63
Biochemistry of Exercise
work output during the same time.
Therefore, 8 students performed
supramaximal exercises at 120% after ingesting
either sodium citrate (OSg/kg body weight) or
placebo in a double blinded cross-over experiment.
A first series concerned the measurement of the
exhaustion time (Td). This latter was significantly
increased in alkalosis (4.9 f 0.8 min vs 4.3 & 0.5
min ,pc0.05). During a 2nd series, each subject was
submitted to the same power output during an
individual time = Td - 20 s in both treatment on
different days. Muscle samples were taken at rest
and at the end of exercise whereas blood artery
samples were obtained at rest and after 3 minutes of
recovery.
PLACEBO
(PLC)
Rac
PCreahs
37.4i8.A
m.oi3.7.
IMP
33i1.5
Glyeop
4688il20.7 414.7il08.7
aUCab6-P 1.6ioS
12J133a
Lsoats
4510.9
101.7i17.0.
Blood
l.aate
2.7il.0
13.8i1.7a
Blood H'
39.4i0.9
625i4.0.
ATP
Blood
unmda
98.9i12.1
248i2.9
Exorarc
48.4il2.6
SODIUM ClTlUTE
(err)
EXERCISE
Rat
PLCICIT
Exerdrc
102.1i9.0
u.ii3.2
37.6i11.4.
19.0i2.&
3.7i2.0
460Ji116.9 355.4i72.h
ld%OJ
11.7i3-51
4.011.4
103.1i173a
23i1.2
349123b
180Ji673s 60.9i113
15.Oi1.9.
5l.li4.7a
M
M
M
M
M
M
p<O.OS
p<O.05
1 5 0 5 i 5 2 . t p<OM
a: significant difference between rest and exercise; b alkalosis
effect on rest values
Muscle metabolites in mmoVkg dry wt. Blood lactate in mM,
blood protons in nM and blood ammonia in pM.
Contrary to thoroughbred horses, in humans
the contribution of anaerobic glycolysis to total ATP
production is not accompanied by a higher glycolytic
rate in alkalosis as compared to control. On the
other hand, muscle pH, while not determined in this
study, has been found higher in alkalosis than in
control at the same time of a supramaximalexercise
(Costill et al. 1984). Consequently, alkalosis could
delay both the fall in muscle pH and the pH
inhibitory effects on the contractile processes. The
slowed decrease in muscle pH associated with a
lower accumulation in blood ammonia might allow
a better peripheral and central tolerance of exercise.
Costill DL, Verstappen F, Kuipers H, Janssen E and
Fink W. Int J Sports Med5: 228-231 (1984)
Greenhaff PL, Harris RC, Snow DH, Sewell DA
and Dunnett M. Eur J Appl Physiol 63 :
129-134 (1991)
COMBINED EFFECTS OF RICE
CARBOHYDRATE DIETS AND
ENDURANCE EXERCISE ON
GLYCOGEN METABOLISM IN RAT
LIVER AND SKELETALMUSCLE
G Garrido', M GuzmiW and JM Odriozola'. ' Dept
Human Performance, National Institute of Physi&l
Education (INEF), Madrid, Spain.
Dept.
Biochemistry and Molecular Biology I, Fac.
Chemistry, Complutense University, Madrid, Spain.
9s
The adaptation of glycogen metabolism to
endurance training and to the administration of 3
different diets rich in carbohydrates (CH) was
studied. Rats were fed ad libitum diets containing
65% of total calories as CH (starch, sucrose or
fructose). Animals were trained on a treadmill
during 3 months, 6 daydweek, 1Wday at 30dmin
and they were not exercised for 24 h prior to killing.
Each experimental group included 5 animals.
In sedentary rats, liver glycogen content
increased by 50-70% with simple CH diets vs. starch
diet. Compared to sedentary animals, trained rats
had similar levels of liver glycogen when fed the
starch diet, but they had much lower levels (30-35%
of controls) when fed the simple CH diets. With
regard to skeletal muscle (gastrocnemius), glycogen
content also increased by 2540% with simple CH
diets vs. starch diet in sedentary rats. However, a
training-induced decrease in glycogen levelswas only
observed in the fructose group (65% of control).
Both in liver and in gastrocnemius, certain changes
were observed in the active fractions of glycogen
synthase and glycogen phosphorylase between the
different experimental groups. Nevertheless,
variations in liver and muscle glycogen content
correlated well with changes in the levels of glucose
6-phosphate (Table), an allosteric activator of
glycogen synthase. In conclusion, diets rich in simple
CH do not seem to be adequate for endurance
training.
Glucose 6-phosphate (pmoVg)
Carbohydrate
Starch
Training Liver
0.72 f 0.23
yes
no
0.78 f 0.15
3.26 f 0.49.
2.21 f 0.44
Sucrose
Yes
no
0.54 f 0.09.
0.84 f 0.21
1.68 0.21.
2.43 f 0.45
Fructose
yes
0.65 f 0.08.
no
0.88 f 0.22
1.41 f 0.51.
2.41 f 0.91
*Significantly different (P< 0.01)
corresponding sedentary group.
*
vs
Supported by a Grant (SAF93-0281) from the Spanish CICYT
the