of stimulting urine output, both of which will dely the rehydrtion process (Gonzlez-Alonzo et l, 1992). It is cler from the results of vrious studies tht rehydrtion fter exercise cn be chieved only if electrolytes s well s wter re replced (Prder, 1942; Hubbrd et l, 1985; Gonzlez- Alonzo et l, 1992). The sodium content of most of the mjor commercil sports drinks is in the rnge mmol.l -1 (Mughn, 1999). The most commonly consumed soft drinks contin virtully no sodium, nd re therefore unsuitble for rehydrtion. The requirement for sodium replcement stems from its role s the mjor ion in the extrcelullr fluid. It my be speculted tht inclusion of potssium, the mjor ction in the intrcellulr spce, would enhnce the replcement of intrcellulr wter fter exercise nd thus promote rehydrtion (Ndel et l, 1990). The inclusion of potssium hs been shown to be s effective s sodium in retining wter ingested fter exercise-induced dehydrtion, in spite of the low levels of potssium lost through swet (Mughn et l, 1994). The most commonly vilble sports drinks contin significnt mount of potssium long with other electrolytes, often in concentrtions similr to those estimted to be present in swet (Mughn, 1999). Mny specil formultion drinks hve been used s rehydrtion drinks fter exercise-induced dehydrtion (Gisolfi et l, 1992; Murry et l, 1999; Coombes nd Hmilton, 2000). However, recently young coconut wter hs been used s rehydrtion drink (St et l, 2002). It hs low sodium content but high potssium content (Iqbl, 1976; Olurin et l, 1972; Cmpbell-Flck et l, 2000) nd hs been shown to hve firly low rehydrtion index. The question of whether the ddition of sodium to the nturl young coconut wter to mke it better rehydrtion drink hs not been studied. Coconut wter contins ll the mjor electrolytes but hs high potssium content. The sodium content of coconut wter is bout 5-10 mmol.l -1, which is lower thn most sports drinks (Iqbl, 1976; Adm nd Brtt, 1992; St et l, 2002). The purpose of this study ws to investigte the effectiveness of young coconut wter with dded sodium s rehydrtion drink fter exercise-induced dehydrtion for whole body rehydrtion. The effectiveness of sodiumenriched fresh coconut wter ws compred with tht of sports drink, plin fresh coconut wter nd plin wter. MATERIALS AND METHODS Subjects Ten helthy physiclly ctive mle subjects prticipted in this study. Their physicl chrcteristics (men± SEM) were: ge 20.7±0.9 yers, body weight (BW) 60.2±2.6 kg; height 169±1.6 cm, nd mximl oxygen uptke (VO 2mx ) 59.9±1.0 ml.kg -1.min -1. Before prticipting in the experimentl trils, the nture nd risks of the experimentl proce- 770 Vol 38 No. 4 July 2007

3 dures were explined nd written informed consent ws obtined. The study ws pproved by the Universiti Sins Mlysi Ethics Committee. Experimentl procedures The study hd rndomized crossover counterblnce design. The subjects prticipted in four experimentl trils, t lest 2 weeks prt. Initil procedure On the preliminry test, ech subject performed continuous incrementl exercise test on motorized tredmill (Quinton 18-60, USA) until volitionl exhustion to determine VO 2mx (Tylor et l, 1955). Experimentl design The subjects rrived t the lbortory t 7:00 AM nd consumed stndrdized brekfst nd drnk 500 ml of wter before ech exercise tril to ensure norml hydrtion sttus (ACSM, 1996). An hour lter, subjects then voided their bldder s completely s possible nd nude BW ws then mesured on precision scle (Tnit, TBF-410, Jpn, weighing ccurcy of ±10g). Therefter, teflon venous ctheter ws inserted into forerm vein, fitted with three-wy stopcock for repeted blood smpling. This ctheter remined in plce for the reminder of the study. An initil blood smple ws obtined, which represented the euhydrted stte. At 9:00 AM the subjects rn on tredmill (Quinton 18-60, USA) t pre-determined intensity of 65% VO 2mx for 90 minutes in n environmentl chmber (32± 0.1ºC, rh 53±0.2%) to dehydrte by ~3% body weight. Immeditely fter completing the dehydrtion exercise, second blood smple ws obtined while the subject remined on the tredmill. Subjects were then llowed 10 minutes to move nd cool down nd then st in thermoneutrl room (23.2±0.3ºC, rh 70±0.4%) which ws then followed by the determintion of the second nude body weight fter the subjects hd completely dried their swet. Thirty minutes fter exercise nd fter twenty minutes of sitting, third blood smple ws obtined which represented the dehydrted stte. A second urine smple ws then collected followed by the determintion of the third nude body weight, which represented the dehydrtion level. Immeditely fterwrds, subjects consumed one rehydrtion beverge. The subjects drnk the equivlent of 50% of BW loss, which signled the beginning of the 2-hour rehydrtion period. Thirty minutes lter, the subjects drnk 40% of BW loss, nd the remining 30% of the rehydrtion beverge necessry to replce 120% of BW loss ws ingested t 60 minutes, similr to the rte of consumption s described previously (Kovcs et l, 2002). The prescribed volume of drink ws lwys ingested within the first 5 minutes of the ingestion period. Blood nd urine smples were collected t 30-minute intervls during the 2-hours rehydrtion period. After ech fluid ingestion nd t 90 nd 120 minutes the subjects were shown fluid senstion scle (scle 1 to 5), which ws dpted from Perym nd Pilgrim (1957) to determine their thirst sttus, sweetness of the drink, feeling of nuse, their sense of stomch fullness nd stomch upset. At the end of the 2-hour rehydrtion period, finl nude body weight ws obtined fter completely emptying the bldder (Fig 1). Beverges Beverges used in this study were fresh young coconut wter (CW), sodium-enriched fresh young coconut wter (SCW), sports drink (SD) (Isomx, Ace Cnning Corp Sdn Bhd, Mlysi) nd plin wter (PW). The compositions of the beverges used re listed in Tble 1. Fresh young coconut wter ws obtined from Green Mlyn Tll Species. An verge of four young coconuts ws used from the sme bunch to obtin 3,000 ml of fresh coconut wter for ech tril, which were thoroughly mixed. To prepre the sodium- Vol 38 No. 4 July

4 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Time nude body weight mesured before exercise, fter exercise, 30-minute post-exercise (dehydrtion level), nd 120-minute post-exercise Resting (temperture: 25ºC, 60% rh) < Exercise <-Rec-> < Rehvdrtion period Running for 90 minutes t Recovery nd rehydrtion period 60% VO 2mx 22ºC, 60% rh temperture: 32ºC, thermoneutrl environment 70% rh < < Blood smple collection Before exercise, end of exercise nd recovery, nd during rehydrtion period t 30, 60, 90 nd 120 minutes Bseline HR Every 10 minutes:hr, rectl nd skin temperture, environmentl temperture Environmentl temperture nd fluid senstion Urine collection Urine collection t 0 minute (dehydrtion level), nd 30, 60, 90, 120 minutes of the rehydrtion period Fluid ingestion (every 30 minutes): 30-minute post-exercise (50% of fluid lost) 60-minute post-exercise (40% of fluid lost) 90-minute post-exercise (30% of fluid lost) 4 experimentl trils were seprted by intervls of two weeks. First tril either wter, crbohydrte-electrolyte beverge, fresh CW or sodium-enriched fresh CW. Order of test condition ws crossover rndomized counterblnce method. Forty-eight hours before tril no strenuous exercise, dietry intke nd physicl ctivity for 48 hours before first experiment tril recorded, subjects dietry intke nd physicl ctivity were then replicted for ech of the subsequent experimentl rms of the tril. Fig 1 Reserch protocol for dehydrtion nd rehydrtion rms of the tril. enriched fresh young coconut wter, the 3,000 ml from the four coconuts fruits ws first mesured for its sodium content using flme photometer (Corning 450, USA). After sodium content determintion, sodium chloride ws dded to increse the sodium content of the coconut wter to level equivlent to pproximtely 20 mmol.l -1, which ws similr to tht found in the sports drink. For the sports drink, the cns were opened nd poured into continer to degs the drinks for two to three hours before consumption. This ws to ensure tht the subjects did not suffer from stomch discomfort s result of the gs (Ryn et 772 Vol 38 No. 4 July 2007

5 Tble 1 Certin chrcteristics of rehydrtion solutions studied. Dt presented s men±sem. Constituent PW SD CW SCW Glucose (mmol.l -1 ) ±19.5,b ± ± 3.6 N + (mmol.l -1 ) ± ±0.1 b 20.1 ±0.2 K + (mmol.l -1 ) ±0.1,b 50.7 ±1.6 c 51.9 ±0.6 c Cl - (mmol.l -1 ) ±0.1,b 34.9 ±0.6 c 44.0 ±1.4 c Osmollity (mosm.kg -1 ) ±1.2,b ±7.7 c ±12.8 c ph 7.3± ±0.0,b 4.6 ±0.1 c 4.7 ±0.1 c Specific grvity PW = Plin wter; SD = Sports drink; CW = Young fresh coconut wter. SCW = Sodium-enriched young fresh coconut wter. significntly different from young fresh coconut wter t p<0.01. b significntly different from sodium-enriched young fresh coconut wter t p<0.01 c significntly different from sports drink t p<0.01. l, 1991; Psse et l, 1997). All the beverges were kept cool in refrigertor t 7ºC before consumption. Mesurement nd nlysis of blood, urine nd composition of nutrients in beverges From 3-ml blood smple, 1 ml ws trnsferred immeditely into n EDTA tube for mesurement of hemtocrit nd hemoglobin to clculte chnges in plsm volume (Dill nd Costill, 1974). Hemoglobin (Hb) ws nlyzed by the cynmethemoglobin method (Drbkins regent) nd hemtocrit by microcentrifugtion (Hettich-Hemtokrit 20, Germny). Another 1 ml of blood ws trnsferred into tube contining sodium fluoride (NFl) nd the blnce of 1 ml ws trnsferred into plin tube. Plsm nd serum were seprted by bench-top centrifugtion (Hettich-Rotin 46 RS, Germny) t 10,000 rpm for 10 minutes nd were then stored t -20ºC for lter nlysis. Glucose ws nlyzed using glucose kit enzymtic clorimetric method (Rndox- Germny). Serum of blood smples nd smples of beverges tken ech time before ech tril nd urine were nlyzed for N + nd K + using flme photometer (Corning, 450. USA). The chloride (Cl - ) level nd osmollity of the serum nd the beverges were mesured using n ion selective electrode nlyser (Hitchi, 912 Rndom Access Chemistry Anlyzer-Jpn) nd freezing depression (Osmomt 030, Gonotec, Germny), respectively. Cumultive urine output The totl urine collected t the selected time intervls ws recorded nd ccumulted during the 2-hour rehydrtion period, which did not include before nd fter exercise urine smples (Mughn et l, 1994). Fluid blnce, percent body weight loss nd rehydrtion level The net fluid blnce ws clculted bsed on body mss loss during exercise-induced dehydrtion, totl volume of fluid ingested nd the cumultive urine output. The percent body weight loss through exercise ws clculted from the differences in the nude body weights before nd fter exerciseinduced dehydrtion divided by nude body weight before exercise multiplied by 100, on the ssumption tht one liter of fluid is equivlent to one kilogrm of body weight. The percent body weight loss tht ws regined ws used s n index for whole body rehydrtion (percent rehydrtion). The percent rehydrtion Vol 38 No. 4 July

6 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH represented the mount of ingested fluid tht ws retined in the body t the end of the two hour rehydrtion protocol (Gonzlez-Alonzo et l, 1992). % Rehydrtion = [BW lost during exercise - (BW euh - Bw reh) (kg)] x 100 Fluid intke (kg) BW euh represented the nude body weight in the euhydrted condition (before exercise) nd BW reh represented the nude body weight t the end of the 2-hour rehydrtion period. The rehydrtion index (RI), ws clculted to provide n indiction of how much of wht ws ingested ctully ws used for body weight restortion (Mitchell et l, 1994). RI = [vol dmin (ml) / wt gin (g)] / [% rehydrtion/100] Sttisticl nlysis All dt were nlyzed using two-wy nlysis of vrince (ANOVA) for repeted mesurement. The significnt differences between the four trils t difference times were determined with the Tukey minimum significnt difference (MSD) test. The differences were considered significnt t p<0.05. All vlues re reported s mens±stndrd error of mesurement (SEM) for the 10 subjects. The Sttisticl Pckge for Socil Science (SPSS) progrm ws used for sttisticl nlysis. RESULTS Body weight chnges, fluid intke, percent rehydrtion nd rehydrtion index On verge, the subjects lost 3.08±0.04% of their euhydrted body weight fter exerciseinduced dehydrtion in the het. The totl volume of fluid consumed during the 2-hour rehydrtion period ws 2,196±269 ml, 2,196±116 ml, 2,304±150 ml nd 2,196±142 ml for the PW, SD, CW nd SCW rms, respectively, with no significnt differences between the rms of the tril. At the end of the 2-hour rehydrtion period, the subjects were still somewht dehydrted in ll the trils (rnge of to kg below the euhydrted body weight). Hypohydrtion ws significntly greter (p<0.05) with PW compred to the other trils. Incomplete rehydrtion resulted from fluid loss during the rehydrtion period in urine, swet nd respirtion. The percent rehydrtion t the end of the 2-hour rehydrtion period ws significntly higher with the SD (p<0.01), SCW (p<0.01) nd CW (p<0.05) compred to PW (Fig 2). The rehydrtion indexes (RI) were 2.50±0.15, 1.80±0.09, 2.00±0.10 nd 1.75±0.07 for the PW, SD, CW nd SCW rms of the tril, respectively. The RI of 1.75±0.07 for SCW ws similr to the SD rm (1.80 ± 0.09) but lower thn the CW rm (2.00±0.10). The RI for PW ws significntly higher (p<0.01) compred to the other trils. Chnges in plsm volume The chnges in plsm volume during the four trils re shown in Fig 3. At the end of rehydrtion period, the plsm volume with CW, SCW nd SD were similr to the euhydrted plsm volume levels. The plsm volume with the PW ws -3.2±0.5%, lower (p<0.01) thn euhydrted plsm volume t the end of the rehydrtion period which ws significntly different (p<0.05) from the SD nd SCW trils. Urine volume nd osmollity The cumultive urine volume t the end of the 2-hour rehydrtion period ws significntly lower (p<0.05) fter ingestion of SD (416.2±57.1 ml) nd SCW (440.4 ± 35.2 ml) compred to PW (590.7±48.40 ml) but it ws not significnt different from the CW (513.8±50.7 ml) (Fig 4). The urine osmollity t the end of exercise-induced dehydrtion ws similr in ll the rms (Fig 5). During the first 30 minutes of the rehydrtion period the urine osmollity ws significntly higher (p<0.01) for ll the trils fter which the urine osmollity begn to decrese. At the end of 774 Vol 38 No. 4 July 2007

7 Plsm volume chnges (%) Fluid volume (kg) ± 1.8% 68.1± 1.6% b PW SD CW SCW Beverge Totl volume retined Totl urine produce Other fluid nd crbon losses 65.1± 1.7% 69.4± 1.4% b significntly different from PW (p<0.05) b significntly different from PW (p<0.01). Fig 2 Fte of ingested volume when compring PW, SD, CW nd SCW. The height of the brs represents the totl mount of fluid ingested (kg). The stcked brs represent the fte of the ingested volume: the ingested fluid ws either retined in the body or lost in the form of urine, sweting, or respirtion Euhydrtion stte PW SD CW SCW Exercise Rest Rehydrtion period significntly different from plsm volume in the euhydrted stte t p<0.01. b significntly different from PW t p<0.05. Fig 3 The chnge in plsm volume fter exercise-induced dehydrtion nd during the 2-hour rehydrtion period. All vlues re expressed s percent chnge from the resting, euhydrted stte. the 2-hour rehydrtion period, the urine osmollity of the PW rm ws significntly lower (p<0.05) compred to SD nd SCW. b Cumultive urine volume (ml) Euhydrtion stte UPW USD UCW USCW Exercise Rest Rehydrtion period significntly lower thn PW t p<0.05 Fig 4 Cumultive urine volume over time. Smples obtined pre-exercise nd fter exercise-induced dehydrtion were not included in the clcultion of cumultive urine volume. Net fluid blnce The net fluid blnce ws negtive t the end of exercise-induced dehydrtion with no significnt differences between trils (Fig 6). The net fluid blnce ws positive with the SD (108.5±41.89 ml) nd SCW (66.1±32.86 ml) rms t 90 minutes of rehydrtion but becme negtive t the end of the rehydrtion period, with no significnt differences between trils. Serum sodium (N + ) potssium (K + ) nd chloride (Cl - ) concentrtions Serum N + nd K + levels were significntly higher fter exercise-induced dehydrtion in ll trils when compred to the pre-exercise euhydrted stte. During the rehydrtion period, the sodium returned to the euhydrted levels in ll trils. However, the sodium ws significntly lower in the PW rm compred to the other three rms (Fig 7). There were no significnt differences in the K + levels between the CW nd SCW t ny time, but the K + levels were significntly higher (p<0.01) thn the PW nd SD rms by 60 minutes during the rehydrtion period (Fig 7). Serum chloride (Cl - ) concentrtions were significntly higher (p<0.05) with CW nd SCW compred to SD Vol 38 No. 4 July

8 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Urine osmollity (mosm.kg -1 ) Net fluid blnce (g) 1, Post exercise PW SD CW SCW b 200 b Exercise Rest Rehydrtion period 0 Euhydrtion stte significntly different from euhydrtion stte t p<0.01. b significntly different from PW t p<0.05. Fig 5 Urine osmollity response fter exercise-induced dehydrtion nd during 2-hour rehydrtion period. Rehydrtion period PW SD CW SCW Fig 6 Net fluid blnce during the 2-hour rehydrtion period. volumes ingested were 50, 40, nd 30% of 120% fluid loss during exercise-induced dehydrtion t 0, 30 nd 60 minutes of the rehydrtion period, respectively. Zero net fluid blnce is stte of euhydrtion. Serum N + (mmol.l -1) Serum K + (mmol.l -1) Serum Cl - (mmol.l -1 ) Euhydrtion stte NPW NCW e NSD NSCW ^ ^ ^ < Exercise > Rest < Rehydrtion period > Euhydrtion stte e b ^ ^ ^ < Exercise > Rest < Rehydrtion period > ^ ^ ^ < Exercise > Rest < Rehydrtion period > Euhydrtion stte e e d significntly higher thn PW t p<0.05 b significntly higher thn PW t p<0.01 c significntly higher thn SD t p<0.05 d significntly higher thn SD t p<0.01 e significntly different from the euhydrtion stte t p<0.05 Fig 7 Serum N +, K + nd Cl - responses fter exercised-induced dehydrtion nd during the 2- hour rehydrtion period. b c,c,c nd PW t the end of the 90-minute exerciseinduced dehydrtion (Fig 7). Serum osmollity Serum osmollity ws significntly higher (p<0.01) t the end of the 90-minute exercise- induced dehydrtion period in ll trils compred to the pre-exercise euhydrted levels. At the end of the 2-hour rehydrtion period serum osmollity returned to level tht ws not significntly different from the euhydrted 776 Vol 38 No. 4 July 2007

9 vlues in ll rms except for PW. Serum osmollity in the PW rm ws significntly lower (p<0.05) thn the euhydrted stte t 90 nd 120 minutes of the rehydrtion period which were lso significntly lower (p<0.05) thn the other three rms (Fig 8). Plsm glucose concentrtion Plsm glucose concentrtions were similr in ll four trils before nd fter the 90- minute exercise-induced dehydrtion period (Fig 9). As expected, the ingestion of the crbohydrte contining beverges (SD, CW nd SCW) resulted in significntly higher plsm glucose levels during the rehydrtion period compred to ingestion of PW. Fluid senstion scle Dt from the fluid senstion scle re presented in Tble 2. There were no significnt differences in thirst senstion mong the rms of the study t ny time during the 2-hour rehydrtion period. The CW, SD nd SCW were significntly sweeter thn PW t ll time points nd there were no significnt differences in sweetness mong SD, CW nd SCW. The senstion of nuse ws similr for ll beverges but ws significntly lower for SCW t 30 nd 60 minutes during the rehydrtion period. Fullness ws significntly less (p<0.05) t 30 nd 60 minutes for SCW compred to PW nd SD. Senstion of stomch upset ws generlly lower with SCW nd CW compred to PW nd SD t ech time point with significntly lower senstion t 30, 60 nd 90 minutes. DISCUSSION The min purpose of this investigtion ws to compre the effectiveness of SCW nd SD with tht of young fresh coconut wter (CW) nd plin wter (PW) on whole body rehydrtion nd plsm volume restortion during 2-hour rehydrtion period following exercise-induced dehydrtion. The dt from this investigtion suggests: (1) sodium-enriched young fresh coconut wter (SCW) ws s ef- Serum osmollity (mosm.kg -1 ) Plsm glucose (g.l -1 ) Euhydrtion stte PW SD CW b SCW c c c c c c Exercise Rest Rehydrtion period significntly different from euhydrtion stte t p<0.05 b significntly different from euhydrtion stte t p<0.01 c significntly different from PW t p<0.05 Fig 8 Serum osmollity responses fter 90 minutes of exercise-induced dehydrtion nd during the 2-hour rehydrtion period Euhydrtion stte PW SD CW SCW Exercise Rest,b Rehydrtion period significntly different from PW t p<0.01. b significntly different from euhydrtion stte t p<0.01 Fig 9 Plsm glucose responses fter 90-minute exercise-induced dehydrtion nd during the 2-hour rehydrtion period. fective s the sports drink (SD) for fluid replcement nd recovery following dehydrtion nd (2) rehydrtion ws similr when CW nd SD solutions were ingested. To our knowledge, the study of St et l (2002) is the only vilble study with regrd Vol 38 No. 4 July

10 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Tble 2 Fluid senstion scle for thirst, sweetness, nuse, fullness nd stomch upset (men±sem). Thirst (1=not thirsty; 5=extremely thirsty) PW 1.5± ± ± ± ±0.0 SD 1.5± ± ± ± ±0.1 CW 2.0± ± ± ± ±0.1 SCW 1.7± ± ± ± ±0.1 Sweetness (1=not sweet; 5=extremely sweet) PW 1.0± ± ± SD 2.5± ± ± CW 2.9± ± ± SCW 2.5± ± ± Nuse (1=no nuse; 5=extremely nuse) PW 1.5± ± ± ± ±0.2 SD 1.6± ± ± ± ±0.3 CW 1.4± ± ± ± ±0.2 SCW 1.4± ± ± ± ±0.0 Fullness (1=no fullness; 5=extreme fullness) PW 2.0± ± ± ± ±0.1 SD 1.7± ± ± ± ±0.3 CW 1.5± ± ± ± ±0.3 SCW 1.4± ±0.1,b 1.2±0.1,b 1.3± ±0.1 Stomch upset (1=not upset; 5=extremely upset) PW 2.0± ± ± ± ±0.2 SD 1.5± ± ± ± ±0.2 CW 1.5± ± ± ±0.3 SCW 1.2± ±0.1,b 1.1±0.1,b 1.0± ±0.0 significntly different from PW t p<0.05 b significntly different from SD t p<0.05 Time (minutes) of the 2-hour rehydrtion period Tble 3 Composition of coconut wter from different studies. Study Specific grvity ph N + (mmol.l -1 ) K + (mmol.l -1 ) Cl - (mmol.l -1 ) Glucose (g. l -1 ) Prder et l, Eisemn, Rjsuriy et l, DeSilv et l, Olurin et l, Iqbl, Kuberski, Msengi et l, Cmpbell-Flck et l, St et l, Current study Vol 38 No. 4 July 2007

11 to rehydrtion fter exercise-induced dehydrtion using coconut wter s rehydrtion drink. In tht study they found the percent rehydrtion fter exercise-induced dehydrtion ws better with sports drink compred to coconut wter perhps due to the lower sodium content in the coconut wter. In this study, sodium ws dded to coconut wter to rise its concentrtion to 20 mmol.l -1 (SCW) which is equivlent to tht of most sports drinks, then we investigted its effectiveness s rehydrtion drink. In this study, fter drinking volume equl to 120% of the body fluid loss during exercise, we observed tht SCW nd SD showed similr results in percent rehydrtion nd rehydrtion index which were different thn CW nd PW. CW lso gve better rehydrtion (Fig 2) thn PW (p<0.05). Previous studies hve shown percent rehydrtion rnges between 50 nd 80% during rehydrtion period of 2-3 hours using vriety of rehydrtion regimens (Costill nd Sprks, 1973; Gonzlez-Alonzo et l, 1992; Lmberts et l, 1992; Murry, 1998; Nose et l, 1988; Ry et l, 1998; St et l, 2002; Singh et l, 2002) or d libitum rehydrtion protocol (Nose et l, 1988b). From these studies, Costil nd Sprks (1973), Nielsen et l (1986), Ry et l (1998) nd St et l (2002) did not find ny significnt differences in the percent rehydrtion mong the rehydrtion solutions used, however both Gonzlez-Alonso et l (1992) nd Singh et l (2002) found significnt differences in the percent rehydrtion of crbohydrte-electrolyte solution when compred with diet col, plcebo or wter. The 68% nd 69% rehydrtion rtes with SD nd SCW during the 2-hour rehydrtion period in our study were similr to other studies (Gonzlez-Alonzo et l, 1992; Singh et l, 2002). A vriety of rehydrtion protocols hve been reported in the literture over the pst severl yers (Costill nd Sprks, 1973; Gonzlez-Alonzo et l, 1992; Lmberts et l, 1992; Mughn et l, 1994; Mitchell et l, 1994; Ry et l, 1998; St et l, 2002), mny of which hve been designed to investigte the influence of electrolyte content nd fluid volume on rpid rehydrtion. Conflicting findings regrding the concentrtion of N + in the beverge nd volume necessry to produce optiml rehydrtion hve been reported. Vritions in the rehydrtion protocols employed my prtilly explin these discrepncies (Costill nd Sprks 1973; Gonzlez-Alonzoet l, 1992; Lmberts et l, 1992; Mitchell et l, 2000; Nielsen et l, 1986; Nose et l, 1988b; St et l, 2002; Singh et l, 2002). Although mny studies hve employed seril feedings, the protocols typiclly employed by Gonzles- Alonso et l (1992), Nielsen et l (1986), Ry et l (1998), St et l (2002) nd Singh et l (2002) involved the ingestion of lrge volumes ( % of fluid losses) nd monitoring over 2-hour rehydrtion period. In the present study, the volume of fluid consumed over the 2-hour period ws given in series of feedings every 30 minutes. This protocol closely resembles ingestion ptterns tht might be used in ctul prctice, s extreme stomch fullness could be voided. On the other hnd, studies by Mughn nd Leiper (1995), Mughn et l (1994) nd Kovcs et l (2002) followed the rehydrtion process for 5-6 hours, which provides more complete picture of the effects of the fluid consumed on kidney function. Studies by Mitchell et l (1994) nd Mughn et l (1997) hve shown tht, to mximize rehydrtion, drink volume greter thn tht of the body mss lost fter exercise should be consumed. In ddition, the solution must contin certin mount of N + or other ction sufficient to prevent significnt urine production. When N + levels in the rehydrtion drinks re reltively low, even lrge volumes of fluid consumed do not pper to be dequte to produce rpid rehydrtion (Shirreffs et l, 1996). With the ingestion of Vol 38 No. 4 July

12 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH fluid with 14 mmol.l -1 N + (volume equivlent to 150% of fluid loss), Mitchell et l (1994), chieved only 73% rehydrtion fter 3 hours of rehydrtion. Mughn nd Leiper (1995) showed 5.5-hours fter ingesting 150% of fluid lost with N + level of 26 mmol.l -1, subjects only chieved 80% rehydrtion. Even with ingesting volumes of 150 nd 200% of the loss, Shirreffs et l (1996) reported tht full fluid blnce ws not chieved fter 6 hours with 23 mmol.l -1 N + solution. These findings suggest tht optiml N + concentrtion is bove 25 mmol.l -1. In the present investigtion, incresing N + concentrtion in CW from 9 to 20 mmol.l -1 to become sodium-enriched young coconut wter (SCW) improved rehydrtion by 4% (65 to 69%), suggesting tht incresing N + concentrtion levels to tht present in sports drinks cn improve the percent rehydrtion with CW. Percent rehydrtion hs been used s useful indictor to mesure the effectiveness of prticulr rehydrtion drink in prticulr protocol. However, due to the vritions in the degree of dehydrtion, volume ingested, durtion of rehydrtion period nd composition, it is difficult to mke meningful comprison between vrious protocols. Mitchell et l (1994) used the term Rehydrtion Index (RI) to rrive t some useful conclusions nd suggested tht vlue of 1.0 is optimum for rehydrtion fluid nd tht nything greter thn 1.0 indictes less effective use of n ingested fluid. The RI for PW in our study is similr to tht reported in other studies where volume equivlent to % fluid loss during exercise ws consumed (Costill nd Sprks, 1973; Nose et l, 1988b; Gonzlez-Alonzo et l, 1992). However, our RI result for PW ws higher those tht reported by St et l (2002) lthough similr protocol ws used. This difference my be due to the percentge of dehydrtion obtined fter exercise-induced dehydrtion. The presence of sodium in the rehydrtion solution my lso improve the RI. RI rnges of 1.80 to 2.60 hve been reported with sodium levels of 20 mmol.l -1, typicl of most sports drinks consumed (Costill nd Sprks, 1973; Gonzlez-Alonzo et l, 1992; Singh et l, 2002). The RI of 1.80 obtined with sports drink contining 20 mmol.l -1 in our study is similr to the expected rnge. However, the RI for SCW in our study of 1.75 ws better thn tht reported in studies using sports drinks. This my be due to the higher potssium content in SCW compred to the sports drink. The higher potssium content of SCW my be due to intrcellulr rehydrtion tht produces better RI. The volume of urine produced is lso relted to the ingested volume; the smllest volume of urine produced ws when 50% of the fluid loss ws consumed nd the gretest volume of urine produced ws when 200% of the fluid loss ws consumed (Shirreffs et l, 1996). Subjects could not return to euhydrtion stte when they consumed volume equivlent to, or less thn, their swet losses, irrespective of the drink composition (Shirreffs et l, 1996; Wemple et l, 1997). In this study, the rehydrtion volume equivlent of 120% of swet loss my still not be sufficient to restore lost fluid s the net fluid blnce ws only slightly positive for SD nd SCW rms t the end of 90 minutes (Fig 6). However, ll the ingested fluid rms of the tril were in negtive blnce t the end of the 2-hour rehydrtion period with no significnt differences between trils. This incomplete rehydrtion during the rehydrtion period my hve resulted from fluid losses in the form of urine, swet nd respirtion (Fig 2). The mjor trget for fluid replcement during exercise nd recovery is to mintin plsm volume, so tht circultion nd sweting cn progress t optiml levels (Leiper nd Mughn, 1986). Rehydrtion evluted from body weight nd plsm volume restortions in this study were similr but incomplete in the 780 Vol 38 No. 4 July 2007

13 four rms of the tril. The percent chnge in plsm volume s result of exercise-induced dehydrtion nd the 2-hour rehydrtion period were similr nd no differences were observed mong the vrious rms up to 90 minutes in the rehydrtion period (Fig 3). However, due to the high volume of urine production throughout the rehydrtion period with PW (Fig 4), plsm volume restortion ws significntly lower (p<0.05) t the end of the 2-hour rehydrtion period when compred to the SD nd SCW rms. Plsm volume levels in the CW rm t the end of the 2-hour rehydrtion period were lso lower thn the SD nd SCW rms, but better thn PW. Our dt suggest tht SD nd SCW re better fluid replcement solutions to restore plsm volume fter exercise-induced dehydrtion where the plsm volume restortion ws greter in drinks contining high sodium concentrtions, which is similr to other studies (Nielsen et l, 1986; Mughn et l, 1997, 2000; St et l, 2002; Singh et l, 2002). Previous studies hve suggested tht ingestion of beverges high in potssium concenttion my dely rtes of plsm volume recovery becuse of restortion of the intrcellulr fluid comprtment t the expense of extrcellulr fluid (Nielsen et l, 1986; Ndel et l, 1990; Mughn et l, 1994). However, in this present study, we observed no differences mong the rtes of plsm volume restortion for CW nd SCW, which hd high concentrtions of K + (~51 mmol.l -1 ) compred to SD. This ws similrly seen in study by Ry et l (1998). Despite ingesting volume of fluid equivlent to 120% of tht lost during exercise-induced dehydrtion, the subjects were still not ble to replce the fluid losses tht occurred. Utilizing protocol very similr to the one employed in this study, Lmberts et l (1992) nd Costill nd Sprks (1973) lso reported tht rehydrtion ws incomplete despite the ingestion of quntity of fluid equl to tht lost during dehydrtion. Ry et l (1998) lso showed tht plsm volume ws not restored completely with crbohydrte electrolyte beverge or plin wter fter 2-hour rehydrtion period. Conversely, St et l (2002) showed blood volume ws restored to higher levels thn tht of the euhydrted vlues when they followed protocol similr to this study. This difference my be due to the percent decrese in blood volume which ws only 4% t the end of the dehydrtion tril (St et l, 2002) compred to decrese of 9% in our study. Gonzlez-Alonso et l (1992) lso reported incomplete restortion of blood volume in the wter tril with dehydrtion of 2.6% nd fluid replcement of 100% of weight loss which is similr to our study in the PW rm. The incomplete restortion of plsm volume with PW in our study could be due to number of resons including urine production during the rehydrtion period. In ddition ll the subjects were still somewht dehydrted fter 2 hours of rehydrtion (rnging from 0.20 to 0.60 kg below the euhydrted body weight). Plsm glucose concentrtions before the exercise-induced dehydrtion tril were similr in ll rms nd within norml rnge of 7.39 to 7.55 mmol.l -1 (Fig 9). These vlues were obtined due to the fct tht stndrd brekfst ws given 1 hour before the exercise-induced dehydrtion run nd fter n overnight fst. The primry benefit of giving stndrd brekfst ws the stndrdiztion of the exogenous crbohydrte stores. Significntly higher plsm glucose levels were obtined with crbohydrte contining beverges (SD, CW nd SCW) compred to the ingestion of PW (Fig 9). The rise in glucose concentrtions ws due to the glucose content of the tril drinks (204.1± 19.5, ±3.94, nd ±3.62 mmol.l -1 for SD, CW nd SCW, respectively). This indictes the crbohydrte contining beverges were emptied nd bsorbed well. During the 2-hour rehydrtion period, plsm glucose concen- Vol 38 No. 4 July

14 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH trtion were significntly higher with the SD compred to CW, SCW (p<0.05) nd PW (p<0.01) t certin time periods. However, in the CW nd SCW rms, plsm glucose ws similr t ll time periods. The ingestion of crbohydrtes during rpid rehydrtion is dvntgeous, since the rte of muscle glycogen resynthesis is reportedly 3 times fster if crbohydrtes re ingested immeditely fter exercise s opposed to dely of two hours (Ivy et l, 1988). Ivy et l (1988b) reported ingestion of crbohydrtes t rte of 1.5 g.kg -1 body weight per hour elicited rtes of muscle glycogen resynthesis of 5.8 nd 4.5 mmol.l -1 kg in wet weight of muscle during the first nd second two-hour periods of recovery from exhustive exercise. Thus, fluid replcement nd crbohydrte consumption with 10% crbohydrte solution is of prcticl importnce for the thlete who must trin or compete in the hours or dys following exercise-induced dehydrtion (Lmberts et l, 1992; Burke, 2000). Serum potssium levels fter ingestion of CW nd SCW were significntly higher (p<0.05) thn SD nd PW t 60 minutes nd 120 minutes during the rehydrtion (Fig 8). Both CW nd SCW contined high K + levels (~51 mmol.l -1 ) nd were significntly different (p<0.01) from SD nd PW. The high K + level in young coconut wter (Tble 3) is consistent with those reported previously (Prder et l, 1942; Cmpbell-Fck et l, 2000). The electrolyte composition of coconut wter resembles intrcellulr fluid more closely thn extrcellulr plsm (Goldsmith, 1962; Cmpbell-Fck et l, 2000). Our study showed tht serum K + levels incresed by ~1.6 mmol.l -1 fter ingesting either CW or SCW during the rehydrtion period (Fig 8). This observtion is similr to the study by Olurin et l (1972) who reported rise in serum K + levels by 1.5 meq.l -1 fter infusion of 2,000 to 3,000 ml of coconut fluid over period of 6 to 12 hours. It hs lso been postulted tht the inclusion of K + in drinks consumed fter swet loss my id in rehydrtion by enhncing the retention of wter in the intrcellulr spce (Ndel et l, 1990). In this study, there ws no relible method to distinguish body wter in the intrcellulr from the extrcellulr spce, so the losses from nd replcement of the intrcellulr nd extrcellulr wter re unknown. Our dt showed tht plsm volume restortion (Fig 3) nd percent rehydrtion (Fig 2) were similr between SCW nd SD during the 2-hour rehydrtion period. One reson for these similrities in plsm volume restortion nd percent rehydrtion between the SD nd SCW despite the high K + concentrtion in the SCW (similr sodium) my be due to the short rehydrtion period. As such, within the 2-hour rehydrtion period, there ppers to be no dditive effect of the high K + in SCW. The high concentrtion of K + in the coconut wter together with N + would be expected to restore higher plsm volume if they cted independently on different body fluid comprtments, s shown by Mughn et l (1994). In nother study, Ry et l (1998) showed tht consuming chicken broth with high concentrtions of K + (25.3 mmol.l -1 ) nd N + (109.5 mmol.l -1 ) s one of the rehydrtion beverges, resulted in significntly greter plsm volume restortion thn consuming wter, crbohydrte-electrolyte drink (16.0 mmol.l -1 N +, 3.3 mmol.l -1 K + ) or soup (333.8 mmol.l -1 N +, 13.7 mmol.l -1 K + ). Tht study nd the present study suggest tht consuming high concentrtions of potssium does not impir rehydrtion provided the sodium concentrtion of the beverge is dequte. Previous studies hve shown ingestion of plin wter fter exercise-induced dehydrtion resulted in rpid fll in plsm osmollity nd in plsm sodium concentrtion (Nose et l, 1988; Mughn, 1999), both these effects will stimulte urine output. The significntly lower (p<0.05) urine osmollity during the PW 782 Vol 38 No. 4 July 2007

15 tril is the result of incresed fluid clernce by the kidneys. Costill nd Sprks (1973) showed tht ingestion of glucose-electrolyte solution (22 mmol.l -1 ) fter dehydrtion (4% of body weight losses) resulted in greter restortion of plsm volume thn did plin wter. A higher urine output ws observed in the wter tril which ws similrly seen in this present study. There were no significnt differences in thirst senstion mong the rms of the tril t ny time point during the 2-hour rehydrtion period. CW, SD nd SCW were significntly sweeter tht PW t ll time points nd there were no significnt differences in sweetness mong SD, CW nd SCW. The sweet tste of CW nd SCW lso incresed the pltbility, which ws importnt, especilly when lrge volumes of fluid hve to be consumed or tken d libitum. The senstion of fullness reduced the stimulus to drink in the PW tril, especilly when they hd to ingest the lst 30% of the 120% bolus, during this period. Incidentlly, there ws higher rting for fullness with SD (2.2 ± 0.3) compred to SCW (1.2 ± 0.1) t this time point s well. Throughout this study, the subjects rted SCW s cusing significntly less fullness nd stomch upset compred to the commercil SD. This ws n interesting finding which my estblish the use of SCW s nturl rehydrtion drink fter exercise since the SD ws reported s cusing stomch upset when used in lrge volumes. Stomch upset senstion ws generlly lower with SCW nd CW compred to PW nd SD t ech time point. The subjects t the 60-minute time point during the rehydrtion period, when they hd to ingest the lst 30% of the 120% of weight loss, took longer time to finish drinking PW nd SD. Interestingly, SCW ws rted to cuse less stomch upset, nuse nd fullness compred to CW. Our dt on fluid senstion showed tht SCW is suitble nd hd better rtings by subjects when compred to SD nd PW. In conclusion, the results of the present study indicte tht fluid replcement fter exercise-induced dehydrtion with SCW ws s effective s commercil SD nd ws better thn CW nd PW. The restortion of plsm volume ws similr with SD nd SCW nd ws significntly better compred with PW. The percent rehydrtion nd rehydrtion index of the SCW ws similr to SD but ws significntly better thn PW (p<0.01) but ws not significntly different from CW. SCW ws rted lower in terms of fullness nd stomch upset nd ws better thn SD, CW nd PW, thus mking SCW esier to consume in lrger quntities compred with PW, SD nd CW. It cn be concluded tht SCW my be used for rehydrtion fter exerciseinduced dehydrtion nd its physiologicl effects re s effective s commercil sports drinks vilble on the mrket. ACKNOWLEDGEMENTS The uthors wish to thnk the subjects for their prticiption nd coopertion throughout this study. This study ws supported by reserch grnt from Universiti Sins Mlysi, Mlysi (304/PPSP/ ). REFERENCES Adm W, Brtt DE. Young coconut wter for home rehydrtion in children with mild gstroenteritis. Trop Geogr Med 1992; 44: Americn College of Sports Medicine (ACSM) position sttement exercise nd fluid replcement. Med Sci Sports Exer 1996; 28: i-vii. Burke L. Nutrition for recovery fter competition nd trining. In: Burke L, Dekin V, eds. Clinicl sports nutrition. NSW: Roseville. 2000: Cmpbell-Flck D, Thoms T, Flck TM, Tutuo N, Clem K. The intrvenous use of coconut wter. Am J Emerg Med 2000; 18: Coombes JS, Hmilton KL. The effectiveness of Vol 38 No. 4 July

16 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH commercilly vilble sports drinks. Sports Med 2000; 29: Costill DL. Sweting: its composition nd effects on body fluids. In: Milvy P, ed. The mrthon: Physiologicl, medicl, epidemiologicl nd psychologicl studies. Ann NY Acd Sci 1977: Costill DL, Cote R, Fink W. Muscle wter nd electrolytes following vried levels of dehydrtion in mn. J Appl Physiol 1976; 40: Costill DL, Sprks KE. Rpid fluid replcement following therml dehydrtion. J Appl Physiol 1973; 34: DeSilv CC, Perer PM, Dis AP. Coconut wter. Peditr Int 1959; 9: Dill DB, Costill DL. Clcultion of percentge chnges in volumes of blood, plsm nd red cells in dehydrtion. J Appl Physiol 1974; 37: Eisemn B. Intrvenous infusion of coconut wter. AMA Arch Surg 1954; 68: Gisolfi CV, Summers RW, Schedl HP. Intestinl wter bsorption from select crbohydrte solutions in humn. J Appl Physiol 1992; 3: Goldsmith HS. Coconut wter for intrvenous therpy. Br J Surg 1962; 49: Gonzlez-Alonzo J, Heps CL, Coyle EF. Rehydrtion fter exercise with common beverges nd wter. Int J Sports Med 1992; 13: Hubbrd RW, Szlyk PC, Armstrong LE. Influence of thirst nd fluid pltbility on fluid ingestion during exercise. In: Lmb DR, Gisolfi CV, eds. Perspectives in exercise science nd sports medicine. Vol 3. Fluid homeostsis during exercise. Crmel: Benchmrk Press, 1985: Iqbl QM. Direct infusion of coconut wter. Med J Mlysi 1976; 30: Ivy JL, Ktz AL, Cutler CL, Shermn WM, Coyle EF. Muscle glycogen synthesis fter exercise: effect of time of crbohydrte ingestion. J Appl Physiol 1988; 64: Ivy JL, Lee MC, Brozinick JT, Reed MJ. Muscle glycogen storge fter different mounts of crbohydrte ingestion. J Appl Physiol 1988b; 65: Kovcs MR, Schmhl RM, Senden JMG, Brouns F. Effect of high nd low rtes of fluid intkes on post-exercise rehydrtion. Int J Sport Nutr Exerc Metb 2002; 12: Kuberski T. Coconut wter s rehydrtion fluid. N Z Med J 1979; 90: Lmberts CP, Costill DL, McConell GK, et l. Fluid replcement fter dehydrtion: influence of beverge crbontion nd crbohydrte content. Int J Sports Med 1992; 13: Leiper JB, Mughn RJ. Absorption of wter nd electrolytes from hypotonic, isotonic nd hypertonic solutions. J Physiol (London) 1986; 373: Mughn RJ. Fluid nd electrolyte loss nd replcement in exercise. In: Mughm RJ, ed. Bsic nd pplied sciences for sports medicine. Surrey: Plnt Tree, 1999: Mughn RJ, Leiper JB. Effects of sodium content of ingested fluids on post-exercise rehydrtion in mn. Eur J Appl Physiol 1995; 71: Mughn RJ, Leiper JB, Shireffs SM. Fctor influencing the restortion of fluid nd electrolyte blnce fter exercise in the het. Br J Sports Med 1997; 35: Mughn RJ, Owen JH, Shirreffs SM, Leiper JB. Post-exercise rehydrtion in mn: effects of electrolyte ddition to ingested fluids. Eur J Appl Physiol 1994; 69: Mughn RJ, Shirreffs SM, Leiper JB. Fluids nd electrolytes during exercise. In: Grrett WE, Kirkendll DT, eds. Exercise nd sport science. Phildelphi: Lippincott, Willims nd Wilkins, 2000: Mitchell JB, Grndjen PW, Pizz FX, Strling RD, Holtz RW. The effect of volume ingested on rehydrtion nd gstric emptying following exercise-induced dehydrtion. Med Sci Sports Exerc 1994; 26: Mitchell JB, Philips MD, Mercer SP, Bylies HL, Pizz FX. Post exercise rehydrtion: effect of N + nd volume on restortion of fluid spces nd crdiovsculr function. J Appl Physiol 2000; 89: Msengi AE, Mbise RL, Msuy PM. The biochemis- 784 Vol 38 No. 4 July 2007

17 try of wter from unripe coconuts obtined from two loclities in Tnzni. Est Afr Med J 1985; 62: Murry R. Rehydrtion strtegies blncing substrte, fluid nd electrolyte provision. Int J Sports Med 1998; 2: S Murry R, Brtoli W, Stofn J, Horn M, Eddy D. A comprison of the gstric emptying chrcteristics of selected sports drinks. Int J Sports Nutr 1999; 9: Ndel ER, Mck GW, Nose H. Influence of fluid replcement beverges on body fluid homeostsis during exercise nd recovery. In: Lmb DR, Gisolfi CV, eds. Perspectives in exercise science nd sports medicine. Vol 3. Fluid homeostsis during exercise. Crmel: Benchmrk Press, 1990: Nielsen B, Sjogrd G, Ugelvig J, Knudsen B, Dohlmnn B. Fluid blnce in exercise dehydrtion nds rehydrtion with different glucose-electrolyte drinks. Eur J Appl Physiol 1986; 55: Nose H, Mck GW, Shi X, Ndel ER. Role of osmollity nd plsm volume during rehydrtion in humns. J Appl Physiol 1988; 65: Nose H, Mck GW, Shi X, Ndel ER. Shift in body fluid comprtments fter dehydrtion in humn. J Appl Physiol 1988b; 65: Olurin EO, Durowoju JEO, Bssir O. Intrvenous coconut wter therpy in surgicl prctice. West Afr Med J 1972; 21: Psse D, Horn M, Murry R. The effects of beverge crbontion on sensory responses nd voluntry fluid intke following exercise. Int J Sport Nutr 1997; 7: Perym DR, Pilgrim PJ. Heding scle of mesuring food reference. Food Technol 1957; 9: Prder ES, Fernndez E, Clderin O. Coconut wter, clinicl nd experimentl study. Am J Dis Child 1942; 64: Rjsuriy K, Hmz MHM, Selvrtnm S. The use of young coconut wter for intrvenous therpy. Ceylon Med J 1954; 2: Ry ML, Bryn BW, Ruden TM, Bier SM, Shrp RL, King DS. Effect of sodium in rehydrtion beverge when consumed s fluid or mel. J Appl Physiol 1998; 85: Ryn AJ, Nvrre AE, Gisolfi AV. Consumption of crbonted nd noncrbonted sports drink during prolonged tredmill exercise in the het. Int J Sport Nutr 1991; 1: Rowell LB. Humn circultion. New York: Oxford University Press, St M, Singh R, Sirisinghe RG, Nwwi M. Rehydrtion fter exercise with young coconut wter, crbohydrte electrolyte nd plin wter. J Physiol Anthropol Appl Humn Sci 2002; 21: Shirreffs SM, Tylor AJ, Leiper JB, Mughn RJ. Post-exercise rehydrtion in mn: Effects of volume consumed nd drink sodium content. Med Sci Sports Exerc 1996; 28: Singh R, Brouns F, Kovcs E. The effect of rehydrtion on cycling performnce fter exercise-induced dehydrtion. Southest Asin J Trop Med Public Helth 2002; 33: Tylor HL, Burskirk E, Henschel A. Mximl oxygen intke s n objective mesure of crdio-respirtory performnce. J Appl Physiol 1955; 8: Wemple RD, Morocco TS, Mck GS. Influence of sodium replcement on fluid ingestion following exercise induced dehydrtion. Int J Sport Nutr 1997; 7: Vol 38 No. 4 July