to one-third of the BMR. For all practical pur-
poses the BMR amounts to an oxygen consump-
tion of 3.5 ml per kg of body weight. Details of
both procedures are given in Table 10. The
“modified” test will only be used in cases ex-

pected to show abnormally low levels of work
capacity.

We are grateful to Don Rowlan, James
Turner and Kamal Shanbour for their assist-
ance in this research.

GRADATIONAL STEP TEST

Normal Procedure Modified Procedure
Stepping Rate: 30/min Stepping Rate: 24/min
Ste Total Step Total
Min. Mets Height Vertical Lift Mets Height — Vertical Lift
em m em m

0 1.0 _— 1 _ _

1 2.5 2 x 2.5 2.5 6

2 3.0 4 1.2 3 5.0 1.2

3 3.5 6 18 3-1/3 6.7 1.6

4 4.0 8 2.4 3-2/3 8.3 2.0

5 4.5 10 3.0 4 10.0 2.4

6 5.0 12 3.6 4-1/3 11.7 2.8

7 5.5 14 4.2 4-2/3 13.3 3.2

8 6.0 16 4.8 5 15.0 3.6

9 6.5 18 5.4 5-1/3 16.7 © 4.0
10 7.0 20 6.0 5-2/3 18.3 44
ll 75 22 6.6 6 20.0 4.8
12 8.0 24 7.2 6-1/3 21.7 5.2
13 8.5 26 78 6-2/3 23.3 5.6
14 9.0 28 8.4 7 25.0 6.0
15 9.5 30 9.0 7-1/3 26.7 6.4
16 10.0 32 9.6 7-2/3 28.3 6.8
17 10.5 34 10.2 8 30.0 7.2
18 11.0 36 10.8 8-1/3 31.7 76
19 11.5 38 11.4 8-2/3 33.3 8.0
20 12.0 40 12.0 9 35.0 8.4

Taste 10: Relationship between stepping height, vertical lift (in meters per minute) and
energy expenditure (expressed as multiples of basal metabolic rate) in the normal
and in the modified Gradational Step Test.

REFERENCES

. Master, A. M., Oppenheimer, E, T.: A Simple Exercise
Tolerance Test for Circulatory Efficiency with Standard
Tables for Normal Individuals. Am. J. of Med. Sci.,
177:223-243, 1929.

2. Master, A. M., Rosenfield, I.: Two Step Exercise Test

Brought up to Date, New York J. of Med., 61:1850-1857,

1961.

»

Johnson, R. E.: Collected Reports from Harvard Univ.

Fatigue Lab., 48, 1942.

4, Balke, B. Ware, R. W.: An Experimental Study of
Physical Fitness ‘of Air Force Personnel, U. S. Armed
Forces Med. J., 10:675-688, 1959.

5. Newton, J. L.: The Assessment of Maximal Oxygen In-
take. J. of Spts. Med. and Phys. Fitness, 3:164-169, 1963.

6. Morehouse, L. E., Miller, A. T.: Physiology of Exercise,
C. V. Mosby Co., St. Louis, 1959,

. Gallagher, J. R., Brouha, L.: A Step Test for Evaluating
Physical Fitness, Yale J. of Biol. Med., 15:769-779, 1943.

8. Fletcher, J. C.: Maximal Work Production in Man. J.
of Applied Physiol., 15:764-767, 1960.

n

2

Hettinger, T., Birkhead, N. C., Horvath, S. M., Izekutz,

B., Rodahl, K.: Assessment of Physical Work’ Capacity,

J.’ of Applied Physiol, 16:153-156, 1961.

10. Darling, R. C., Johnson, R. E., Pitts, G. C., Consolazio,
F. C,, Robinson, P. F.:' Effects of Variations in Dietary

Protein on the Physical Well Being of Men Doing Man-

ual Work. J. of Nutr., 28:273-281, 1944.

Graybiel, A., West, H.: The Relationshin between Physi-
cal Fitness and Success in Training of U. S. Naval Flight
Students. J. Aviation Med., 16:242-249, 1945.

12, Rhyming, I: A Modified Harvard Step Test for the
Pvaluation of Physical Fitness, Arb, Physiol. 15:235-250,
953.

UU.

13. Asmussen, E., Christensen, E. H., Nielsen, M.: Die Be-
deutung der Korperstellung fur die Pulsfrequenz bei Ar-
beit, Skand. Arch, Physiol., 81:225,1939,

14. Naughton, J., Balke, B., Poarch, A.: Modified Work Ca-
pacity Studies in Individuals with and_ without Coronary
pare Disease. J. Spts. Med. and Phys. Fitness (In

ress).

—12—


ranges of work intensity. A split-plot design fac-
torial analysis was applied to the oxygen data
obtained on the treadmill at the 8 and 14 per
cent grade as compared to those on the 20 and
30 em level of the stepping box; the data from
the other workload levels appeared to be in-
sufficient for inclusion. The analysis indicated
that there were no significant differences in the
values of oxygen intake for the two types of
exercises at the work intensity levels chosen for
comparison.

On the basis of the similarity in metabolic
costs between these established levels of work
on either the 4-step box or on the treadmill it
was postulated that the final treadmill perform-
ance — which, so far, had been used for the
assessment of work capacity or of “physical
fitness” — might be predicted from an extra-
polation of the heart rates measured at the vari-
ous stepping levels on the box. On graph paper.
with the per cent grade of the treadmill and the
corresponding stepping height on the abscissa
and with the heart rate on the ordinate, the pulse
rates measured during stepping at the various
levels of work were properly plotted (Figure
2). Then a line of best fit was drawn through
these observed values. At the intersection with
the pulse line of “180”— considered as the

HEART RATE
(BEATS / MIN)

STEP HEIGHT oem 20em 306 ‘sem
womve 12345678 9 ORB HS wT W192

(OF TREADMILL,
WORK LOAD

Illustration of pulse extrapolation technique for
predicting the peak treadmill performance of 2
subjects from the 4-box step test.

Figure 2:

“critical” pulse frequency of the “average
man” — the perpendicular was drawn and the
potential treadmill performance was read off
the abscissa. Table 2 presents the values of
treadmill performance predicted from the step
test versus the actually measured treadmill per-

formance.
Treadmill Performance

Subject Actual Predicted
1 30 29
2 27 26
3 23 25
4 24 24
5 24 21
6 16 19
7 18 17
8 17 16
9 17 15

10 16 15
1l 15 12

Taste 2: Comparison of peak treadmill performances actu-
ally achieved in a standardized Work Capacity
Test and of treadmill performances predicted from
extrapolation of heart rate data in the 4-box step
test. The figures represent the minute of the
treadmill test in which the heart rate of 180 was,
or would ‘have been attained during the W.C.T.
on the treadmill.

A comparison of the predicted and actual
treadmill performance data yielded an r =
.94. The regression line y = 2.6 + .9x with 5
per cent error estimates is shown in Figure 3.

305
w
g 284
$8
a”)
ae
4%
Zu 4
28
oa
fe
Wo
e104
x
2
z
2
e 54
=z

4

T T T T T T T 1

1 5 10 15 20 25 30 35
PREDICTED TREADMILL PERFORMANCE
% GRADE

Ficure 3: Regression line for prediction of peak treadmill
performance from 4-box step test.

—3—



subvecT ~ AN.

Ve (61PS) Von

og (on/min)

wo.

HEART RATE
(BEATS/MIN)

Ficure 6: Oxygen intake and ventilation equivalent (Ve: Voz) correlated with heart rate in
both the Work Capacity Test on the treadmill and the Gradational Step Test Pro-

cedure III.

Procedure III. Twenty normal male adults par-
ticipated in this test series and a few more per-
formed the step test only for additional infor-
mation on the metabolic costs of this procedure.
The latter are depicted in Table 7 which, for
comparison, also shows the average oxygen in-
takes of a large population for identical min-
utes of work in the standard treadmill test*.

intervals of work, there were differences in
hemodynamic qualities at the higher workload
levels which resulted in a lower peak oxygen

intake at the maximum heart rate in the step
test (see Figure 6). These differences may ex-
plain the shorter test durations in the step tests
as compared to the treadmill test (Table 8).

Although the oxygen requirements almost Calculation of a correlation coefficient yielded
matched each other in both tests during the same an r = .95.
GRADATIONAL
SUBJECT STEP TEST, PROC. Il W.C.T. ON TREADMILL
‘Time (min) "Time (min)
1 18
2 18 22
3 16 20
4 16 20
5 16 19
6 15 19
7 13 17
8 13 7
9 13 16
10 13 16
ll 13 15
12 13 13
13 12 15
14 12 14
15 12 13
16 1 14
17 10 13
18 10 11
19 8 12
20 8 9

Taste 8: Peak performance in the Step Test, Procedure II,
(rate_ “30,” 2 cm-step_ increments) and in the
W.C.T. on the treadmill.

—38—


Gradational Step Test

The previous experimental work had shown
that the 4-box step test proved useful for pre-
dicting work capacity in close agreement with
that actually measured by the standard tread-
mill test. The observation was made, however,
that the increments in load from step to step
were too large. At the rate of 30 body lifts per
minute many testees displayed signs of physio-
logical limitations before progressing to the
third (30 cm) stepping height. On the other
hand, a reduction of the stepping rate to 24
per minute did not provide the near maximum
load required for adequately testing subjects
in good physical condition. Therefore, attempts

were made to develop and construct a stepping
device allowing for a quick adjustment of any
desirable platform height up to 50 centimeters.
The finally acceptable end product (See Figure
5) consisted of a platform attached to the verti-
cal aluminum frame structure with a roller ar-
rangement. Through the rearward base of the
platform runs a jack-screw rod that, when turned
either by hand (for field use) or by a small
electric motor (in the laboratory) moves the
platform up or down. The motor was controlled
by a simple toggle switch held and activated
by the investigator. The height of the platform
was variable from 2.5 to 50 cm above ground
and any height adjustments could be made
while the subject continued stepping.

Ficune 5: Gradational stepping device and method of measuring physiological parameters.

—5—



An Abbreviated Treadmill Test

The results and experiences with the 4-box
step test encouraged us to use, parallel to the
step test, an equivalent testing procedure on
the treadmill especially on such days when con-
fronted with a physical fitness evaluation of 40
to 50 subjects within 4-5 hours time. The work
loads on the treadmill were set nearly identical
to those imposed in the step test by running the
treadmill belt at a constant speed of 91.5 m/min
at grades of 3, 8, 14 and 22 per cent for 3 min-
utes each in continuous succession. As in the
step test, heart rate and blood pressure were
measured toward the end of each minute and

the test was terminated in accordance with the
criteria used in the 4-box step test.

Results

For a critical evaluation of the usefulness of
such an abbreviated test of work capacity on
the treadmill twelve subjects were given the
standard test (gradual minute-by-minute in-
creases of workload) and — after sufficient re-
covery or in reversed sequence — the abbrevi-
ated treadmill test. In both tests the respiratory
gas exchange was determined at the grades of
8, 14 and 22 per cent, in the “abbreviated test
during the third minute on these levels. The
oxygen consumption during the one-minute
period on the same grade during the standard
test was slighly less (See Table 3), indicating
that steady state work conditions were not com-
pletely achieved. However, a statistical analy-
sis revealed no significant differences between
the oxygen intakes for equal loads due to the
different exercise treatments,

Subjects Treadmill Grade Oxygen Intake, ml/kg/min
N % Wr. Abbrev. TT.

12 8 23.610 24.8 = 1.8*
12 14 32.5£1.5 33.3 = 2.7
3 22 643.715 44.3+18

*Standard Deviation

Taste 3: Comparison of oxygen consumption during work
on the treadmill at the same grade: in the stand-
ardized W.C.T. -the loads were increased from
minute-to-minute, in the abbreviated treadmill
test every three minutes whereby oxygen consump-
tion was determined during the third minute.

With the establishment of the similarity in
metabolic costs anu pulse response the heart
rate extrapolation technique as described previ-
ously was applied. The intersection of the line
of best fit drawn through the pulse rates meas-
ured in the abbreviated test with the pulse rate
line of “180” was used for the prediction of the
performance to be expected in the standard
treadmill test. A comparison of predicted and
actually measured work capacity (See Table 4)
give the latter a slight edge of 2 per cent. The

Treadmill Performance
ctual

Subject Predicted
1 30 31
2 24 24
3 20 20
4 20 19
5 20 18
6 19 ~ 18
7 15 17
8 19 16
9 17 16

10 16 16
ll 15 16
12 16 15

‘Taste 4: Comparison of peak treadmill performance actially
achieved in a W.C.T. and that predicted from ex-
trapolation of heart rate data in the abbreviated
treadmill test. The figures represent the minute in
which the heart rate of “180” was, or would have
been attained during the W.C.T. on the treadmill.

correlation coefficient was r = .95. The regres-
sion line y = 1.6 + .9x with 5 per cent error
estimates is shown in Figure 4.

m7
z
ig
g2
2
ge
4
28
gs
Pid
Ex
4
2
1 8 © 2% 2% % 3
PREDICTED TREADMILL PERFORMANCE:
% GRADE

Ficure 4: Regression line for prediction of peak treadmill

performance from abbreviated treadmill test.

—4—


Peak Heart Rate

Peak Vo, Peak Vo,: Pulse

Body Wt. (beats/min) (ml/min) (ml/beat /min)
Kg. Treadmill Step Proc. 11 Treadmill Step Proc. II Treadmill Step Proc.
52.6 180 176 1316-1112 73 6.3
58.0 180 180 1561 1237 8.7 6.9
86.5 182 180 2337-2185 12.8 12.1
99.2 180 182 2871 2604. 16.0 14.3
77.2 184 184 2595 2312 14.1 12.6
97.2 184 180 3112-2966 16.9 16.5
77.2 182 184 2335 2223 12.8 12.1
739 184 184 2348 2447 12.8 13.3
113 184 182 2634 «2394. 14.3 13.2
814 180 180 2886 2400 16.0 13.3
65.7 180 180 2389 =—-:2375 13.3 13.2
67.2 182 180 2607 2601 14.3 14.5
74.5 182 180 2831-2561 15.6 14.2
66.3 182 180 2941 —-2520 16.2 14.0
749 _ 182 _ 180 _ 3533 _ 2840 _ 194 _ 158

X=182 X—181  X~2553 X-2318  X—-140 X=128

Taste 6: Comparison of peak values for oxygen intake, heart rate and oxygen pulse during
‘T. on the treadmill and Procedure II of the Gradational Step Test.

Unexpectedly, inconsistencies in performances
occurred among two better trained individuals.
There was also a tendency seen, in this step
test, that performances were grouped in a rela-
tively narrow range. This might indicate that
the initial load and the minute-by-minute incre-
ments of work intensity were too high to de-
lineate the finer differences in the compensa-
tory functional capacities of individuals.

A comparison of the peak values for oxygen
intake, heart rate and oxygen-pulse (Table 6),
revealed nearly the same maximum pulse fre-
quency for both types of test work but a lower
peak oxygen intake for the work of stepping.

Gradational Step Test, Procedure III
Vo,

The average oxygen pulse, which is the fraction
of oxygen taken out of the volume of blood
moved into circulation with one heart contrac-
tion, amounted to 14 ml at the peak load on
the treadmill but to only 12.8 ml at the maxi-
mum level of stepping. This is of interest in so
far as it shows that even for similar or related

types of work the pulse rate response cannot
be considered an accurate indicator of the me-
tabolic load involved. The mean difference in
oxygen pulse (ml of oxygen intake per heart
beat) between the two tests proved to be signifi-
cant in a paired t-test (P < .01).

W.C.T. on Treadmill

Subjects le Heart Rate Subjects. Vo, —_-Heart Rate

Min, N ml/kg/min beats/min N  ml/kg/min beats/min
2 28 16.7 = 2.0* 125 22 15.2 120
4 25 19.7 = 1.7 131 21 18.5 127
6 27 22.6 = 2.2 146 22 21.7 136
8 28 25.9 = 2.3 157 22 25.0 146
10 27 28.2 + 2.5 168 22 28.3 158
12 21 31.1 + 2.1 175 21 31.6 166
14 14 34.1 + 2.1 180 16 34.8 171
16 10 36.6 = 1.5 186 13 38.1 177
18 2 41.3 + 1.4 181 9 41.3 184
20 6 44.6 186
22 2 47.9 184

*Standard Deviation

Tante 7: Comparison of oxygen consumption and heart rate during the same minutes of the
Step Test, Procedure II, and the W.C.T. on the treadmill.

—7—



AM 64-3

THE GRADATIONAL STEP TEST FOR
ASSESSING CARDIORESPIRATORY CAPACITY:
AN EXPERIMENTAL EVALUATION OF
TREADMILL AND STEP TEST PROCEDURES

Francis Nagle
Bruno Balke
Biodynamics Branch

Approved by Released by.
Shantey RUMERL? Wd. Whe
Srantey R. Mouuer, M.D. M. S. Warre, M.D.

Diecron, CARI FEDERAL AI SURGEON

FEDERAL AVIATION AGENCY
Office of Aviation Medicine
Civil Aeromedical Research Institute
Oklahoma City, Oklahoma
January 1964



Rhyming"? modified the Harvard Step Test,
selecting a 40 cm step for men (33 cm step for
women) and a rate of 22.5 steps per minute.
These changes allowed for a working duration
of 5 minutes at sub-maximal responses. How-
ever, the procedure necessitated the use of a
pulse extrapolation technique for the prediction
of aerobic work capacity.

Master’s Test’ as originally described and
updated? utilizes a 2-step bench (22.5 cm per
step). The stepping rate is determined from
tables based on weight and age. Work is con-
tinued for 114 minutes, or for 3 minutes in the
Double Master’s Test. For satisfactory perform-
ance the subject’s pulse and blood pressure must
return to resting levels within 2 minutes follow-
ing the cessation of exercise. Master’s Test is
not suitable for our purposes for three reasons:
1) his concept of an exercise tolerance (capac-
ity) is hardly definitive. Data from Master’s
tables shows that for the age-weight ranges for
males from 16—66 years and 120—190 lbs.,
the vertical lift made, in’ meeting test criteria,
ranges from 5 to 8 meters per minute. Based on
data compiled in this laboratory for metabolic
costs of stepping at various heights, the cost of
this work would vary from approximately 6 to
9 times the basal metabolic rate. When one con-
siders that the work capacity (expressed as
Mets = multiples of basal metabolic rate) may
vary from 2 Mets for “sub-normal” individuals
to 18 Mets for trained athletes, the 6 to 9 Mets
range of Master’s Test is hardly adequate. While
the test grossly discriminates between “normals”
and “‘sub-normals” it does not accurately gauge
the physical capability of individuals; 2) there
may be considerable variation in response to
the exercise stress within one age-weight group
due to physical conditioning differences. Since
the minimum metabolic demand is 6 Mets the
possibility of overloading certain individuals is
present; 3) the range of movement of a subject
in performing the Master’s Test make the moni-
toring of physiological parameters very diffi-
cult during the work.

Experimentation with a 4-box stepping de-
vice showed that the instrument was not ideally
suited to the intended purpose. In many cases
work at the third step was accompanied by sub-
maximal responses but moving to the fourth

step induced considerable anaerobic work. The
application of a pulse extrapolation technique,
however, (Figure 2) showed the test could be
quite useful in predicting maximal treadmill
performance from sub-maximal responses to
work. While the use of extrapolation may limit
accuracy this is more than offset by the useful-
ness of the test in evaluating large groups of
individuals where time is an important consid-
eration.

Of the methods investigated with the Grada-
tional Stepper, Procedure III appeared most
suitable for “normal” population use as the high
correlation (r = .95) between treadmill and
Procedure III performances would indicate.
The physiological responses to stepping in Pro-
cedure III approximated most closely those ob-
served in treadmill walking (Table 9). It was
repeatedly observed during the different types
of work requiring identical values of oxygen in-
take that pulse rates were higher in stepping
than in treadmill walking (Tables 7, 9). One
can only speculate on the cause. Asmussen,
Christensen and Nielsen'* have reported dis-
crepancies of this nature when comparable work
was performed in different positions. They rea-
soned that the blood shift to the lower extremi-
ties in standing caused a diminished blood pres-
sure in the central veins, leading to a pulse ac-
celeration. On the other hand, an increase of the
blood pressure in the central veins in a horizon-
tal or head-down position was followed by a
slowing of the heart rate. It appears possible,
now, that the more violent vertical jerks in step-
ping affect the venous blood return hydrostat-
ically in such a way that a lower central venous
blood pressure results than in walking. The
auxiliary blood pump of respiratory movements
may become ineffective because inspiration, fa-
vorable for venous return, usually coincides
with the upward movements in stepping which
tends to decrease the central venous pressure.
There is another possibility for the heart rate
to be higher in stepping up and down than in
walking, at otherwise equal energy expenditures.
In stepping, more localized muscle groups are
doing the bulk of work. Much stronger impulses
from the central nervous system to these muscles
are required especially at the greater stepping
heights and reflectively the heart rate may be-

—10—


Procedure IV. With this procedure, which du-
plicated the former in stepping rate and gradu-
ated increments in height but differed in the
rhythm of work, the test duration as well as the
peak heart rate response approached the values
observed in the treadmill test but the peak oxy-
gen intake was even lower than in procedure
III (see Table 9). The four participating sub-
jects experienced about the same subjectively
limiting symptoms — local muscle fatigue and
severe dyspnea — in all three tests. Use of
Duncan’s multiple range test showed that the
differences in oxygen-pulse were not significant
between any two tests. 2

DISCUSSION

For reasons previously cited a sound step
test procedure would have great utility to re-
searchers and clinicians in measuring physical
performance capacity. Attempts have been made
to devise such a procedure based on a proven
and widely used treadmill test procedure called
the Balke Test®. Work in the test is graded from
light to heavy over a time period which allows

“normal” individuals to adapt, minute-by-
minute, to the increasing loads, up to some
maximum established by physiological limita-
tions. The duration of the test ranges from 7
to 30 minutes, the average being 15 minutes.

Such a step test requirement precludes con-
sideration of many procedures currently in use.
The original Harvard Step Test® in which a
single level bench 20 inches (50 cm) in height
is used with a stepping rate of 30 per minute,
requires maximal effort from the onset of exer-
cise. This results in a high level of anaerobic
work and prevents an accurate evaluation of
aerobic capacity. Morehouse® states that the
test is useful for selecting men for hard work
and for evaluating the progress of physical
training. On this basis it would not appear ap-
plicable for the performance testing of a “nor-
mal” population. The same would seem to ap-
ply to some modifications of the Harvard Step
Test or similar procedures described by Galla-
gher and Brouha’, Fletcher*, Hettinger et al.°,
and the “Pack” tests used: by Darling et al.’°
and Graybiel et al. **.

—9—

Standard Treadmill Test

Max.
Pulse

(Beats /min)

Step
Time

(min)

Max.
Voy

Step Procedure IV

Max.
Pulse
(Beats /min)

Step
Time

‘Subj. (min)

Step Procedure Ill
Max. Max.
Vo, Vo,

Max.
Voy
ml/min

ml/min Pulse

Max.
Pulse

ml/min

Pulse

18.8
19.1
16.0
14.9

3307
3675
3000
2685

176
192
188
180

22
22
19
13

17.4
18.1
15.2
14.1

3060
3408
2865
2507

176
188
188
178

18
18
16
10

15.3
18.0
14.5
12.8

2824
3386
2719

2283

184
188
188
178

20
20
17
13

aN

minute of work in Step Test Procedure III and IV and in the W.C.T. on the

Taoue 9: Comparison of heart rate, oxygen, intake and oxygen, pulse during the, peak (final)
treadmill.



With this device attempts were made to de-
velop a procedure most closely copying the
energy demands of the standard treadmill test.
Four test procedures were subsequently evalu-
ated, all starting out with an initial stepping
height of 8 cm. At this height the metabolic de-
mands in stepping up and down at a rate of 30
per minute were nearly the same as during the
first minute on the treadmill (at 1% grade
and 91.5 m/min). The four procedures were:
Procedure 1: Stepping at a rate of 24 body
lifts per minute, raising the platform 2 cm at
the beginning of each minute.

Procedure I]: Stepping at a rate of 30 hody
lifts per minute and raising the platform 2.54
cm (1 inch) each minute.

Procedure Il]: Stepping rate of 30 but min-
ute-by-minute increments of 2 cm in stepping
height.

Procedure IV: The stepping rate was main-
tained at thirty and the load increments at 2
cm but the technique of stepping up and down
was altered. On count “4” the foot was not
returned to the ground but allowed to rest on
the platform. Thus, the leg lift on count “1”
of the next stepping cycle was avoided which
reduced somewhat the metabolic costs of work
for each level.

Procedures 1 through 3 were performed iden-
tically: the subject stepped onto the platform
(“one-two”) to a completely erect stance on
both feet and returned (“three-four”) to the

ground. Subjects were encouraged to change the
leading leg frequenuy. This was accomplished
by just tapping the foot coming down on count
“4” and lifting it again on count “1.”

In all tests the heart rate and blood pressure
were continuously monitored and the respira-
tory gas exchange was determined periodically
and always during the peak minute. The test
was terminated when the attainment of a maxi-
mum heart rate became obvious or when the
pulse pressure began declining at pulse rates
considered near maximum.

Results

Procedure I was quickly discarded when trained
individuals in good physical condition reached
the highest platform level of 50 cm without at-
taining cardio-respiratory and/or local muscu-
lar limitations. The test duration in this type
of step test exceeded that of the standard tread-
mill test performed for comparison. Therefore,
this procedure was judged inadequate for phys-
ical fitness screening of a normal healthy pop-
ulation.

Procedure II was evaluated in experiments with
2 female and 13 male volunteers. The subjects
ranged from 16 to 56 years of age. All partici-
pants took the standard treadmill test and the
gradational step test at two different occasions
several days apart. The performance data are
presented in Table 5. Calculation of a correla-
tion coefficient for the data yielded an r = .76.

SUBJECT STEP TEST PROCEDURE I TREADMILL W.CT.
Time Vertical Lift Time ‘Vertical Lift
min m/min min m/min

1 6 6.2 10 9.2
2 6 6.2 10 9.2
3 6 6.2 12 11.0
4 8 V7 12 11.0
5 10 9.3 14 12.8
6 10 9.3 14 12.8
7 10 9.3 15 13.7
8 10 9.3 16 14.6
9 11 10.0 16 14.6
10 12 10.8 16 14.6
ll 12 10.8 16 14.6
12 12 10.8 22 20.1
13 12 10.8 22 20.1
14 13 11.6 16 14.6
15 14 12.6 18 16.5

Taste 5: Peak performances in the Gradational Step Test, Procedure II, (rate “30.” minute-
by-minute increments of 1 inch in stepping height),
treadmill (in which the % grade is the same as the indicated minute). All tests

were terminated at a heart rate of “180.”

—6—

and in the W.C.T. on the


Ficure 1: 4-Box stepping device.

indicative of approaching limitations in the
ability to make the adequate adjustments need-
ed for the next higher step. Pulse rate and blood
pressure were measured in the conventional way
during the second half of each minute on each
platform level.

Results

Preliminary experimental data indicated that
the oxygen costs of stepping to the heights of

4-Box Step Test

10, 20, 30 and 40 cm approximated the energy
expenditures observed in walking on the tread-
mill at a speed of 91.5 m/min (equal to 300
feet/min or 3.4 m.p.h.) and at grades of 3, 8,
14 and 22 per cent, respectively. Subsequently,
more experiments were carried out with 12 male
volunteers who were given the standard tread-
mill test and the 4-box step test. The oxygen in-
take data, presented in Table 1, confirmed the
previous findings, especially for the middle

4-Grade Treadmill Test

Time Subjects Height Oxygen Intake Grade Oxygen Intake
Min. N cm mi/kg/min % mi/kg/min
3rd 5 10 16.9 = .8* 3 16.1 + 1.2
6th 10 20 23.2 + 2.6 8 23.1 1.4
9th 10 30 31.9 + 2.6 14 317+ 14
12th 5 40 41.9 +21 22 44.8 + 1.7

“Standard Deviation

Taste 1: Oxygen intakes during the third minute of work at the progressive loads indicated.
Stepping was performed at a rate of 30 per minute, walking at a velocity of 91.5

m/ minute.

—2—




THE GRADATIONAL STEP TEST FOR ASSESSING
CARDIORESPIRATORY CAPACITY: AN EXPERIMENTAL
EVALUATION OF TREADMILL AND
STEP TEST PROCEDURES

FRANCIS NAGLE, Ed.D.
BRUNO BALKE, M.D.

“Physical Fitness” — the potential capacity
for making adequate functional adjustments to
increased metabolic demands — is most mean-
ingful and accurately assessed in the laboratory
by making physiological measurements on the
experimental subject while he is walking on a
motor-driven treadmill or riding a stationary bi-
cycle ergometer. For the physician in his cardio-
respiratory examination room both types of
equipment are too bulky. He prefers a less com-
plicated test apparatus and uses, most common-
ly, a single-level or two-level stepping box as
suggested by Master’. For field studies on
athletes and on soldiers various other stepping
devices with and without additional loading of
the subjects have been suggested and utilized
and the widest preference was given to the Har-
vard Step Test* performed on a bench of 20
inches in height. The disadvantage of all these
stepping devices is their restriction to a fixed
workload as long as the stepping rhythm is held
at one constant rate. Considering the great dif-
ferences of physical fitness in a large popula-
tion, the fixed workload might be either ade-
quate, or of insufficient intensity, or more or
less beyond an individual’s working capacity.
The most useful procedures for the assessment
of physical competence are those in which the
cardiorespiratory adjustments are allowed to
progress gradually from the resting state
through various phases of increasing energy de-
mands until the approach of limitations can
objectively be determined. With a single-level

or double-level stepping device such variation
of work intensity requires a gradual speeding
up of the stepping cadence. Such a procedure
has not proven practical. In attempts to devise
a testing procedure equally useful and appli-
cable in the research laboratory as well as in
the general practioner’s medical examination
room and also under any type of experimental
field conditions, other stepping devices and
methods were tried and evaluated against the
standard treadmill test used in this labora-
tory. *

The 4-Box Step Test

As a simple precursor to any following multi-
level stepping device a wooden box was con-
structed having four arbitrarily chosen plat-
forms of 10, 20, 30 and 40 cm each (Figure 1).
A stepping rate of 30 vertical lifts per minute
was selected and this rhythm was audially and/
or visually maintained by a metronome. Work
was begun at the lowest platform and proceeded
after a stepping period of 3 minutes, without
interruption, to the next higher level of the box.
The increments in load were continued until
a) the subject fell behind the rhythm indicated
by the metronome and was unable to resume the
stepping rate of 30 per minute; b) when a
definite decline in systolic blood pressure was
observed at pulse rates to be considered maxim-
al (usually in the vicinity of 180 beats per min-
ute ; c) when at the end of any 3-minute period
the pulse rate had reached a level of 168 beats
per minute and the efforts of the subjects were

—1—





come affected. This particular problem deserves
further investigation.

The Gradational Stepper may also be used
by the clinician interested in assessing the work
capacity of normal and sub-normal individuals.
A method using treadmill work for pathological
cases is described in detail by Naughton and
Balke’*. Basic to the method is the use of work-
loads calling for energy expenditures in multi-
ples of resting metabolic rates. A similar tech-
nique is applicable using the Gradational Step-
per. Step test experiments, performed at step-
ping rates of 24 and 30 per minute, revealed
that with both rates the energy expenditure was

505

404

30-5

20 +

Vo, (mI/kg/min)

practically identical for the same unit of verti-
cal lift in a unit of time (see Figure 7). As
can be noted, the cost of stepping forward and
back on a horizontal level at the rate of “24”
amounted to approximately 2 Mets. In all fu-
ture work with this stepping device for evalu-
ating physical competence a normal or a modi-
fied procedure will be followed: for the normal
test the first-minute workload will require an
energy expenditure of 2.5 Mets, the second min-
ute 3 Mets. From then on the minute-by-minute
increments for the “normal” procedure will add
one-half of the basal metabolic rate to the pre-
vious load, while for the “modified” step test
this increase in metabolic rate will only amount

T T T T T
° i 2 3 4 5

T
6 7 8 9 10 i} 2

T T T T T 1

VERTICAL ASCENT (METERS /MINUTE)

Ficure 7: The relationship between energy cost and total stepping height at working rates
of 30 and 24 steps per minute. Points plotted are mean values for 3 subjects.

—1l—