Eur J Appl Physiol (1992) 65:421-426
European Journalof
Applied
Physiology and Occupational Physiology © Springer-Verla9 1992
Oxygen consumption following exercise of moderate intensity and duration Carl M. Maresh, Avron Abraham, Mary Jane De Souza, Michael R. Deschenes, William J. Kraemer, Lawrence E. Armstrong, Molly S. Maguire, Catherine L. Gabaree, and Jay R. Hoffman Human Performance Laboratory, Department of Sport, Leisure, and Exercise Sciences, and Department of Physiology and Neurobiology, The University of Connecticut, Storrs, CT 06269, USA Accepted July 9, 1992
Summary. To study the effects of exercise intensity and duration on excess postexercise oxygen consumption (EPOC), 8 men [age=27.6 (SD 3.8) years, I?Oama~ = 46.1 (SD 8.5) ml m i n - 1 k g - 1] performed four randomly assigned cycle-ergometer tests (20 min at 60% ~rO2 . . . . 4 0 m i n at 60% ~rO2max , 2 0 m i n at 70% l?O2m~, and 40 min at 70°/o l?O2max). 02 uptake, heart rate and rectal t e m p e r a t u r e were measured before, during, and for 1 h following the exercise tests. Blood for plasma lactate measurements was obtained via cannulae before, and at selected times, during and following exercise. 17"O2rapidly declined to preexercise levels following each of the four testing sessions, and there were no differences in E P O C between the sessions. Blood lactate and rectal temperature increased ( P < 0 . 0 5 ) with exercise, but had returned to preexercise levels by 40 min of recovery. The results indicate that 1202 returned to resting levels within 40 rain after the end of exercise, regardless of the intensity (60% and 70% I?O2m~x) or duration (20 min and 40 rain) of the exercise, in men with a moderate aerobic fitness level.
ers have described a sustained elevation in energy expenditure lasting 8-48 h following exercise (Bahr et al. 1987; Gore and Withers 1990b; Maehlum et al. 1986). Differences in the exercise intensity may be the primary factor in explaining these diverse results. Although there are exceptions in the literature, the majority of studies that have shown a prolonged E P O C have employed exercise at about 70°70 of the maximal aerobic power (DrO2max) over periods ranging f r o m 20 min to 80 rain (Poehlman 1989). Nevertheless, there currently appears to be no obvious combination of exercise intensity and duration that will consistently produce prolonged elevations in EPOC. It was our contention that additional research should examine E P O C following exercise performed at intensities and durations commonly employed in fitness training programs. Thus, the purpose of the present study was to examine carefully the effect of different combinations of exercise intensity and duration on E P O C .
Materials and methods Key words: Exercise intensity - Exercise duration - plasm a lactate - Rectal temperature
Introduction Several studies have examined the interaction of intensity and duration of exercise on excess postexercise oxygen consumption (EPOC) (Bahr et al. 1987; Brehm and Gutin 1986; Chad and Quigley 1991; Chad and Wenger 1985; Gore and Withers 1990a, b; Hagberg et al. 1980b; Sedlock et al. 1989). While some investigators have reported a rapid return of oxygen uptake to preexercise levels (Brehm and Gutin 1986; Sedlock et al. 1989), oth-
Correspondence to: C. M. Maresh, Human Performance Laboratory, Sports Center, U-110, 2095 Hillside Road, The University of Connecticut, Storrs, CT 06269-1110, USA
Subjects. Eight healthy men volunteered for this study. All were active, but had not engaged in sport-specific training for at least 2 years. Furthermore, none of them had been involved in more than 4 h of physical activity each week during the previous year. The men's activity patterns remained consistent throughout the duration of the study and none was taking medications. After a complete and accurate verbal description of the procedures, risks and benefits associated with the study, subjects provided written informed consent. Selected characteristics of the subjects are presented in Table 1. Experimental design. The men completed a familiarization session, two maximal exercise tests, and four experimental exercise test sessions. The percentage of body fat was also determined (Jackson and Pollock 1978) during the familiarization session. All of the exercise tests were performed on a cycle ergometer (Mijnhardt, Odijk, Holland; KEM-2). No other exercise was performed before testing on those days, and subjects had refrained from any strenuous exercise for 36 h before the tests. Tests were conducted in the laboratory (22° C) during the months of February and March, between 0800 and 1100 hours following a 12-h fast during which only water was allowed. No alcohol or caffeine was con-
422
Table 1. Subject characteristics and mean (SD) results from the initial maximal exercise test Age (years) Mass (kg) Height (ram) Body fat (%) l?O2m~x (mlmin -1 kg -1) Respiratory quotient Heart rate (beats min -1) Rating of perceived exertion Plasma lactate (mmol1-1)
27.6 (3.8) 78.7 (13.8) 1778 (75) 18.1 (8.3) 46.1 (8.5) 1.18 (0.06) 194.6 (10.6) 19.4 (0.7) 11.7 (2.1)
sumed for at least 24 h prior to testing. All tests for each subject were performed at the same time of day. The subjects were asked to give themselves ample time to get to the laboratory for the experimental testing sessions; four drove and four walked less than 800 m from their dormitory rooms. All subjects reported having a normal night of sleep, averaging 7.3-+ 1.1 h, before the tests. Four randomly assigned tests were performed: (A) 20 and (B) 40 min of exercise at 60% ~rO2max;(C) 20 and (D) 40 rain of exercise at 70°7o 1202m~. A period of 72 h separated each test. Tests A-D were performed after the two maximal exercise tests. Maximal exercise testing. The first maximal test was used to determine each subject's 1202m~ and the percentage of 12Ozmaxassociated with the onset of blood lactate accumulation. During that test subjects began cycling at 25 W for 3 min, with increases of 25 W included every 3 min until volitional exhaustion. Prior to testing, a 20-gauge Teflon cannula, maintained patent with isotonic saline, was inserted into a superficial forearm vein. Blood samples for measurement of plasma lactate were drawn before exercise, during the last 15 s of each exercise intensity, and 5 min after exercise. The 1202m~ measured during the test was also used to establish the exercise intensity (percentage of PO2m~x)to be employed during the subsequent experimental sessions. The second maximal test was performed 48 h later and was used to verify each subject's 1202max. During that test, subjects began cycling at 25 W for 1 min; increases of 25 W were imposed every minute to volitional exhaustion. A 5-min postexercise blood sample was obtained using a 20-gauge needle and syringe to measure plasma lactate. The criteria of 1202maxwere at least four of the following five (Thoden et al. 1982) (a) an increaseqn oxygen consumption no greater than 150 ml m i n - 1 despite an increase in exercise intensity; (b) attainment of a heart rate within five beats of the predicted maximal heart rate; (c) a respiratory exchange ratio greater than 1.1; (d) a rating of perceived exertion of 18 or greater; and (e) a plasma lactate value of at least 10 mmol 1-1 5 min after exercise. Results of the first maximal exercise test are shown in Table 1. Experimental test sessions. On arrival at the laboratory, subjects were weighed in shorts and socks to the nearest 0.1 kg, ECG electrodes were attached, a rectal temperature probe was inserted 150 mm beyond the external anal sphincter (Saltin and Hermansen 1966), and a 20-gauge Teflon cannula, maintained patent with isotonic saline, was inserted into a superficial forearm vein. During the next 30 min, subjects sat quietly in a comfortable chair while breathing into a mouthpiece connected to the metabolic measurement system (Medical Graphics Corporation). Preexercise 1202 was defined as the average 1202 during the last 10 min of that rest period. A preexercise blood sample was then obtained and subjects were seated on the ergometer. Subjects took about 2 min to attain the desired percentages of 1202max. At that point, the 20- or 40-min exercise period began. Subjects cycled continuously for the designated duration at the appropriate exercise intensity to maintain the desired percentage of f'O2 . . . .
During exercise, oxygen uptake was measured continuously and heart rate, rectal temperature and ratings of perceived exertion (Borg 1961) were recorded every 5 rain. For the 20-min exercise sessions, a blood sample was collected during the last 30 s of cycling. During the 40-min sessions, blood was collected after 20 min of exercise and during the last 30 s of exercise. A 60-min recovery period followed the exercise. Subjects remained seated on the cycle ergometer until a blood sample had been collected 5 rain after exercise, and then moved to a comfortable chair for the remainder of the recovery period. Oxygen uptake was measured continuously, and heart rate and rectal temperature were recorded 5, 20, 40 and 60 min after exercise. Blood samples were also obtained at those times, but only after the oxygen uptake, heart rate and rectal temperature measurements had been recorded. A lightweight blanket was provided for the subjects and they were asked to cover themselves if they became chilled at any time during the recovery period. Measurements. Subjects breathed into a high-velocity valve (Hans Rudolf, Incorporated) connected by corregated plastic tubing to the inlet of a pneumotach. Expired air samples were measured using an on-line system (Medical Graphics Corporation, series 2000). Expired flow, 02 concentration and CO2 concentration were continuously sampled. The analyzers Were calibrated before and after each test with standard gas mixtures. Heart rate was recorded using an electrocardiogram. Rectal temperature was measured by a thermistor (Yellow Springs, 700 series). Blood was collected in a plastic syringe and immediately transferred to heparinized test-tubes. Aliquots of heparinized blood were used for hematocrit and hemoglobin determinations. The remaining blood was immediately centrifuged at 2000g for 20 min, and the plasma was stored at - 8 0 ° C until analysis. Hematocrit was measured in triplicate using microcapiUary tubes centrifuged at 4000g for 5 min. Hemoglobin was measured in duplicate from whole blood using a reflective photometer (Boehringer Mannheim Diagnostics). The percentage change in plasma volume was calculated from hematocrit and hemoglobin values (Dill and Costill 1974). Plasma lactate was measured in triplicate using an automated analyzer (YSI Model 23L, Yellow Springs Instruments). Data analysis. Analysis of variance was used to compare differences among the four experimental exercise sessions across time for plasma lactate, oxygen uptake, heart rate and rectal temperature. Tukey post-hoc tests were utilized to determine pairwise differences. Simple linear regressions were used to examine selected bivariate correlations. Statistical significance was chosen as PI
Recovery
TIME
.2." 0
E E
A
6
/[
Q U
"~
4
U
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Session
4'0
6'0
(min)
6
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....
2'0
Recovery
~,
European Journalof
Applied
Physiology and Occupational Physiology © Springer-Verla9 1992
Oxygen consumption following exercise of moderate intensity and duration Carl M. Maresh, Avron Abraham, Mary Jane De Souza, Michael R. Deschenes, William J. Kraemer, Lawrence E. Armstrong, Molly S. Maguire, Catherine L. Gabaree, and Jay R. Hoffman Human Performance Laboratory, Department of Sport, Leisure, and Exercise Sciences, and Department of Physiology and Neurobiology, The University of Connecticut, Storrs, CT 06269, USA Accepted July 9, 1992
Summary. To study the effects of exercise intensity and duration on excess postexercise oxygen consumption (EPOC), 8 men [age=27.6 (SD 3.8) years, I?Oama~ = 46.1 (SD 8.5) ml m i n - 1 k g - 1] performed four randomly assigned cycle-ergometer tests (20 min at 60% ~rO2 . . . . 4 0 m i n at 60% ~rO2max , 2 0 m i n at 70% l?O2m~, and 40 min at 70°/o l?O2max). 02 uptake, heart rate and rectal t e m p e r a t u r e were measured before, during, and for 1 h following the exercise tests. Blood for plasma lactate measurements was obtained via cannulae before, and at selected times, during and following exercise. 17"O2rapidly declined to preexercise levels following each of the four testing sessions, and there were no differences in E P O C between the sessions. Blood lactate and rectal temperature increased ( P < 0 . 0 5 ) with exercise, but had returned to preexercise levels by 40 min of recovery. The results indicate that 1202 returned to resting levels within 40 rain after the end of exercise, regardless of the intensity (60% and 70% I?O2m~x) or duration (20 min and 40 rain) of the exercise, in men with a moderate aerobic fitness level.
ers have described a sustained elevation in energy expenditure lasting 8-48 h following exercise (Bahr et al. 1987; Gore and Withers 1990b; Maehlum et al. 1986). Differences in the exercise intensity may be the primary factor in explaining these diverse results. Although there are exceptions in the literature, the majority of studies that have shown a prolonged E P O C have employed exercise at about 70°70 of the maximal aerobic power (DrO2max) over periods ranging f r o m 20 min to 80 rain (Poehlman 1989). Nevertheless, there currently appears to be no obvious combination of exercise intensity and duration that will consistently produce prolonged elevations in EPOC. It was our contention that additional research should examine E P O C following exercise performed at intensities and durations commonly employed in fitness training programs. Thus, the purpose of the present study was to examine carefully the effect of different combinations of exercise intensity and duration on E P O C .
Materials and methods Key words: Exercise intensity - Exercise duration - plasm a lactate - Rectal temperature
Introduction Several studies have examined the interaction of intensity and duration of exercise on excess postexercise oxygen consumption (EPOC) (Bahr et al. 1987; Brehm and Gutin 1986; Chad and Quigley 1991; Chad and Wenger 1985; Gore and Withers 1990a, b; Hagberg et al. 1980b; Sedlock et al. 1989). While some investigators have reported a rapid return of oxygen uptake to preexercise levels (Brehm and Gutin 1986; Sedlock et al. 1989), oth-
Correspondence to: C. M. Maresh, Human Performance Laboratory, Sports Center, U-110, 2095 Hillside Road, The University of Connecticut, Storrs, CT 06269-1110, USA
Subjects. Eight healthy men volunteered for this study. All were active, but had not engaged in sport-specific training for at least 2 years. Furthermore, none of them had been involved in more than 4 h of physical activity each week during the previous year. The men's activity patterns remained consistent throughout the duration of the study and none was taking medications. After a complete and accurate verbal description of the procedures, risks and benefits associated with the study, subjects provided written informed consent. Selected characteristics of the subjects are presented in Table 1. Experimental design. The men completed a familiarization session, two maximal exercise tests, and four experimental exercise test sessions. The percentage of body fat was also determined (Jackson and Pollock 1978) during the familiarization session. All of the exercise tests were performed on a cycle ergometer (Mijnhardt, Odijk, Holland; KEM-2). No other exercise was performed before testing on those days, and subjects had refrained from any strenuous exercise for 36 h before the tests. Tests were conducted in the laboratory (22° C) during the months of February and March, between 0800 and 1100 hours following a 12-h fast during which only water was allowed. No alcohol or caffeine was con-
422
Table 1. Subject characteristics and mean (SD) results from the initial maximal exercise test Age (years) Mass (kg) Height (ram) Body fat (%) l?O2m~x (mlmin -1 kg -1) Respiratory quotient Heart rate (beats min -1) Rating of perceived exertion Plasma lactate (mmol1-1)
27.6 (3.8) 78.7 (13.8) 1778 (75) 18.1 (8.3) 46.1 (8.5) 1.18 (0.06) 194.6 (10.6) 19.4 (0.7) 11.7 (2.1)
sumed for at least 24 h prior to testing. All tests for each subject were performed at the same time of day. The subjects were asked to give themselves ample time to get to the laboratory for the experimental testing sessions; four drove and four walked less than 800 m from their dormitory rooms. All subjects reported having a normal night of sleep, averaging 7.3-+ 1.1 h, before the tests. Four randomly assigned tests were performed: (A) 20 and (B) 40 min of exercise at 60% ~rO2max;(C) 20 and (D) 40 rain of exercise at 70°7o 1202m~. A period of 72 h separated each test. Tests A-D were performed after the two maximal exercise tests. Maximal exercise testing. The first maximal test was used to determine each subject's 1202m~ and the percentage of 12Ozmaxassociated with the onset of blood lactate accumulation. During that test subjects began cycling at 25 W for 3 min, with increases of 25 W included every 3 min until volitional exhaustion. Prior to testing, a 20-gauge Teflon cannula, maintained patent with isotonic saline, was inserted into a superficial forearm vein. Blood samples for measurement of plasma lactate were drawn before exercise, during the last 15 s of each exercise intensity, and 5 min after exercise. The 1202m~ measured during the test was also used to establish the exercise intensity (percentage of PO2m~x)to be employed during the subsequent experimental sessions. The second maximal test was performed 48 h later and was used to verify each subject's 1202max. During that test, subjects began cycling at 25 W for 1 min; increases of 25 W were imposed every minute to volitional exhaustion. A 5-min postexercise blood sample was obtained using a 20-gauge needle and syringe to measure plasma lactate. The criteria of 1202maxwere at least four of the following five (Thoden et al. 1982) (a) an increaseqn oxygen consumption no greater than 150 ml m i n - 1 despite an increase in exercise intensity; (b) attainment of a heart rate within five beats of the predicted maximal heart rate; (c) a respiratory exchange ratio greater than 1.1; (d) a rating of perceived exertion of 18 or greater; and (e) a plasma lactate value of at least 10 mmol 1-1 5 min after exercise. Results of the first maximal exercise test are shown in Table 1. Experimental test sessions. On arrival at the laboratory, subjects were weighed in shorts and socks to the nearest 0.1 kg, ECG electrodes were attached, a rectal temperature probe was inserted 150 mm beyond the external anal sphincter (Saltin and Hermansen 1966), and a 20-gauge Teflon cannula, maintained patent with isotonic saline, was inserted into a superficial forearm vein. During the next 30 min, subjects sat quietly in a comfortable chair while breathing into a mouthpiece connected to the metabolic measurement system (Medical Graphics Corporation). Preexercise 1202 was defined as the average 1202 during the last 10 min of that rest period. A preexercise blood sample was then obtained and subjects were seated on the ergometer. Subjects took about 2 min to attain the desired percentages of 1202max. At that point, the 20- or 40-min exercise period began. Subjects cycled continuously for the designated duration at the appropriate exercise intensity to maintain the desired percentage of f'O2 . . . .
During exercise, oxygen uptake was measured continuously and heart rate, rectal temperature and ratings of perceived exertion (Borg 1961) were recorded every 5 rain. For the 20-min exercise sessions, a blood sample was collected during the last 30 s of cycling. During the 40-min sessions, blood was collected after 20 min of exercise and during the last 30 s of exercise. A 60-min recovery period followed the exercise. Subjects remained seated on the cycle ergometer until a blood sample had been collected 5 rain after exercise, and then moved to a comfortable chair for the remainder of the recovery period. Oxygen uptake was measured continuously, and heart rate and rectal temperature were recorded 5, 20, 40 and 60 min after exercise. Blood samples were also obtained at those times, but only after the oxygen uptake, heart rate and rectal temperature measurements had been recorded. A lightweight blanket was provided for the subjects and they were asked to cover themselves if they became chilled at any time during the recovery period. Measurements. Subjects breathed into a high-velocity valve (Hans Rudolf, Incorporated) connected by corregated plastic tubing to the inlet of a pneumotach. Expired air samples were measured using an on-line system (Medical Graphics Corporation, series 2000). Expired flow, 02 concentration and CO2 concentration were continuously sampled. The analyzers Were calibrated before and after each test with standard gas mixtures. Heart rate was recorded using an electrocardiogram. Rectal temperature was measured by a thermistor (Yellow Springs, 700 series). Blood was collected in a plastic syringe and immediately transferred to heparinized test-tubes. Aliquots of heparinized blood were used for hematocrit and hemoglobin determinations. The remaining blood was immediately centrifuged at 2000g for 20 min, and the plasma was stored at - 8 0 ° C until analysis. Hematocrit was measured in triplicate using microcapiUary tubes centrifuged at 4000g for 5 min. Hemoglobin was measured in duplicate from whole blood using a reflective photometer (Boehringer Mannheim Diagnostics). The percentage change in plasma volume was calculated from hematocrit and hemoglobin values (Dill and Costill 1974). Plasma lactate was measured in triplicate using an automated analyzer (YSI Model 23L, Yellow Springs Instruments). Data analysis. Analysis of variance was used to compare differences among the four experimental exercise sessions across time for plasma lactate, oxygen uptake, heart rate and rectal temperature. Tukey post-hoc tests were utilized to determine pairwise differences. Simple linear regressions were used to examine selected bivariate correlations. Statistical significance was chosen as PI
Recovery
TIME
.2." 0
E E
A
6
/[
Q U
"~
4
U
"J
Session
4'0
6'0
(min)
6
=
C Session
....
2'0
Recovery
~,
