Eur J Appl Physiol (1982) 49:369-377 European Journal o f

Applied Physiology' and Occupational Physiology �9 Springer-Verlag 1982

Square-Wave Endurance Exercise Test (SWEET) for Training and Assessment in Trained and Untrained Subjects*

II. Blood Gases and Acid-Base Balance

Manuel Gimenez 1, Emilio Servera 1, Claude Saunier 1, and Jacques Lacoste 2

1 Laboratoire de Physiologic de l'Exercice Musculaire Unit6 14 INSERM, case officielle 10, F-54511 Vandoeuvre les Nancy Cedex, France 2 Service des Examens de la Fonction Respiratoire, C. H. U. de Brabois, F-54500 Vandoeuvre les Nancy, France

Summary. In order to obtain information about physiological and ho- meostasic responses at the Maximal Intensity of Endurance of the 45 rain "Square-Wave Endurance Exercise Test" (MIE45), three arterial blood samples were taken: (a) at rest; (b) at the 45th rain of the SWEET; (c) after 15 rain of recovery, to measure paO2, paCO2, [H+], [Hb], and [lactate] in 14 normal male subjects: four trained (T) six well trained (WT) and four others untrained (U). Total mechanical work (TMW) corresponding to MIE45 was significantly higher (~ + SEM) respectively in WT (9.22 + 0.65 kJ �9 kg -1, p < 0.001), than in T (7.17 + 0.18 kJ �9 kg -I, p < 0.01) and U subjects (4.44 + 0.36, p < 0.001). Because of this the lactate level, which rose significantly during exercise, differed between U and WT subjects (p < 0.05). In spite of the exhaustive character of the MIE45, [H +] and PaO2 remained within the range of normal values. These results suggest that trained and untrained subjects can be trained with the exhausting MIE45 exercise while maintaining a constant [H +] and paO2 at the 45th rain of exercise.

Key words: Lactate - Arterial blood gases - Total mechanical work - Maximal intensity of endurance - Training - 1)O2 max - Men

Studies using high intensity (> 100% VO 2 max) interval training (Fox et al. 1977; Mathews and Fox 1976) have indicated that the intensity of training rather than the frequency or distance is the most important factor in improving maximal oxygen uptake (1?O2 max). Hickson et al. 1977, using strenuous endurance exercises found a linear increase in 1)O2 max throughout a 10 week training program.

Physiological and homeostatic responses to ergometric tests of endurance training have not been throughly investigated. An aerobic-anaerobic threshold,

* Supported in part by the European Economic Community (EEC) Luxembourg Offprint requests to." M. Gimenez, MD (address see above)

0301-5548/82/0049/0369/$ 01.80

370 M. Gimenez et al.

as de r i ved f rom ene rgy m e t a b o l i s m , was p r o p o s e d by K i n d e r m a n n et al. (1979), to d e t e r m i n e o p t i m a l w o r k - l o a d in tens i t ies dur ing e n d u r a n c e t ra in ing. I n the p r e s e n t w o r k ac id -base ba l ance and m e t a b o l i c r e sponses we re s tud i ed dur ing the M a x i m a l In t ens i ty of E n d u r a n c e for 45 min (MIE45) of the S q u a r e - W a v e E n d u r a n c e Exe rc i se Tes t ( G i m e n e z et al. 1982).

Material and Methods

Fourteen normal male subjects volunteered for this study after having been informed of the protocol involved. Four of the subjects were untrained (U), six trained (T) doing from 4 to 6 h of various sports per week. Four others were endurance athletes who trained intensively and regularly for more than 10 h per week and were considered in this study as well trained subjects (WT). Mean values and range of age and physical characteristics of the three groups are reported in Table 1. All completed a medical questionnaire and had normal cardiopulmonary and electrocardiographic examination.

Direct measurements of maximum oxygen uptake and of the Maximal Intensity of Endurance during the 45 rain of the SWEET (MIE4s) are given in the description of the tests reported previously (Gimenez et al. 1982).

Total ventilation (VEBTPS), oxygen uptake (I)O2STPD), carbon dioxide production (IkCO2 STPD), respiratory frequency (f) and tidal volume (Vr) were measured continuously with an open circuit, using a Jaeger Ergo-Pneumotest with a Dataspir EDV 70 data processing system (E. Jaeger, Wtirzburg, FRG). Heart rate was also monitored continuously on the electrocardiogram (Siemens Cardiostat 3T). The tests were performed on a Jaeger or a Fleisch cycle ergometer at 60 revolutions per minute (rpm).

After having previously measured the 1;102 max and the total mechanical work (TMW) corresponding to the MIE45, the subjects arrived at the laboratory at approximately 8 : 00 a.m. on the day of the examination,having eaten a non-fat breakfast 11/2 h earlier. They rested on a couch for about 30 rain. A flexible catheter was placed in the radial artery under local anaesthetic. The first measurement was made after about 45 rain of rest. Then the subject was seated on the cycle ergometer and was connected to the Ergopneumotest and the electrocardiograph. The subject then performed the appropriate MIEns. A second blood sample was taken at the end of the last peak (45th min), and a third after 15 rain of recovery, the subject being again seated on the couch. The same ventilatory and cardiorespiratory measurements as described previously were continuously recorded. Arterial pH, carbon dioxide (paCO2) and oxygen (paO2) pressures were immediately measured in duplicate with a Radiometer BSM 3. Arterial oxygen saturation (SaO2) and hemoglobin (Hb) were also measured in duplicate with a Radiometer OSM2, along with hematocrit (Hcte); the concentration of bicarbonate in plasma was calculated from arterial pH and paCO2. Base Excess (BE) or Base Deficit (BD) were also calculated. For lactate measurement, blood was immediately added to a solution of cold perchloric acid, as required in the enzymatic method. Statistical analysis included comparison of two mean values, and the paired t-test.

Results

T a b l e 1 shows the m e a n va lues of 1)O2 max and the M a x i m a l In tens i ty of E n d u r a n c e dur ing 45 min (MIE45) expres sed as % M T P and k J . kg -1. T sub jec t s had s ignif icant ly h igher va lues than U subjec ts . T h e r e was no s ignif icant d i f f e rence in 1/O2 max b e t w e e n T and W T subjec ts , bu t the % M T P and the kJ �9 kg -1 of the MIE4s we re h igher in the W T subjec ts . M e a n va lues of a r t e r i a l b l o o d gases and h e m o g l o b i n are s u m m a r i z e d in T a b l e 2. PaCO 2 was down at the end of MIE4s in t he t h ree groups whi le [Hb] rose s ignif icant ly , and then d e c r e a s e d dur ing recovery . PaO2 t e n d e d to d imin ish dur ing exerc i se and

Tab

le 1

. P

hysi

cal

char

acte

rist

ics,

1)O

2 m

ax a

nd M

axim

al I

nte

nsi

ty o

f E

nd

ura

nce

dur

ing

45 r

ain

(MIE

45)

Of

the

subj

ects

stu

died

O �9

g a g >

Ag

e W

eigh

t H

eig

ht

1)O

2 m

ax

MIE

45

(yea

r)

(kg)

(c

m)

(ml.

kg-

} �9

min

-1)

% M

TP

T

MW

(kJ

�9 k

g vl

)

Un

trai

ned

(4

)

Tra

ined

(6

)

Wel

l T

rain

ed

(4)

5~

29.3

74

.5

178

SE

M

2.7

3.7

1.5

:~

27.5

70

.8

175

SE

M

1.47

4.

57

3.34

-40.

9 2.

0

56.3

2.

49

30,5

70

17

3 -6

3.5

SE

M

3.66

2.

49

2.2

2.9

-49 2.

9

58.8

2.

49

71.5

2.

85

4.44

0.

36

7.17

0.

18

.9.2

2 0.

65

VJ

0~

m

~q

MT

P =

Max

imal

To

lera

ted

Po

wer

dur

ing

3 m

in o

f th

e pr

ogre

ssiv

e ex

erci

se (

30W

/3 m

in)

kJ =

kil

oJou

les

* =

p <

0.0

5; *

* =

p <

0.0

1; *

** =

p

< 0

.001

Tab

le 2

. A

rter

ial

bloo

d ga

ses

and

hem

oglo

bin

paC

O2

Tor

r pa

O2

Tor

r H

b g

�9 1

-1

Res

t E

x.

Rec

. R

est

Ex.

R

ec.

Res

t E

x.

Rec

.

Unt

rain

ed

(4)

Tra

ined

(6

)

Wel

l tr

aine

d (4

)

s 35

.3

31.5

S

EM

3.

2 1.

36

r

s 37

.4

33'.1

S

EM

1.

49

2.41

s 40

'.0

29'.'6

S

EM

1.

08

1.93

36.5

96

92

82

14

.8

**

16.1

15

.5

1.62

2.

7 3.

9 1.

3 0.

64

0.67

0.

64

* N

S

NS

**

#

*

36.0

96

91

86

13

~.0

1413

13

18

1.06

3,

76

3,77

1.

96

0.40

0.

42

0.47

[

I

**

f

F 34

11

86

85

85

15.4

..

..

16.7

*

15.9

2.

2 2.

4 3.

1 3.

2 0.

3 0.

3 0.

21

Ex

= 45

th m

in o

f th

e M

IE45

R

ec =

Rec

over

y, 1

5th

min

*

=p

<

0.05

; **

=p

<

0.01

; **

* =

p

< 0.

001

paC

O2

and

paO

2 =

Art

eria

l ca

rbon

dio

xide

and

oxy

gen

pres

sure

s H

b =

Hem

oglo

bin

Blood Gases and Acid-base Balance During SWEET 373

. . =

i 3 6 - -

12_ i

@ w 8- E

-i,-, 0 .,.., l, t J 0 .-,,

0

26. I

22. I.iJ E

18_

1~_

,55 / j - - ~ . % ,

~ ~ j ~ g - * * *'-'~ **

Untra ined

�9 Trained

x WeLL t ra ined

6 /o'5 B'0 rain EXERCISE RECOVERY

Fig. 1. Acid-base balance in arterial blood. During the long and exhaustive MIE45, lactate rose while the bicarbonate fell. The concentration of [H +] remains within normal range in T and U subjects and rose moderately but significantly in WT subjects

recovery, but no significant variations were observed. Arterial oxygen saturation was maintained within the normal physiological range (SaO 2 > 94%).

Figure 1 represents the evolution of [H+], [lactate] and [bicarbonate]: [lactate] rose significantly during exercise then decreased significantly during recovery in all groups without returning to the rest values. The mean value of [lactate] in the WT subjects was double that of the T and U subjects. [Bicarbonate] followed an inverse variation symmetrical with that of [lac- tate].

In spite of the exhaustive character of the MIE45, the value of [H +] did not increase significantly except in the WT subjects. At the 45th rain of MIE45 there was a significant difference of [H +] between the U and WT subjects. Nevertheless, for 12 subjects the [H +] at exercise was in the normal range of variation observed at rest (37-43 nEq. 1-1). The other two subjects had values below 46 nEq. 1-1 (Fig. 2).

374 M. Gimenez et al.

L W

E i

U

15

10

�9 Untroined

a Troined

x Weft troined y = 0.Z,61 x - I0.7

r 0.6t. 6 x

p<O.05 x /

A A

( ' i i i I

30 4O 50 [H +] nEq.t - I

Fig. 2. Values observed at the 45th rain of MIEr Arterial hydrogen concentration is we]] correlated with lactate

Discussion

Despite the exhausting work rate, which ends with a 1 rain peak at maximal tolerated power (MTP), the MIE45 do not change the constancy of arterial oxygen saturation and [H+], which indicates homeostasis in both athletes and untrained subjects.

Progressive metabolic acidosis during intermittent exercise (1 rain at 1)O2 max, 4-min rest, etc.) is more severe than during continuous rectangular exercise (Hermansen and Osnes 1972). ~strand et al. (1960) found, in one subject, a lower lactate production during intermittent exercise of 30 s followed by 30 s of rest than for 3 min-exercise followed by 3 min-rest. Kepler et al. (1969) observed strong lactic acidosis during alternations of i min at VO2 max and 1 min-rest, and six times less lactic acidosis when 30 s of exercise was followed by 1 min-rest and, subjectively exercise was also tolerated better. These studies indicate that the lactate increase requires more than 30 s of intense exercise, the delay being caused by the time required for the aerobic use of glucose (Kepler et al. 1969): On the other hand, recuperation is slower, of the order of 3 rain after a peak at VO2 max. These results have led us to propose, after various clinical and biological controls, a SWEET with 1 min-peaks, separated by 4 rain-periods at lower intensity (Gimenez et al. 1982). The choice of MIE45 seems to be well founded, because the [H +] remains constant in the three groups of subjects (Fig. 1). This relative homeostasis appears to arise from: (1) periods of relative hyperventilation observed during and after each peak and (2) the consumption of lactate by the muscles during work at the least level of exercise.

The subsequent discharge of muscle lactate into the blood during the periodic peaks at VO2 max produces a metabolic acidosis (Hermansen and Osnes 1972) with a corresponding influence upon the ventilatory response (Chiesa et al. 1969). This ventilatory response, increased by the 0 2 debt incurred

Blood Gases and Acid-base Balance During SWEET 375

15.

i -

, Io. E

i i iIJ

o 5 u

....I [ I

0

Untrained Trained

x Well trained

x x

A

A �9

&

AA &

y= 0.247 x+ 5.51

r -- 0 . 3 4 1

N .S

X

&

&

I I

0 5

A [H+] ,.,Eq.t-1 Fig. 3. Correlation between the differences Rest-Exercise (A) for [lactate] and [H +]

I

10

during the peak periods, is characterised by an elevation of/r which rises to a maximum value in the 1st rain of the base exercise. Toward the 3rd or 4th min of this phase, //e returns to the approximate values of the preceding base levels (Gimenez et al. 1982).

Gisolfi et al. (1966) and Hermansen and Stenvold (1972) have shown, during recovery, that the consumption of lactate was more rapid when muscles continued to work at submaximal power than at rest. Recently, in spite of exhaustion, low lactic acid concentration with simultaneous increase in pH was found by Boning et al. (1979) after a 2-h exercise with a constant heart rate of 150-160 beats per minute. The base exercise levels of MIE45 in both T and U subjects correspond: (1) to the zone of. 1)O2 refered to by Hermansen and Stenvold (1972), (less than 65% of the VO 2 max); (2) to the zone of cardiac frequency mentioned by Boning et al. (1979), and (3) to the optimal intensity of work for endurance training establish according to the aerobic-anaerobic threshold proposed by Kinderman et al. (1979). It is noteworthy, moreover, that WT subjects have roughly twice the lactate of the T or U subjects (Fig. 1) and a heart rate approaching or even greater.than 170 beats �9 rain -1. This reflects the fact that the WT subjects had a higher VO2 max and work at a higher fraction of their MTP (Table 1) and suggests that they have superior muscular metabolic mechanism (Osnes and Hermansen 1972). There is in fact a good correlation between lactate and MIE45 (% MTP) (r = 0.669, p < 0.001) and between lactate and TMW in kJ �9 kg -1 (r = 0.732, p < 0.001).

During most forms of exercise, any increase in plasma [lactate] is accompanied by an equivalent fall in [bicarbonate]. The values observed at the 45th minutes of exercise, show a good negative correlation (r -- -0.723, p < 0.001) between [lactate] and [bicarbonate]. There is not a significant correlation (r = -0.238) between [H +] and [CO3H] but between [H § and [lactate] (Fig. 2). Nevertheless, Fig. 3 shows that there are no significant

376 M. Gimenez et al.

correlations between/~ [lactate] and/x [H+]. The constancy of [H +] while the [lactate] increased during the MIE45 is largely due to blood buffering (Jones 1980), in which ventilatory mechanisms were described during and after the peaks of MIE45 (Gimenez et al. 1982). Nevertheless, the evolution of blood and muscle pH during other exercise protocols could differ from this. Hermansen and Osnes (1972) have shown that the evolution of blood and of muscle pH during intermittent exercises are different: blood pH tends to diminish progressively after each peak of work, while muscle pH tends to return to the initial value after the recovery phase. Moreover, after maximal exercise, the increase in arterial Base Deficit (BD) is higher than the corresponding accumulation of lactate (Osnes and Hermansen 1972; Sahling et al. 1978), while during exercise BD increases by the same amount as lactate + pyruvate (Sahling et al. 1978). This suggests that [H +] during exercise accompanies the transport of lactate from the site of production into the blood, while this relation disappears during the early part of recovery (Sahling et al. 1978). The MIE45 having alternate phases of maximum and submaximum ("recovery") loads, both mechanisms could be implicated. Moreover the paCO2 is lower in all subjects but more so in WT subjects (Table 2). Sutton et al. (1980) showed that if [ C O 3 H - ] is lowered in normal subjects, plasma lactate is the less for a given level of exercise and muscle lactate is relatively higher. In the absence of simultaneous lactate muscle values, the interpretation of this discrepancy during MIE4s remains questionable. It is worth mentioning however that this constancy of [H +] may increase the endurance capacity of the subjects (Jones et al. 1977). Further studies are still necessary to clarify the behavior of the evolution of acid-base balance between the least level exercise and the peaks of the MIE45 at different stages of it's evolution.

In summary, Maximal Intensity of Endurance during 45 rain of SWEET is an exhausting exercise which can be achieved by trained and untrained sub- ects while still maintaining a constant [H § and SaO2 at the 45th min of exercise.

Acknowledgements. We are greatly indebted to Doctor B. Dull and Miss J. Bainbridge for their assistance in preparing the English manuscript. We wish also to thank Miss F. Poincelot, Miss Th. Colas for technical assistance and the secretaries Miss B. Clement and Mrs. P. Ulmer for typing the manuscript and Miss M. C. Rohrer for illustrations.

References

Astrand I, Astrand PO, Christensen EH, Hedman R (1960) Intermittent muscular work. Acta Physiol Scand 48:448-453

Boning D, Skipka W, Heedt P, Jenker W, Tibes U (1979) Effects and post-effects of two-hour exhausting exercise on composition and gas transport functions of blood. Eur J Appl Physiol 42 : 117-123

Chiesa A, Stretton TB, Massoud AAE, Howell JBL (1969) The effects of inhibition of carbonic anhydrase with dichlorphenamide on ventilatory control at rest and on exercise in normal subjects. Clin Sci 37:689-706

Fox EL, Bartels RL, Klinzing J, Ragg K (1977) Metabolic responses to interval training programs of high and low power output. Med Sci Sports 9:191-196

Blood Gases and Acid-base Balance During SWEET 377

Gimenez M, Salinas W, Servera E, Kuntz C (1981) VO 2 max during progressive and constant bicycle exercise in sedentary men and women. Eur J Appl Physiol 46:237-248

Gimenez M, Servera E, Salinas W (1982) Square-Wave Endurance Exercise Test (SWEET) for training and assessment in trained and untrained subjects. I. Description and cardiorespiratory responses. Eur J Appl Physiol 49:359-368

Gisolfi G, Robinson S, Turrel ES (1966) Effects of aerobic work performed during recovery from exhausting work. J Appl Physiol 21:1767-1772

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

Hermansen L, Stenvold I (1972) Production and removal of lactate during exercise in man. Acta Physiol Scand 86:191-201

Hickson RC, Bomze HA, Holloszy JO (1977) Linear increase in aerobic power induced by a strennous program of endurance exercise. J Appl Physiol 42:372-376

Jones NL (1980) Hydrogen ion balance during exercise. Clin Sci 59:85-91 Jones NL, Sutton JR, Taylor R, Toews CJ (1977) Effect of pH on cardiorespiratory and metabolic

responses to exercise. J Appl Physiol: Respirat Environ Exercise Physiol 43 : 959-964 Kepler D, Keul J, Doll E (1969) The influence of the form of exercise on the arterial concentrations

of glucose, lactate, pyruvate and free fatty acids. In: Biochemistry of exercise, vol 3. Medicine and Sport, Karger, Basel New York, pp 132-136

Kindermann W, Simon G, Keul J (1979) The significance of the Aerobic-Anaerobic transition for determination of work load intensities during endurance training. Eur J Appl Physiol 42: 25 - 34

Mathews DX, Fox EL (1976) The physiological basis of physical education and athletics, vol 1. WB Saunders, London

Osnes JB, Hermansen L (1972) Acid base balance after maximal exercise of short duration. J Appl Physiol 32:59-63

Sahling K, Alvestrand A, Brandt R, Hultman E (1978) Acid-base balance in blood during exhaustive bicycle exercise and the following recovery period. Acta Physiol Scand 104:370-372

Sutton JR, Jones NL, Toews CJ (1980) The effect of pH on muscle glycolysis during exercise. Clin Sci 61 : 331-338

Accepted March 22, 1982