Pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise in young trained and untrained adults

Eur J Appl Physiol (1995) 70:442-450 © Springer-VerIag 1995 K. Chamari • S. Ahmaidi • C. Fabre • M. Ramonatxo C. Pr~faut Pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise in young trained and untrained adults Accepted: 13 November 1994 Abstract To investigate pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise and to study the effects of physical fitness on these responses, nine trained and nine untrained healthy male subjects aged 18-33 years performed the force-velocity (F-v) exercise test. This test consisted of 6-s sprints against increasing braking forces (F) separated by 5-min recovery periods. Oxygen uptake (VQ2), carbon dioxide output (VCO2), and ventilation (Ve) were continuously measured during the test and the magnitudes of their responses to the sprints were then calculated. For all subjects 1202 increased rapidly after beginning the sprints, and the peaks of the responses (F = 13.4; P < 0.001), end of recovery values (F = 6.5; P < 0.01), and VO2 magnitudes of response (F = 12.4; P < 0.001) rose significantly with the repetition of the sprints. The VO2 magnitudes of response correlated with the corresponding sprint power outputs (r = 0.55; P < 0.001) and with the sprint repetitions (r = 0.5.1, P<0.001). The I/CO2 ( F = 7 . 1 ; P < 0 . 0 1 ) and VE (F = 5.0; P < 0.01) peaks of response increased with the initial load incrementation, then stabilized when the subjects attained peak power output. End of recovery VCO2 ( F = l S . 0 ; P < 0 . 0 0 1 ) and I)E ( F = 1 4 . 1 ; P < 0.001) values rose with increasing F. The F-v peak 1)O2, VCO2, V~, tidal volume and respiratory frequency responses attained 53%, 40%, 44%, 66%, and 82% of the peak values measured at exhaustion of maximal graded exercise, respectively. Trained and untrained subjects had the same first sprint power output and braking, force. Nevertheless, the trained subjects had higher VOe peaks (F = 35.2; P < 0.001) and VO2 K. Chamari" S. Ahmaidi" C. Fabre' M. Ramonatxo. C. Pr6faut Laboratoire de Physiologie des Interactions Adaptations R6adaptation/t l'Exercice, Montpellier, France K. Chamari ( ~ ) Laboratoire Central d'Explorations Fontionnelles Respiratories, H6pital Arnaud de Villeneuve, 371 Av. du Doyen G. Giraud, F-34295-Montpellier Cedex 05, France magnitudes of response (F = 30.0; P < 0.001) than the untrained subjects for all sprints. The higher peak 1)O2 values represented similar percentages of maximal oxygen uptake in the trained and untrained subjects. In summary, the present study showed that in brief intense intermittent exercise, i.e. the F-v test, the 1)O2, 1)CO2, and ventilatory responses in young subjects were submaximal with respect to the peak values attained at exhaustion of maximal graded exercise. The !)O2 magnitude of response increase was related to the power output rise in the corresponding sprints and to the repetition of sprints. Moreover, the trained subjects presented higher VO2 peaks and magnitudes of response to the sprints than the untrained subjects. Key words Gas exchange • Ventilation • Intermittent exercise • Force velocity test • Training status introduction Numerous studies have investigated the peak pulmonary gas ex.change (oxygen uptake, VO2, carbon.dioxide output, VCO2) and ventilatory (ventilation, VE; tidal volume VT; respiratory frequency, f~) responses to maximal aerobic efforts with the corresponding effects of physical training adaptations (Whipp and Wasserman 1972; Hickson et al. 1978; Whipp et al. 1982 Hirakoba et al. 1992). However, it is widely acknowledged that intermittent exercise including repeated periods of maximal or all-out effort with varying loads constitutes the physical activity of a great number of people (Gaitanos et al..1993), Despite this, few studies have investigated the VO2, VCO2 and ventilatory responses to single bursts of exercise or to brief intermittent trials (Christensen et al. 1960; Fujihara et al. 1973; Green et al. 1987; Bakker et al. 1980). Moreover, in these studies effort was not maximal; only Christensen 443 et al. (1960), in a case report, have compared the intensity of these responses to the peak responses reached at exhaustion of maximal graded exercise but no data were given as to the effects of training on these responses. The force-velocity test (F-v) described by Pdres et al. (1981) has been widely used (Vandewalle et al. 1987; Bedu et al. 1991; Mercier et al. 1991; Delgado et al. 1993; Linossier et al. 1993) and consists of intense intermittent periods of exercise against increasing braking forces. This test thus would appear to be an appropriate model to obtain brief intense intermittent exercise and to allow the study of !202, 1)CO2, and ventilatory responses to such exercise. The aim of the present investigation was to study the following: 1. The manner and the extent to which the 1)O2, 1)CO2, and 1)E of young subjects responds to brief intense intermittent exercise, and 2. The effects of physical training as a means of improving these responses, by comparing trained and untrained subjects. Methods Subjects A group of 18 healthy men aged 18-33 years participated in this study. The trained subjects (n = 9, 6 long distance runners and 3 sprinters) trained 6-8 h ' w e a k - 1 and competed in national or international events. The untrained subjects (n = 9) performed less than 1.5 h of physical activity each week and had not participated in any sports competition for at least 5 years. The anthropometric characteristics of the subjects are reported in Table 1. All the subjects provided informed written consent before the study. Exercise To compare the peak I)O2, !)CO2, and ventilatory responses to the F - v test with the peak values attained at exhaustion of maximal graded exercise, the subjects came twice to the laboratory, once to perform the F - v exercise test and the second time, a maximal graded exercise (maximal oxygen uptake gO2max). F v test This test allowed the measurement of peak power output (PPO) for each subject (P+res et al. 1981) and was performed on a cycle ergometer (Monark 814 E, Varberg, Sweden). The subjects remained in a sitting position for both sprints and recovery periods. This exercise test consisted of repetitive short intense sprints against increasing braking forces (F). The duration of each sprint was fixed at 6 s, the maximal time it took for the highly motivated subject to attain maximal velocity (Vmax)for each sprint after the starting signal. The duration of each recovery period was fixed at 5 min. The Vmax and F v relationships were assessed during the test by an automatic system as described in an earlier study (Mercier et al. 1991). The test began against an F of 2 kg for all subjects. Thereafter, F was increased by 2 kg except at the end of the test when pedalling frequency dropped below 130 rpm. The F was then increased by 1 kg to obtain a peak power that was as precise as possible. For each sprint,power output (PO) was obtained by calculating the product F x Vma×.AS has been pointed out by Vandewalle et al. (1987), the relationship between F and v can be expressed as follows: v = b - aF or v = vo - voF/Fo = v0(1 F/Fo) where vo is the intercept with the v axis, i.e. the Vmaxfor a braking F equal to zero, and Fo the intercept with the F axis, i.e. the maximal braking F corresponding to a v equal to zero. These were calculated by extrapolation from the linear relationship linking F and v at a pedalling frequency greater than 90 rpm. Given the linear F v relationship, the power-force relationship is parabolic. The PPO was defined as the highest PO calculated for the different braking F. It was assumed that the subject attained PPO if an additional load induced a power decrease. Depending on their physical fitness the subjects performed 5 7 sprints each session. Maximal graded exercise This was performed on a calibrated cycle ergometer (Monark 818 E) and consisted of a warm-up of 3 min at 30 W at a pedalling rate of 60 rpm, immediately followed by increments of 30 W ' m i n - 1 to exhaustion. The 1)'O2 was considered maximal if at least three of the following criteria were achieved: (1) a levelling-off of l)Oe despite an increase in intensity, (2) a respiratory gas exchange greater than 1.10, (3) attainment of age-predicted maximal heart rate (HRmax): 210 0.65 - age _+ 5%, and (4) an inability of the subject to maintain the required pedalling frequency despite maximal effort and verbal encouragement. The power developed by the subjects while attaining l)'O2max was assumed to be peak aerobic power (PAP). Exhaustion occurred within 9 to 13 rain of exercise for all subjects. Measurement o f the !202, ]JCO2, and ventilatory variables During both exercise tests the subjects were connected to a breathby-breath automated metabolic system (CPX Medical Graphics, St Paul, Mich., USA). This system allowed us to measure continuously the pulmonary gas exchanges and ventilation during the pre-exercise, exercise, and recovery periods of both tests. Prior to each test the gas analysers were calibrated with gases of known concentration. The subjects were connected to the CPX system and breathed through a 100-ml dead-space, low-resistance valve. As the I202, 1)CO2, and ventilaroty variables are related to heart rate (HR), the exercise metabolic system was coupled with a three-lead electrocardiogram (ECG: Quinton Q 3000, Seattle, Wash., USA) that allowed HR recording. Protocol All the subjects were accustomed to the exercise tests performed. At least 2 days separated the exercise tests and all the experiments were done in the afternoon (between 2 to 5 pro) at a laboratory temperature of approximately 20 22°C. The subjects were asked to abstain from performing physical exercise for 1 day before the experiment and from smoking and drinking coffee in the 4 h preceding the test. On their arrival the subjects received instructions as to the test procedure. They underwent physical examinations including resting ECG and then anthropometric measurements were made. Expression of results Because of the numerous and unequal number of periods of exercise performed by the subjects during the F - v test, only three of the sprints and the respective recovery periods were studied. Expressed as a percentage o f F against which the subjects attained PPO (Fppo) , 444 the first sprint (A) ranged from 18% to 33% of Fpeo; the second one (B), from 50% to 66% of Fpeo; and the third sprint (C) corresponded to Fpeo (Table 1). As the subjects had different ventilatory responses during the F-v sprints, with some .holding their breath during the 6 s (Fujihara et al. 1973), only VO2, VCO2, and ventilatory responses during recovery were studied. To assess each variable during pre-exercise and the sprint recoveries, the values were averaged over eight respiratory cycles (Wasserman et al. 1986). This sliding technique provided a value at each respiratory cycle that was averaged over the cycle concerned and the seven preceding ones. Peak ]/O 2 and peak I?CO2 were followed separately and the ventilatory variables noted with respect to peak VCO2 (see Discussion). Because of its relative stability, HR was averaged over 30 s at pre-exercise and at the end of each recovery period (from 4 rain 15 s to 4 rain 45 s). However, to assess accurately peak HR responses to the sprints, HR was averaged over 5 s and the highest value considered as peak HR. During maximal graded exercise 1202, l?COz, and ventilatory variables were averaged over the eight sliding cycles, and HR was averaged over the last 20 s of every minute. Calculations The l)O> I)CO2, ventilatory, and HR magnitudes of response to each sprint were calculated by the difference of the presprint value preceding every exercise period and the following peak of response. Statistics The comparison between the two groups for anthropometric characteristics, vo, Fo, F-v variables, PAP, VO2, I)CO2, l)z, and HR measured at exhaustion of maximal graded exercise was performed using an unpaired Students t-test. To study the time course of the pulmonary gas exchange, ventilatory, and HR responses during the F v test, a two-way analysis of variance (ANOVA) was conducted (level of load and training status). The ANOVA was also conducted on sprints PO and on the magnitude of response to the sprints for VO2, VCO2, !2E, and HR. When the ANOVA F ratio was significant the analysis was then completed by a contrast test. Linear regression coefficients were calculated between sprint PO, the number of sprint repetitions and corresponding I202, VCO> ventilatory, and HR peaks and magnitudes of response. Statistical significance was fixed at P < 0.05. Results The anthropometric characteristics of the subjects and the mechanical variables calculated for the F-v test are listed in Table 1. The PO measured during sprints A, B, and C increased significantly and differed from one another (F = 160.6, P < 0.001). During the first sprint all the subjects pedalled against a braking F of 2 kg and PO did not differ between groups. The trained subjects had significantly higher PPO and PPO per kilogram than the untrained (F = 10.8, P < 0.01 and F = 15.0, P < 0.01, respectively). The PAP, gas exchange, and ventilatory variables reached by the subjects at exhaustion of maximal graded exercise are listed in Table 2. The trained subjects had significantly higher values than the untrained for PAP (t = 3.9, P < 0.01), 1)O2 Table 1 Anthropometric characteristics and force-velocity mechanical variables. Comparison between trained (n = 9) and untrained (n = 9) subjects (total n = 18). PO Sprint power output, PPO peak power output, (A) sprint A. A, B, and C 18%-33%, 50%-66%, and 100% of force at peak power output respectively, vo maximal velocity at zero force, Fo maximal force at zero velocity. All subjects Untrained subjects Trained subjects Mean SEM Mean SEM Mean SEM Age (year) Body mass (kg) Height (cm) PO (A) (W) PO (B) (W) PPO (C) (W) (W.kg 1) vo (rpm) Fo (kg) 24.0 1.1 24.1 1.5 24.0 1.8 NS 66.5 1.3 67.4 1.8 65.5 2.0 NS 176.2 1.8 177.8 2.9 174.5 2.2 NS 379.5 18.7 366.2 27.9 392.7 26.5 NS 787.2 18.4 730.3 28.5 844.1 24.9 * 996 27.4 925 33.5 1066 45.5 ** 14.9 0.4 13.8 0.5 16.0 0.6 ** 216.8 4.6 212.7 6.0 221.0 7.2 NS 18.0 0.8 17.3 1.1 18.8 1.2 NS NS Non-significant, * P < 0.05, **P < 0.01 Table 2 Peak mechanical and physiological variables attained at exhaustion of maximal graded exercise (maximal oxygen uptake). Comparison between trained (n = 9) and untrained (n = 9) subjects (total n = 18), PAP Peak aerobic power, VO2 oxygen uptake, !2CO2 carbon dioxide output, I?E ventilation, VT tidal volume, fR breathing frequency, HR heart rate All subjects Untrained subjects Trained subjects Mean SEM Mean SEM Mean SEM PAP (W) (/'O2 (ml'min-1) (ml-min l'kg-1) I)CO2 (ml'min -1) (/E (lmin 1) VT (ml) fR HR (rain -1) (beats.rain -1) 287.8 13.1 250.0 12.2 325.5 15.0 3590 177 3125 205 4055 191 4784 219 4232 296 5336 203 ** 126.0 6.0 109.4 7.5 142.6 5.2 ** 3312 127 3165 163 3459 192 NS 40.3 1.7 36.9 1.2 43.7 2.8 * 54.1 2.6 46.3 2.7 61.9 2.7 NS Non-significant, * P < 0.05, ** P < 0.01, ***P < 0.001 185.2 3.3 183.7 5.7 186.8 3.8 NS 445 and VO 2 per kilogram (t.= 3.3, P < 0.01 and t = 4.1, P < 0.001, respectively), VCO2 (t = 3.1, P < 0.01), !)~ (t = 3.6, P < 0.01), a n d f ~ (t = 2.2, P < 0.05). and ¢ 0 2 magnitudes of response (F = 30.0, P < 0.001; Fig. 3) to the sprints. The higher peak 1/O2 value represented similar percentages of VO2m,x in the trained and untrained subjects~ 2500 l ) O : responses to the F - v test Tra~r~ed~ ~ U~ztrc~r~ed For a l l s u b j e c t s 2000 The m e a n l)O2values (Fig. 1) for all subjects s h o w e d that b o t h sprint B and C peaks of response were higher than A (F = 13.4, P < 0.001). In c o m p a r i s o n to the pre-exercise values, 1)O: end of recovery values increased with rising F (F = 6.5, P < 0.01). The 1)O2 1500 magnitudes of response to the sprints increased with rising F (F = 12.4, P < 0.001) and were correlated to the c o r r e s p o n d i n g sprint P O (r = 0.55, P < 0.001) and to the repetition of periods of exercise (r = 0 . 5 1 , P < 0.001). The higher p e a k ¢ O : value represented 53% of VO2max m e a s u r e d at e x h a u s t i o n of m a x i m a l ~z 1000 graded exercise. o Pre-ex T h e y had similar pre-exercise and end of recovery 1)O2 values but the trained subjects had higher VO2 peaks (F = 35.2, P < 0.001 for A and B, P < 0.05 for C; Fig. 2) (5~) 2000 (4~) ***/Peak (41%) ***/Peak A //> /// /// I 1000 /// /// /// 500 (~ ~ ~ ) /// /// ¢'// //2 "/.4, (ta~) **/Pez // // // gx pt~ag a RFCOF, A PEAK B R~COV, B P~AK C B Peak C Fig. 2 The oxygen uptake (l)O:) responses of trained and untrained subjects to the force-velocity test. Results of the trained (n = 9) and untrained (n = 9) subjects. The short histograms represent the preexercise (pre-ex) and end of recovery (Rec) values, the tall histograms show the peaks of response to sprints A, B, and C, i.e. 18%-33%, 50% 66%, and 100% of the braking force at peak power output, respectively. Comparison is made between trained and untrained subjects. *P < 0.05, ***P < 0.001 ["'7 UTdrecir~ed +(~) 1~oo T (A) dff" //// ///.,'1 [ .~ 1400 T ~ * * "/% (ss~) **//~z 1200 r// r/I e./.~ 2 "0 .-i/ 1ooo RECOV. C h./ i// (Pzx) Fig. 1 The oxygen uptake 1)O2 response to the force-velocity. Results of all subjects (n = 18). The short histograms represent the pre-exercise and end of recovery values (4 min 30 s of recovery), the tall histograms show the peaks of response to sprints A, B and C, i.e. 18%-33%, 50%-66%, and t00% of the breaking force at peak power output, respectively. The numbers above the columns represent the percentages of the peak values attained at exhaustion of maximal graded exercise (maximal oxygen uptake). Comparisons are made with respect to pre-exercise (pex) for the end of recovery values and with respect to the first sprint peak (peak A) of response for the B and C peaks. **P < 0.01, ***P < 0.001. ///z ~'/i., ills r/J., b. /// /// /// /// /// /// P~E I// Ree C Ree B Peak A /// /// /// /// /// /// /// /// /// /// /// /// /// /// /// /// 1500 Rec A Peak A Trained and untrained s u b j e c t s I/I //I 1is f//i i//.{ t'i/j r//~, r/iz N i//I 1i/i FI/~ iiii i//I iiiI r//I ///'A ill/ //// l/is //// ~00 Ma 9 A Ma 9 B Mccg C Fig. 3 The oxygen uptake (1202) magnitude (mag) of response to the force velocity test. Results of trained (n = 9) and untrained (n = 9) subjects. Comparison is made between groups (*) and between magnitudes of response to sprints A, B, and C (+), i.e. 18%-33%, 50%-66%, and 100% of the braking force at peak power output, respectively. **P < 0.05, **P < 0.01, + + +'***P < 0.001 ( + significance Mag A, B and C), * significance trained compared to untrained. 446 g c o 2 responses to the F-v test (44%) 70 **/Peak A (43%) **/Peak For all subjects i// 60 The mean 19CO2 values (Fig. 4) for all subjects showed that both sprint B and C peaks of response were higher than A (F = 7.1, P < 0.001 for B and P < 0.01 for C) but peak C tended to decrease in comparison to peak B. In comparison to the pre-exercise values, 19CO2 end of recovery values increased with rising F (F = 18.0, P < 0.001). The 19CO2 magnitudes of response to the sprints did not vary with rising F. The higher peak 1)CO2 value represented 40% of gCO2max measured at exhaustion of maximal graded exercise. ~I (30%) 5o T rl., ¢'/I ¢./,¢ ¢-fl ¢.z.I ~ 4o ~ so zo 10 (1 t%) ¢'1/ lj/ ffJ /.I,¢ ¢'1/ (t.5%) ¢.lJ ¢.j/ ¢./j PRI~ EX (Pez) PEAK A RECOV. A Ill /// /// /// /// /// III /// iii III III /// /// /// PEAK T /// /// /// /// /// /// I/I I/~ II/ III III /// III III /// /// /// /// ili /// (t7%) ***/Pex /// Ill /// /// /// /// B RECOY. E PEAK REeOV. C Fig. 5 Ventilation (VE) response to the f o r c e velocity t e s t . For comments see Fig. 1. **P < 0.01, ***P < 0.001 Trained and untrained subjects They had similar 1/CO2 values (Fig. 4) and l)COz magnitudes of response to the sprints. I)B responses to the F-v test For all subjects 2500 m Trained Untrained (38%) (40%) +++J ++/ Peak Pear A A £000 (~o~) I $ f500 , I000 I m +++/ +++/I IW~+++/ Pex The mean I)E values (Fig. 5) for all subjects showed that both sprint B and C peaks of response were higher than A (F = 5.0, P < 0.01). In comparison to the pre-exercise values, VE end of recovery values increased with rising F (F = 14.1, P < 0.01 for A and P < 0.001 for B and C). The I)E magnitudes of response to sprint B increased in comparison to A (F--2.5, P < 0.05).. There was a positive relationship linking 1/~ and VCO2 peaks of response (r = 0.83, P < 0.001, y = 0.44x - 20.13). The higher peak I)E value represented 44% of maximal l/> measured at exhaustion of maximal graded exercise. 600 Trained and untrained subjects Pre-ex (Pex) Rec B Bec A Peak A Peak B Bee C Pea& C Fig. 4 The carbondioxide output (l)COz) response to the f o r c e - v e locity test. Results of the trained (n = 9) and untrained (n = 9) subjects. The short h i s t o g r a m s represent the pre-exercise ( P e x ) and end of recovery values, the tall h i s t o g r a m s show the peaks of response to sprints A, B and C, i.e. 18% 33%, 50% 66%, and 100% of the braking force at peak power output, respectively. Comparison between trained and untrained subjects shows no difference of response. For all subjects comparison is made with respect to P e x for the end of recovery values and with respect to the first sprint peak of response for the B and C peaks ( + ). The n u m b e r a b o v e the columns represent the percentages of the peak values attained at exhaustion of maximal graded exercise (maximal oxygen uptake). ++P < 0.01, + + +P < 0.001./Pex a n d / P e a k A , in comparison to P e x and P e a k A, respectively They had similar I)E values and I?E magnitudes of response to the sprints. VT response to the F v test For all subjects The VT values for all subjects showed that the sprint peaks of response were constant whereas the end of recovery values increased in comparison to the preexercise values (F = 2.9, P < 0.05). The VT magnitudes of response did not vary with rising F. The higher peak Vs value represented 66% of maximal VT measured at exhaustion of maximal graded exercise. 447 Trained and untrained subjects They had similar VT values and response to the sprints. VT magnitudes of A and P < 0.001 for B and C). The HR magnitudes of response to the sprints were constant with rising F. The higher peak HR value represented 83 % of HRmax measured at exhaustion of maximal graded exercise. fR response to the F-v test Trained and untrained subjects For all subjects They had similar mean HR values. However, the trained subjects had lower pre-exercise and end of recovery values and higher HR peaks; thus, their first sprint HR magnitude of response was higher (F = 11.0, P < 0.05). ThefR values for all subjects showed that the peaks of response to the sprints increased with rising F (F = 3.0, P < 0.05) whereas fR end of recovery values were similar to pre-exercise. The fR magnitudes of response to sprint C increased in comparison to A (F = 2.5, P < 0.05). The higher peakfR value represented 82% of maximalfR measured at exhaustion of maximal graded exercise. Trained and untrained subjects They had similar fR values and fR magnitudes of response to the sprints. HR response to the F-v test For all subjects The mean HR values (Fig. 6) for all subjects showed that both sprint B and C peaks of response were higher than A (F = 7.3, P < 0.05 for B and P < 0.001 for C). In comparison to pre-exercise values, end of recovery HR increased with the rising F (F = 11.7, P < 0.05 for (83%) (sty) leo ***,/Peak A /Peak (7~) I 120 1~0 (47%) //J I l l i l l I l l I l l f l l / I / II] I l l I l l f / i ,r/i / / / / [ i [1[ I f i I l l / / / I l l f i t 80 60 I Y 140 g$ T // // // 1 / / i ~..f j f/J Pre-ex (P~-) t/J fiJ liJ /iJ (53%) */Pea: V//1 1iJ f/j 1/J ~,/j //j 1///1 fiJ / i / **/Ree A *,*/p~ /i ]I ~/ !' ***/Pex f// /J/ /// /// /// l l / I l l / / / * / Rec /// /// //./ Y/d f/'j 4ll F.fJ ff.~ Rec A Peal A ,,"il"v/"'illz (Go%) ~59%, /// /// /// / / / ,,'ix /// /// /ll /// /// //J / / / / / i l i i /f / Bee B Peak B g/ T I / A ~ I/A I/A I/A I/A ~./A ~/A ,,./A I / ~ I / A / / A /JA Rec C PeM¢ C Fig. 6 H e a t rate (HR) response to the force-velocity test. F o r c o m m e n t s see Fig. 1. *P < 0.05, **P < 0.01, ***P < 0.001 Discussion The present study showed that in response to the F v test, a model of brief intense intermittent exercise, 1)O2 peaks and magnitudes of response to the sprints increased in the adults studied as did the end of recovery values in com.parison to the pre-exercise values. The 12CO2 and VE peaks of response reached a plateau after an initial increase and end of recovery values increased. The l)Oa, I)CO2, and ventilatory peak responses to the F-v test were submaximal in comparison to the peak values attained at exhaustion of maximal graded exercise. The trained subjects had higher 1202 peaks and magnitudes of response than the untrained subjects despite similar percentages of 1202 .... but both groups had similar values for VCOa and ventilatory variables. The F-v test, which determined the PO corresponding to Vmax, did not take into account the flywheel inertia. The PPO did not therefore directly express the maximal anaerobic power sustained by the subjects (Lakomy 1986). However, calculated PPO, Vo, and Fo variables were assessed in the same conditions for all subjects and thus provided power, v, and F characteristics which allowed group comparisons (Linossier et al. 1993). Furthermore, in the present study, the F-v test was used as a model that allowed us to record the pulmonary gas exchanges and ventilatory responses to intense brief intermittent exercise. In this study 1)O2 peaked after the end of the sprint. This rise may be due to the concomitant peak HR observed. Indeed, Whipp et al. (1982) have proposed a "cardiodynamic" response of VO2, presumably related to the rapid change in pulmonary blood flow. This rise in VO2 would also replenish the 02 body stores, i.e. 02 content of the lungs, physically dissolved 02, and 02 bound to the myoglobin and haemoglobin used for such exercise (Astrand et al. 1960; Whipp and Wasserman 1972; Cerretelli and Di Prampero 1987). The 1902. peaks of response to the sprints increased, as did the VO2 magnitudes of response that were correlated to the corresponding sprint PO during the F v test. 448 This indicated that the VO 2 response was quantitatively related to the amount of work done (Bakker et al. 1980 t . However, sprint repetition was also related to the g o 2 increase. Indeed, this factor cannot be ruled out since a 1?O2 increase was also observed by Weltman et al. (1979), Buono and Roby (1982), Green et al. (1987), and Vollestad et al. (1990), all of whom studied intermittent exercise with repetitive constant exercise intensities. Our exercise protocol did not allow us to determine which of the two factors, i.e. the intensity increments or the sprint repetition, was predominantly responsible of the VO2 increase. The increased end of recovery VO2 noted in this study may have been due to lactate oxidation during the inactive recovery (Brooks 1991). Indeed, it has been shown in our laboratory that during the F-v test venous plasma lactate concentration is already increased by the end of the first sprint recovery. (Mercier et al. 1991). The VCO2 peaks of response after the start of the sprint may be attributed to both the "cardiodynamic" effect (Whipp et al. 1982) and excess VC02 reflecting the amount of CO2 eliminated to compensate for changes in the acid-base balance (Cerretelli and Di Prampero 1987). However, the latter hypothesis probably explains only a relatively small part of the response as the peak response occurred in the first seconds of recovery and it has been shown that lactate concentration is significantly increased only later during recovery (Mercier et al. 1991). The peak 1)CO2 responses to sprints B and C were similar but much higher than the response to sprint A. This result would seem to be in contradiction with the results of Bakker et al. (1980), who have suggested linearity of 17CO2 in response to short single exercises. However, this trend towards a plateau of 17CO2 may be due to an increased aerobic contribution to energy metabolism which is consistent with the hypothesis of Robergs et al. (1991) and Gaitanos et al. (1993). The increased end of recovery 1/CO2 was consistent with the results of Green et al. (1987) and may be attributed to the buffering of H + from lactic acid in the muscle (Cerretelli and Di Prampero 1987; Hirakoba et al. 1992) as glycogenolysis has been shown to be already activated in such short intensive exercise.(Mercier et al. 1991; Gaitanos et al. 1993). The VE was followed with respect to 12CO2 because it has been established that VC02 responses lead those of l/e (Diamond et al. 1977; Bakker et al. 1980; Wasserman et al. 1986; Whipp and Pardy 1986). Indeed, VE responds to the F-v test in the same way as does VCO2. The VE response.to exercise is multifactorial (Paterson 1992); thus, the VE peaks are probably the sum of the following three phenomena: 1. The "cardiodynamic" response, as the initial rise in 1?~ roughly parallels changes in HR (Fujihara et al. 1973; Wasserman et al. 1986); 2. The induced catecholamine (CA) rise (Wasserman et al. 1986; Pluto et al. 1988; Paterson 1992), as the increase in CA in response to the F v sprints was shown in our laboratory by Caillaud et al. (1991) and confirmed by Gaitanos et al. (1993) in 6-s intermittent exercise; and 3. The above-mentioned increases in CO2 and H ÷ production (Buono and Roby 1982; Wasserman et al. 1986). The increased 1/E peaks of response to sprints B and C with respect to A were not in accordance with the results of Fujihara et al. (1973) and Bakker et al. (1980), who have suggested the linearity of this variable in response to short periods of exercise. However, the peak VE time course can be explained by CO2 production as it roughly paralleled that Of the V C O 2 observed in the present study. It is likely that the increased end of recovery VE values (Green et al. 1987) are closely related to the concomitant increased end of recovery I)CO2. From the time course of V T and fR it appears that the changes in I/E during the F-v test were clearly different between the first and last minutes of recovery. Indeed, the increased !)E at the end of recovery was caused in the main by an increased VT, whereas I?E peaked because of a steep increase of fR. Despite the postexercise measurements, these results were similar to those found in maximal graded exercise where two distinct phases (range one and two, respectively) have been differentiated with increasing load (Whipp and Pardy 1986). For the entire population of subjects, the percentages of the F-v peak VO> VCO:, VE, VS, fR, and HR (53%, 40%, 44%, 66%, 82% and 83% respectively), with respect to the maximal values measured at exhaustion of maximal graded exercise, showed that these responses were submaximal. Thus, because of the long recovery periods (Christensen et al. 1960), the F-v test maximally involved the subject's muscles without overloading the cardioventilatory system. This is consistent with the results of Hurley et al. (1988), with a 1)O2 representing only 45% of 1/O2 .... in a high intensity strength-training session. The results of the two groups showed that the trained subjects had higher sprint A VO2 peaks and magnitudes of response than the untrained subjects despite the same sprint power output. This may have been due to the higher first sprint HR magnitude of response of the trained subjects. Indeed, the more rapid adaptation to gas exchange in the trained state has been underlined by Hagberg et al. (1978), Hickson et al. (1978), and Cerretelli and Di Prampero (1987), who have concluded that the adaptations induced by endurance training seem to induce a faster oxidative participation by a faster cardio-acceleration. Since the VO2 magnitudes of response of the trained subjects were higher than those of the untrained subjects, despite the same HR magnitudes of response for sprints B and C, another cause of this difference may be the increased muscle 02 extraction following adaptations to exercise training (Hagberg et al. 1978; Hickson et al. 1978). Furthermore, because during the F-v test the two 449 groups of subjects t o o k up oxygen to the same relative extent, i.e. similar percentages of 1202 . . . . the higher 1202 peaks of response for the trained subjects m a y have been due to their higher absolute 1202max(Granier et al. in press). The trained and untrained subjects had similar 12CO2 values in response to the sprints. T o our knowledge, there have been no studies dealing with the effects of training status on these responses to short exercise; we therefore c o m p a r e d our results to those of H i r a k o b a et al (1992),. w h o have studied the effects of training status on the VCO2 responses to m a x i m a l graded .exercise. These authors have observed an enhanced VCO2 in post-training which is not in accordance with the present findings on brief intense intermittent exercise. Indeed, it is generally accepted that p e a k b l o o d lactate concentration m e a s u r e d after m a x i m a l graded exercise is higher in trained t h a n in untrained subjects; however, the results have been shown to be different in other exercise conditions, e.g. constant s u b m a x i m a l exercise (Brooks 1991). Despite higher P O for the B and C sprints, the trained subjects h a d 12CO2 values similar to those of the untrained subjects. Thus, it can be hypothesized that the trained subjects did not have higher lactacidaemia due to an increased participation of the oxidative m e t a b o l i s m to energy p r o d u c t i o n in these subjects ( H a g b e r g et al. 1978). The similar responses of the trained and untrained subjects for VE, despite increased 1202 responses, would suggest a better yield of l) E to 1202 in the trained state. This result was also observed in m a x i m a l graded exercise and could be explained by the a b o v e - m e n tioned higher oxygen extraction in the trained state. In s u m m a r y , the present study showed that in brief intense intermittent exercise, the m a g n i t u d e of response of 1202 was closely related to the corresponding sprint P O and to the repetition of sprints. F u r t h e r m o r e , the 1202, I?CO2, and ventilatory responses of the y o u n g adults to the F- v test were s u b m a x i m a l with respect to the peaks attained at exhaustion of m a x i m a l graded exercise. Lastly, the participation of oxidative m e t a b o l ism in brief intense intermittent exercise was higher in the trained than in the untrained subjects. References Astrand I, Astrand PO, Christensen EH, Hedman R (1960) Intermittent muscular work. Acta Physiol Scand 48:448-453 Bakker HK, Struikenkamp RS, De Vries GA (1980) Dynamics of ventilation, heart rate, and gas exchange: sinusoidal and impulse work loads in man. J Appl PhysioI 48:289-301 Bedu M, Fellmann N, Spielvogel H, Falgairette G, Van Praagh E, Coudert J (1991) Force-velocity and 30 s Wingate tests in boys at high altitudes. J Appl Physiol 70:1031-1037 Brooks GA (1991) Current concepts in lactate exchange. Med Sci Sports Exerc 23:895-906 Buono M J, Roby FB (1982) Acid-base, metabolic, and ventilatory responses to repeated bouts of exercise. J Appl Physiol Respir Environ Exerc Physiol 53:436-439 Caillaud C, Collomp K, Audran M, Chanal JL, Prefaut C (1991) Influence d'un exercise bref et intense sur les concentrations plasmatiques d'adr6naline et de noradr6naline. CR Soc Biol 185:84 90 Cerretti P, Di Prampero P (1987) Gas exchange in exercise. Handbook of Physiology secion 3. The respiratory system Vol 4 (Gas exchange). Americal Physiological Society, Bethesda, Md., pp 313 323 Christensen EH, Hedman R, Saltin B (1960) Intermittent and continuous running. (A further contribution to the physiology of intermittent work.) Acta Physiol Scand 50:269 286 Delgado A, Allemandou A, P6res G (1993) Changes in characteristics of anaerobic exercise in the upper limb during puberty in boys. J Appl Physiol 66:376-380 Diamond LB, Casaburi R, Wasserman K, Whipp BJ (1977) Kinetics of gas exchange and ventilation in transitions from rest or prior exercise. J Appl Physiol Respir Environ Exerc Physiol 43: 704-708 Fujihara Y, Hildebrandt JR, Hildebrandt J (1973) Cardiorespiratory transients in exercising man. I. Tests of superposition. J Appl Physiol 35:58 67 Gaitanos GC, Williams C, Boobis H, Brooks S (1993) Human muscle metabolism during intermittent maximal exercise. J Appl Physiol 75:712 719 Granier P, Mercier B, Mercier J, Anselme F, Pr6faut C (1995) Aerobic and anaerobic contribution to Wingate test performance in sprint and middle-distance runners. Eur J Appl Physiol (In press) Green H J, Hughson RL, Thomson JA, Sharratt MT (1987) Supramaximal exercise after training-induced hypervolemia. I. Gas exchange and acid-base balance. J Appl Physiol 62:1944 1953 Hagberg JM, Nagle FJ, Carlson JL (1978) Transient 02 uptake response at the onset of exercise. J Appl Physiol Respir Environ Exerc Physiol 44:90-92 Hickson RC, Bomze HA, Holloszy JO (1978) Faster adjustment of 02 uptake to the energy requirement of exercise in the trained state. J Appl Physiol Respir Environ Exerc Physiol 44:877 881 Hirakoba K, Maruyama A, Inaki M, Misaka K (1992) Effect of endurance training on excessive CO2 expiration due to lactate production in exercise. Eur J Appl Physiol 64:73-77 Hurley BF, Hagberg JM, Goldberg AP, Seals DR, Ehsani AA, Brennan RE, Holloszy JO (1988) Resistive training can reduce coronary risk factors without altering gO2max or percent body fat. Med Sci Sports Exerc 20:150 154 Lakomy HKA (1986) Measurement of work and power output using friction-loaded cycle ergometers. Ergonomics 29:509 517 Linossier MT, Denis C, Dormois D, Geyssant A, Lacour JR (1993) Ergometric and metabolic adaptations to a 5-s sprint programme. Eur J Appl Physiol 67:408-414 Mercier J, Mercier B, Pr6faut C (1991) Blood lactate increase during the force velocity exercise test. Int J Sports Med 12:17-20 Paterson DJ (1992) Potassium and ventilation in exercise. J Appl Physiol 72:811 820 P~res G, Vandewalle H, Monod H (1981) Aspect particulier de la relation charge-vitesse sur cycloergom+tre. J Physiol (Paris): 77 Pluto R, Cruze SA, Weil3 M, Hotz T, Mandel P, Weiker H (1988) Cardiocirculatory, hormonal, and metabolic reactions to various forms of ergometric tests. Int J Sports Med [Suppl] 9:79-88 Robergs RA, Pascoe DD, Costill DL, Fink WJ, ChwalbinskaMoneta J, Davis JA, Hickner R (1991) Effects of warm-up on muscle glycogenolysis during intense exercise. Med Sci Sports Exerc 23:37 43 Vandevalle H, P6res G, Hellen J, Panel J, Monod H (1987) Force velocity relationship and maximal power on a cycle ergometer. Eur J Appl Physiol 56:650-656 VMiestad NK, Wesche J, Sejersted OM (1990) Gradual increase in leg oxygen uptake during repeated submaximal contractions in humans. J Appl Physiol 68:1150-1156 450 Wasserman K, Whipp BJ, Casaburi R (1986) Respiratory control during exercise. Handbook of physiology section 3. The respiratory system vol 2, part 2. Control of breathing. American Physiological Society, Bethesda, Mass pp. 595-613 Weltman A, Stamford BA, Fulco C (1979) Recovery from maximal exercise: lactate disappearance and subsequent performance. J Appl Physiol Respir Environ Exerc Physiol 47:677-682 Whipp BJ, Wasserman K (1972) Oxygen uptake kinetics for various intensities of constant-load work. J Appl Physiol 33:351-356 Whipp BJ, Pardy RL (1986) Breathing during exercise. Handbook of physiol section 3. The respiratory system vol 3, part 1. Mechanics of breathing. American Physiological Society, Bethesda, Mass pp. 608-611 and 623 Whipp BJ, Ward SA, Lamarra N, Davis JA, Wasserman K (1982) Parameters of ventilatory and gas exchange dynamics during exercise. J Appl Physiol Respir Environ Exerc Physiol 52:1506 1513