Eur J App| Physiol (1986) 55:524--529

European Journal of

Applied Physiology and Occupational Physiology �9 Springer-Varlag 1986

The effect of sodium bicarbonate and sodium citrate ingestion on anaerobic power during intermittent exercise

M. Parry-Billings and D. P. M. MacLaren

Department of Sport and Recreation Studies, Liverpool Polytechnic, Byrom Street Liverpool L3 3AF, Great Britain

Summary. The effect of sodium bicarbonate and sodium citrate ingestion on cycling performance in three 30 s Wingate Anaerobic Tests separated by 6 min recovery periods has been studied using 6 male subjects. Subjects ingested either sodium bi- carbonate (B), sodium bicarbonate plus sodium citrate (BC), sodium citrate (C) or sodium chlo- ride (P) 2.5h prior to exercise in a dose of 0.3 g kg -1 body weight. Pre-exercise blood pH was 7.44+0.06, 7.42_+0.05, 7.41+0.05 and 7.38+0.04 in the C, BC, B and P conditions re- spectively. Mean and peak power output were sig- nificantly reduced by successive Wingate tests but not significantly affected by the treatments. Per- formance in the second and third tests was high- est following C, BC and B ingestion. The total work done in the 3 tests was 103%, 102% and 101% of that achieved in the P condition after C, BC and B ingestion respectively. The increased al- kali reserve recorded subsequent to bicarbonate and citrate treatment reduced mean post-exercise acidosis, although pH was significantly higher only in the C condition (p <0.05) compared to P after each exercise bout. No significant differ- ences in plasma lactate concentration were re- corded at any time. Citrate ingestion appears to be most effective in elevating blood pH and [HCO~-], and in enhancing performance in short- term intermittent exercise. This study demon- strates that alkali ingestion results in significant shifts in the acid-base balance of the blood and has a small, but non-significant, effect on anae- robic power and capacity as measured in a series of 3 Wingate Anaerobic Tests.

Offprint requests to: D. P. M. MacLaren at the above address

Key words: Bicarbonate -- Citrate -- Intermittent exercise -- Wingate Anaerobic Test -- Anaerobic power and capacity

Introduction

In short-term, all-out exercise anaerobic glycoly- sis is the most important energy system, produc- ing the largest proportion of ATP. This depend- ance on a high rate of glycolysis results in a large lactic acid production and a concomitant fall in blood and muscle pH. An increase in hydrogen ion (H +) concentration has been suggested as the major cause of fatigue in this type of exercise, H + ions having their effect mainly through the inhibi- tion of key glycolytic enzymes particularly phos- phofructokinase (Danforth 1965; Sutton et al. 1981). In addition, a low pH adversely affects the contractile mechanism. Calcium ion binding to troponin and release from the sarcoplasmic reti- culum is inhibited at reduced pH, resulting in im- paired tension (Donaldson and Hermansen 1978; Fabiato and Fabiato 1978). Thus much evidence supports pH as a critical limiting factor.

The action of the body's buffer systems is to combat any shifts in acid-base balance. The bicar- bonate ion (HCO~-) is the major blood buffer and so the administration of sodium bicarbonate should enhance the body's capacity for prevent- ing a decline in pH, hence delaying the onset of fatigue. Recently, "bicarbonate loading" has re- ceived considerable attention. Previous studies using sodium bicarbonate administration have presented variable results. Several studies claimed that a prior alkalotic state had no effect on per- formance (Johnson and Black 1953; Margaria et

M. Parry-Billings and D. P. M. MacLaren: Effect of bicarbonate and citrate ingestion on anaerobic power 525

al. 1971; P o u l a s et al. 1974; K i n d e r m a n n et al .

1977). I n c o n t r a s t m a n y w o r k e r s h a v e r e p o r t e d the b e n e f i c i a l e f f ec t s o f i n d u c e d a l k a l o s i s ( J o n e s et al. 1977; S u t t o n et al. 1981; M a c L a r e n a n d M o r g a n 1985). T h e s e s i g n i f i c a n t i m p r o v e m e n t s h a v e b e e n s h o w n in e x e r c i s e o f 2 - - 5 r a in d u r a t i o n . W i t h an e x e r c i s e p e r i o d o f 30 s o f i n t e n s e w o r k o n l y m i n o r i n c r e a s e s in t o t a l w o r k h a v e b e e n a c h i e v e d ( I n b a r et al. 1983; M c C a r t n e y et al. 1983). T h e r e f o r e it c a n b e a s s u m e d b i c a r b o n a t e l o a d i n g e n h a n c e s a n a e r o b i c " c a p a c i t y " , w h i l s t i ts e f f ec t o n sho r t - t e r m a n a e r o b i c " p o w e r " r e m a i n s q u e s t i o n a b l e . I n t e r m i t t e n t w o r k has b e e n s h o w n to i n d u c e a m o r e a c i d i c e n v i r o n m e n t t h a n is a c h i e v e d d u r i n g c o n t i n u o u s w o r k ( H e r m a n s e n a n d O s n e s 1972), t hus p r o v i d i n g a m o r e s eve re t es t to t he p r o c e d u r e o f b i c a r b o n a t e l o a d i n g . C o s t i l l et al. (1984) s h o w e d e n d u r a n c e t i m e in t h e l a s t e x e r c i s e b o u t i n c r e a s e d 42%, w h i l s t W i j n e n et al. (1984) re- p o r t e d o n l y a s m a l l i n c r e a s e a f t e r H C O 3 t r ea t - men t . T h e s e s t u d i e s o n l y c o n s i d e r e d p e r f o r m a n c e in t he l as t " o p e n - e n d e d " e x e r c i s e b o u t .

Th i s s t u d y a i m s to : 1. E x a m i n e the e f fec t s o f b i c a r b o n a t e l o a d i n g

d u r i n g i n t e r m i t t e n t exe rc i se , i ts e f fec t o n the p e r f o r m a n c e in e a c h w o r k p e r i o d a n d o n a c i d - b a s e p a r a m e t e r s d u r i n g e x e r c i s e a n d r e c o v e r y .

2. R e s o l v e t h e a p p a r e n t u n c e r t a i n t y as to w h e t h e r b i c a r b o n a t e l o a d i n g is b e n e f i c i a l to s u p r a m a x i - m a l e x e r c i s e o f s h o r t (30 s) d u r a t i o n .

3. N o t e t he e f fec t s o f s o d i u m c i t r a t e i n g e s t i o n o n t h e s a m e e x e r c i s e p r o t o c o l .

Materials and methods

Six male subjects volunteered to take part in the study. All subjects were active, highly motivated and experienced with the Wingate anaerobic test protocol.

The subjects performed an exercise test after drinking so- lutions of either sodium bicarbonate (B), sodium citrate (C), a sodium bicarbonate plus sodium citrate mixture (BC), or so- dium chloride, the placebo treatment (P) using a blind cross- over procedure. The doses were 0.3 g kg-~ body weight and were ingested in a flavoured soup (Powell and Scholefield Ltd., Liverpool, England, GB) during a 5--10 min period 2.5 h prior to commencing exercise. (A time course study had pre- viously shown blood bicarbonate to be significantly elevated after this time.) The order of testing was randomly deter- mined.

Exercise was performed on a cycle ergometer (Monark 864, Sweden), using a basket arrangement with weights for ap- plying the test load. The saddle height was adjusted so that when the leg was fully extended in the pedal there was flexion of approximately 15 ~ at the knee, and feet were fitted into toe- clips. A standardized warm-up was performed which involved a 3 min ride at a low load, interespersed with three 5 s sprints at the Wingate test load. This was followed by a 6 min rest period before 3 Wingate tests were performed with 6 rain re-

A

0 lO 19o

Fig. 1. Schematic F = Blood samples;

B C D E F

VIM~,(mi.)

illustration of study's protocol. A - n=Inges t ion period; N=Warm-up;

�9 = Wingate Anaerobic Test

covery between each (Fig. 1). In all recovery periods subjects were encouraged to cycle slowly.

The Wingate anaerobic test involved a 30 s all-out sprint, during which time the subjects were encouraged to maintain maximum effort and instructed to avoid pacing. The subjects pedalled against a load suggested by Dotan and Bar-Or (1983) using a rolling start. Pedal revolutions were detected photoop- tically, by a light sensitive diode. Power output was calculated for each second of the test by a computer package (Bayley and .Reilly 1984). The following indices were also calculated: 1. Mean Power, the average power over the 30 s test (W and

Wkg -I) 2. Peak Power, the highest power output during any 5 s period

(W and W kg- 1). Blood samples from fingerpricks were obtained prior to

ingestion, 3 min post warm-up, 3 min after each Wingate test, and also 30 rain after the final Wingate test (Fig. 1).

Two 20 gl samples were taken and mixed directly with cold perchloric acid before being centrifuged and the superna- tant frozen for later analysis for plasma lactic acid. Lactate was determined using an enzymatic assay (Gutmann and Wah- lefield 1974). A single 100 ~tl sample was taken in a heparin- ized capillary tube and analysed immediately for blood pH and carbon dioxide partial pressure (Pco,), using a blood mi- cro-system (BMS 3 Mk 2, Radiometer, Copenhagen) and a di- gital acid-base analyser (PHM 72, Radiometer, Copenhagen). Blood bicarbonate values were determined using the Siggaard- Anderson Alignment Nomogram (Siggaard-Anderson 1971).

The statistical analysis employed for the blood variables involved an analysis of covariance, with mean resting values for each treatment used as the covariate; F ratios were consid- ered significant at the 5% level. In addition pair-wise compari- sons between mean values for the different treatments were carried out using the Tukey Minimum Significant Difference test. Performance data were analysed using a 3-way analysis of variance to determine if differences in performance existed at each exercise period between treatments. The correlation be- tween mean power (watts) and subject body weight was calcu- lated and a 3-way analysis of variance was subsequently car- ried out with tile effect of body weight removed to provide a more sensitive test. The average w, ork done in all 3 exercise periods with each treatment was determined and the differ- ences between means were analysed using paired t tests for related samples. Furthermore, paired t tests were employed on the successive Wingate tests for each treatment to note if there were any changes in mean and peak power output.

Results

A p a t t e r n e m e r g e d w i th r e g a r d to b o t h m e a n p o w e r a n d p e a k p o w e r v a l u e s in so f a r as s ign i f i -

526 M. Parry-Billings and D. P. M. MacLaren: Effect of bicarbonate and citrate ingestion on anaerobic power

Table 1. Mean and peak power output for successive Wingate tests. " denotes significant difference (P< 0.05) from first Wingate test. b denotes significant difference (P<0 .05) from second Wingate test. ~ denotes significant difference (P<0,05) from third Wingate test

Treatment Wingate Mean power (W) Peak power (W) Test

Bicarbonate First 710.9 ( +__ 118.0) a'c 972.1 ( • 245.2) c (B) Second 654.6 (+_ 94.0) a 912,8 ( _ 188.2) c

Third 582.7 ( • 90.3) a 802.1 (+212.1) "'b

Citrate First 703.4 ( • 112.3) b'~ 930.3 ( • 196.3) (C) Second 663.7 ( • 102.7) a'~ 936.5 ( • 189.1)

Third 605.9 ( • 84.8) a'b 852.3 ( • 157.0)

Placebo First 712.3 ( + 118.6) b'c 969.8 (• ~'~ (P) Second 641.4 ( • 102.9) a'c 878.9 ( • 187.0) . . . .

Third 566.2 ( • 88.2) a'b 758.4 ( • 145.6) ~'b

Bicarbonate + Citrate First 714.8 ( • 117.8) a' b 938.5 (• 166.9) ~ (B + C) Second 660.5 ( + 98.5) a'c 891.4 (+_ 163.2)

Third 591.9 ( + 90.5) a'b 772.4 ( _ 160.7) a

Table 2. Analysis of covariance for blood pH and bicarbonate concentrat ion

Variable Time F ratio (d f= 3,14) Level of significance

Blood pH Post warm-up 2.50 NS Post Wingate 1 4.50 p <0.05 Post Wingate 2 7.00 p < 0.01 Post Wingate 3 4.00 p < 0.05 Recovery 1.33 NS

Blood[bicarbonate] Post warm-up 2.95 NS Post Wingate 1 4.17 p < 0.05 Post Wingate 2 2.82 NS Post Wingate 3 5.17 p < 0.05 Recovery 2.07 NS

cant decreases in performance were observed be- tween successive Wingate tests (Table 1), thereby indicating greater fatigue. Statistical analysis re- vealed no significant differences in any of the ex- ercise bouts for the different treatments. When mean power output was correlated to subject body weight, a high correlation was found (r= 0.72). An analysis of variance with the effect of body weight removed however, yielded no sig- nificant differences between the treatments.

The average work achieved in all three exer- cise bouts under each condition was calculated. Total work done was 103%, 102% and 101% of that achieved in the P condition after C, BC and B ingestion respectively. Despite this, pairwise com- parisons of the means for each treatment using t- tests gave no significant results.

Figure 2 illustrates the changes in pH with time. Analysis of covariance revealed no signifi- cant differences in pH post warm-up or after re-

7.5 . 5 , T

7.1-

0 ,9' 1~6 202.5 21~9 2i5.5 242 Time,(men)

Fig. 2. Changes in mean ( • SD) blood pH in the 4 experimen- tal conditions ( x - - = bicarbonate, [] - - = bicarbonate + ci- trate, A . . . . citrate, and [ ] - - =placebo)

M. Parry-Bil l ings a n d D. P. M. M a c L a r e n : Effect o f b i ca rbona te a n d citrate inges t ion on anae rob ic power 527

covery, but did highlight significant differences after each of the three Wingate tests (Table 2). The mean pH values in conditions B, BC and C were higher than those recorded in condition P. Similar findings were obtained for blood HCO~ levels in so far as similar patterns of separation were obtained (Fig. 3), although ANCOVA re- vealed significant differences between conditions B, BC and C with condition P only after the first and the third Wingate tests (P<0.05).

A separation of blood lactate concentrations with the four treatments was observed (Fig. 4), but analysis of covariance demonstrated the differ- ences to be non-significant at all times (P> 0.05).

30-

E E

I: o 20 o

1 i ==

lO

0 0 196 202.5 209 215.5 242

Time,(min~

Fig. 3. C h a n g e s in m e a n ( + SD) b lood b ica rbona te concen t ra - t ion in the 4 epxe r imen ta l condi t ions . ( • [ ] - - = b i c a r b o n a t e + c i t r a t e ; A . . . . . citrate, and [ ] - - = placebo)

161 14

12-

10"

"= 6

4

m 0 . //

0 1w ~ . s 20e 2~5.5 242 TIME, /min)

Fig. 4. C h a n g e s in m e a n ( + SD) b lood lactate concen t ra t ion in the 4 expe r imen t a l condi t ions . ( • - - = b i c a r b o n a t e , [] - - - = b i ca rbona te + ci trate; A . . . . . citrate, and [] - - = p lacebo)

Discussion

The study's main finding is that bicarbonate and citrate ingestion have no significant effect on per- formance during a series of Wingate tests. Nev- ertheless their beneficial effect on both mean and peak power appears to be present, but remains equivocal. The absence of any ergogenic effect of the treatments in the first exercise period is in concordance with other studies employing intense exercise of less than 1 minute duration (Kinder- mann et al. 1977; McCartney et al. 1983). These findings however conflict with those of Inbar et al. (1983), who recorded relatively minor, but sig- nificant, increases in Wingate mean power subse- quent to bicarbonate loading, although no effect of the treatment on peak power was recorded. Studies using intermittent exercise protocols pro- vide inconclusive results; Costill et al. (1984) found time to exhaustion in the final exercise bout was significantly increased in alkalosis, whereas Wijnen et al. (1984) found longer endu- rance in the alkalotic condition in only 3 out of the 5 subjects.

During short-term intense exercise (30 s dura- tion) lactic acid production and distribution is not maximal; plasma lactate concentrations ranged from 7.5--10.6 mmol 1-1 after the first exercise bout (Fig. 4). Therefore the maximum buffering capacity is not utilized to the full and so the ben- efits are limited. With subsequent bouts, produc- tion and distribution of lactic acid are increased; lactate concentration after the third bout ranged from 11.2--13.8 mmol 1-i. It can be hypothesized that the longer time period allows the elevated plasma bicarbonate reserve to increase lactic acid efflux from the muscle (Mainwood and Worsley- Brown 1975; MacLaren and Mellor 1985) and en- hance hydrogen ion buffering. This idea is sup- ported by the differences in work done over all exercise bouts under the 4 conditions. In the alka- lotic conditions, where lactic acid efflux and buf- fering are enhanced, the greatest amount of work is achieved. These results are in agreement with McCartney et al. (1983) who also demonstrated that work done after N a H C Q ingestion was 101% of that achieved with a placebo. The importance of exercise time on the effect of bicarbonate load- ing has been studied by Costill et al. (1984), who found that oral NaHCOs had no measurable in- fluence on exercise leading to exhaustion in less than 1 min. The most significant effects of bicar- bonate ingestion were seen during longer term ex- ercise (6--8 min) resulting in near maximal lactic

528 M. Parry-Billings and D. P. M. MacLaren: Effect of bicarbonate and citrate ingestion on anaerobic power

acid production and distribution (Jones et al. 1977).

The non-significant differences between treat- ments in blood pH and bicarbonate concentra- tion, [HCO~], before exercise were partly due to completion of the warm-up. This included three 5 s periods of intense cycling, which contributed to an increase in plasma lactate concentration from 1.0-- 1.5 mmol 1-1 atrestto 2.4--4.3 mmol 1-1. Citrate, bicarbonate plus citrate and bicarbonate ingestion did however result in higher pre-exer- cise pH and [HCO~-] compared to the placebo. The increase in blood pH and [HCO3] at rest was equivalent to or greater than that reported in all other studies reviewed. The significant differences in these two parameters (Figs. 2 and 3) after each exercise bout are in agreement with the results of Inbar et al. (1983) and Costill et al. (1984). In con- trast McCartney et al. (1983) found no significant differences in bicarbonate concentration between alkalosis and placebo at any time (0--10 min) after 30 s of supramaximal cycling.

It is likely that short-term, intense exercise does not permit maximal lactic acid production. After the third exercise bout lactate concentra- tions ranged from 11.3-- 13.8 mmol 1-1 compared to 28.2 mmol 1-1 after cycling to exhaustion at 125% l)o2m,x (Katz et al. 1984). The submaximal rate of lactic acid production may restrict the de- tection of significant differences in blood lactate between the treatments.

In postulating why bicarbonate and citrate loading had no effect on performance despite ele- vation of blood pH and [HCO3], intramuscular events must also be considered. As the total exer- cise time was short (90 s) the importance of extra- cellular events is questionable. The administration of bicarbonate has no effect on resting muscle pH (Rupp et al. 1983), the sarcolemma being im- permeable to HCO3 (Robin 1961). Therefore the enhancement of intramuscular buffer capacity re- suiting from the treatments is negligable. It is hy- pothesized that the natural intramuscular buffer concentrations are an important factor contribut- ing to short-term exercise performance (Park- house and McKenzie 1984). Our results support this idea, as increasing extracellular buffering had a non-significant effect on performance. The crea- tine kinase reaction is one mechanism for seques- tering hydrogen ions within the muscle. In supra- maximal exercise this reaction is an important mechanism for ATP resynthesis. Therefore at the same time it is a vital buffering mechanism, re- ducing the importance of the bicarbonate ion. In contrast it becomes less critical in long-term exer-

cise, where bicarbonate loading has been demon- strated to be most effective in buffering hydrogen ions extracellularly.

One surprising result was the significant in- creases in blood pH and [HCO31 following so- dium citrate ingestion compared to those re- corded after bicarbonate loading. Mean power and peak power in the second and third exercise bouts were also highest with the citrate treatment. It appears that "citrate loading" is most effective in inducing beneficial acid-base changes post-ex- ercise and in enhancing performance. Early stud- ies using fruit juices (high in potassium citrate) and alkaline salts of citric acid in combination with sodium bicarbonate reported highly signifi- cant improvements in swimming and running per- formance (Hewitt and Calloway 1936; Dennig et al. 1937). Similar treatments have been shown to have no effect on cross-country and treadmill run- ning performance (Johnson and Black 1953; Mar- garia et al. 1971), whilst Simmons and Hardt (1973) found increased performance in competi- tive swimmers. Recent studies into the effects of alkalosis on exercise have, in contrast, used Nail- CO3 administration exclusively. However, in view of our results it would appear that citrate inges- tion may be more effective in offsetting fatigue in- duced by lactacidosis. Other advantages of the treatment include its ease of ingestion and the ab- sence of the side effects experienced by some in- dividuals with NaHCO3. The precise mechanism for the action of the citrate preparation remains unresolved. Citrate is metabolized at a number of sites with the formation of bicarbonate (Hawk et al, 1947). This may provide a slower release of HCO3 into the blood, resulting in a reduced ex- cretion and a more prolonged elevation of blood [HCO3]. Clearly further research into the effect of citrate loading on exercise performance is re- quired.

Acknowledgements. The authors wish to thank Mr. P. McLean (Department of Pharmacy, Liverpool Polytechnic) and Mr. S. Meilor (Department of Sport and Recreation Studies, Liver- pool Polytechnic) for their valuable assistance with blood gas analysis. The advice of Dr. T. Reilly (Department of Sport and Recreation Studies, Liverpool Polytechnic) is gratefully ac- knowledged as is that offered by Mr. G. Brooke (Department of Mathematics, Liverpool Polytechnic). Finally, the authors wish to thank Powell and Scholefield Ltd. (Liverpool, Eng- land) for their technical support with regard to the products used.

References

Bayley K, Reilly T (1984) The relationship between anaerobic power on a swim bench and swimming performance of young swimmers. J. Sports Sci 2:162--163

M. Parry-Billings and D. P. M. MacLaren: Effect of bicarbonate and citrate ingestion on anaerobic power 529

Costill DL, Verstappen F, Kuipers H, Janssen E, Fink W (1984) Acid-base balance during repeated bouts of exercise: influence of bicarbonate. Int J Sports Med 5:228--231

Danforth WH (1965) Activation of glycolytic pathway in mus- cle. In: Chance B, Estabrookes RW (eds) Control of energy metabolism. Academic Press, New York, pp 287--297

Dennig H, Talbott JH, Edwards HT, Dill DB (1937) (0ber stei- gening der K6rperlichen Leistungsf~ihigkeit durch Engriffe in den sauerbasen Haushalt. Dtsch Med Wochenschr 63:736

Donaldson SKB, Hermansen L (1978) Differential direct ef- fects of H + on Ca 2 § force of skinned fibres from the soleus, cardiac, adductor magnus muscles of rabbits. Pflfigers Arch 376:55--65

Dotan R, Bar-Or O (1983) Load optimization for the Wingate anaerobic test. Eur J Appl Physiol 51:409--417

Fabiato A, Fabiato F (1978) Effects of pH on the myofila- merits and the sarcoplasmic reticulum of skinned cells from cardiac and skeletal muscles. J Physiol 276:233-- 235

Gutmann I, Wahlefield AW (1974) L-(+)-Lactate determina- tion with lactate dehydrogenase and NAD. In: Bergmeyer HU (ed) Methods of enzymatic analysis. Second edition. Verlag Chemic Weinheim and Academic Press Inc, New York and London, pp 1464--1468

Hawk PB, Oser B, Sumerson W (1947) Practical physiological chemistry. Churchill Press, London

Hermansen L, Osnes J-B (1972) Blood and muscle pH after maximal exercise in man. J Appl Physiol 32:304--308

Hewitt JE, Calloway EC (1936) Alkali reserves of blood in re- lation to swimming performance. Res Quart 7:83-93

Inbar O, Rotstein A, Jacobs I, Kaiser P, Dlin R, Dotan R (1983) The effects of alkaline treatment on short-term max- imal exercise. J Sports Sci 1:95--104

Johnson WR, Black DH (1953) Comparison of effects of cer- tain blood alkalinizers and glucose upon competitive endu- rance performance. J Appl Physiol 5:588--578

Jones NL, Sutton JR, Taylor R, Toews CJ (1977) Effect of pH on cardiorespiratory and metabolic responses to exercise. J Appl Physiol 43:959--964

Katz A, Costill DL, King DS, Hargreaves M, Fink WJ (1984) Maximal exercise tolerance after induced alkalosis. Int J Sports Med 5:107--110

Kindermann W, Keul J, Huber G (1977) Physical exercise after induced alkalosis (bicarbonate and Tris-buffer). Eur J Appl Physiol 37:197--204

MacLaren DPM, Mellor S (1985) The effect of alkalosis and acidosis on the anaerobic threshold. (Paper presented at British Association of Sports Medicine "Congress '85", Birmingham)

MacLaren DPM, Morgan GD (1985) Effects of sodium bicar- bonate ingestion on maximal exercise. Proe Nutr Soc 44: 26A

Mainwood GW, Worsley-Brown P (1975) The effects of extra- cellular pH and buffer concentration on the efflux of lac- tate from frog sartorius muscle. J Physiol 250:1--22

Margaria R, Aghemo P, Sassi G (1971) Effect of alkalosis on performance and lactate formation in supramaximal exer- cise. Int Z Angew Physiol 29:215--223

McCartney N, Heigenhauser GJF, Jones NL (1983) Effects of pH on maximal power output and fatigue during short- term dynamic exercise. J Appl Physiol: Respirat Environ Exercise Physiol 55:225--229

Parkhouse WS, McKenzie DC (1984) Possible contribution of skeletal muscle buffers to enhanced anaerobic perform- ance: a brief review. Med Sci Sports Exerc 16:328--338

Poulas AJ, Docter HJ, Westra HG (1974) Acid-base balance and subjective feelings of fatigue during physical exercise. Eur J Appl Physiol 33:207--213

Robin ED (1961) Of men and mitochondria -- intracellular and subcellular acid-base relations. N Engl J Med 265 : 780--785

Rupp JC, Bartels RL, Zuelzer W, Fox EL, Clark RN (1983) Effect of sodium bicarbonate ingestion on blood and mus- cle pH and exercise performance. Med Sci Sports Exerc 15:115

Siggaard-Anderson O (1971) An acid-base chart for arterial blood with normal and patho physiological reference ar- eas. Scand J Clin Lab [Suppl 70] 15:

Simmons RWF, Hardt AB (1973) The effect of alkali ingestion on the performance of trained swimmers. J Sports Med 13 : 1 5 9 - - 163

Sutton JR, Jones NL, Toews CJ (1981) Effect ofpH on muscle glycolysis during exercise. Clin Sci 61:331--338

Wijnen S, Verstappen F, Krupers H (1984) The influence of intravenous sodium bicarbonate administration on interval exercise: acid-base balance and endurance. Int J Sports Med [Suppl] 5:130--132

Accepted April 4, 1986