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Energy metabolism during post exercise recovery in man
Article  in  American Journal of Clinical Nutrition · August 1985
DOI: 10.1093/ajcn/42.1.69 · Source: PubMed
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Introduction
The metabolic and hormonal changes oc-
curring during exercise and the early recovery
period have been well documented (1-6).
However, less attention has been given to the
late recovery period, and in particular to the
stimulation of energy expenditure following
meal ingestion after exercise.
The present study was undertaken in order
to answer two questions:
1) What is the magnitude and duration of
the residual effect of a 3-h exercise (50%
V02 max) in terms of energy expenditure?
2) What is the nature of fuel oxidized
when a mixed meal is ingested during the
recovery period?
69
Energy metabolism during the postexercise
recovery in man1’2
R Bielinski, Y Schutz, and E J#{233}quier
ABSTRACT In order to explore the magnitude and duration of the long-term residual effect
of physical exercise, a mixed meal (55% CHO, 27% fat and 18% protein) was given to 10 young
male volunteers on two occasions: after a 4-h resting period, and on the next day, 30 mm after
completion of a 3-h exercise at 50% VO2 m�- � Energy expenditure and substrate utilization were
determined by indirect calorimetry for 17 h after meal ingestion. The fuel mix oxidized after the
meal was characterized by a greater contribution of lipid oxidation to total energy expenditure
when the meal was ingested during the post-exercise period as compared with the meal ingested
without previous exercise. During the night following the exercise, the stimulation of energy
expenditure observed during the early recovery period gradually faded out. However, resting energy
expenditure measured the next morning was significantly higher (+4.7%) than that measured
without previous exercise. It is concluded that intense exercise stimulates both energy expenditure
and lipid oxidation for a prolonged period. Am J C/in Nuir 1985;42:69-82.
KEY WORDS Exercise, energy metabolism, indirect calorimetry, energy expenditure, respiratory
quotient, substrate oxidation, FFA, insulin, heart rate
nature of the investigation before giving his consent to
participate.
Experimental design (Fig 1)
One week before the test, each subject’s maximal
oxygen consumption (V02 ,,,,�) was assessed. No strenuous
exercise was allowed during 48 h before the test and
each subject was eating a mixed diet over the same
period of time. They also spent one night in a respiration
chamber in order to get accustomed to the measurement
conditions.
The experimental protocol was divided into two parts:
1) a control period (day 1); 2) an exercise period (day II)
including a 3-h exercise on a treadmill at 50% V02
Each subject served as his own control and underwent
the whole protocol. No randomization for this sequence
was considered, since a prolonged (more than 24 h)
effect of the exercise could not be excluded. The energy
expenditure of each subject was monitored for 42 h
nearly continuously from 1400 on day I up to 0800 in
the morning following day II.
Materials and methods ‘From the Institute of Physiology-Faculty of Med-
icine, University of Lausanne, Rue du Bugnon 7, 1011
Subjects Lausanne, Switzerland.
Ten young men in good physical condition participated 2Add� reprint requests to: Professor E J#{233}quier,
in the experiment. Their physical characteristics as well Institute of Physiology, Faculty of Medicine, University
as the type of sports they were regularly practicing are of Lausanne, Rue du Bugnon 7, CH-l0l 1 Lausanne
shown on Table I. None was on any special diet, and (Switzerland).
none was using any medication; all subjects were non- Received September 5, 1984.
smokers. Each individual was fully informed about the Accepted for publication January 15, 1985.
The American Journal of Clinical Nutrition 42: JULY 1985, pp 69-82. Printed in USA
© 1985 American Society for Clinical Nutrition
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EE
and
RQHeart _______
rate �
Blood �
70 BIEUNSKI ET AL
FIG 1. Experimental protocol.
TABLE 1
Physical characteristics of the subjects
Subject Age Weight Height
Body
fat
Usual sports
activities ‘iO�
y kg cm % L/min mi/kg
FD 23 77.0 183 13.6 Basketball 4.773 62.0
YE 21 82.5 186 14.3 Decathlon 5.276 63.9
MH 20 62.4 176 8.7 Middle
distance
3.568 57.2
PH 21 60.4 165 11.9 Soccer 3.438 56.9
NM 22 74.6 178 12.3 Middle
distance
5.449 73.0
PM 23 87.3 191 10.3 Soccer 4.483 51.4
FF 22 78.1 183 12.3 Soccer 5.003 64.1
DB 22 72.8 181 12.4 Cycling 5.031 69.1
JMS 23 70.4 185 10.2 Cross-country
skiing
4.182 59.4
JK 21 66.5 170 12.7 Cross-country 4.532 68.2
Mean ±SD
21.8
0.3
73.2
2.8
179.8
2.5
11.9
0.6
4.573
0.215
62.5
2.2
During the control period of day I (after a baseline
measurement), the subjects were given a mixed meal at
1430 and the metabolic response at rest was continuously
followed from 1500 up to 1900 using an indirect calo-
rimeter (hood system). Energy expenditure was subse-
quently determined during the evening and the night up
to the next morning using a respiration chamber. Resting
metabolic rate was measured early in the morning of
day II. The same protocol as day I was followed during
day II but with the inclusionof an exercise period
performed on a treadmill for 3 consecutive h (from 1100
to 1400). A speed of 4.1 km/h was kept constant while
percentgrade was progressively increased during the first
‘unch Diner
1�.3O 19.00
V V
ten minutes of exercise to reach the individual target
slope which ranted from 15 to 22% depending upon
their individual VO2 max� The effective load represented
51.9 ± 1.2% ofthe predicted V02 ,,,�. Energy expenditure
was continuously measured during the entire exercise
period.
The protocol was approved by the human subjects
committee of the University.
Energy allowance and dietary intake (Table 2)
For estimating energy needs on the exercise day (day
II), 2 conditions were considered:
Breakfast Lunch Diner
8.00 1�.30 19.00
V V V
22.00 7.00 11.00 1L1.flO
I Nl�ht I 1 I�Exerc1se1
22.00
____I Night 11
7.00
p4
Day I Day II
p
Hood Chamber H Chamber Hood
- � g �k � � � ‘� Chamber H�-p 4-
FLttEP_t� ,�Afternocn,1Evening
Urines
Nlaht ftirnlno F�rr1s� Aftermrs, Fvcntrn Nlahr
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ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 71
TABLE 2
Energy intake during the study (mean ± SEM)
Breakfast
(0800)
Lunch
(1430)
I)ing�ex
(1900) Total E intake
kcai/meal kcai/24 I,
Day I (control) 470 ± 60 1300 ± 50 1300 ± 50 3060 ± 120
Day II (exercise) 1300 ± 50 1300 ± 50 1300 ± 50 3880 ± 160
* Test meals.
1) The allowances during the chamber periods were
based on our previous data on resting energy expenditure
(30 kcal/kgJ24 h).
2) The allowances for the extra energy cost of exercise
as predicted from 50% V02 .,.�- results.
The total energy intake on the exercise day was
divided into 3 equal standardized meals (Table 2).
On the control day identical test meals were served
for lunch and dinner. In order to avoid excess energy
intake during the control day, the size of the breakfast
was reduced. Two conditions were again considered: 1)
The energy allowances during the chamber periods as
previously mentioned (30 kcal/kg/24 h). 2) The allow-
ances for the period during which the energy expenditure
was not measured (ie from 0800 until 1400 on day I)
was estimated from National Academy of Science rec-
ommended dietary allowances (42 kcal/kgJ24 h).
The meals were served at 0800, 1430 and 1900
respectively, and were consumed within 20 to 30 mm.
Each test-meal was composed of bread, low fat swiss
cheese, butter, orange juice, a chocolate bar, and a coffee
flavored milkshake. The latter was used as an adjustment
for individual differences in energy requirements (due to
variation in body size and cost of exercise). Each test
meal provided 1300 ± 50 kcal (SEM) (1 8% ofthe energy
derived from protein, 27% from fat and 55% from
carbohydrates). The adjustable component (milkshake)
had the same relative composition (% kcal) as the fixed
remaining part of the meal so that any adjustment would
not affect the overall qualitative composition of the meal.
Measurements
1) Energy expenditure. Energy expenditure was mea-
sured in an airtight respiration chamber (5 m long, 2.5
m wide and 2.5 m high) which forms an open circuit
ventilated indirect calorimeter. The accuracy of the
chamber has been shown to be within 2% (9) under
ordinary conditions of measurements (7). However for
the postprandial periods and for resting metabolic rate
(RMR), a ventilated hood system was used (8) in order
to get a faster response time. The accuracy of the hood
system has been determined to be within 1%.
2) Respiratory chamber. The respiratory chamber is
an airtight room in which outside air is continuously
drawn by a blower. The flow rate of the air at the outlet
of the chamber is measured using a pneumotachograph
with a differential manometer (Digital Pneumotacho-
graph, Model 47 303A Hewlett Packard, USA). A fraction
of the extracted air is continuously drawn through an
02 analyzer (Magnos 2T, full scale range 19-21%, Hart-
mann and Braun, Germany) and an infrared CO2 analyzer
(Uras 2T, full scale range 0-1%, Hartmann and Braun,
Germany). These analyzers are calibrated twice a day
using a gas mixture prepared immediately from a pro-
portional mixing pump (H Wossthoff, Bochum, Ocr-
many). Air flow rate, 02 and CO2 concentration of the
outfiowing air are computed on-line through an automatic
data acquisition system (HP 3052A) interfaced to a HP
9825A computer, V02, VCO2, RQ and consequently
energy expenditure are calculated and printed at 15 mm
intervals using the equations described by J#{233}quier(9).
3) Ventilated hood. The computerized open-circuit
indirect calorimeter using a ventilated hood has been
described previously (8). Briefly, a transparent plastic
ventilated hood is placed over the subject’s head and
made airtight around the neck. To avoid air loss, a slight
negative pressure is maintained in the hood. Ventilation
is measured with a pneumotachograph and a constant
fraction ofthe air flowing out ofthe hood is continuously
drawn for gas analysis. The oxygen concentration is
measured by the same thermomagnetic analyzer as that
used with the chamber and carbon dioxide concentration
with the same infrared analyzer. The nonprotein respi-
ratory quotient is calculated from calorimetric values
and urinary nitrogen. The quantity of urinary nitrogen
excreted during each study period is used to obtain an
index of the amount of protein oxidized. Carbohydrate
(CHO) and lipid oxidation rates are calculated as previ-
ously reported (9).
The thermogenic response to the meal was expresssed
in 2 different ways: 1) as a percentage of the premeal
energy expenditure; 2) as a percentage of the energy
content of the test meal.
. 4) Estimate of maximal oxygen consumption
(V02 �. Steady state VO2 and heart rate were simul-
taneously measured while walking on a treadmill at 4.1
km/h. Incremental work loads were achieved by a stepwise
increase in the percentage grade (6 different levels ie 0-
5-10-15-25#{176}). Individual correlation between heart rate
and V02 was performed. From the predicted maximum
heart rate of the subject (220 beats/mm minus age in
years(l0)), V0� could be estimated using the regression
line for each individual. Although a ±15% error of
prediction is to be expected by using this procedure (11),
this degree of uncertainty on V02,,,5� was not estimated
to be prejudicial to this study.
5) Physical activity outside the exercise periods. In
the 4.5 h period of post-exercise recovery, the study was
performed in the sitting position. During the evening in
the chamber, physical activity was sedentary but spon-
taneous. The level of this activity was monitored using
a radar system based on Doppler effect as previously
described (12) and was expressed as a percentage of the
time during which the subject was moving.
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16
12
2.0
1.0
0
#{149}DAY I
#{149}DAY II
s-I
a
N
(
a
N
a
N
RNR
SLEEP
72 BIELINSKI ET AL
FIG 2. Changes in energy expenditure during the course of the day (Mean ± SEM).#{149},DAY I = control day;#{149},
DAY II = exercise day. E = exercise, M = meal, RMR = resting metabolic rate, 5p <0.05.
6) Heart rate. Heart rate was recorded by means of
a portable light-weight electronic device (heart rate mem-
ory, Difa, Benelux). The ECO signal picked up by 2
chest electrodes is processed by a preamplifier with
automatic gain control and by filters for detection of the
R wave. During a preselected interval (30 sin the present
study), one complete R-R interval is measured and each
period is successively accumulated in a memory (2 or
4K) with preservation of a time relationship. A matching
read out unit (Difa, Benelux) can automatically convert
each R-R interval into frequency, so that the resulting
numbers represent the measured heart rate (beats/mm).
These heart rates are retrieved successively by the read
out unit which was connected to a microcomputer (HP
9830). The latter stores all the data on a floppy disc so
that they can be processed and analyzed subsequently.
7) Blood samples. A teflon catheter (Abbocath#{174}) was
insertedinto an antecubital vein forthe blood sampling
and kept patent with an infusion of isotonic saline. On
day I, blood samples were taken every half hour from
1400 to 1900. On day II, four additional samples were
drawn at 0800 (postabsorptive), 1030, 1100 (basal) and
1230 midpoint of exercise respectively. Blood samples
were analyzed for glucose in duplicate (Beckmann au-
toanalyzer II enzymatic method, Fullerton, CA). Free
fatty acids were extracted using the method of Dole and
Meinertz (13), and determined according to Heindel et
al (14). Plasma glycerol, immunoreactive insulin (15),
plasma glucagon (Unger antiserum 30K immunoenzy-
matic method) and blood urea nitrogen (enzymatic
method) were also measured.
8) Urine samples. Twenty-four h quantitative urinary
lii
D
I-
a
z
lii
a.
LU
>.
C,
LU
z
LU
KCAL /MIN
collections were divided into 5 pools: morning (0800-
1100), exercise period (1100-1400), afternoon (1400-
1900), evening (1900-2200) and night (2200-0800). They
were analyzed for urinary nitrogen (16), urea (enzymatic
method), creatinine (Jaffe reaction), 3-methyl-histidine
(amino acid autoanalyzer) as well as epinephrine and
norepinephrine (17). The subjects were put on a 3 day
free-meat diet the days preceding the test.
9) Statistical analysis. Results are given as mean
values with their standard errors. Statistical analysis was
made with Student’s I test for paired values, each subject
being his own control.
10) Data analysis. During the control baseline, the
4.5 h post-exercise recovery and the RMR, energy ex-
penditure was calculated from calorimetric (hood) mea-
surements for 2-mm intervals. The values presented for
energy expenditure, RQ and substrate oxidation are the
mean of 30-mm periods. In the chamber, energy expen-
diture was averaged over 30-mm periods during exercise
and over a 1-h period during the evening and the night.
In order to calculate the overall (17 h) substrate
balance during the post-exercise period, the mean sub-
strate oxidation was subtracted from the nutrient intake
(2 meals) over the same period of time.
Results
Energy expenditure (Figs 2 and 3)
During the control period (day I), the
baseline (premeal) energy expenditure was
8 11 14 17 20 23 2 5 8
REAL TIME (H)
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ant’uiu
1.8
1.6
a
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CD
1.,
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.�
p 0.05
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0.9
a
a�
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2 DAYS
US
1 2 DAYS
ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 73
FIG 3. Effect of the exercise on energy expenditure, respiratory quotient and heart rate during resting post-
absorptive conditions. #{149},the morning following the control day (Day I); #{149},the morning following the exercise day
(Day II).
1.35 ± 0.02 kcal/min. The consumption of
the test meal induced an increase in energy
expenditure (ie thermogenesis) which reached
peak values of 1.92 ± 0.07 kcal/min at 90
mm and progressively decreased to 1.71
± 0.05 kcal/min 4.5 h postprandial. When
the net increase in energy expenditure during
the 5 h postprandial phase on day I was
related to the energy content of the meal, the
postprandial thermogenesis was found to be
10.5 ± 0.8% or an increase averaging 32.8
± 2.6% over the premeal baseline.
On day II, during the exercise, energy
expenditure increased progressively from 10.3
± 0.6 kcal/min at 30 mm to 12.3 ± 0.6 kcal/
mm at 120 mm of exercise. It remained close
to this value during the last h (120 to 180
mm) of exercise. As an average the subjects
expended 2100 kcal/3 h for the entire exercise
period. In the post-exercise postmeal period
significantly greater energy expenditure values
were obtained than in the control period.
There was a progressive decrease from 2.18
± 0.07 kcal/min, 30 mm postprandial, to
1.81 ± 0.07 kcal/min, 4.5 h after the con-
sumption of the test meal. The cumulated
energy expenditure, from 0.5 to 4.5 h after
meal ingestion, was 9% greater (ie 40 kcal, p
<0.05) on the exercise day than on the
control day. Postprandial thermogenesis was
however not calculated on day II since the
present design did not allow separation of
the residual effect of the exercise from the
residual effect of the meal.
The time course of energy expenditure
during the late recovery period (ie evening
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B/MIN
#{163}
N
150
LU
I-
D( 120
LU
I 60
30
#{149}DAY I
#{149}DAY II
#{163} #{163}
N N
RNI
E
SLEEP
8 11 14 11 20 23 2 5 8
REAL TIME (H)
74 BIELINSKI ET AL
FIG 4. Changes in heart rate during the course of the study (Mean ± SEM).U, DAY I = control day; #{149},DAY
II = exercise day.
+ night) is shown on Figure 2. No significant
difference in energy expenditure was found
during the evening and during the sleep
period between the 2 days. By contrast, on
the morning following the exercise (ie 18 h
later), resting metabolic rate was found
slightly but significantly greater than during
the control period, ie 1.44 ± 0.06 kcal/min
vs 1.37 ± 0.05 kcal/min (+4.7%; p <0.05)
(Fig 3).
Heart rates (Fig 3 and Fig 4)
On day I during the baseline measurement,
the premeal heart rate was 58 ± 2 beats/mm
and was stimulated by the consumption of
the meal, reaching values of 68 ± 2 beats/
mm (2.5 h postprandial) and progressively
decreasing to baseline (59 ± 2 beats/mm) at
4.5 h postprandial. During the exercise period
itself (day II), the heart rate increased from
137 ± 5 beats/mm at 30 mm after the onset
of exercise to 140 ± 4 beats/mm at 90 mm,
to 143 ± 3 beats/mm at 150 mm, reaching
158 ± 5 beats/mm (p <0.01) at the end of
the exercise period.
During the afternoon the post-exercise
heart rate decreased continuously from 105
± 4 beats/mm at 30 mm post-exercise to 67
± 2 beats/mm at 4.5 h. During the entire 4.5
h postprandial period all the values were
significantlymore elevated during day IIthan
during day I (p <0.005). The time course of
heart rate during the evening and night as
well as sleeping period is shown on Figure 4.
No significant difference between both nights,
nor during RMR (Fig 3) was found. The
mean heart rate during sleep dropped to a
value of 50 ± 2 beats/mm.
Physical activity
As measured by the radar system, no sig-
nificant difference in physical activity was
found during the afternoon while sitting un-
der the hood (control day: 2 ± 0.3%, post-
exercise day: 2 ± 0.2%) nor during sleep (ie
2 ± 0.1% during the control and 2 ± 0.4%
during the post-exercise night).
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1.0 RQ
0.9
#{149}.
V
S
a a a
N N N
(
#{149}DAY,
#{149}DAYII
SLEEP
8 11 14 17 20 23 2 5 8
ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 75
FIG 5. Changes in respiratory quotient (RQ) during the course of the study (Mean ± SEM).�, DAY I = control
day;., Day II = exercise day. E = exercise, M = meal, RMR = resting metabolic rate.
Respiratory quotients (Fig 3 and Fig 5)
During the control period, the premeal
RQ was 0.775 ± 0.0 10. Ingestion of the meal
(day I) increased RQ to average values of
0.899 ± 0.011 at 90 mm postprandial; then
RQ slowly decreased to reach 0.875 ± 0.008,
4.5 h postprandial.
The mean RQ during the exercise period
itself(day II)was 0.913 ± 0.0 16 with a rising
pattern at the beginning of the exercise period
(0.945 ± 0.011 at 60 mm) followed by a
sharp decrease 90 mm after the onset of
exercise to reach a value of 0.869 ± 0.0 10 (p
<0.05), towards the end of the exercise
period.
During the postprandial post-exercise pe-
riod, a similar RQ pattern was found as on
day I, but all RQ values were lower (p
<0.001) than that of day I. The lower RQs
which were observed during the postprandial
period of the exercise day remained depressed
during the evening and the sleep period (Fig
5). Even 18 hours after the cessation of
exercise, the RQ during the post-absorptive
state was still lower (p <0.001) as compared
to the same conditions without exercise
(Fig 3).
Substrate utilization and balance
(Fig6, Table 3)
During the premeal baseline period (day
I), 16% of the energy expenditure was derived
from CHO oxidation, 62% from fat and 22%
from protein. The meal induced a large in-
crease in CHO oxidation (56% of energy
expenditure) and a concomitant reduction in
fat oxidation (27% of energy expenditure).
By contrast, when averaged for the whole
postmeal period, on day II (ie in the postmeal
post-exercise period), fat contribution to en-
ergy expenditure increased (38%); simmlarly,
protein oxidation was greater on day 11(24%)
than on day 1(18%).
Substrates intake, oxidation and balance
measured from 1 h post-exercise up to 0800
in the next morning are shown in Table 3.
There was a significantly greater carbohydrate
storage (p <0.001) after exercise and a lower
I-
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(I)
LU
0.7
REAL TIME (H)
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LU
I-
a
z
LU
a.
LU
>.
C,
LU
z
LU
KCAL/MIN
DAY I
CI,
F AT
2.0
1.5
1.0
0.5
0
PlOT
14 15 16
N
17 18 19
-PUT
14 15
N
16 17 18 19
REAL TIME (H)
76 BIELINSKI ET AL
FIG 6. Proportion of substrates oxidized before and after the test meal (M) (Mean ± SEM).U, DAY I = control
day;#{149},DAY II = exercise day. Prot = protein, CHO = carbohydrate.
fat storage (p <0.005) as compared to the
control day.
Changes in nutrient balance (Fig 7)
Changes in CHO, fat and protein retention
were calculated from an mnmtmal baseline ar-
bitrarily set at zero balance at 1400 on day
TABLE 3
Carbohydrate (CHO), fat and protein (Prot) balance on
control day (Day I) and on exercise day (Day II)
Substrate
intake
Substrate
oxidationt
Substrate
balance
CHO
Dayl
DayIl
g/17h
355 ± 15
g/17h
233±15
157±131
g/!7h
123±11
198±15*
Fat
Dayl
Dayll
78 ± 3
45±5
72±6t
34±6
6±5t
Prot
Dayl
DaylI
* 2 isocal
118 ± 5
onc test-meals (lu
73±5
92±4t
nch and dinner).
46±4
27±5f
t From 1500 to 0800 on the following day, ic excluding the
first hour post-exercise.
tP <0.005.
<0.001 vs Day I.
I. Cumulative changes expressed in absolute
kcal at various times throughout the study
were obtained from nutrient intakes during
the considered period minus nutrient utili-
zation as measured by indirect calorimetry.
Comparing the period before exercise vs after
exercise, the relative contribution of CHO to
energy expenditure was about twice that of
fat. In addition, the recovery period was
characterized by a restoration of CHO stores
whereas fat stores remained essentially un-
changed. The results are shown graphically
in Figure 7.
Blood parameters (Figs 8 and 9)
On day II (exercise), postprandial plasma
glucose was characterized by a higher peak
(60 mm after the meal) and a delayed return
to baseline values (Fig 8). The hyperinsu-
linemic response was significantly depressed
from 60 to 90 mm after the meal (Fig 9) as
compared to day I. On the exercise day,
postprandial plasma FFA levels decreased
from the high post-exercise values to reach
the control level within 2.5 h (Fig 8). A
similar pattern was found for plasma glycerol
(Fig 8).
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DAY 1 DAY 2
exercise
-J
0
1000’
800’
600’
400�
200-
0-
-200-
-400-
-600-
- CHO
c� FAT
E: PROT.
4s h. post
lunch
(before
diner)
12h. post
diner
(before
breakfast)
3 h. post
brea kfast
(before
exercise)
4� h. post 12 h. post
lunch
(before
.) diner)
diner
(before
breakfast)
in nutrient balance at various times throughout the study. An initial baseline is
ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 77
FIG 7. Cumulative changes
arbitrarily set at zero at 1400 on DAY I.
The significantly elevated glucagonemia
found at the end of the exercise period
showed a rapid return (60 mm postprandial)
to control values (Fig 9). Blood urea nitrogen
rose significantly (when compared to the
postabsorptive values) during the exercise
period from 5.8 ± 0.3 mmol/l to 7.4 ± 0.4
mmol/1 (p < 0.001). It was still elevated at
7.6 ± 0.3 mmol/1 5 h after the end of the
exercise.
Urinary parameters (Table 4)
During the control period, the pattern of
urinary nitrogen excretion was stable up to
the late afternoon where an increase was
observed from an average value of 0.66 to
1.0 g N/h. During sleep the values returned
to baseline excretion of 0.59 g N/h. On day
II there was a significant increase in nitrogen
excretion only during the post-exercise period.
The values reached 1.11 g N/h in the after-
noon (p <0.001) and 1.16 g N/h in the
evening (p <0.05). There was no significant
difference in creatinine and 3-methyl-histidine
excretions between both days.
On the control day, norepinephrine excre-
tion (Fig 10) was stable during day time and
significantly decreased during the night. On
the exercise day, there was a 2.8-fold rise
in norepinephrine excretion during the exer-
cise period itself (3824 ± 314 ng/h vs 1384
± 181 ng/h on the corresponding period
without exercise). The norepinephrine values
remained significantly greater during the af-
ternoon (p < 0.05) but not during the rest
of the night. The pattern found in epinephrine
excretion was similar to that found with
norepinephrine but with absolute values ap-
proximately 3 times lower (Fig 10).
Discussion
Metabolic measurements
The present study has attempted to assess
the effect of an acute exercise on the energy
metabolism during the recovery phase under
strictly controlled conditions of measure-
ments. For example, our experimental design
allowed us to make up for the extra cost of
exercise by giving more food prior to the
onset of the test (breakfast) so that the ap-
parent energy balance of each subject at the
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iN
a
Vsa
IN
CD
N
YS
a a
N ( N
$ I * Ii U 13 14 15
Nil
. SAY I
. SAY II
$ 17 1$ II
SEAt TINE III)
UN
I
#{149}SAY I
#{149}SAY ii Early post-exercise
$ I 1 Il It II 14 IS $ 17 11
N.M T� II)
#{149}SAY I
* SAY II
3.5
3.1
2.5
a
- II
C.)
‘.5
CD
I.’
#{149}LL-J-
$ 1 * II It U 14 15 N 11 Ii a
SEAL TIlL Ill
FIG 8. Changes in plasma glucose, free fatty acid
(FFA) and glycerol (Mean ± SEM) during the control
day (#{149},DAY I), and during the exercise day (#{149},DAY II).
E = exercise, M = meal.
78 BIELINSKI ET AL
completion of the exercise would be similar
to that obtained without exercise. If this had
not been done, the post-exercise period would
not have been entirely comparable, since a
markedly different state of energy balance
would be obtained which would affect the
RQ’s (18). Both test meals (lunch and dinner)
were however identical in composition for
each subject.
Exercise period
The pattern of RQ during exercise was
most interesting since it showed an initial
increase followed by a rapid decrease approx-
imately 90 mm after the initiation of exercise.
Although the decrease in RQ could be related
to a number of interrelated factors such as
reduced glycogen stores, elevated plasma FFA
levels and reduction in plasma insulin levels,
it also coincided with the time at which the
energy fed during the breakfast (1 300 ± 50
kcal) was apparently utilized. The latter was
calculated by cumulative energy expenditure
for the overall postprandial period (morning)
plus that due to the first hour and a half of
exercise.
In the early post-exercise and postprandial
period, both the post-exercise recovery and
the meal ingestion affect metabolic rate and
substrate oxidation. Recent studies have
shown that the oral administration of a glu-
cose load during the recovery period following
a severe exercise is characterized by 2 major
changes: there is a large fraction of the ex-
ogenous glucose which escapes hepatic reten-
tion (19) and the muscle glycogen stores,
which have been diminished during the ex-
ercise, are progressively reconstituted (3, 20).
Thus, muscle glycogen repletion takes priority
over hepatic glycogen repletion. In the post-
exercise period of the present study, there
was a depressedinsulin response (Fig 9) and
an increased lipid oxidation rate (Fig 6),
consistent with the elevated free fatty acid
and glycerol plasma levels (Fig 8). The stim-
ulation of lipid oxidation was observed as
long as 18 h after the cessation of exercise
(Figs 3 and 5); during the 5 h post-exercise,
it represented 38% of total energy expenditure
as compared to 27% in the corresponding
postprandial period of day I, without exercise
(Fig 6).
Although the individuals were essentially
in a state of energy equilibrium, there was a
shift of energy metabolism towards fat oxi-
dation when compared to the control day,
so that 27 g (250 kcal) of extra fat were used
over a 17 h period (Table 3). Glycogen dim-
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.
.
160
140
120
100
-J
= 80
C,)
�60
40
20
0
PG/NI
250
�200
-a
‘� 150
11X1
50
8 9 10 11 12 13 14 15 16 17 18 19
REAL TINE (H)
#{149}DAY I
. DAY II
#{163} a
N E N
ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 79
8 9 10 11 12 13 14 15 16 17 18 19
REAL TINE (H)
FIG 9. Changes in plasma insulin and glucagon (mean ± SEM) during the control day (#{149},DAY I), and during
the exercise day (�, DAY II). E = ecercise, M = meal.
inution caused by exercise and increase in
FFA concentration are undoubtedly two fac-
tors of importance for the subsequent com-
pensatory reduction in CHO oxidation and
the concomitant increase in fat oxidation
during the recovery period.
An interesting phenomenon observed by
Krzentowski et al (21) after a 100 g glucose
load in the post-exercise period was the lack
of proportionality between total lipid oxida-
tion measured by indirect calorimetry and
plasma free fatty acid levels. Similarly, in
this study, 3 to 4 h postprandial, FFA levels
were normalized whereas lipid oxidation rate
was still enhanced on the exercise day. Plasma
FFA levels depend upon the rate of lipolysis
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272±26 414±56 348±57
p<0.01
410±42* 1169± 154t 593±47t
433±61 141±22
483±72 158±14
0.583 ± 0.053 0.612 ± 0.056 0.660 ± 0.038 1.008 ± 0.117 0.591 ± 0.062
0.643 ± 0.065 0.686 ± 0.076 1.107 ± 0.054t 1.160 ± 0.089� 0.694 ± 0.029
191.1 ± 15.5
179.3 ± 8.6
10.6 ± 1.1
8.9 ± 1.1
317 ±34
372 ± 31
80 BIELINSKI ET AL
TABLE 4
Urinary excretion of catecholamines and nitrogenous metabolites
0800 Morning 1100 Exercise 1400 Afternoon 1900 Evening 2200 Night 0800
Epincphrine
(ngfh)
Day I
Day II
Norepinephrine
(ng/h)
Day I
Day II
Urinary-N (g/h)
Day I
Day II
3-methyl-histidine
(mmol)
Day I
Day II
Creatinine
Day I
Day II
Urea
Day I
Day II
1204 ± 147 1383 ± 181 1055 ± 120 1324 ± 167
1524 ± 256 3824 ± 3l4t 1398 ± 108 1248 ± 93
564 ± 85
628 ± 51
95.2 ± 9.4
89.0 ± 8.1
13.0± 1.5
11.9± 1.3
433 ± 40
480 ± 42
* p <0.05, t p <0.01, � p <0.001 vs Day I.
and the rate of lipid uptake. It is likely that
both processes were activated during the post-
exercise period.
Controversy still exists about the effect of
physical exercise on protein catabolism and
amino acid oxidation (22). In the present
study, the rate of nitrogen excretion during
the exercise itself was not significantly greater
than during the corresponding period without
exercise. By contrast, in the 5 h period post-
exercise, the nitrogen excretion nearly dou-
bled (Table 4), indicating an increased amino
acid utilization. That exercise substantially
increases nitrogen excretion not during the
exercise itself but only after the completion
of exercise has been observed by others (22).
During exercise the increase in urea produc-
tion is associated with a decreased kidney
blood flow and urine production. After ex-
ercise a normalization of renal blood flow
occurs. Consequently a compensatory in-
crease in urea excretion takes place which
does not reflect an increased protein oxidation
in the post-exercise period but rather during
the preceding exercise itself.
Corrections for protein oxidation from
changes in blood urea nitrogen levels were
too uncertain to be performed since no urea
space was measured in the present study.
Late metabolic effects of exercise
Very few investigators have measured the
energy expenditure during the post-exercise
recovery for periods as long as 18 h (23). We
found that the postabsorptive resting meta-
bolic rate was still elevated for 9 h after the
cessation of exercise, but this was not the
case during the sleeping period, ie from 9 to
17 h post-exercise. The possible mechanism
operating during the long term post-exercise
recovery period which contributes to stimu-
late energy expenditure could be attributed
to various factors, including: 1) the extra
energy cost of storing the exogenous CHO
into glycogen in the liver and muscles (18);
2) hormonal changes (2); 3) a stimulation of
protein synthesis (24) or/and an increased
substrate cycling; 4) the effect of body tem-
perature elevation (Qlo effect).
Stoichiometric calculations show that 2
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1.2
0.9
0.6
0.3
0
CD
.
DAY I
DAY II
CD
I’.’
UN
=
L&.I
a-
IaJ
UN
UN
=
UN
=
a-
UN
UN
UN
=
8-11 11-14 14-19 1912 22-8 COLLECTION
PERIODS (H)
.�MG/H
CD
a
Ni
(#5
C.)
4.0
3.0
2.0
1.0
0
r1�]1�
- CD
-
-
-[Lfl{fl
DAY I
� DAY II
=
CD
rr:.
8-11 11-1414-19 19-22
FIG 10. Changes in urinary epinephrine and norepineph.rine excretion (Mean ± SEM) at various periods during
the course of the study. #{149},DAY I = control day;., DAY II = exercise day. 1p <0.05.
22-8 COLLECTION
PERIODS (H)
ENERGY METABOLISM DURING POST-EXERCISE RECOVERY 81
mol of ATP are required per mol glucose
transformed into glycogen, ie 5.3% of the
energy content of glucose (18). The CHO
storage (ie CHO intake minus oxidation) on
the exercise day was compared to the control
day; there was an extra CHO storage aver-
aging 18 g/4.5 h, so that this would account
only for approximately 10% of the excess
energy expenditure durin the post-exercise
period. Another factor which may contribute
to explain the excess energy expenditure dur-
ing the recovery period is the exercise induced
stimulation of sympathetic activity. An ele-
vated urinary catecholamines excretion was
indeed observed not only during exercise but
also during the 4.5 h post-exercise period
(Fig 10).
Finally recent studies have demonstrated
that protein synthesis is depressed during the
exercise period itself, but in the post-exercise
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82 BIELINSKI ET AL
period there is a compensatory phenomenon
so that total body protein turnover appears
to be stimulated (24). Since the process of
protein synthesis is very expensive (6 ATP
are necessary per mol peptide bound formed)
(18), this mechanism may also contribute to
the long lasting post-exercise stimulation of
energy expenditure.
In conclusion, the main implication of the
present study is that the post-exercise energy
expenditure was moderately stimulated over
4 to 5 h, as well as during RMR on the
following day. This rise in energy expenditure
was accompanied by a marked and contin-
uous stimulation of lipid oxidation for at
least 18 h. These results emphasize the long
lasting metabolic effect of an acute bout of
exercise. Whether these findings are of prac-
tical importance for athletes or individuals
who attempt to reduce body fat remains to
be demonstrated. 13
References
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