Clinical Science (1972) 42, 355-370.
MULTISTAGE T R E A D M I L L W A L K I N G P E R F O R M A N C E
AND ASSOCIATED C A R D I O R E S P I R A T O R Y RESPONSES
OF M I D D L E - A G E D M E N
W. C. ADAMS, M. M. McHENRY*
AND
E. M. B E R N A U E R
Human Performance Laboratory, Physical Education Department, University of California,
Davis, California
(Received 21 October 1971)
SUMMARY
1. Eighty apparently healthy sedentary males, aged 31-69 years, undertook a
multistage treadmill walking test that was terminated at maximum tolerable effort.
2. An electrocardiogram (ECG), blood pressures and respiratory metabolism
measures were taken at rest, during the walk and for 15 min post-exercise. The mean
values for four age groups of twenty subjects each were analysed statistically.
3. A near rectilinear decrease in walk-time and maximum oxygen uptake ( VO~,,,,,~.)
(ml m i d kg-') with advancing age was observed. A difference in VO~,,,,,~.
of
26.5% between the oldest and youngest groups was decreased to 17.7% when expressed in ml min-lkg-' of lean body weight (LBW). Heart rate (HR) and pulmonary
ventilation (VE) at maximum tolerable effort also declined with age.
4. There were no age-related differences in VE and HR during submaximal work,
whereas significant differences in Po2 were observed only during early stages.
5. It was concluded that the decline in maximum performance with age was not
due to differences in the efficiency of aerobic energy utilization but to factors
limiting energy production.
6. Prediction of walk-time utilizing anthropometric, resting and submaximal work,
measurements proved unsatisfactory. Although an r value of -0.69 between age
~ ~ . walk-time yielded an r or 0.93, thus
and walk-time was obtained, V O ~ , , ,and
indicating that chronological age alone was not adequate to assess work capacity.
Key words : oxygen uptake, physiological ageing, submaximal work response, work
capacity.
Man's capacity for strenuous physical work gradually diminishes during middle age, although
physical training, nutrition and disease may modify it (Robinson, 1938;Buskirk & Counsilman,
1960;Astrand, 1968).In both cross-sectional and longtitudinal studies of sedentarymales, maxi-
* Present address: Cardiopulmonary Laboratory, Sutter Memorial Hospital, Sacramento, Calif.
Correspondence:Professor W. C. Adam, Department of Physical Education, University of California, Davis,
California 95616, U.S.A.
355
356
W . C. Adams, M . M . McHenry and E. M. Bernauer
mum heart rate (HR) has been observed to diminish by approx. 15% between 30 and 70 years,
declines by 25-30% (Robinson, 1938; Astrand,
whereas maximum oxygen uptake ( vozmax.)
1956). An additional cause for decreased performance with increasing age might be a less
efficient cardiorespiratory response at submaximal workloads. However, investigations at
submaximal workloads on the treadmill have revealed both no differences in HR and Po,
with advancing age (Robinson, 1938; Mahadeva, Passmore & Woolf, 1953; Balke & Ware,
1959; Hanson, Tabakin & Levy, 1968), and significantly higher values in older subjects
(Durnin & Mikulicic, 1956; Harris & Thomson, 1958; Grimby & Soderholm, 1962).
Until recently, maximum cardiorespiratory capacity has been determined by measuring
responses to a single relatively brief bout of strenuous physical exercise (Taylor, Buskirk &
Henschel, 1955; Mitchell, Sproule & Chapman, 1958). However, if one is interested in cardiorespiratory response to exercise stress in subjects varying widely in age and fitness, as well as
in patients with cardiovascular disease, multistage tests involving progressive increments in
workload have several advantages (Dill, 1963; Kemp & Ellestad, 1967).
Significant cardiorespiratory results on a large number of middle-aged subjects have been
obtained with the Balke (Balke &Ware, 1959)and Bruce (Bruce, Blackmon, Jones &Strait, 1963;
Kasser & Bruce, 1969) multistage treadmill tests. However, in the Balke test the initial workload is probably too great for safe use with elderly and diseased subjects, whereas the arbitrary
180 HR cut-off point is submaximal for younger men and rarely observed in healthy elderly
men (Robinson, 1938; Astrand, 1958). Although the initial intensity of the Bruce test is
satisfactory for the testing of elderly and diseased subjects, a significant disadvantage exists
in the subsequent abrupt intensification of workloads. The least fit subjects may be forced
into anaerobic energy sources at a point too early for accurate assessment of voZmar.,
thus
failing to discriminate clearly between various ‘ability’ groups (Bruce et al., 1963) and prohibiting valid comparison of age-related submaximal cardiorespiratory responses.
It was our purpose to develop a multistage treadmill test with gradual intensification and
a maximum tolerable effort end-point that would be suitable for evaluating performance capacity and associated cardiorespiratory responses for subjects of widely varying age with or
without cardiovascular disease. A preliminary analysis of its suitability for trained post-myocardial infarct patients has been reported (McHenry, Adams & Bernauer, 1969). In the present
paper a comparison of the rate of loss in performance and maximum cardiorespiratory capacity
with advancing age is made with other work-capacity-testing procedures. In addition, the results
are analysed to see if decreased capacity with age is reflected in higher cardiorespiratory
responses at submaximal workloads.
MATERIALS A N D METHODS
Eighty apparently healthy normal males, aged 31-69 years, served as subjects. All were sedentary volunteers who had not participated in a systematic physical training programme for
2 years before testing.
Experimental routine
Resting measures. Respiratory metabolism with the subject in the post-absorptive state
was assessed after he had sat quietly for 15 min. Various anthropometric data including
whole body density via the densitometric technique were determined. Estimated residual lung
Age, treadmill performance and associated responses
357
volume was taken as a fraction of age-adjusted vital capacity (VC) according to the method
of Brozek (1960).
Electrocardiograms, utilizing the Mason & Likar (1966) lead-placement system, and blood
pressures via auscultation were obtained in the recumbent position. Venous blood was
secured for subsequent analysis of serum cholesterol (Hycel method) and plasma lactate via
the modified Barker and Summerson colorimetric method (Huckabee, 1956).
Exercise. The treadmill test was initiated at a speed of 50 m/min on a level grade and the
workload increased every 3 min, first by increasing the speed 10 m/min up to a maximum of
80 m/min, and then by increasing the inclination 2% up to a maximum of 22% grade at 42:OO.
Each subject was asked to walk to the point of maximum tolerable effort as denoted by marked
dyspnoea and/or noticeably tired and weak legs.
The subject breathed through a Collins triple-J valve, which was connected to a ParkinsonCowan respiratory gas meter, Type CD-4, and a 3.2 1 lucite mixing chamber with baffling
by 3.8 cm i.d. plastic tubing. Ventilation volumes were read every 3 rnin and during the last
minute of exercise, while expired air samples were extracted at 6 s intervals by a 50 ml oiled
glass syringe into a 2 1 butyl rubber bag. All expired air samples were analysed within several
minutes of collection for percentages of COz and O2 on a Godart pulmoanalyser, type 44A-2,
and a Beckman E-2, in tandem. Respiratory metabolism values were obtained with expired
air volumes corrected to S.T.P.D. Respiratory rate (RR) was determined every 5 rnin and
during the last minute of exercise. An ECG was taken for several seconds near the end of
each 3 rnin period and during the last few seconds of the walk. Blood pressures were taken
every 5 min and during the last minute of exercise.
Recovery. Measurements of all parameters were made for 15 rnin immediately after cessation
of walking at the same time-intervals used during exercise. Venous blood was drawn 5 rnin
post-exercise and prepared for subsequent lactate analysis.
Analysis of results
The eighty subjects were divided by decade into four equal groups and the mean, standard
deviation and range determined for each anthropometric and physiological measurement. A
one-way analysis of variance (ANOV) was used to determine if there was a significant difference in the age group mean values. If ANOV indicated a significant difference in the mean
values for a parameter, Student’s t test was applied. In each case, the 0.05 level of significance
was applied.
Because of the time, personnel and equipment necessary for monitoring cardiorespiratory
response to maximal stress testing, correlation analysisof variables related to length of walk-time
was considered to be of prime practical importance. Age and anthropometric data were used
in stepwise multiple regression analyses, whereas maximal and recovery cardiorespiratory
values were excluded for obvious reasons. Only late submaximal (stage 8) cardiorespiratory
measurements were included, since any existing anticipatory effect would have been attenuated
and actual physiological disequilibrium more likely achieved. The 0.05 level of significance
was used to eliminate non-contributary variables.
RESULTS
Basic anthropometric and resting cardiorespiratory data for each group are summarized in
Table 1. There were no significant group mean differences in height, resting HR and resting
46.4
2.5
41-49.9
54.2
3.0
50-59.5
648
2.8
6IM8.8
Group 11: n = 20
Mean
SD
Range
Group 111: n = 20
Mean
SD
Range
Group IV: n = 20
Mean
SD
Range
175.7
8.6
162-191
177.8
7.5
159-190
178.9
6.8
168-190
176.3
5.2
165-187
Height
(cm)
75.1
9.0
64-91
82.6
11.6
65-102
82.5
11.5
64-103
77.7
9-7
62-96
Weight
(kg)
28.38
5.9
19.C38.3
26.47
6.0
15.9-35'5
22.52
6.0
104-34.3
19.99
5.5
76-30.7
250
44.1
196-349
244
37.4
184-303
264
53.2
180-375
231
36.2
177-31 6
3.75
0.8
2.4-5.3
4.08
0.7
2.5-5'2
4.57
0.7
3.1-5'6
4.65
0.3
43-5.3
68.1
106
52-87
72.5
11.0
54-96
69.0
12.3
48-96
666
12.9
52-94
Heart rate
(beats/rnin)
2.745
0.5
3.46
3.67
0-6
2.7-5.4
3.51
0.9
2.5-5.4
-
98-190
60-1 10
143183
143189
118-20
70-110
60-10
131/78
100-160
122175
90-140
60-90
(mmHg)
V02
(dmin-' kg-')
3.45
04
2-8-4.4
Supine
blood
pressure
Sitting rest
* Calculated from formula according to Brozek, Grande, Anderson & Keys (1963).
35.1
2.1
31-39'8
Group I: n = 20
Mean
SD
Range
Age
(years)
Body fat*
Serum
Vital
(% of body cholesterol capacity
weight)
(mg/100 d) (1)
TABLE
1. Basic anthropometric and resting cardiorespiratory data
R
b
?
3
Age, treadmill performance and associated responses
359
vo2. However, the mean differences in body weight (BW) between Groups I1 and N ,and
between Groups I11 and IV were significant. Increases with advancing age in fat expressed as
percentage of BW and blood pressures, along with decreased VC, were observed, although
some intergroup differences were not statistically significant.
Submaximal workloads
An outline of the multistage treadmill test, together with the number of subjects attempting
each stage and their mean HR and vo2 (ml min-' kg-I), is given in Table 2. All subjects
completed the first seven stages encompassing 21 min. Only four failed to attempt stage 9,
which was accepted as the upper end of submaximal work.
Group mean Po2, HR, and O2 pulse observations at submaximal workloads are depicted
in Figs. 1-3. Significantly different Vo2values were observed between the younger groups and
TABLE
2. Multistage treadmill test description, with mean heart rate and oxygen uptake for each work level
Exercise
stage
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
No. of subjects
Elapsed
attempting each stage
time
Treadmill
Heart rate Oxygen uptake
(min) speed and inclination 30-39 40-49 50-59 6569 Total (beatslmin) (ml min-' k g ' )
0-3 :OO
3-6 :OO
6 9:00
9-12:OO
12-15:OO
15-18:OO
18-21 ZOO
21-24:OO
24-27:00
27-30 ZOO
30-33 :OO
33-36100
3639:OO
3942:OO
4245 :00
50 m/min, level
60 m/min, level
70 m/min, level
80 m/min, level
80 m/min, 2%
80 m/min, 4%
80 m/min, 6%
80 m/min, 8%
80 m/min, 10%
80 m/min, 12%
80 m/min, 14%
80 m/min, 16%
80 m/min, 18%
80 m/min, 20%
80 m/min, 22%
20
20
20
20
20
20
20
20
20
20
20
20
16
8
1
20
20
20
20
20
20
20
20
20
20
20
16
7
3
1
20
20
20
20
20
20
20
20
20
20
17
12
7
3
0
20
20
20
20
20
20
20
19
16
11
10
4
1
0
0
80
80
80
80
80
80
80
79
76
71
67
52
31
14
2
942
96.5
100.2
102.9
108.0
113.7
121.5
1308
140.3
1500
162.1
168.8
179.0
182-2
175.5
1070
11.60
12.31
13.41
14.46
16.50
18.84
21.41
24.07
27.14
30.01
32-81
35.80
38.93
41.78
Group IV at stages 2, 3 and 5. However, once the treadmill speed reached 80 m/min and the
incline was raised periodically, there were no further significant differences except those
between Groups I and I11 and I and IV at stage 6. Although Group I tended to have a lower
HR in the initial stages, there were no significant group mean differences. The plot of O2
pulse against walk-time reveals a near-consistent pattern for all groups including stage 5.
From that point, however, the rate of increase in the oldest group was less than that in the
other groups.
Our subjects in the fifth and sixth decades did not show decreased respiratory efficiency,
but those in the seventh decade had a significantly higher ventilatory equivalent and RR (Figs.
4 and 5). However, we did not observe a significantly higher PEin these subjects (Fig. 6).
The systolic and diastolic blood pressure patterns during submaximal workloads were
essentially the same for all groups (Fig. 7). Higher systolic pressure for the two oldest groups
360
W. C. Adams, M . M. McHenry and E. M. Bernauer
8
24 -
22 -
2
20-
Y
m
I
E
-E
-E
18-
Y
a,
163
c
a,
m
x
2
14-
I2 -
10-
,
I
I
I
3
I
I
I
I
15
9
I
I
21
27
Group
1451
I35
-
125-
E
\
v)
+
0
-0"
115-
$,
105-
.Ym.
-
I
95
-
8 55t
I
3
I
I
9
I
I
I
15
Walk time (min)
I
l
21
FIG.2. Group mean heart rate responses to submaximal workloads.
0 , Group 111; m, Group IV.
l
27
0 , Group
I; 0 , Group 11;
Age, treadmill performance and associated responses
14
-
-
I3 -
c
0
f
-E
z
a
12-
11-
C
a0
l
h
10-
9I
0
L
I
I
I
l
I
9
3
l
15
l
l
I
21
27
Walk time (min)
FIG.3. Group mean oxygen pulse responses to submaximal workloads. 0 , Group I, 0,Group
11: 0 . Group 111; W, Group IV.
-
-
0;
2.7v)
0 " -
2.6 -
0
-
r
0
E
0
\
J
,--.,.--., \.--..,-,
\
\
.\\
2.5-
L
I
3
I
I
9
I
I
l
15
l
21
I
1
27
Walk time (min)
FIG.4. Group mean ventilatory equivalent responses to submaximal workloads. 0,Group I;
0,Group 11; 0 , Group 111; m, Group IV.
36 1
362
W. C. Adams, M. M. McHenry and E. M . Bernauer
/
7
/
/
25
/
I
/
/
24
.,
Walk time (min)
FIG.5. Group mean respiratory rate responses to submaximal workloads. 0,Group I ; 0,Group
11; 0 , Group 111;
Group IV.
25t
5
I
3
l
l
9
I
I
I
15
I
21
I
I
27
Walk time ( m i n )
FIG. 6. Group mean pulmonary ventilation responses to submaximal workloads. 0,Group I;
0 , Group 11; 0 , Group 111; M, Group IV.
Age, treadmill performance and associated responses
200
363
-
180-
-
-I 160" E
-E2
140-
-
I
I
5
I
I
10
15
20
Wolk time (rnin)
I
25
FIG.7. Group mean blood pressure responses to submaximal workloads. 0,Group I; 0 , Group
II; 0 , Group 111; W, Group IV.
and a higher diastolic pressure for Group I11 appeared to be manifestations of differences
evidenced at rest (Table 1).
Maximum tolerable eflort
Group mean values for walk time and selected cardiorespiratory measurements are presented
followed a parallel declinewith advancing age. The strength
in Table 3. Walk-time and vo2max.
of these relationships is depicted in Figs. 8 and 9. Group mean values for HR and VE at
maximum tolerable effort, also presented in Table 3, demonstrate a consistent decline with
TABLE
3. Mean values for selected cardiorespiratory parameters at maximum tolerable effort
Walk
time
Group (min)
I
I1
I11
Iv
HR
(beats/
voz
min) (ml min-' kg')
Oxygen
A
R
Vent. equiv.
RR
pulse
(l/min, (~coz/~oz)
(1 h/
(breaths/
(ml/beat) B.T.P.S.)
100rnl Vo2) min)
Blood
pressure
(mmHg)
39.0
36.3
345
292
183.9
177.6
1709
155.2
36.6
33.8
32.4
26.9
15.5
15.7
15.7
13.1
93.8
88.0
86.7
707
1.02
099
1.00
094
2.74
2.62
2-69
2-88
30.2
29.5
30-6
31.8
193/67
205/74
219/85
208181
24.2
201
21.2
6.7
8.8
4.5
1*4
1-1
3.3-9.5
F
ratio
F ratio of 2-73 is significant at the 0 0 5 level with 76 and 3 df.
364
W . C. Adams, M . M . McHenry and E. M . Bernauer
age over the four-decade period. However, not all of the differences between successive age
groups were statistically significant. Although there were no significant differences in O2
pulse among the three youngest groups, a highly significant 15% decrease for the oldest group
was noted. Group IV also had a significantly lower respiratory quotient (R). There were no
age-related differences in ventilatory equivalent or RR. Terminal systolic and diastolic blood
pressures increased with age in the three younger groups, whereas the oldest group showed
intermediate values.
A number of post-exercise plasma lactate samples were inadvertently mishandled. However,
it was found that the age group mean walk-times of those subjects whose lactate samples
were included for analysis differed very little from those for the total groups. There was a
general decline with age, with values of 68.9, 58.1, 62.7 and 52.1 mg/100 ml for Groups I,
11, I11 and IV, respectively. The mean comparisons between Groups I and 11, I and IV, and
111 and IV were significantly different.
45r
y
-.'.
I:L
15 11
n
=
48.57-0.3225~
sYx = 3 71
r
= -0693
U
*
a
'4
m
m
30
m'
m
I
I
I
I
40
50
60
70
Age ( y e a r s )
FIG.8. Relationship of maximum oxygen uptake to age. 0,Group I; 0 , Group 11; 0, Group 111;
m, Group IV.
Recovery
There were no consistent significant differences between Groups 1-111 in recovery cardiorespiratory measurements. Although the oldest group had a significantly lower mean H R at
maximum tolerable effort, this was not observed during recovery. The oldest group's mean
vo2 values were significantly lower throughout recovery (possibly attributable to their
lower maximum exercise value).
Correlation analyses
Product moment correlation coefficients of selected variables with length of walk time are
given in Table 4. A stepwise multiple regression analysis of cardiorespiratory measurements
at stage 8 submaximal workload and length of walk-time yielded an equation with VE,systolic
Age, treadmill performance and associated responses
365
451
.,
Walk time ( m i n)
FIG.9. Relationship of maximum oxygen uptake to maximum walk time. 0 , Group I; 0 , Group
11; 0 , Group 111;
Group IV.
TABLE4. Product moment correlation coefficients
of selected variables with length of walk-time
Variable
Max. oxygen uptake (ml min-' k g ' )
Age
Body density
Peak pulmonary ventilation (I/min)
Terminal systolic blood pressure
Vital capacity
Exercise (25 :OO) systolic blood pressure
Stage 8 pulmonary ventilation (l/min)
Log of total skinfolds
Stage 8 heart rate
Exercise (25 :OO) diastolic blood pressure
Resting heart rate
Reciprocal ponderal index
Serum cholesterol
Body weight
r
0.928
-0704
0685
0.617
-0454
0.450
-0.417
-0.400
-0.353
-0.326
-0.316
-0.224
0.223
-0.186
-0.157
r 0.218 is significant at the 0.05 level.
blood pressure and ventilatory equivalent as independent variables. The multiple R was 0.54,
which is quite unsatisfactory for predictive purposes. A second stepwise regression analysis
including age and selected anthropometric and resting cardiorespiratory measurements on
length of walk-time resulted in the following equation :
W T = -98.20-0*212X, -0*0624X2+ 141.75XS
366
W. C. Adams, M. M. McHenryandE. M . Bernauer
where: WT = length of walk time, X, = age in years, X, = resting HR in beats/min, and
X, = body density in g/ml. The multiple R was 0.81, with a standard error of estimate of
3.17 min.
DISCUSSION
Maximum tolerable effort
The method used in this study for determining fioZmax.
appears to be valid by the criterion
of Taylor et al. (1955) i.e. a plateau, as indicated by < 2.1 ml min-' kg-' increase for each
increment in workload. We observed a tendency to plateau, as evidenced by a mean increase
in Vo, of 2.3 ml min-' kg-' in the last workload attempted, as compared with a near steady
mean increase of 3.0 ml min-' kg-' for each of the three immediately preceding stages.
Further, our mean VoZmax.
values approximate closely to those observed for sedentary males
of similar age by Cumming (1967) and Mitchell et al. (1958) during single-stage tests and by
Naughton & Nagle (1965) during a multistage test. Since the rates of decline in work performance and fioZmax.
in this study were almost precisely equal over the age range examined
(Table 3, Figs. 8 and 9), decreased work capacity appears to be largely a function of decreased
aerobic capacity.
Buskirk & Taylor (1957) contend that when Pozmax.
is used to indicate the capacity to
perform exhausting work, the values should be expressed per kg of BW, whereas to indicate
the performance of the cardiorespiratory system, they should be expressed per kg of LBW.
A decline in mean PoZmax.
from 36.6 ml min-' kg-' in Group I to 26.9 ml min-' kg-' in Group
IV (26.5%) is decreased to 17.7% when expressed in ml min-' kg-' of LBW (mean decrease
from 45.7 to 37.6). Thus, because of the close correlations between Volmar.
and walk-time,
and between BW and fio2 at stage 9 (0.89), approx. one-third of the decreased work performance of the oldest group is due to an increased proportion of total body weight as fat.
Clearly, other factors accounting for decreased work capacity with advancing age are of
importance. We observed a progressive decrease in maximum VE with advancing age, but
other investigators (Robinson, 1938; Astrand, 1956) have concluded it is not a limiting
factor in determining the capacity of men for severe work. Since no clear ageing trend in
ventilatory equivalent at maximum tolerable effort was evident in our study, it would appear
that decreased
is not due to a loss in ventilatory capacity or in the efficiency of oxygen
utilization per unit of ventilated air.
We observed no age-related differences in 0, pulse among the three youngest groups,
although maximum HR and
(ml min-' kg-' of LBW) in Group I11 were 93 and 96%
respectively, of the Group I values. Group IV, however, demonstrated a 15% decrease in 0,
pulse. According to the Fick equation, decreased 0, pulse could be indicative of a lower SV
and/or a - v 0, difference. Julius, Amery, Whitlock & Conway (1967) observed decreased
work capacity with advancing age and found that cardiac output (0)was lower in older
subjects at maximum effort, and that their a-v 0,difference levelled off as they approached
their maximum. In our subjects the terminal systolic and diastolic pressures were lower in
the younger groups. Whether extremely high blood pressures at maximal workloads act to
restrict SV is not entirely clear (Julius e f al., 1967; Hanson et al., 1968). Our results indicate
that decreased performance capacity in Groups 1-111 apears to be the result of an increasing
proportion of BW as fat and of decreased 0 (the latter primarily as a function of decreased
HR). On the other hand, our oldest subjects (60-69 years) suffered the additional restriction
Age, treadmill performance and associated responses
367
of a significantly decreased O2 pulse (probablyindicative of further decrease of by decreased
SV).
The post-exercise lactate results did not show a clear progressive decline with advancing
age, although the mean value of the oldest group was significantly lower than the others.
This may reflect individual differences in physical condition and ability to tolerate an increasing degree of anaerobic metabolism, or that the oldest men were less inclined to exert
themselves maximally.
Submaximal workload responses
Our Vo2 values for submaximal workloads agree rather closely with those observed previously during single-stage walk tests of sufficient duration to permit metabolic equilibrium
(McDonald, 1961;Hanson et al., 1968). Hence, no appreciable circulatory-respiratorylag was
apparent during the continuous 3 min sampling period at each workload.
One explanation for the discrepancy in age-related submaximal treadmill Vo2 observations
in previous studies could be failure to consider the influence of BW on energy expenditure
of walking (McDonald, 1961). In our study an increase in product moment correlation
coefficients from 0.685 at stage 1, to 0.726 at stage 5 and steadily to 0-889 at stage 9, was
observed. Apparently, the higher the grade during submaximal workloads, the more important BW became in affecting energy expenditure.
Results of previous investigations (Durnin & Mikulicic, 1956; Harris & Thomson, 1958;
Grimby & Soderholm, 1962) reveal a higher Vo2 for older subjects at walking rates slower
than 80 m/min and faster than 93 m/min. However, even at workloads requiring higher rates
of energy expenditure while walking up grade within this speed range, no such tendency has
been noted (Robinson, 1938; Balke & Ware, 1959; Hanson el al., 1968). This suggests the
possibility of an optimum walking speed for older subjects (Murray, Kory & Clarkson,
1969). Our results are consistent with this contention, in that significantly higher Vo2 was
observed for the older subjects until the treadmill speed was increased to 80 m/min. Thereafter,
no further significant differences, other than between Groups I and I11 and I and IV at stage
6, were observed.
The three youngest groups showed no clearly discernable differences in HR, O2 pulse,
ventilatory equivalent, RR, or VE at submaximal workloads. On the other hand, Group IV
had significantly higher ventilatory equivalents and RR throughout submaximal work.
However, these observations do not appear to have effected decreased work capacity, since
Group IV’s ventilatory equivalent at maximum tolerable effort showed a similar increase
over submaximal values to that observed for other groups. Although their RR was higher
(and, thus tidal volume lower), this was probably a function of decreased VC rather than
respiratory inefficiency, as there were no significant differences in submaximal R.
Our submaximal work correlation analyses indicate that the prediction of work capacity
of individuals of different age cannot be satisfactorily accomplished on the basis of cardiorespiratory response to moderate work. This can be attributed, in part, to the fact that older
subjects have restricted ranges of response from resting to maximal values. Thus, our observations suggest that the decisive mechanisms conditioning the decline in maximal performance
with age are not differences in the efficiency of the utilization of aerobic energy, but factors
limiting energy production.
W. C. Adams, M. M . McHenry and E. M . Bernauer
Clinical aspects
Repeat testing of eight clinically stable patients with prior documented myocardial infarction and who had been engaged in a physical-conditioning programme for 6-12 months,
was performed within a mean elapsed time of 103 days. Results presented in Table 5 indicate
that no preliminary practice is required to obtain reliable cardiorespiratory responses from
middle-aged male subjects.
Since none of the stepwise multiple-regression analyses proved adequate for predictive
purposes, it is necessary to complete the test at maximum tolerable effort to assess work
capacity. Clinically, it would appear advisable to estimate volmax.
from walk-time ( r = 0.93,
with standard deviation of 1.99 ml min-' kg-'), and to monitor the ECG for age-related
maximum HR, arthymias, and ST depressions not apparent at rest or submaximal workloads
(Ellestad, Allen, Wan & Kemp, 1969).
The multistage test presented in this paper appears to have some practical advantages over
those previously developed. For example, the true aerobic capacity of older subjects and
patients may not be assessed accurately by the Bruce test because of the great abruptness in
increased work intensity during later stages (Bruce et al., 1963). To test older subjects and
those with cardiovascular disease, the Balke test has been modified (Naughton, Sevelius &
TABLE
5. Mean test-retest data for multistage treadmill walking test
VE
Work stage
(I/min,
R
Vent. equiv.
B.T.P.S.) ( Vco2/Po2) (1 v ~ / l 0 ml
0 Vo2)
v02
(I/min)
HR
(beats/min)
1 (50 m/rnin, level grade)
20.65
20.52
0.72
0.69
2.45
2.43
0.700
0.702
94
87
5 (80 m/min, 2%)
30.64
29.5 1
55.64
52.87
71.26
70.96
0.83
0.79
0.96
088
1.03
0.97
2.48
2.38
1.027
1.03 1
2.59
2.44
2.73
2.58
1-784
1.799
2.178
2.255
110
104
144
143
165
164
9 (80 m/min, 10%)
Maximum tolerable effort
Blood
pressure
(mmHg)
169189
155183
191191
179180
195190
193184
~~
Mean test-retest walk times for these subjects (n = 8) were 31.8 and 32.1 min, respectively.
Balke, 1963), but has the disadvantage of ending at submaximal levels for most middle-aged
men. Our test starts at a very low intensity and imposes gradually increasing workloads that
permit even elderly subjects and patients with cardiovascular disease to adjust with a minimum
of anticipation. The continued gradual increases in workload are of sufficient intensity in the
later stages to tax most sedentary middle-aged males to their maximum. However, even with
the test's predictive power for vo2max.
obviating the necessity for measurement of this time
consuming and expensive parameter, it would still require approximately 1 h to prepare and
test each subject. This represents the main clinical disadvantage of our testing procedure.
ACKNOWLEDGMENTS
This study was supported in part by a grant from the Sacramento-Yolo-Sierra Heart Association, and by U.S. Air Force Grant AFOSR-69-1659.
Age, treadmill performance and associated responses
369
The authors wish to acknowledge the helpful suggestions for analysis of the data afforded
by Dr Richard F. Walters, Human Physiology, Medical School, University of California,
Davis, and to his assistant, Mrs Jean Washington, for computer programming.
REFERENCES
I. (1958) The physical work capacity of workers 50-64 years old. Acta Physiologia Scandinavica, 42,
ASTRAND,
73-86.
ASTRAND,
P-0. (1956) Human physical fitness with special reference to sex and age. Physiological Reviews,
36,307-335.
ASTRAND,P-0. (1968) Physical performance as a function of age. Journalof the American Medical Association,
205,729-733.
BALKE,B. & WARE,R.W. (1959) An experimental study of physical fitness of Air Force personnel. United
States Armed Forces Medical Journal, 10, 675489.
BROZEK,
J. (1960) Age differences in residual lung volume and vital capacity in normal individuals. Journal of
Gerontology, 15, 155-160.
BROZEK,J., GRANDE,F., ANDERSON,
J.T. & KEYS,
A. (1963) Densitometric analysis of body composition.
Revision of some quantitative assumptions. Annals of the New York Acadamy of Sciences, 110, 113-140.
BRUCE,R.A., BLACKMON,
J.R., JONES,
J.W. & STRAIT,
G. (1963) Exercise testing in adult normal subjects and
cardiac patients. Pediatrics, 32, 742-756.
BUSKIRK,
E.R. & COUNSILMAN,
J.E. (1960) Special exercise problems in middle age. Science and Medicine of
Exercise and Sports (W.R. Johnson, ed.), pp. 491-507. Harper, New York.
BUSKIRK,
E.R. & TAYLOR,
H.L. (1957) Maximal oxygen intake and its relation to body composition, with
special reference to chronic physical activity and obesity. Journal of Applied Physiology, 11,72-78.
CUMMINO,
G.R. (1967) Current levels of fitness. Canadian Medical Association Journal, 96,868-877.
DILL, D.B. (1963) The influence of age on performance as shown by exercise tests. Pediatrics, 32,737-741.
DURNIN,J.V.G.A. & MIKULICIC,
V. (1956) The influence of graded exercise on the oxygen consumption, pulmonary ventilation and heart rate of young and elderly men. Quarterly Journal of Experimental Physiology,
41,442452.
ELLESTAD,
M.H., ALLEN,W., WAN,M.C.K. & KEMP,G.L. (1969) Maximal treadmill stress testing for cardiovascular evaluation. Circulation,39,517-522.
GRIMBY,
G. & SODERHOLM,
B. (1962) Energy expenditure of men in different age groups during level walking
and bicycle ergometry. Scandinavian Journal of Clinical and Laboratory Investigation, 14, 321-328.
HANSON,
J.S., TABAKIN,B.S. & LEVY,A.M. (1968) Comparative exercise-cardiorespiratory performance of
normal men in the third, fourth and fifth decades of life. Circulation, 37, 345-360.
HARRIS,E.A. & THOMSON,
J.G. (1958) The pulmonary ventilation and heart rate during exercise in healthy
old age. Clinical Science, 17, 349-359.
HUCKABEE,
W.E. (1956) Control of concentration gradients of pyruvate and lactate across cell membranes in
blood. Journal of Applied Physiology, 9, 163-170.
JULIUS,
S., AMERY,A., WHITLOCK,L.S. & CONWAY, J. (1967) Influence of age on the hemodynamic response
to exercise. Circulation, 36, 222-230.
KASSER,I.S. & BRUCE,R.A. (1969) Comparative effects of aging and coronary heart disease on submaximal
and maximal exercise. Circulation, 39, 759-774.
KEMP,G.L. & ELLESTAD,M.H. (1967) The current application of maximal treadmill stress testing. Culvornia
Medicine, 107, 406-412.
MAHADEVA,
K., PASSMORE,
R. & WOOLF,B. (1953) Individual variations in the metabolic cost of standardized
exercises. The effects of food, age, sex and race. Journal of Physiology, 121,225-231.
MASON,R.E. & LIKAR,I. (1966) New system of multiple-lead exercise electrocardiography. American Heart
Journal, 71, 196-205.
MCDONALD,
I. (1961) Statistical studies of recorded energy expenditure of man. 11. Expenditure on walking
related to weight, sex, age, height, speed and gradient. Nutrition Abstracts and Reviews, 31, 739-762.
MCHENRY,M.M., ADAMS, W.C. & BERNAUER,
E.M. (1969) Evaluation of a progressive treadmill test for
cardiac patients. Clinical Research, 17,103.
I
370
W. C. Adams, M . M . McHenry and E. M. Bernauer
MITCHELL,
J.H., SPROULE,
B.J. & CHAPMAN,
C.B. (1958) The physiological meaning of the maximal oxygen
intake test. Journal of Clinical Investigation, 37, 538-547.
MURRAY,
M.P., KORY,R.C. & CLARKSON,
B.H. (1969) Walking patterns in healthy old men. Journal of Gerentology, 24, 169-178.
NAUGHTON,
J.P. & NAGLE,F. (1965) Peak oxygen intake during physical fitness program for middle-age men.
Journal of the American Medical Association, 191, 899-901.
NAUGHTON,
J.P., SEVELIUS,
G. & BALKE,
B. (1963) Physiological responses of normal and pathological subjects
to a modified work capacity test. Journal of Sports Medicine and Physical Fitness, 3,201-207.
ROBINSON,
S. (1938) Experimental studies of physical fitness in relation to age. Arbeitsphysiologie, 10,251-323.
TAYLOR,
H.L., BUSKIRK,
E.R. & HENSCHEL,
A. (1955) Maximal oxygen intake as an objective measure of
cardiorespiratory performance. Journal of Applied Physiology, 8, 73-80.