Encdurance Capacity for Continuous Eflon in Terms of Aerobic and

ENDURANCE CAPACITY FDR CONTINUOUS EFFORT IN TERMS OF
AEROBIC AND ANAEROBIC FRACTION OF OXYGEN SUPPLY
J. SEN GUPTA. S.S. VERMA AND N.C. MAJUMDAR
Defen::e Institute of Physiology and Allied Sciences. Delhi Cantt - 170010
Bnd
Defence Science Laborarory, Delhi-llD U06
Summ.ry: Studies hIve been conducted on 13 young healthy adulla 01 average fitness on endurance
work of varying dUfatlons lasting for 2·31 minutes using bicycle e<gometer. Aerobic-anal:!fOblc
o
fractions of oxygen supp1v during each effort was determined. The data from Astrand and Aodahl
on aerobic O~ - supply and duration in ffiallimlll eltolls flom 1-120 minutes on a highly trained subjoct
havo also been considered. Tho plol of log endurance lime against log (all/obic/anaerobic ralio) exhiblls
a slIght deparlUllI Irom IiOElI/itl', ;ndiclIling Independent contributions from aerobIC and anaerobic fractiofls of oxygen supply. An equallon was derived of the form :
T _ Au. k1 uz- k2
where
UI end U2 are the aerobIC and anaerobic fractions respeclivelywhich has been found to yield highly
signO/jcanl correlation cooffident botween log-eslimated and
10g-obselVed enduraflce time
(09996 for Astralld and Rodahl's dala on a sillgle sublect and 0.9640 for lhe present data on 13 subJocls). This index IS. therefore. Quite suitable for the llssessmenl of elldurence capacity in terms of a single
physiological parameter. and Is likely to be superior 10 illdices in current use.
Key words:
endurar!ce work
aerobic and anaerobic
fraction of oxygen supply
INTRODUCTION
Assessment of endurance work capacity of individuals is a problem of considerable
imparlance in industrial and military situations. and also in sports. Light work can be
sustained for an indefinite period because the energy requirement is met exclusively by
aerobic process. While anaerobic energy yielding processes assume significant importance with increasing work load (19.20.21). It has also been fairl~' well established that
the use of work load relative to the individual's aerobic capacity ('JO: max) eliminates
most of the differences in endurance capacity among ind~viduals (12). However, a
trained athlete can work at a relatively higher oxygen uptake relative to hj,;; maximum
(70-75 per cent) without any significant increase in oxygen deficiency and b:ood lactate
concentration (9.10,28). Untrained subjects. on the other hand. show a r,se in O2 debt and
lactate accumu alion at only about 45-55% of their aerobic capacity (3 16.28). Experiments
with animals and may have revealed that this adaptation in trained individuals is primar
110
Sen GUptll
~r
July-September 1 9~9
Imt J. Ph".~iol. Phllfmitc.
al
due to a change in the capacity of aerobic metabolism brought about by an increase in the
e:lzymatic capacity for oxidati'Je phosphorylation (17) and also due to higher perC!lntage
of 5T fibers (10.13,14).
Prolonged work at a high intensity reduces the available energy stores and thereby
limits the supply processes (1.5.18.23). Other associated factors limiting endurance
effort are hypertharmia and dehydration (10.24,29.30).
It w'll thus be clear from the foregoing that assessments of individual er:dJrance
capacity from physiological mea~urements is a complex problem and that any simple index
for the purpose b :sed on a single parameter like aerobic capacity cannot have general
applicability. Recently we observed a high degree of correlation between endurance work
and combined cardiorespiratory stresses (26).
In one of our earlier study (25). it was observed that endurance time for heavy work
was highly related to the aerobic-anaerobic ratio of oxygen supply (27). The present
study was undertaken with a view to examining the merits of this alternative approach.
MATERIALS
AND
METHODS
Thirteen young healthy subjects of average fitness status were selected for the
Mean age. height and weight of the subjects were 23.8 years. 166.6 cm. and
56.3 kg respectively their mean VO, max was 2.36 1/min (42.5 mt/kg/min) and mean
maximum heart rate, 187.5 beats/min.
study.
The subjects reported in the laboratory in the morning after a light breakfast and
after one hour rest. the resting 02 consumption, pulmonary ventilation and heart rales
were noted. The subject was then asked to perform a fixed rate of 800.1000 or 1200 kg/
min work on bicycle ergometer till exhaUSTion which was taken to be the moment when
the subject failed to maintain the fixed speed of 60 rpm. Endurance time was noted when
the speed dropped to 50 rpm inspite of his besl effort. Different work rates of 800·1200
kg/min were given to the same subject at intervals of 4-5 days to m'lnimize any training
effect. During exercise. the subjects were breathing through a Collin's Triple 'J' low - resistance breathing valve. The expired air volumes were collected continuously in large
meteorological rubber baloons over a period of 5 minutes through a three-way stopcock.
The volume of expired air from each baloon wa!> measured by passing through Koffranyi
Michaelis Respirometer and an aliquot sample collected during the process. Expired air
samples were analysed for CO: and '0 1 in Scholander Microgas Analyser. Thus the
total O~ consumed during the effort was determined (Exercise V01 ).
After
cessation
Vo!-Jmo
r-.umbcr
n
[nflUfarlCe
J
Caparilll fOf Cominuous Hfofl
171
of exercise, recovery oxygen consumption over the resting level was also estimated for
30 min (recovery VOl). Thus the total aerobic and "anaerobic" 0 1 utilised during the effort
were calculated.
The studies were conducted indoors with room temperature and relative humidity
v':>rying from 20 - 22°C and 50-55 per cent respectively. Motivation of the subject
was achieved by creating competitive spirit and seeking their best cooperation.
RESULTS
In Table I. experimental data on the 13 subjects have been presented which inc'ude
end!.Jrance time (T) in minutes. 0 1 consumed (above resting level). during work (Ex V02)
and during recovery (Rec V02). total O2 requirement of the work. all expressed in
litres at STPD. aerobic (lla) and anaerobic (uz) fraction as well as aerobic/anaerobic
ratio ( l!u,) 0) supply.
In Fig. 1, log T has been plotted against log (U 1/U2) for all the 31 observations on
the 13 subjects (solid circles). The correlation appears to be reasonably linear. but to
close inspection of the points indicates a slight departure from linearity.
o
However, Astrand and Rodahl (4) have reported similar observations on a single
subject of athletic type (V02 max 5.01/min) with endurance time varying from 1 to 120
min. These data are represented in Table II and the 7 corresponding points (open circles)
plDlted in Fig. 1 which lie Dn a smDoth curve (hand fitted). The curve clearly shDws a
slight departure fr)m linearitY. and the 31 pDints from the present study exhibit a very
similar trend but mostly lie above the curve.
A simple mathematical appro3ch :
It is well known that from moderately heavy to very heavy work. the endurance
time decreases primarily due tD a decrease in the aerobic fraction (u.) of Oz supply. The
anaerobic fractiDn (u\-,-l-uJl increase at the same time. and is likely tD reduce the endurance time independently. If that be the case, the slight nDn-linearity of the curve in
Fig. 1 can be easily explained Dn the basis of the folloWing assumptions:(i)
Endurance time (T) is determined nDt by the ratiD
tions U 1 and ul respectively.
(ii)
Relative changes in u. and U2 cause
thDUgh (n opposite directions.
proportional
(ul/uz) but by the frac·
relAtive changes in T.
172
Ju!v-Sepl~mt>er
Sen GUptll et .".
197~
Ind. J. PhyslOI. PharmJc.
TABLE I : Aerobic. Anaerobic fraction of O2 utilization 0113 subjects in different endurance tasks.
Ex. V0 2
Endu-
ranee
S"b
S. No.
R",.
V02
(1m" (T)
MSS
SA
12.0
2
3
80
2.0
DN
RD
AnaerObic
frection
26.08
17 .85
3.60
4.25
5 33
3 71
Aerobicl
anaerobic
rallO
-",
(Ul)
1
(ud u,)
(ul)
30 33
23.18
7.31
f.86
0
0.77
0.49
0.23
0.51
51 20
066
0.14
6
34.07
80'
0.83
0.17
0.58
4.88
0.72
0.23
0.25
0.48
3.35
"
6 14
3.35
0.96
,
19.0
5
12.0
6
2.0
7
8
11.0
23.17
6.92
6.0
2.0
12.97
, 32
3.84
3.54
10
11
23.0
11.0
44.28
3.84
3.29
48.12
0.92
0.89
0.08
29.91
0.11
'1.50
8.09
12
13
13.0
29.09
5 14
34.23
0.85
0.15
5.67
2.0
4.13
5.26
.39
0.44
0.56
079
14
15
16
23.0
51.36
18.98
3.80
508
56.44
27.51
9.51
0.91
0.69
0.40
o O.
10.11
8.53
5.71
0.31
0.60
223
067
19.61
3.30
5.21
7.70
24 82
11 00
0.79
021
o 70
3.76
o 3D
5"
D67
•
AS
Aerobic
frection
flJqulfe·
min
AKG
Tote/
0,
8.0
2.0
44.04
28.27
3.40
25.62
7.16
5.80
4.69
30.09
17.29
7.38
0.42
077
0.75
0.52
14
3.00
, .08
17
10.0
18
2.D
19
8.0
2.D
15.70
299
5 37
18 69
D84
016
358
895
0.40
0.60
42.78
13.10
3.89
3.72
4.13
3.74
46 50
17.73
7.63
D92
0.76
0.51
D 08
D24
23
21 D
6.D
20
24
16.0
31 22
"
8.0
2 0
16.14
3.79
3 47
6 28
394
34.69
22.42
27
120
2.0
29.66
367
33.33
28
, D'
3.44
748
089
064
0.46
809
1 17
DB
29
31 D
59.61
313
62 74
D95
D 05
1900
BB
30
31
19 0
10 S
35 15
24.09
306
3.92
38 21
28.01
092
0.08
0.86
o
11 50
6.14
NR
PC
2D
VP
21
22
JS
26
8R
773
0.90
0.72
0.49
0.49
0.10
D28
DOl
D 11
14
D43
11.50
3.17
1.04
'00
257
0.96
Volume 2J
N'JIT:b"r 3
Enduflnre Cftpaclty IOf Continuous EHoH
173
Assumption (ii) may be mathematical.y put in the form : -
aT
=
T
~
kl
k ~
_
LI
•
.... (1)
u.
where k l and k! are positive constrtnts.
Integration of eqn (1) finally leads to
T = A
(ulkl/Ulk2)
(2)
It may be noted that in the special case when k, = kz = k. eqn (2) reduces to
T = A (UdU2)k
(3)
in which case alone. fog T will be linearly related to log (aerobic/anaerobic ratio).
It may be concluded. therfore, that the non-linearitY of the curve in Fig. 1 is because
k1 /k.:;t.1.
Statistical analysis
From eqn (2) we have
.... (4)
log T = Log A+k j log Ut-"2 log U1
which is of the form :
+
b,
Xl
where Y=log T.
XI
=
Y= a
..J,..
b.
Xl
log v"
••..
X2
= log uz. a =
log A.
(5)
b I = k 1 b. =-kl .
Eqn (5) was fitted to the data of Table 11 by the method of least squares and the
values obtained for the constants were :
a = 0.3971. b,
=
1.1087 and b 1 =-0.7631
.... (6)
which were found to be highly significant (P <0.001). The standard error of the estimate
was 0.0268. The coefficient of correlation (r) between observed and estimated log T
was 0,9996 indicating almost a perfect linear relationship.
Similar analysis was performed with the present data on Indian subjects (Table I).
It was found that the constant b. and b2 do not change significantly while the constant
'a' differs significantly (P<O.05) from that in (6) being equal to 0.5184. The coefficient
of correlation (r) between observed and estimated log T for this set of data was 0.9640.
The equations fitting the two sets of data
noted above are : -
T
=-
3.3C (U I
1.1087
07631
/Vz
(Table; I and 11) with the constants
.... (7)
174
Ju :y-SeptlJmber 1979
Ind. J. Physio!. Pharmac.
Sen Gupta et al.
(Present data on 13 Indian Subjects)
and
T
=
2.50
(u 1
...... (8)
!.!OS7/U2 °'7 631 )
(Data of Astrand and Rodahl (4) on one subject)
2·2
2·0
z-
~
r
1· 8
.:
1· 6
w 1."
~
1· 2
•
~
••
1·0
UJ
U
Z
LEGEND
0·8
<[
-
cr
-'
0·6
C1
Z
UJ
•
DATA FROM
ASTRAND to ROOtlHAL
0
I
0·'
en
0
1970
J
0·2
~
o.0_
~....L.....---L._.l.....----L...----L_..L.---'-----JL-...L.....-..L._.l.....--'----L.--L
1·6
Fig
PRESENT DATA
,~
0·0 0·2 0·1. 0·6 0·8 1·0 1·2 H. 1·6 1·8 2·C 2·2 2·/.
L09 (AEROBIC/ ANAEROelC ) RATIO
Relationship between p.nduranrc time <>n:l 3crobir.-anaJrobi:: ril';O of oxygen
1
•
~uppl'l.
TABLE II : Aerobic. anaerobiC fraclIon of 02 utilization of one subject in
different endurance tasks (Data from Astrand and Rodahl. 1970)
S. IVa.
Endurance
time (T)
Rec.
V0 2
Total O2
requiremcnt
Aerobic
fraction
min
2
3
4
120
60
30
10
5
4
6
7
2
1
1
(L I)
480
260
140
50
20
3
4
6
7
9
4
9
!)
8
483
264
146
57
29
18
12
°
994
0.985
o 959
0877
o 690
0.500
o 333
Anaerobic
fraction
(L1 2 )
0.006
0.015
0.041
0.123
0.310
0.500
0.667
Aerobic I
anaerobic
ratio
(u l /Ll2)
166
65.7
23.4
713
2 23
1.00
0.50
EndLl:.~1CC
'.o!umll 21
Num!:'er :3
CJpll~iW
for Conlinuo~s rf:mt
1711
Observed and estimated endurance time for both sets of data have been compared
in Fig. 2 using respective constants as given in eqns (7) and (8).
l~G("O
o
6
100
'0
10
PA[~('d
0 ... '7.\
o.. t.
'laO'" '\S'IIAHO AI,!.
ROOAHl f I ''0 I
,
. ..
U
50
w
::>
z
.... lI.NE OF PUFEel
CO"RElAIl!lN
'0
i
!
10
.
,
.'" •
~
o
!
10
~
;>
,~
1
I
.'"
w
~
~
:l
\
'-I
0
,
' I 1 I ...
~If.wt~ (IOU-'
rrr'J
'>.
"lal;6n~hiD. el.-.e
n obsprv'!d
W",
II
'I~!'
enc'l;r~nce
'0
co
II "" .. , . , .
101
IN MI!IIu1£5
limo; ·.il" estim. lEd enduran-:e time.
DISCUSSION
Limited information is available in the literature on estimation of endurance time
for continuous heavy physical effort in terms of work load relative to individual V0 2 max
(2.22). Bink (6) and Bon1er(7.8) proposed an expon2ntial equation connecting endurance time and work load which reduces to a linear relationship between log T and work
lood. Recently. GIeser and Vogel (12) also derived a similar equation on the basis of data
obtained with eight sub/ects of a average fitness both before and after 4 weeks of physical
traming. Training has been shown to effect the constants of the equation significantly,
despite the fact that work load was expressed re[ati'le to the individual V0 2 m<.Jx which
is. by itself. a measure of the degree of training.
Sen G\:pt~ et a/.
i 76
July·Se!>tember 1919.
Ind. J. Phy:.101. f'harmac.
Gross-Lordemann and Muller (15) on the other hand. have used the general hyperbolic equation which is equivalent to a linear relationship between log T and log (w rk
load). Tornvall (27) also used a similar relationship in his studies on capacity for short
and prolonged work. However. he related his results with the maximum work rate that
could be sustained for 6 min (Wmax/min) instead of aerobic capacity ('J0 2 max).
None of the above two types of relationship have been found to be valid over the
entire range of endurance time (1-120 min) covered by the data (Table II) of Astrand an \
Rodahl (4). as may be evident from Fig. 3 (a and b). in which log T has been plotted
DATA ON ONE SUIJECT (YO,,..
I
"01/"',,,
,AST"ANO&' ROO .... l
•••• '1
6
" 2
0·'
0·2
0·)
l09f Vol/V02 MAX )
o.()
rig. 3: RelalJCnship between log endurance time witll relau'/'l work load llnd log rel:ltivg \/\,or\' 1')3d.
against relative work load (V02/V02 max) and its logarithm respectively. Both the
curves are resonably linear down to about 6-8 min, corresponding to a relative work load
of about 1.2. The graph with respect to log (VO,.IVOl max) actually consists of two
linear portions with different slopes. meeting at a point where T is about 6 min. This suggests the existence of two distinct ranges (viz., submaximal and supermaximal) of work
load which are satisfied by general hyperbolic equations (15) with different constants.
In the lower range (T < 6 min), endurance is primarily limited by anaerobic power which
is not adequately reflected in either of the two relationships mentioned above
Vclurrc
Numtx.r
n
Fnl'!u'~nce C~pa':l!y
for
Conllf\1I0'1~
ffinrl
177
3
That aerobic capacity alone is not a reliable index of endurance performance has been
well demonstrated by observations all long-distance. and marathon runners (9.10.11).
The present approach based on a:robic and anaerobic fractions of O2 supply. has
been found to be quite satisfactory in so far as a single equation (No.8) fits the data of
•
Astrand and Aodahl (4) almJst perfectly over the entire range of T (1-120 min). An
equation of th3 same type (No.7) fits the present data reasonably well «(=0.9640).
the observed scatter (Fig 2) being mainly due to individual difference among the 13 subjects ard possible errors in 0 1 estimations. particularly for UI > 0.9. The values of Tare,
on the average. 32% higher than those reported by Astrand and Rodahl (Fig.1). The I tter
data pertain to an athletic subject
(Val max= 5.0 1/min). whereas the
Indian subjects of the
present study are of average fitness (mean VOl max = 2.38 l/min). Any rossible effect
of training on the proposed equation can. therefore. be safely ruled out. The unexpected
difference in T for the same aerobic fraction of 0 1 supply for the two sets of data (Tables I
and II) may be possibly due to superior thermoregulatory mechanism of the heat-acclimatised Indian subjects. However. no definite conclusion in this regard. can be drawn from the
•
present study. particularly because the data of Astrand and Rodahl pertain to a single
individual.
In view of the high degree of correlation between observed and estimated log T
on the basis of aerobic and anaerobic fraction of O2 supply (r=0.9996 and 0.9640 for the
two sets of data). it appears that this index in terms of a single physiological parameter is
quite suitable for the assessment of endurance capacity. However. it will be interesting to
study the effect of various other factors limiting endurance of this index. Some of these are.
initial glycogen level in muscles (1) hyperthermia and dehydration (24,29) and relative
distribution of ST fibers (11.13.14).
ACKNQI.'VLEDGEMENTS
Thanks are due to Sarvashri T. Sampathkumar. N. Srinivasulu, P.B.S. Pillai and
B.S. Arora for technical assistance and to the soldiers for their whole hearted cooperation.
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r.>UOI~
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III
Ind
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