Applied Physiology
Eur J Appl Physiol (1992) 64:134-138
European Journal of
and Occupational Physiology @ Springer-Verlag 1992
Blood pressure and heart rate during rest-exercise and exercise-rest transitions K. Baum, D. Efifeld, D. Leyk, and J. Stegemano Physiologisches Institut der Deutschen Sporthochschule K61n, Carl-Diem-Weg 6, W-5000 Cologne 41, Federal Republic of Germany Accepted September 30, 1991
Summary. The transients of mean arterial blood pressure (BPa) and heart rate (fc) during rest-exercise and exercise-rest transitions have been studied in six healthy sport students. After 5 rain of rest in an upright position on a cycle ergometer they exercised for 15 min and remained seated for a further 5 min. The subjects exercised at four different constant intensities (40 W, 80 W, 120 W, 160 W) in r a n d o m order separated by at least 24 h. The BPa was determined by a noninvasive and continuous method. During the first minute of exercise, three phases of response could be distinguished, with the first two showing no clear relationship to intensity. Phase 1 consisted of simultaneous increases in b o t h f o and BP during the first 6 s. In phase 2, BPa decreased while f¢ continued to increase. During phase 3, BPa a n d f c approximated constant values or a linear increase. Both parameters showed no comparable intensity-independent reactions during the off-transients. In conclusion, during the first 15 s of rest-exercise transitions there seems to be a fast and uniform cardiovascular drive which overrode other influences on ft.
Key words: Exercise - Humans - Blood pressure Heart rate - Transients
narsson 1974; Karlsson et al. 1975) or even a decrease (Beaver and Wasserman 1968; Fujihara et al. 1973; Karlsson et al. 1975; Miyamoto et al. 1982). Since the early component of fc response can be abolished by prior administration of atropine, this phase has been attributed to a rapid vagal withdrawal followed by a temporary increase in vagal tone (Fagraeus and Linnarsson 1976). The origin of this change is still unclear. Fagraeus and Linnarsson (1976) have suggested that the baroreceptor reflex plays a leading role. Unfortunately, a meaningful interpretation of suchfc data is hampered by the lack of simultaneous blood pressure recordings. This is due to methodological problems: the RivaRocci method commonly used in exercise physiology does not allow a sufficiently small time resolution so that invasive approaches have been the only accepted alternative so far. Recently, a noninvasive continuous method originally described by Penaz (1973) has been made commercially available (Finapres TM, Ohmeda 2300). Comparisons with invasive methods have shown good agreement during rest if potential differences in hydrostatic pressure are taken into account. In the present study we have used a Finapres device to compare the on- and off-responses in f~ and mean arterial blood pressure (B---P~) during changes between rest and constant intensity exercise at four levels.
Introduction Blood pressure and heart rate (f~) adjustments following transitions between rest and exercise are more complex than exercise-exercise transients. The onset of the "muscle pump", a greater relative influence of vagal withdrawal, and the onset o f cardiac output redistribution have to be taken into account. The initial fc responses to rest-exercise steps have been reported to consist of a rapid increase followed by a transient flattening (Broman and Wigertz 1971; Lin-
Offprint requests to: K. Baum
Methods Subjects. Six healthy sport students [three male, three female; mean age 22 (SEM 2) years, mean body mass 71 (SEM 3) kg, mean height 176 (SEM 11) cm] participated in the study. Experimental protocol. Exercise tests consisted of constant intensity cycling at four different levels in the upright position (40 W, 80 W, 120 W, and 160 W; 15 min duration each). The subjects exercised at the different intensities in random order with time intervals of at least 1 day between two tests. Before and after exercise, the subjects sat quietly on the cycle ergometer for 10 rain and 5 rain, respectively.
135 At 30 s, 5 s, immediately before and the end of exercise, the subjects were informed by an acoustic signal to start and terminate cycling. At the start of exercise, steady-state intensities were reached within 2 s to 4 s. The BPa was measured continuously by Finapres. A small finger cuff was placed around the middle phalanx of the third finger. A fast feedback loop including an infrared light source and detector, an air pump, and a microprocessor keeps the wall of the finger arteries at the so-called "unloaded size". At this p____ointthe cuff pressure equalled the arterial blood pressure. The BP~ were computed from the pressure integrals between two R-waves. Since the peripheral blood pressure measurement is sensitive to changes in hydrostatic pressure, the hand with the finger cuff was placed on a padded platform at the level of the heart. The fc was determined separately by means of standard electrocardiogram leads. Oxygen uptake (1202, standard temperature and pressure, dry) was measured by a breath-by-breath technique described earlier (El3feld et al. 1987). The subjects breathed room air through a mask connected to a Fleisch sensor, Fenyves and Gut, Basel. Pneumotachogram and mass spectrometer readings for N2, 02, and CO2 were recorded by a microprocessor system. During a final off-line analysis the mass spectrometer values were corrected for transportation delay, response time, and vapour pressure. Gas exchange values were computed as differences between inspired and expired volumes (body temperature, pressu__re, saturated). Measurements of exercise intensity,, f c, BP, and VO2 were stored on a microprocessor. Individual VO2 data were calculated as consecutive means over 10-s intervals. Intervals of 2 s were chosen to evahmte the on- and off-responses in exercise intensity, f~ and BP~. Pre- and postexercise controls were taken as means of the last minute during rest and recovery.
180- -
40W
~
~ 8ow 1 60 ] .-. ,2ow -
m-m
160W
140O)
£ D I13 _(2
120 ]
oo5 8°i 60
,,,, 0
5
10
15
20
25
time (rain)
Fig. 1. Time course of heart rate before, during, and after cycling (mean values, n = 6)
took about 5 rain before 1202 stabilized at 2.38 (SD 0.07) 1- m i n - 1. In contrast to 1~O2, steady-state responses in fc (Fig. 1) could be obtained only at 4 0 W [97 (SD 4) beats, min-5]. In the other tests fc increased from the 5th to the last exercise minute by 6 beats, r a i n - ~ (80 W), 12 beats.rain -1 (120 W), and 15 b e a t s . m i n -a (160 W). As for I202 andf~, the mean steady-state increases in BPa were correlated to the exercise intensity and amounted to 7 m m H g (40W), 1 0 m m H g (80W), 12 m m Hg (120 W), and 16 mm Hg (160 W).
Results
Kinetics of f~ and blood pressure
Steady responses of f~ and blood pressure The pre- and postexercise values are given in Table 1. After about 2 rain o f exercise, VO2 reached the following steady-state values at 40 W, 80 W, and 120 W: 0.98 (SD 0.13) l . m i n -1, 1.42 (SD 0.09) 1.rain -a, and 1.93 (SD 0.19) 1.min -1, respectively. At the 160-W level it Table 1. Oxygen up___take(1202), heart rate (fc) and mean arterial blood pressure (BPa) during the 5-min pre- and postexercise (mean and SD, n=6) Exercise intensity (W)
Pre-exercise (5 min)
Post-exercise (5 min)
fO 2 (1.min -~)
40 80 120 160
mean 0.38 0.36 0.36 0.37
SD 0.03 0.02 0.04 0.04
mean 0.39 0.36 0.40 0.42
SD 0.04 0.03 0.04 0.05
f~ (beats.min -1)
40 80 120 160
80 74 76 79
4 5 5 7
80 80 88 101
6 5 6 6
40 80 120 160
88 91 85 91
5 4 5 4
93 96 94 95
7 6 8 5
BPa (ram Hg)
On-response. During the initial phase of exercise three phases could be distinguished (Figs. 2, 3): phase 1 - f c and BPa increased simultaneously (0 s-6 s) phase 2 - the BPa decreased while fo continued to increase (6 s-12 s) phase 3 - both parameters approximated constant values or a linear increase. The kinetics of phases 1 and 2 showed no obvious relationship to the exercise intensity. The "notches" in f~ between phases 2 and 3 were inversely related to changes in BP~ with a time delay o f several seconds. Off-response. No comparable kinetics were seen during the off-responses. Almost monophasic reductions in fo occurred after a time delay o f a few seconds (Fig. 4). At the end of cycling at the higher workloads BPa transiently declined below postexercise steady-state values (Fig. 5). Discussion In the present study we measured finger blood pressure rather than central blood pressure. Peripheral blood pressure is characterized by a greater systolic-diastolic amplitude and a greater sensitivity to thermoregulatory events (Rowell et al. 1968; Hildebrandt et al. 1991). We are not aware of any direct comparison o f results from
136 qc ul
~d x:
Eur J Appl Physiol (1992) 64:134-138
European Journal of
and Occupational Physiology @ Springer-Verlag 1992
Blood pressure and heart rate during rest-exercise and exercise-rest transitions K. Baum, D. Efifeld, D. Leyk, and J. Stegemano Physiologisches Institut der Deutschen Sporthochschule K61n, Carl-Diem-Weg 6, W-5000 Cologne 41, Federal Republic of Germany Accepted September 30, 1991
Summary. The transients of mean arterial blood pressure (BPa) and heart rate (fc) during rest-exercise and exercise-rest transitions have been studied in six healthy sport students. After 5 rain of rest in an upright position on a cycle ergometer they exercised for 15 min and remained seated for a further 5 min. The subjects exercised at four different constant intensities (40 W, 80 W, 120 W, 160 W) in r a n d o m order separated by at least 24 h. The BPa was determined by a noninvasive and continuous method. During the first minute of exercise, three phases of response could be distinguished, with the first two showing no clear relationship to intensity. Phase 1 consisted of simultaneous increases in b o t h f o and BP during the first 6 s. In phase 2, BPa decreased while f¢ continued to increase. During phase 3, BPa a n d f c approximated constant values or a linear increase. Both parameters showed no comparable intensity-independent reactions during the off-transients. In conclusion, during the first 15 s of rest-exercise transitions there seems to be a fast and uniform cardiovascular drive which overrode other influences on ft.
Key words: Exercise - Humans - Blood pressure Heart rate - Transients
narsson 1974; Karlsson et al. 1975) or even a decrease (Beaver and Wasserman 1968; Fujihara et al. 1973; Karlsson et al. 1975; Miyamoto et al. 1982). Since the early component of fc response can be abolished by prior administration of atropine, this phase has been attributed to a rapid vagal withdrawal followed by a temporary increase in vagal tone (Fagraeus and Linnarsson 1976). The origin of this change is still unclear. Fagraeus and Linnarsson (1976) have suggested that the baroreceptor reflex plays a leading role. Unfortunately, a meaningful interpretation of suchfc data is hampered by the lack of simultaneous blood pressure recordings. This is due to methodological problems: the RivaRocci method commonly used in exercise physiology does not allow a sufficiently small time resolution so that invasive approaches have been the only accepted alternative so far. Recently, a noninvasive continuous method originally described by Penaz (1973) has been made commercially available (Finapres TM, Ohmeda 2300). Comparisons with invasive methods have shown good agreement during rest if potential differences in hydrostatic pressure are taken into account. In the present study we have used a Finapres device to compare the on- and off-responses in f~ and mean arterial blood pressure (B---P~) during changes between rest and constant intensity exercise at four levels.
Introduction Blood pressure and heart rate (f~) adjustments following transitions between rest and exercise are more complex than exercise-exercise transients. The onset of the "muscle pump", a greater relative influence of vagal withdrawal, and the onset o f cardiac output redistribution have to be taken into account. The initial fc responses to rest-exercise steps have been reported to consist of a rapid increase followed by a transient flattening (Broman and Wigertz 1971; Lin-
Offprint requests to: K. Baum
Methods Subjects. Six healthy sport students [three male, three female; mean age 22 (SEM 2) years, mean body mass 71 (SEM 3) kg, mean height 176 (SEM 11) cm] participated in the study. Experimental protocol. Exercise tests consisted of constant intensity cycling at four different levels in the upright position (40 W, 80 W, 120 W, and 160 W; 15 min duration each). The subjects exercised at the different intensities in random order with time intervals of at least 1 day between two tests. Before and after exercise, the subjects sat quietly on the cycle ergometer for 10 rain and 5 rain, respectively.
135 At 30 s, 5 s, immediately before and the end of exercise, the subjects were informed by an acoustic signal to start and terminate cycling. At the start of exercise, steady-state intensities were reached within 2 s to 4 s. The BPa was measured continuously by Finapres. A small finger cuff was placed around the middle phalanx of the third finger. A fast feedback loop including an infrared light source and detector, an air pump, and a microprocessor keeps the wall of the finger arteries at the so-called "unloaded size". At this p____ointthe cuff pressure equalled the arterial blood pressure. The BP~ were computed from the pressure integrals between two R-waves. Since the peripheral blood pressure measurement is sensitive to changes in hydrostatic pressure, the hand with the finger cuff was placed on a padded platform at the level of the heart. The fc was determined separately by means of standard electrocardiogram leads. Oxygen uptake (1202, standard temperature and pressure, dry) was measured by a breath-by-breath technique described earlier (El3feld et al. 1987). The subjects breathed room air through a mask connected to a Fleisch sensor, Fenyves and Gut, Basel. Pneumotachogram and mass spectrometer readings for N2, 02, and CO2 were recorded by a microprocessor system. During a final off-line analysis the mass spectrometer values were corrected for transportation delay, response time, and vapour pressure. Gas exchange values were computed as differences between inspired and expired volumes (body temperature, pressu__re, saturated). Measurements of exercise intensity,, f c, BP, and VO2 were stored on a microprocessor. Individual VO2 data were calculated as consecutive means over 10-s intervals. Intervals of 2 s were chosen to evahmte the on- and off-responses in exercise intensity, f~ and BP~. Pre- and postexercise controls were taken as means of the last minute during rest and recovery.
180- -
40W
~
~ 8ow 1 60 ] .-. ,2ow -
m-m
160W
140O)
£ D I13 _(2
120 ]
oo5 8°i 60
,,,, 0
5
10
15
20
25
time (rain)
Fig. 1. Time course of heart rate before, during, and after cycling (mean values, n = 6)
took about 5 rain before 1202 stabilized at 2.38 (SD 0.07) 1- m i n - 1. In contrast to 1~O2, steady-state responses in fc (Fig. 1) could be obtained only at 4 0 W [97 (SD 4) beats, min-5]. In the other tests fc increased from the 5th to the last exercise minute by 6 beats, r a i n - ~ (80 W), 12 beats.rain -1 (120 W), and 15 b e a t s . m i n -a (160 W). As for I202 andf~, the mean steady-state increases in BPa were correlated to the exercise intensity and amounted to 7 m m H g (40W), 1 0 m m H g (80W), 12 m m Hg (120 W), and 16 mm Hg (160 W).
Results
Kinetics of f~ and blood pressure
Steady responses of f~ and blood pressure The pre- and postexercise values are given in Table 1. After about 2 rain o f exercise, VO2 reached the following steady-state values at 40 W, 80 W, and 120 W: 0.98 (SD 0.13) l . m i n -1, 1.42 (SD 0.09) 1.rain -a, and 1.93 (SD 0.19) 1.min -1, respectively. At the 160-W level it Table 1. Oxygen up___take(1202), heart rate (fc) and mean arterial blood pressure (BPa) during the 5-min pre- and postexercise (mean and SD, n=6) Exercise intensity (W)
Pre-exercise (5 min)
Post-exercise (5 min)
fO 2 (1.min -~)
40 80 120 160
mean 0.38 0.36 0.36 0.37
SD 0.03 0.02 0.04 0.04
mean 0.39 0.36 0.40 0.42
SD 0.04 0.03 0.04 0.05
f~ (beats.min -1)
40 80 120 160
80 74 76 79
4 5 5 7
80 80 88 101
6 5 6 6
40 80 120 160
88 91 85 91
5 4 5 4
93 96 94 95
7 6 8 5
BPa (ram Hg)
On-response. During the initial phase of exercise three phases could be distinguished (Figs. 2, 3): phase 1 - f c and BPa increased simultaneously (0 s-6 s) phase 2 - the BPa decreased while fo continued to increase (6 s-12 s) phase 3 - both parameters approximated constant values or a linear increase. The kinetics of phases 1 and 2 showed no obvious relationship to the exercise intensity. The "notches" in f~ between phases 2 and 3 were inversely related to changes in BP~ with a time delay o f several seconds. Off-response. No comparable kinetics were seen during the off-responses. Almost monophasic reductions in fo occurred after a time delay o f a few seconds (Fig. 4). At the end of cycling at the higher workloads BPa transiently declined below postexercise steady-state values (Fig. 5). Discussion In the present study we measured finger blood pressure rather than central blood pressure. Peripheral blood pressure is characterized by a greater systolic-diastolic amplitude and a greater sensitivity to thermoregulatory events (Rowell et al. 1968; Hildebrandt et al. 1991). We are not aware of any direct comparison o f results from
136 qc ul
~d x:
