Eur J Appl Physiol (1982) 49:379-387 European Journal of

Applied Physiology and Occupational Physiology �9 Springer-Verlag 1982

Square-Wave Endurance Exercise Test (SWEET) for Training and Assessment in Trained and Untrained Subjects* III. Effect on VO2 max and Maximal Ventilation

Manuel Gimenez 1, Victor Cereceda 2, Dan Teculescu 1, Francois Aug 1, and M. Claire Laxenaire 3

1 Laboratoire de Physiologie de l'Exercice Musculaire Unit6 14 INSERM, case offici611e 10, F-54511 Vandoeuvre les Nancy Cedex, France 2 Recipient of a CIES, was on leave from the Medical School of Concepcion, Chili 3 Ddpartement d'Anesth6siologie, C. H. R. Nancy, France

Summary. The effect of training on lkO; max, endurance capacity (EC) and ventilation during maximal exercise (Vemax) were studied in 17 normal subjects aged 21-51 years. At the beginning of the study 11 of the subjects (eight women and three men) were untrained (U) and six others (three women and three men) trained regularly (T). A maximal intensity exercise (on a cycle ergometer) which could be sustained for 45 rain (MIE45) was performed three times per week for 6 weeks; the total mechanical work (TMW) corresponding to the MIE45 per session varied between 3.14 and 9.24 kJ . kg -1. Before training, 1?O2 max (a) , / / e max (b), and TMW (c) were higher in T than in U subjects. Training increased these variables in most of the subjects; the increase being significantly higher (~ + SEM) in U (a = +29.9 _+ 3.8%; b = 49.6 + 6.5%; c = 47 + 6.9%) than in T subjects (a = 6.6 + 3.8%; b = 17.5 + 3.6%; c = 19.1 + 2.8.%). In all but three cases the % increase of TMW was higher than that of VO2 max, suggesting a higher sensitivity of TMW in measuring EC. The significant increase in Ve max, maximal voluntary ventilation, peak flows (inspiratory and expiratory) and static maximum pressures indicate that this training protocol improves in healthy subjects the performance of respiratory muscles as well.

Key words: Exhaustive ergometric test - Training - 1?O2 max - Endurance capacity - Total mechanical work - Healthy subjects - Peak flow rates - Maximal ventilation - Static maximum pressures

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

0301-5548/82/0049/0379/$ 01.80

380 M. Gimenez et al.

Introduction

Prev ious s tudies conce rn ing e n d u r a n c e t ra in ing p r o g r a m s have shown an inc rease in m a x i m a l oxygen u p t a k e , ( l ?O2max) (Sal t in et al. 1968; S h e p h a r d 1968; Po l lock et al. 1969; Dav ies and Kn ibbs 1971; Go l ln i ck et al. 1973; F o x et al. 1973; K e a r n e y et al. 1976; M a t h e w s and Fox 1976; A t o m i and M i y a s h i t a 1980) whi le o the r s have shown no re la t ionsh ip b e t w e e n 1)O2 m a x and t ra in ing (Kasch and W a l l a c e 1976; Dan ie l s et al. 1978). F o x et al. 1973, in a s tudy dea l ing wi th in te rva l t ra in ing , have f o u n d tha t t ra in ing in tens i ty r a the r than t ra in ing d i s tance was the mos t i m p o r t a n t fac tor in improv ing VO2 max. H i c k s o n et al. (1977) using s t r enuous e n d u r a n c e exerc ises f o u n d a l inea r inc rease of up to 44% VO2 m a x with inc rease in exerc ise endu ranc e .

This s tudy p re sen t s the effects of t ra in ing using 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 ( S W E E T ) on VO 2 max , e n d u r a n c e capac i ty (EC) and ven t i l a t o ry va r i ab le s in n o r m a l t r a ined and u n t r a i n e d subjec ts .

Material and Methods

Seventeen normal subjects (11 women and six men), between 21-51 years of age, volunteered for this study after having been informed of the protocol involved. Eleven of the subjects were untrained (eight women and three men) and six others (three women and three men) were endurance athletes who trained regularly. All completed a medical questionnaire and had normal cardiopulmonary and electrocardiographic findings.

Preta!ning data consisted in spirographic examination and measurements of respiratory muscle strength, VO2 max, and Maximal Intensity of Endurance during 45 rain of the SWEET (Gimenez et al. 1982). The spirographic determinations included vital capacity (VC), forced expiratory volume in 1 s (FEV1) and maximal voluntary ventilation (MVV); the latter was always measured during 10 s at respiratory rates higher than 40 breaths per minute (Gimenez et al. 1981). Three to five maximal expiratory and inspiratory flow volume curves were obtained to allow the measurement of peak expiratory flow CPEF), peak inspiratory flow (PIF) and maximal exPiratory (~'E max 50) and inspiratory flow (V t max 50) at 50% of VC. The volume and flow measurements were made using a Jaeger Ergopneumotest, whose computer records the maximal value of at least three manoeuvers. Calibrations of the pneumotachograph were carried out before and after each examination (Gimenez et al. 1981).

Static maximal (Pstat) inspiratory and expiratory mouth pressures were measured according to the technique of Black and Hyatt (1969). The subject breathed through a mouthpiece and a three way-value which could be connected either to room air, to a bell spirometer or to a fixed resistance (1 mm orifice). A manometer (Statham P23 Db), connected to a tap of the mouthpiece recorded mouth pressure during maximal expiratory efforts (positive pressure) at full inspiration or inspiratory efforts (negative pressure) at full expiration. Several trials were done at each level and the greatest value recorded.

Measurements of 1)O2 max, in duplicate, and the Maximal Intensity of Endurance of the SWEET (MIE4s) were made as reported previously (Gimenez et al. 1981, 1982). It should be noted that MIE45 is expressed as Total Mechanical Work (TMW) in kJ per kg of weight (Gimenez et al. 1982). The value of minute ventilation recorded at the maximal exercise (VO2 max) is expressed as VEmax (Gimenez et al. 1981).

Training was performed on a Jaeger bicycle ergometer at MIE4s level. The frequency of training was one session of 45 min every other day, three times a week, for 6 weeks. In all sessions HR was systematically controlled during MIE45 before and after each peak. Every 10 days the level of TMW was retested, and if higher than control values the peaks of MIE4s were readjusted to the new values. Also, the initial work of MIE45 (% MTP) was made progressively heavier according to the subject's

Effect of SWEET Training 381

impressions and heart rate response to the preceding MIE45 (Gimenez et al. 1982). The subjects were considered exhausted when HR was near maximal (220-age) at the 8th peak, and maximal (220-age) at the 45th min (9th peak).

Body weight was measured before and after the training period. Statistical analysis included comparison of the mean values and the paired t-test.

Results

The mean values (~ + SEM) of physical characteristics, 1702 max, and maximal intensity of endurance (MIE45), before training are represented in Table 1. The limited number of subjects precludes statistical assessment between subgroups. For both sexes, trained subjects had clearly higher l?O2max and MIE45. The spirographic variables (recorded in 14 of the 17 subjects) exceeded the predicted values obtained from the European Economic Community formula (1971).

The variations of lv'O 2 max, VE max, and MIE45 are represented in Figs. 1, 2, and 3. The increase of V Q m a x (U = 29.9 + 3.8%; T = 6.6 + 3.8%) and VEmax (U = 49.6 + 6.5%; T = 17.5 + 3.6%) was significantly higher in untrained subjects. As can be seen in Fig. 1, in all but three cases the increase in TMW (U = 47 + 6.9%; T = 19.1 __+ 2:8%) is higher than the increase in 1)O2 max. Figure 2 shows that while the VO2 max and MIE45 of the U subjects improved significantly, in the T subjects only the increase in MIE45 was significant. The VE max always increased after training (Fig. 3). Table 2 shows the mean values of some spirographic variables. VC rose slightly, FEV1 and r)Emax 50 as expected did not change, while peak expiratory flow, peak inspiratory flow and maximal inspiratory flow at 50% of VC increased significantly after training (Fig. 4).

Static maximal pressures (measured in nine subjects, six females and three males; one trained and eight untrained) showed increase at both volume levels.

Table l . Physical characteristics, l)O2max and maximal intensity of endurance during 45 rain (MIE45)

Age Weight Height 1)O2 max MIE45 (year) (kg) (cm) (ml. kg -1 �9 rain -1) (kJ- kg -1)

Untrained (n = 11) Women s 34.6 (n = 8) SEM 3.74 Men ~ 37 (n = 3) SEM 5.4

Trained (n = 6) Women :~ 35 (n = 3) SEM 4.4 Men ~ 35 (n = 3) SEM 6.8

55.4 162 34.5 7 4.27 -q 2.8 2 1.87/ 0.31 /

64.3 171 39.0 [ *** 5.64[ ***

4.6 4.6 3.3 J 1.1 l

60.7 167 54.4 6.82 4.4 2.9 0.48 0.18

75.3 178 54.4 7.84 5.5 5.5 6.2 0.94

kJ = kilojoules *** p < 0.001

382 M. Gimenez et al.

E o .>

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Untr. Tr. �9 o Women �9 ~ Men

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Fig. 1. Comparison between % variation of 1'O2max and MIE4> In general, after training, the subjects endurance capacity (AkJ �9 kg -1) increases more than 1"O2 max, with the exception of three cases

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Before training

After trGinlng kJ.kg-1

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TRAINED (n:6)

Fig. 2. Effects of training o n 1'O 2 max and MIE45. While untrained subjects improved significantly in 1)O2 max and endurance capacity, trained subjects improved only endurance capacity (kJ. kg -1)

Pstat max at total lung capacity rose in every subject (Fig. 5); the average increase of 10 cm H20 (from 88 _+ 24 to 98 + 8 cm H20), i.e., 11.4%, was highly significant. The negative Pstat max, at residual volume (RV) increased in eight out of nine subjects (Fig. 5); the mean increase of 12 cm H20 (78 _+ 21 and 90 + 25 cm H20 respectively) i.e., 15.4%, was significant (p < 0.02).

Effect of SWEET Training 383

Before

200-

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Fig. 3. Effects of training on maximal ventilation a t VO 2 max level. Maximal ventilation i n c r e a s e d significantly after training, especially in untra ined subjects

T a b l e 2. Effects of SWEET on vital capacity and flows in trained and untrained subjects

VC MVV FEV1 l)max 50% 1 1 �9 rain -1 1 1 �9 s - I

B A B A B A B A

Untrained :~ 4.15"** 4.75 125"** 145 3.57 3.65 4.0 4.04 (n = 11) SEM 0.25 0.26 9.4 9.67 0.25 0.23 0.21 0.31

Trained ~ 4.89* 5.11 155 188 4.26 4.28 3.72 3.94 (n = 3) SEM 0.53 0.57 15 23.7 0.39 0.42 0.35 0.45

VC = Vital Capacity; MVV = Maximal Voluntary Ventilation; FEV1 = Forced Expiratory Flow in o n e second; Vmax 50 = Maximal Expiratory Flow at 50% of VC B = Before training; A = After training * = p < 0.05; *** = p <0.001

In a control group of six healthy subjects (24-48 years, three females, three males; four untrained who remained sedentary, and two trained who continued their usual training) flows, 1?O2 max, V E max and MIE45, were measured twice, at 6 - 8 weeks intervals: no changes were observed. There were no adverse clinical effects during the various maximal tests nor during training sessions. No significant differences in pre- and post-training body weights within groups were observed. Nevertheless three subjects lost between 2 and 4 kg after training while two other subjects gained 1 kg.

384

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[~3 Before training After training

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M. Gimenez et al.

Hg. 4. Maximal flows increase significantly after training. PEF = peak expiratory flow; PIF = peak inspiratory flow; Vlmax 50 = maximal inspiratory flow at 50% of VC for the 11 subjects

After 120_

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Fig. 5. Effect of training on maximal static pressures in eight untrained and in one trained subjects. All but one improved PImax and PEmax. TLC = Total Lung Capacity; RV = Residual Volume

Discussion

The present investigation was designed to assess the effects of training, with an 'iinterval-training" ergometric session of 45 min of high intensity (MIE4s), on VO2 max, endurance capacity and/r max during exercise. An increase of these variables was observed after 6 weeks of training; the largest changes occurred in the untrained subjects. The 6 weeks training period was chosen because Fox et al. (1973) found no differences among training groups after 7 weeks and was also based on the results obtained in a preliminary study (Salinas et Gimenez 1981).

Effect of SWEET Training 385

In untrained subjects the increase in 1r max corresponds in men to those observed by Sa!tin et al. (1968), Shephard (1968) Pollock et al. (1969), Davies and Knibbs (1971), Gollnick et al. (1973), Fox et al. (1973), Kearney et al. (1976), and Eddy et al. (1977); in women it was larger than those observed by Kearney et al. (1976), Eddy et al. (1977), and Atomi and Miyashita (1980) (for an equivalent period of training). It corresponds to the values obtained by the last authors after 31 weeks of training. Because the frequency of training sessions were similar in the quoted studies, the highest values observed in this study with a shorter period of training suggest that improvement in VOzmax was significantly related to training intensity. The present study bears similarities with that of Hickson et al. (1977); however, several differences must be stressed: (a) exercise was bicycling alternating with running in their study, while only the cycloergometer was used by us; (b) the Hickson's et al. study used one training session every day, 6 days/week; we adopted only three sessions/week (alternate days); (c) the duration of the peak exercise bout was longer (5 rain against 1 rnin) and the interval between bouts shorter (2 min against 4 rain) for the authors quoted above, as compared to the present study; (d) while for Hickson et al. (1977) endurance represents the work load resulting in exhaustion within 2 - 5 min, we chose to consider endurance as the total mechanical work done during the MIE45 (see below).

It is well known that, followi.ng training, the change in VO 2 max is inversely related to the subjects initial VOzmax (Saltin et al. 1968; Shephard 1968; Knuttgen et al. 1973; Daniels et al. 1978). In trained subjects VO2 max did not change significantly with training (Fig. 1); this finding is in agreement with previous observations (Kasch. and Wallace 1976; Daniels et al. 1978). The importance of changes in VO2max related to improvement in running performance with training has been analyzed by Daniels et al. (1978) before and after 4 - 8 weeks of training. In untrained subjects VO 2 max increased during the first 4 weeks of training but failed to increase further, even in the presence of an increased training load. However runn!ng performances improved throughout the training period. In trained subjects VO2 max did not change, dispite running performance improvement. Our results agree with those of Daniels et al. (1978), with the largest increase in l/O2max and EC in untrained subjects.. The % increase in total mechanical work was significantly higher than that of VO2 max in both T and U subjects. While the contribution of non-physiological factors (learning, motivation, collaboration) can not be excluded, it is probable that some physiological changes could play a role. Henriksson and Reitman (1977) indicated that the adaptation of skeletal muscle to training may occur somewhat independently of changes in s 2 max, A number of studies have revealed that physical training in endurance results in increased activities of enzymes in the Krebs cycle and in fat oxydation (Gollnick et al. 1973; Benzi et al. 1975; Saltin et al. 1976). High values for skeletal muscle oxidative enzyme activity have been shown in elite runners (Costill et al. 1976).

Endurance athletes tend to ventilate less than non-athletes at equal heavy absolute work loads (Milic-Emili et al. 1962) and at comparable exercise intensities (Martin et al. 1979). Our results show that at VOzmax level the respiratory equivalent for oxygen (//JVO2) is higher than 30 in all subjects

386 M. Gimenez et al.

(35.8 +_ 0.7, n = 17), with no significant differences between T and U subjects, which is in agreement with Atomi and Miyashita (1980). The ventilatory profile observed during the MIE45 (Gimenez et al. 1982) and the high level of ventilation sustained during 45 min (Salinas and Gimenez 1981) suggest that the MIE45 can also train the ventilatory muscles (VM). Leith and Bradley (1976) and Keens et al. (1977), after specific training of ventilatory muscles (VM), found an improvement in endurance capacity. In our subjects, training increased the peak expiratory flow, peak inspiratory flow, MVV and maximal inspiratory flow at 50% of VC. This was accompanied by a significant increase in the static pressures developed by ventilatory muscles at both extremes of vital capacity (Fig. 5). To exclude the influence of learning, measurements were repeated (in the same conditions) at several days interval in a separate group of eight subjects (two females and six males) who were not submitted to training. No significant differences of static maximal pressures were found at TLC (89.5 + 6.9 and 91 + 7.1 cm H20, NS) and RV (86.3 + 6.9 and 87.6 + 7.5 cm H20, NS). Our results confirm those of Leith and Bradley (1976) and Keens et al. (1977), indicating that ventilatory muscle strength was improved by training.

In conclusion, after 6 weeks of training with the SWEET (MIE45) we observed in normal subjects a significant improvement of 1)O 2 max, VE max and endurance capacity (kJ �9 kg-1). Improvement of 1;102 max was more obvious in untrained than in trained subjects. The increase in endurance capacity was significantly higher than that of VO2max, suggesting that l?O2.max reflects endurance capacity less faithfully than MIE45. The increase in VEmax after training corresponds to a better endurance capacity and increase in force of the ventilatory muscles. Thus, the MIE45 may be applied for endurance training of both skeletal and ventilatory muscles.

The proposed MIE45 has several advantages as compared to other tests used for endurance training. First, it is an objective physiological test. Second, the MIE45 satisfies the conditions of an efficient training session: sufficient duration, intensity and significant amount of work. Finally, despite this intensity, the MIE45, performed at constant arterial pH and oxygen saturation, indicating homeostasis, is subjectively well tolerated.

Acknowledgements. The authors would particularly to thank the contribution of the physiotherapists Miss M. Khayech (Tunis), Miss L. Delorme (Sherbrooke), Miss B. Preneuf (Limoges) and Mr. D. Baldo (Bordeaux) for their careful and perseverant aid in the subject's training. They also wish to thank the subject's cooperation during the study, Miss M. C. Rohrer for illustrations and Miss B. Clement for typing the manuscript.

References

Aide-mdmoire pour la pratique de l'examen de la fonction ventilatoire par la spirographie, 26me ed, vol I/XI. Commission des Communaut6s Europ6ennes, Luxembourg 1971

Atomi Y, Miyashita M (1980) Effect of training intensity in adult females on aerobic power, related to lean body mass. Eur J Appl Physiol 44:109-116

Benzi G, Panceri P, De Bernardi M, Villa Arcelli E, D'Angelo L, Arrigoni E, Berte F (1975) Mitochondrlal enzymatic adaptation of skeletal muscle to endurance training. J Appl Physiol 38 : 565-569

Effect of SWEET Training 387

Black LF, Hyatt RE (1969) Maximal respiratory pressures. Normal values and relationship to age and sex. Am Rev Respir Dis 99:696-702

Costill DL, Fink WJ, Pollock ML (1976) Muscle fiber composition and enzyme activities of elite distance runners. Med Sci Sports 8:96-100

Daniels JT, Yarbrough RA, Foster C (1978) Changes in ~zO 2 max and running performance with training. Eur J Appl Physiol 39:249-254

Davies CTM, Knibbs AV (1971) The training stimulus: the effects of intensity, duration and frequency of effort on maximum aerobic power output. Int Z Angew Physiol 29:299-305

Eddy DO, Sparxs XL, Adelizi DA (1977) The effects of continuous and interval training in women and men. Eur J Appl Physiol 37:83-92

Fox EL, Barrels RL, Billings CE, Mathews DK, Bason R, Webh WM (1973) Intensity and distance of interval training programs and changes in aerobic power. Med Sci Sports 5:18-22

Gimenez M, Salinas W, Servera E, Kuntz C (1981) 1)O2 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

Gollnick PD, Armstrong RB, Saltin B, Saubert CW, Sembrowich WL, Shepherd RE (1973) Effect of training on enzyme activity and fiber composition of human skeletal muscle. J Appl Physiol 34:107-111

Henriksson J, Reitman JS (1977) Time course of changes in human skeletal muscle suecinate dehydrogenase and cytochrome oxidase activities and maximal oxygen uptake with physical activity and inactivity. Acta Physiol Scand 99:91-97

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

Kasch FW, Wallace JP (1976) Physiological variables during ten years of endurance exercise. Med Sci Sports 8 : 5-8

Kearney JT, Stull GA, Ewing Jr JL, Strein JW (1976) Cardiorespiratory responses of sedentary college women as a function of training intensity. J Appl Physiol 41:822-825

Keens TG, Krastins IRB, Vannamaker EM, Levison H, Crozier DN, Bryan AC (1977) Ventilatory muscle endurance training in normal subjects and patients with cystic fibrosis. Am Rev Respir Dis 116:853-860

Knuttgen HL, Nordesjo LO, Ollander B, Saltin B (1973) Physical conditioning through interval training with young male adults. Med Sci Sports 5:220-226

Leith DA, Bradley M (1976) Ventilatory muscle strength and endurance training, J Appl Physiol 41 : 508-516

Martin B J, Sparks KE, Zwillick CW, Weil JV (1979) Low exercise ventilation in endurance athletes. Med Sci Sports 11:181-185

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

Milic-Emili G, Petit JM, Deroanne R (1962) Mechanical work of breathing during exercise in trained and untrained subjects. J Appl Physiol 17:43-49

Pollock ML, Cureton TK, Greninger L (1969) Effects of frequency of training on working capacity, cardiovascular function and body composition of adult men. Med Sci Sports 1:70-74

Salinas W, Gimenez M (1981) Sujets s6dentaires. Entrafnement ~ l'exercice exhaustif en cr6neaux (45 rain). Med Sport 55:208-215

Saltin B, Blomquist G, Mitchell JH, Johnson RL, Wildenthal K, Chapman CB (1968) Response to exercise after bed rest and after training. Circulation 38 [Suppl 7]

Saltin B, Nazar K, Costill DL, Stein E, Jansson E, Essen B, Gollnick PD (1976) The nature of the training response: Peripheral and central adaptations to one-legged exercise. Acta Physiol Scand 96 : 289-305

Shephard RJ (1968) Intensity, duration and frequency of exercise as determinants of the response to a training regime. Int Z Angew Physiol 26:272-278

Accepted March 22, 1982