Underwater Treadmill for Exercise and Injury Prevention for the Elderly
1Faculty of Engineering, Srinakharinwirot University
Nakhon Nayok, THAILAND
2Faculuty of Physical Education, Srinakharinwirot University, Nakhon Nayok, THAILAND
*Corresponding author
Abstract: This research is to develop an underwater treadmill for ageing people who have osteoarthritis problems or the
elderly who need physical therapy or exercise by designing the structure of the treadmill to be strong, portable and safe to
use. As Thai society in the present is becoming an aging society, most of the elderly have symptoms of osteoarthritis. This
underwater treadmill device is essential to reduce knee injuries while exercising. It is also effective to use for walking or
running as regular treadmill. In addition, the COVID-19 pandemic made life difficult for the elderly to do regular exercise
in normal fitness place or a public sport complex due to the need to observe the social distancing and vigilant COVID-19
prevention. In this experiment, a total of 7 subjects were used with subjects running on a treadmill (on land) and on an
underwater treadmill (in water) developed for walking or running in water. Seven parameters are collected for both (land
and water) running to compare the performance of both treadmills and their feelings after using an underwater treadmill
with 7 parameters: 1) VO2 2) VO2 /kg 3) Heart rate 4) %Heart rate 5) Respiratory Exchange Ratio (RER) 6) Total Energy
Expenditure (Total EE)
7) Rating of Perceived Exertion (RPE). The results showed that the underwater treadmill had
higher exercise energy efficiency than the land-based electric treadmill while running with the same speed. Moreover, the
underwater treadmill can reduce impact on the knees with the help the water resistance and uplift during the exercise.
Keyword: Underwater treadmill, osteoarthritis, elderly people, exercise
Received: April 16, 2023. Revised: October 27, 2024. Accepted: November 19, 2024. Published: December 20, 2024.
1. Introduction
Osteoarthritis of Knee is a condition in which the knee
joint deteriorates as a result of articular cartilage, which is
constantly corroded over time, or subchondral bone
thickening, as well as synovial fluid that helps to lubricate
the joints. [1] From statistics in 2017, it was found that
there are more than 6 million cases of the disease and it is
likely to increase every year. [4] The most degenerative
joint is knee arthritis. Most people think that osteoarthritis
occurs in the elderly because it deteriorates the body with
age, but the fact that the disease can also occur in
adolescents and working ages. The knee joint is classified
as the largest joint in the body, acting to help hold about 3-
4 times the weight of the body. If you are overweight or
perform high impact activities, it will result in a greater
burden on the knee joint. This is one of the leading causes
of osteoarthritis. People with extreme osteoarthritis, if not
treated or treated properly, will cause pain. Deformed knee
joints, irregular walking. [5] Activities during
inconvenient days can be suffered both physically and
mentally. This water treadmill, also known as Underwater
Treadmill, is another option of a new workout. [6 ]
Underwater Treadmill is burning four times as much
calories as it does. It can also treat sports injuries as well
as help with physiotherapy for patients. As a result,
leading fitness facilities and hospitals in Thailand have
incorporated it into Tara Therapy physiotherapy to
strengthen health and rejuvenate the body from illness.
Figure 1. High-cost commercial underwater treadmill.
Figure 1 is a high-cost commercial underwater treadmill
which is one of the two main types of underwater
Treadmills: glass cabinets and the other for use in the pool.
As the elderly in many countries may not be able to afford
the high-cost glass cabinet type of the underwater
treadmill, a non-electric underwater treadmill as a device
for underwater exercise to reduce the risk of knee joint
damage for the elderly was developed for the purpose and
the treadmill was tested to evaluate the effectiveness
comparing to normal electrical treadmill. The device was
designed to be lightweight, easy to carry, to be used in the
pool without harm to people around or the environment.
2. Design Structure of Treadmill
2.1 Structure Design
The overall structural design of the underwater treadmill
was designed with SolidWorks (SolidWorks) program.
International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
W. Senavongse, C. Paarethaanon,
T. Aurprayoon, S. Punthipayanon, T. Senakham
E-ISSN: 2945-0489
87
Volume 3, 2024
W.SENAVONGSE1,*, C. PAARETHAANON1, T. AURPRAYOON1,
S. PUNTHIPAYANON2, T. SENAKHAM2
Studies and research have shown that curved treadmill
users have less injuries from osteoarthritis than flat
treadmills, so this underwater treadmill was designed to be
curve in shape that can reduce knee pain better than the
flat model. From human anthropology, the human pace has
a length of approximately 35-50 centimeters, which from
the survey of the length of the treadmill showed that 32
treadmill machines had the average width of 46 cm and the
length of 128 cm. The curved treadmill was larger than the
typical slope treadmill. From this finding, the developing
treadmill machine was designed to have a width of 47
centimeters and a length of 160 centimeters as shown in
Figure 2. As for the length, it must be calculated to
calculate the height from the slope. and find the
appropriate length (net length).
(a)
(b)
Figure 2. (a) The drawing of treadmill design and (b)
Finite Element Analysis of simulation of loading damage
to treadmill structural
2.2 Calculation of Loading Damage
Calculation of damage that may occur to an underwater
treadmill using the Solid work program is divided into 2
main sections. There are 2 parts which are the treadmill
structure and pipe section:
1) Calculate the damage of the treadmill
structural part.
The load is set to 1000 Newtons at the connection point
with 2 pipes in all 3 locations, namely the front, middle
and rear areas, to simulate stepping and to support the
weight while resting (this is a calculation of an underwater
treadmill for use on land to obtain the force acting in the
direction at the maximum load)
2) Calculation of the damage of the pipe section
as shown in Figure 3.
The load is set to 1000 N at the pipe's contact surface. To
simulate stepping and weight support (this is an
underwater treadmill calculation for land use in order to
get the maximum strength to carry the load)
Figure 3. Calculation of the damage of the pipe section
Having designed and assembled the structure of the
underwater treadmill, the assembled treadmill was
designed to strengthen the frame on both sides and the
front axle. Additionally, it is reinforced with wheels. To
make it easier to transport. For the handle area, it is firmly
assembled with the pivot point and the nut attachment. The
completely assembled treadmill can be tested and
evaluated to find out the efficiency when it is actually used
in water comparing to the ordinary land treadmill.
a
b
Figure 4. The Fully Assembled Treadmill
International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
W. Senavongse, C. Paarethaanon,
T. Aurprayoon, S. Punthipayanon, T. Senakham
88
Volume 3, 2024
3. METHODS to compare the
efficiency between a conventional
and a curved underwater treadmill
This experiment was set to compare the
performance between a conventional treadmill and a
curved underwater treadmill. The experiment was
determined to consist of 7 participants. In the experiment,
a gas analyzer (PNOE, California, United States) was used
to display results through an application on mobile phone
or a tablet. The PNOE was used to find the values of
interest between using a general land treadmill and a
curved underwater treadmill. The values which were of
interest are VO2 (Oxygen consumption), HR (Heart Rate),
RER (Respiratory Exchange Ratio), Total EE (Total
Energy Expenditure ) and RPE ( Rating of Perceived
Exertion ), which are values used to analyze the
differences between conventional treadmills and curved
underwater treadmills.
A total of 7 healthy subjects were recruited with the
subjects running on a treadmill (on land) and on an
underwater treadmill (in water) developed for walking or
running in water. As mentioned, seven parameters are
collected for both (land and water) running to compare the
performance of both treadmills and their feelings after
using an underwater treadmill with 7 parameters: 1) VO2
2) VO2 /kg 3) Heart rate 4) %Heart rate 5) Respiratory
Exchange Ratio (RER) 6) Total Energy Expenditure (Total
EE) และ 7) Rating of Perceived Exertion (RPE).
Seven volunteers of healthy university student subjects
with informed consent were recruited to perform running
on conventional treadmills and curved underwater
treadmills.
No.
Weight(kg)
Height
(cm)
Gender
1
58
180
male
2
81
170
male
3
63
174
male
4
60
174
male
5
52
165
female
6
45
153
female
7
80
165
male
Figure 5. The details of the subjects.
As this trial was done during the COVID-19 pandemic,
healthy volunteers were used to avoid any risks to the
elderly. The details of the subjects are in Figure 5.
3.1 General Treadmill Experiment
A conventional treadmill ( h/p/cosmos, Munich, Germany
) was used in comparison with an underwater treadmill.
This comparison was done because the conventional
treadmill is an exercise option that many exercisers focus
on and prefer to use in the normal exercise. Therefore, it is
compared with an underwater treadmill in order to see the
difference and show the suitability of the actual use.
Initially, each subject wore a mask to the gas analyzer and
a chest heart rate monitor. By setting the treadmill speed
randomly ordering all the speeds used from 4 values: 2.8
km/h , 3.28 km/h , 3.78 km/h and 2.8 km/h, it takes 5
minutes to walk at each speed. alternate with rest In the
land treadmill experiment, an average pedometer was
installed per minute (Step/min) of each subject. To use the
average number of steps per minute obtained in an
underwater treadmill experiment. After walking on a
normal treadmill at a random speed, the values that interest
us are recorded in the data for analysis to determine the
difference. The setup of gas analyzer on the subject is
shows in Figure 6 below.
Figure 6. The subject wearing the Gas Analyzer
3.2 Curved Underwater Treadmill Experiment
Since the curved treadmill is a non-electric treadmill, it is
not possible to set a constant speed to an underwater
treadmill like a conventional treadmill. Therefore, the
average steps per minute data at various speeds of general
treadmill experiments were determined as individual
cadences at each speed. which uses a metronome to create
a cadence of steps on a curved underwater treadmill The
experiment uses a gas analyzer in the experiment with the
characteristics of the experiment, like all conventional
treadmill trials. Each subject wears a mask, gas analyzer
and wears a chest heart rate monitor to be tested in a pool
at a depth of 1.2 m. Provides a cadence for walking
through a metronome that corresponds to four speed
values: 2.8 km/h, 3.28 km/h, 3.78 km/h and 2.8 km/h. It
takes 5 minutes to walk at each speed, alternating with a
rest. After the experiment was completed, the obtained
values were recorded and recorded. The comparative data
was obtained between a conventional treadmill and an
underwater treadmill.
International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
W. Senavongse, C. Paarethaanon,
T. Aurprayoon, S. Punthipayanon, T. Senakham
89
Volume 3, 2024
(a) A subject in water
(b) Underwater view of
subject
Figure 7. underwater treadmill experiment
4. Results and Discussion
The test measured the performance of an
underwater treadmill compared to a land treadmill with
seven evaluation values:
1) VO2 (Oxygen consumption) indicates the
efficiency of aerobic metabolism in milliliters per minute
(ml/min).
2) VO2/kg Each exercise, how much oxygen does 1
kg of our body use in this process in 1 minute ml per 1 kg
of body weight per minute (ml/min /kg)
3) HR (Heart Rate) is the heart rate. Our heart's
pulse BPM is an abbreviation for beats per minute, or
BPM, which stands for Beats Per Minute.
4) %HR is our heart rate. to indicate that the level
of fatigue It also helps to determine the intensity of the
exercise as well. The heart rate zone is divided into 5
zones as shown in Figure 8.
Figure 8. The Heart rate zone
4.1 The results of the VO2 test on land and underwater
treadmills
VO2
of land treadmill
2.8 km/hr
3.3 km/hr
3.8 km/hr
2.8 km/hr
subject 1
387
384.7
488.9
416.2
2
644.4
776
876.9
643.6
3
597.2
607
691.6
533.9
4
576.1
652.2
700.2
585.9
5
335
403.1
424.9
383.3
6
279.1
356.2
362.3
299.4
7
699.9
733.4
750.4
679.3
mean
502.67
558.94
613.6
505.94
SD
165.73
175.27
189.71
142.56
VO2
of underwater
2.8 km/hr
3.3 km/hr
3.8 km/hr
2.8 km/hr
subject 1
478.3
525.1
660.7
493.5
2
1096
1043.7
1674.8
851.8
3
1082.4
1044
1182.3
859.1
4
623.7
827.5
1078.2
795.7
5
774
801.6
1048.6
777.3
6
458.3
517.3
613.9
484
7
896.4
830.5
912.4
803.6
mean
772.73
798.53
1024.41
723.57
SD
265.66
214.51
357.02
163.11
Figure 9. Results of VO2 of Land and Underwater
Treadmill
4.2 The results of the Heart Rate on land and
underwater treadmills
International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
W. Senavongse, C. Paarethaanon,
T. Aurprayoon, S. Punthipayanon, T. Senakham
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Paired t-test
2 tails
HR at 2. 8 km/hr
land vs
underwater
HR at 3.3 km/hr
land vs
underwater
HR at 3.8 km/hr
land vs
underwater
HR at 2.8 km/hr
land vs
underwater
P-value
0.022
0.127
0.001
0.156
Figure 10. Statistics of Paired t-test, 2-Tailed of HR
A summary of results to compare the efficacy and
parameters obtained from the land and underwater
treadmill can be shown in Figure 11.
Figure 11. Summary of comparison of all parameters
The results showed that the underwater treadmill had
higher exercise energy efficiency than the land-based
electric treadmill while running with the same speed.
Moreover, the underwater treadmill can reduce impact on
the knees with the help the water resistance and uplift
during the exercise. The satisfaction assessment results
indicated that subjects were satisfied with 91.4% of the
structure's strength and design, 82.9% of usability, 88.6%
of its cost-effectiveness, and overall practicality and injury
reduction performance of the knee 91.4%. Due to the
COVID-19 pandemic, the developed prototype could not
be tested by the elderly as it was too risky under the
COVID-19. Therefore, the prototype was tested by the
seven healthy adult subjects. Furthermore, the elderly care
specialist assessed and evaluated the prototype as
moderately safe usage results were obtained. The average
level of satisfaction from the elderly care specialist is 70%
as there is a concern about the need to prevent the elderly
fall. The findings from this study are promising for the
future development of exercising devices for ageing
people who have osteoarthritis problems or the elderly
who need physical therapy or regular exercise without the
risk of knee or joint injury.
5. Conclusion
This research was conducted to develop an underwater
treadmill for ageing people who have osteoarthritis
problems or the elderly who need physical therapy or
exercise by designing the structure of the treadmill to
be strong, portable and safe to use. The findings show
that the results are in the same direction as expected.
For protocols used in general treadmill walking groups.
The speed used cannot cause the recognition of a
person. The underwater treadmill is more effective
than a normal treadmill. In terms of weight, fatigue
energy and reducing the negative effects on the knee
joint resulting from the support of water and walking
in the form of the natural gait of the human body, it is
suitable for people with osteoarthritis. Elderly or
overweight. In this way, it is also effective to use for
walking or running as regular treadmill. In addition, as
the COVID-19 pandemic made life difficult for the
elderly to do regular exercise in normal fitness place or
a public sport complex due to the need to observe the
social distancing and vigilant COVID-19 prevention.
The intensity of walking on an underwater treadmill
was found to be higher and significantly different from
that of a general treadmill which can help the exercise
and injury prevention of the elderly.
Acknowledgments
The author would like to acknowledge the financial
support from the Faculty of Engineering, Srinakharinwirot
University, through the Conference Sponsorship.
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International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
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T. Aurprayoon, S. Punthipayanon, T. Senakham
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
The authors equally contributed in the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflict of Interest
The authors have no conflicts of interest to declare
that are relevant to the content of this article.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
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International Journal on Applied Physics and Engineering
DOI: 10.37394/232030.2024.3.12
W. Senavongse, C. Paarethaanon,
T. Aurprayoon, S. Punthipayanon, T. Senakham
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Volume 3, 2024