Body resistance
on and under
the water surface
J. Jiskoot and J. P. Clarys
Many reports of studies dealing with the water resistance of the human body
can be found in the literature. The results of these studies, however, have
been obtained by utilizing a towing device with a dynamometer attached
(Alley, 1952; Counsilman, 1955, 1968; Karpovich, 1933; Schramm, 19581959), or a tethered swimming device with force transducers.
Most of the results in the existing literature were obtained with a small
number of subjects. Experiments with a larger number of subjects, therefore,
appeared to be justified. It seemed even more essential to use a number of
different tests with the same group to provide for a more complete analysis.
PURPOSE
The purpose of this study was to determine ihe body resistance on the water
surface and 60 cm under the water surface for a group of male subjects. It
was assumed that under the water there is less resistance than on the surface
(Schramm, 1958-1959) because the resistance of the waves is eliminated. The
total resistance is the sum of the wave resistance, frictional resistance, and
eddy resistance (Karpovich, 1933). The results of this study, therefore, might
make it possible to distinguish the different resistance components (Clarys et
al., 1973). One must realize that resistance data obtained by towing bodies
through the water are not the same as results from measurements of swi..mming as Alley (1952) found and as we have found in previous studies. But the
results from towed bodies were required in order to-provide complete data
and to make comparisons with actual swimming. Comparisons were also made
with the earlier data reported by Schramm (1958-1959).
105
106
Jiskoot and Oarys
METHODS
Male physical education students (N=43) were selected for this investigation.
They were average to good swimmers. Their individual freestyle swimming
velocity ranged from 1.2 to 1.85 m per sec. The tests were carried out in the
200-m high speed towing tank of the Netherlands Ship Model Basin in
Wageningen. The tank was filled with fresh water for this study. The apparatus consisted of an electrically driven towing carriage, a photoelectric cell
system for velocity control, a telescopic towing device, force transducers, and
an ultraviolet strip chart recording unit. A detailed description of this apparatus can be found in previously published studies (De Goede et al., 1971;
Clarys et al., 1973). The apparatus is shown in Figure I.
The pretest procedure was carried out with extreme body types in order
to validate the procedures for the main investigation. The results of the
pretest were presented by Clarys et al. (197 4 ). The test conditions consisted
of: a) measurements of the body resistance on the water surface at speeds
ranging from 0.7 to 2.0 m·sec- 1 , at increments of 0.1 m·sec- 1 ; b) measurements of the body resistance 60 cm under the surface of the water at speeds
Figure 1. Test apparatus at the Netherlands Ship Model Basin, Wageningen.
Body resistance on and under water surface
107
ranging from 1.5 to 1.9 m ·sec- 1 , in increments of 0.1 m ·sec- 1 • Both test
conditions were repeated after some months. The water temperature during
the first test series was l8°C, and at the time of the second test series it was
24°C. Comparisons between both types of tests were made at speeds of 1.5,
1.6, 1.7, 1.8, and 1.9 m ·sec- 1 • The body positions in the tests were similar.
The subjects were taught to maintain a prone position, head between the
arms (arms against the ears), legs extended and together, and feet in plantar
flexion. They were instructed to hold their breath after a normal inhalation.
The body position of all subjects was controlled by one of the examiners
during the tests. Photographs were taken of all the subjects d'uring the test to
study the flow pattern of the water.
RESULTS AND DISCUSSION
The results of the tests and retests and the statistical treatment are shown in
Table 1. The mean resistance of the tests and retests at specific speed ranges
are presented in Figure 2. There was a relationship between the resistance
curves on the surface and under the surface of the water as well as between
the test and retests. There was a significant difference between the means of
Table f. Mean, standard deviation, correlation coefficient of the total
water resistance on and under the water surface (test and retest) (N=43)
Velocity
(m/sec)
Mean resistance
test on water surface
(kg) (l)
SD
Mean resistance
retest on water
surface (kg) (2)
SD
Mean resistance
test under water
surface (kg) (3)
SD
Mean resistance
retest under water
surface (kg) ( 4)
SD
r1,2
r3,4
rl,3
rz.4
1.9
1.7
1.8
7.958
8.835
9.886
11.005
0.7673
6.581
0.9001
7.391
0.8931
8.361
0.9190
9.253
1.1265
10.616
0.9103
8.749
0.9242
9.693
10431
10.719
1.1851
11.819
1.3146
13.142
1.1027
8.047
1.0754
8.916
1.0955
9.884
1.2561
11.070
1.3870
!2.479
1.0536
0.63
0.55
0.39
0.49
0.8893
0.67
0.57
0.37
0.48
0.9911
0.70
0.65
0.47
0.53
l.l277
0.72
0.73
0.56
0.57
1.4120
0.77
0.73
0.47
0.55
1.5
1.6
7.019
108
Jiskoot and Clarys
<N=43l
R (kg)
"
- - test 0"1 the surface
- - - retest on the surface
- - - test under the surface
- --·- retest under the surface
10
'·'
,_.
1.8
1.9
V(m...C')
Figure 2. Mean total water resistance on tests and retests.
the data on the test and re test. This might have been the consequence of the
different water temperatures. It is recommended that in the future the
influence of the water temperature on body resistance be investigated as an
experimental variable. The results indicated that the resistance under the
water surface increased on the average about 21 percent in the test and 20
percent in the retest when the towing velocity was increased from 1.5 to 1.9
m·sec- 1 (mean of increased resistance at the tested speeds, N=43). This result
was in contradiction to the findings of Schramm (1958-1959), who concluded that the resistance under the water surface decreased about 11.5
percent (N=2) as speed increased. The body positions were similar in the two
studies.
CONCLUSION A-l'IJD REMARKS
Based on the hypothesis that in towing under the surface of the water, the
resistance of the waves is for the most part eliminated, it might be possible to
determine the frictional resistance plus the eddy resistance of the water. It
appears that the total resistance while being towed under the surface of the
water, consisting of the total frictional resistance plus the total eddy resistance, is higher than the total water resistance on the surface. The resistance
on the surface consists of the sum of wave resistance, partial frictional
resistance, and partial eddy resistance. This means that the additional corn-
Body resistance on and under water surface
109
bined frictional resistance and eddy resistance as a result of immersing the
total body in the water are greater than the resistance afforded by the waves
to a partially submerged body. Using the anthropometric data of all subjects,
we intend to calculate the results in standard body dimensions, so that we
might be able to derive a relationship between body form and water resistance. When applied to the practice of swimming, this means, as far as water
resistance is concerned, it is preferable to swim on the surface instead of
under the surface of the water.
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Clarys, J.P., J. Jiskoot, and L. Lewillie. 1973. A kinematographic, electromyographic and resistance study of waterpolo and competition front crawl.
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