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Objectives: The present study aimed to investigate the effect of squat exercises with weight shift on muscle strength and postural control during pregnancy. Materials and Methods: The squat group comprised 21 pregnant women in their 20s and 30s with no exercise habits while the control group consisted of 20 randomly selected pregnant women in their 20s and 30s with no exercise habits. The squat group was instructed to perform two sets of daily squat exercises with weight shift in the anterior, posterior, right, and left directions, with 10 repetitions counted as one set, for 10 weeks. The stabilometer was used to measure postural control ability in the second and third trimesters. Meanwhile, muscular strength was taken as the toe grip force and quadriceps muscle strength before and after the intervention. Results: In the squat group, significant increases were observed in the index of postural stability and the stability area. Conversely, however, significant decreases were detected in the average rectangular area. In addition, in the intervention group, significant declines were observed in the rectangular area in the posterior, right, and left directions. However, a considerable increase in muscular strength was only seen after the intervention in toe grip force. Conclusions: Based on the results, it was concluded that everyday squat exercises which were performed during pregnancy improved postural control. The improvement of postural control during squat movements was thought to have a greater impact on plantar sensation than on muscle strength. These findings suggest that squat exercises with weight shift may promote fall prevention.
Introduction
According to previous studies, falls are reported by
18%–25% of women during pregnancy (1-3). Although
temporary, reduced postural control ability such as
postural sway and displacement of the anterior-posterior
center of gravity is often detected in pregnancy (2-4).
A survey of fall situations in Japan reported that falls
due to wobble during anti-weight/gravity actions like
descending the stairs and squatting/rising from sitting
increased during pregnancy (5). Several factors have been
identified to reduce postural control ability in pregnancy
including increased spinal lordosis, reduced strength
of the abdominal muscles, and loosening of the major
joints (2). Previous studies reported that pregnant women
who experience a fall show increased rectangular areas
in the posterior, lateral direction and decreased stability
limits from the second trimester, and a sharp increase
in abdominal circumference from the second to third
trimester (6). The lack of awareness of sudden changes
in abdominal circumference from the second to the
third trimester was also considered as another factor of
falling (6).
These reports suggest a need to incorporate exercises
that improve awareness in addition to enlightenment
and guidance regarding the prevention of falls during
pregnancy. During this period, the load to the lower limbs
increases day by day in antigravity actions such as standing
up and sitting (7). Therefore, antigravitational exercise is
essential to improve postural control during pregnancy
and promote muscle activity that supports self-weight
while being conscious of wobble owing to the weight shift
in the front, back, left, and right directions. In addition,
these exercises should be performed every day to allow
changes in weight and the displacement of the center of
gravity during the course of pregnancy so that this period
is perceived more easily by the women.
The squat is listed as an antigravitational exercise.
The squat movement includes crouching and rising
elements that are necessary for activities of daily living.
When squat exercises are performed with a weight shift
in the anterior, posterior, right, and left directions, the
exercise load changes as well. In previous studies, higher
muscle activity was observed in the quadriceps femoris
and tibialis anterior muscles while in the squat position
the center of gravity line was displaced in the posterior
direction (8,9). When squatting with anterior weight shift,
Abstract
Objectives: The present study aimed to investigate the effect of squat exercises with weight shift on muscle strength and postural
control during pregnancy.
Materials and Methods: The squat group comprised 21 pregnant women in their 20s and 30s with no exercise habits while the
control group consisted of 20 randomly selected pregnant women in their 20s and 30s with no exercise habits. The squat group was
instructed to perform two sets of daily squat exercises with weight shift in the anterior, posterior, right, and left directions, with
10 repetitions counted as one set, for 10 weeks. The stabilometer was used to measure postural control ability in the second and
third trimesters. Meanwhile, muscular strength was taken as the toe grip force and quadriceps muscle strength before and after the
intervention.
Results: In the squat group, significant increases were observed in the index of postural stability and the stability area. Conversely,
however, significant decreases were detected in the average rectangular area. In addition, in the intervention group, significant
declines were observed in the rectangular area in the posterior, right, and left directions. However, a considerable increase in
muscular strength was only seen after the intervention in toe grip force.
Conclusions: Based on the results, it was concluded that everyday squat exercises which were performed during pregnancy improved
postural control. The improvement of postural control during squat movements was thought to have a greater impact on plantar
sensation than on muscle strength. These findings suggest that squat exercises with weight shift may promote fall prevention.
Keywords: Pregnant women, Postural control, Squat
Do Squat Exercises With Weight Shift During Pregnancy
Improve Postural Control?
Kaname Takeda1*
ID
, Hiromi Yoshikata2, Masumi Imura3
Open Access Original Article
International Journal of Women’s Health and Reproduction Sciences
Vol. 7, No. 1, January 2019, 10–16
http://www.ijwhr.net doi 10.15296/ijwhr.2019.02
ISSN 2330- 4456
Received 15 June 2018, Accepted 9 September 2018, Available online 2 October 2018
1Division of Physical Therapy, Department of Rehabilitation Sciences, Faculty of Allied Health Sciences, Kansai University of Welfare Sciences,
Osaka, Japan. 2Yoshikata Obstetrics and Gynecology, 2430 Kozukuecho, Kohoku Ward, Yokohama, Kanagawa 222-0036, Japan. 3Japanese Red
Cross College of Nursing, Graduate School of Nursing, International Health Care and Midwifery, 4-1-3 Hiroo, Shibuya-ku, Tokyo 150-0012,
Japan. .
*Corresponding Author: Kaname Takeda, Tel: +81729780088, Email: takeda@tamateyama.ac.jp
Introduction
Throughout the history of the world, the ones who had
confronted the bitterest face of poverty and war had al-
ways been the women. As known poverty and war affects
human health either directly or indirectly, the effects of
this condition on health and status of women in the so-
ciety should not be ignored. This study intends to cast
light on the effects of war and poverty on the reproductive
health of women. For this purpose, the face of war affect-
ing the women, the problem of immigration, inequalities
in distribution of income based on gender and the effects
of all these on the reproductive health of women will be
addressed.
War and Women’s Health
Famine, synonymous with war and poverty, is clearer for
women; war means deep disadvantages such as full de-
struction, loss of future and uncertainty for women. Wars
are conflicts that destroy families, societies and cultures
that negatively affect the health of community and cause
violation of human rights. According to the data of World
Health Organization (WHO) and World Bank, in 2002
wars had been among the first ten reasons which killed
the most and caused disabilities. Civil losses are at the rate
of 90% within all losses (1).
War has many negative effects on human health. One of
these is its effect of shortening the average human life.
According to the data of WHO, the average human life is
68.1 years for males and 72.7 years for females. It is being
thought that severe military conflicts in Africa shorten
the expected lifetime for more than 2 years. In general,
WHO had calculated that 269 thousand people had died
in 1999 due to the effect of wars and that loss of 8.44 mil-
lion healthy years of life had occurred (2,3).
Wars negatively affect the provision of health services.
Health institutions such as hospitals, laboratories and
health centers are direct targets of war. Moreover, the wars
cause the migration of qualified health employees, and
thus the health services hitches. Assessments made indi-
cate that the effect of destruction in the infrastructure of
health continues for 5-10 years even after the finalization
of conflicts (3). Due to resource requirements in the re-
structuring investments after war, the share allocated to
health has decreased (1).
Mortalities and Morbidities
The ones who are most affected from wars are women and
children. While deaths depending on direct violence af-
fect the male population, the indirect deaths kill children,
women and elders more. In Iraq between 1990-1994, in-
fant deaths had shown this reality in its more bare form
with an increase of 600% (4). The war taking five years
increases the child deaths under age of 5 by 13%. Also 47%
of all the refugees in the world and 50% of asylum seekers
and displaced people are women and girls and 44% ref-
ugees and asylum seekers are children under the age of
18 (5).
As the result of wars and armed conflicts, women are
Abstract
War and poverty are ‘extraordinary conditions created by human intervention’ and ‘preventable public health problems.’ War and
poverty have many negative effects on human health, especially women’s health. Health problems arising due to war and poverty are
being observed as sexual abuse and rape, all kinds of violence and subsequent gynecologic and obstetrics problems with physiological
and psychological courses, and pregnancies as the result of undesired but forced or obliged marriages and even rapes. Certainly,
unjust treatment such as being unable to gain footing on the land it is lived (asylum seeker, refugee, etc.) and being deprived of
social security, citizenship rights and human rights brings about the deprivation of access to health services and of provision of
service intended for gynecology and obstetrics. The purpose of this article is to address effects of war and poverty on the health of
reproduction of women and to offer scientific contribution and solutions.
Keywords: Poverty, Reproductive health, War
Women on the Other Side of War and Poverty: Its Effect
on the Health of Reproduction
Ayse Cevirme1, Yasemin Hamlaci2*, Kevser Ozdemir2
Open Access Review
International Journal of Women’s Health and Reproduction Sciences
Vol. 3, No. 3, July 2015, 126–131
Received 12 December 2014, Accepted 25 April 2015, Available online 1 July 2015
1Department of Nursing, Sakarya University, Sakarya, Turkey. 2Department of Midwifery, Sakarya University, Sakarya, Turkey.
*Corresponding author: Yasemin Hamlaci, Department of Midwifery, Sakarya University, Sakar ya, Turkey. Tel: +905556080628,
Email: yaseminhamlaci@gmail.com
http://www.ijwhr.net doi 10.15296/ijwhr.2015.27
ISSN 2330- 4456
Takeda et al
International Journal of Women’s Health and Reproduction Sciences, Vol. 7, No. 1, January 2019 11
hip joint extension and ankle flexion muscle group activity
are required. Conversely, when squatting with posterior
weight shift, knee extension activity is needed. Moreover,
while squatting with weight shift in the lateral direction, hip
abductor muscle group activity is necessary. In addition,
squatting with weight shift entails postural control ability
that does not deviate from the center of pressure in terms
of stability limits. Increases in body weight accompanying
pregnancy become a type of resistance exercise, and daily
exercising to adapt to positional changes in the center of
gravity can help rebuild the body schema. However, to
the best knowledge of the authors, no prior studies have
examined exercise for the purpose of fall prevention and
postural control maintenance.
Mental and physical exercise guidance and conditioning
are therefore considered important for fall prevention
during the pregnancy. Accordingly, the purpose of this
study was to explore the effect of squat exercises with
weight shift on postural control and muscle strength.
Materials and Methods
The participants in the squat intervention group included
21 healthy pregnant women in their 20s and 30s. All
the participants understood the purpose and content of
the study and consulted the Obstetrics and Gynecology
Department before providing their written informed
consent in order to participate. The exclusion criteria were
having a history of lower limb or lower back injuries or
regular exercise habits. The participants of the squat group
were given both oral and written instructions regarding
the intervention method, which involved performing
two sets of daily squat exercises with weight shift in the
anterior, posterior, right, and left directions including 10
repetitions counted as one set, for 10 weeks.
Either the starting position of the limbs or how to apply
the load during the squat exercises were in accord ance with
the locomotor training squat method targeting the elderly
advocated by the Japanese Orthopedic Association (10).
The starting position of the upper limbs was with the arms
slightly wider than shoulder width, and that of the lower
limbs included the feet apart with the toes facing outward
at about a 30° angle. Squats were performed at a steady
1-second pace while breathing regularly and maintaining
a knee flexion angle that ensured no burden (less than
90°). Regarding the weight shift method, the participants
were taught to squat while shifting their weight to the toes
as the anterior movement, and then to continue squatting
whereas moving the weight sequentially to the heel, the
right foot, and the left foot, and subsequently to repeat
these steps again from the beginning.
During the intervention, participants in poor physical
conditions could stop at any time based on their own
judgment. The Cybozu Live smartphone application
(Cybozu Co., Ltd., Tokyo, Japan) was used to record a daily
implementation report. If there was no report logged by
10 , the app notified the participant for confirmation in
order to prevent them from forgetting to enter their data.
Periodic medical examinations were conducted by a
gynecologist before performing the measurements after
confirming the participant’s physical condition.
For quantitative evaluation of postural control ability,
two stabilometers (JK-101 II, Unimec Co., Tokyo, Japan)
and a personal computer (Dynabook B553, TOSHIBA
Co., Ltd., Tokyo, Japan) were employed. As a measurement
task, each participant was instructed to maintain a
stationary standing position on the two stabilometers
while barefoot, with the medial malleoli 100 mm apart.
The participants were instructed to signal “yes” when they
considered body sway stable, and then to maintain the
same posture for another 10 seconds. They were then asked
to maintain a stable posture while their center of gravity
was moving as far as possible in the anterior direction, in
the same manner as that while standing. Thereafter, the
center of gravity was moved in the posterior direction in
the same manner, and then to the right and left. In each
case, data were extracted for 10 seconds from the time the
participant signaled to move the center of gravity in each
position. These tasks were conducted twice during each
measurement session.
The parameters analyzed in the second and third
trimesters were as follows: 1) Index of postural stability
(IPS), 2) Average rectangular area in each position, 3)
Stability limits, and 4) Rectangular area for posture held
for 10 seconds in the anterior, posterior, right, and left
directions. The IPS measures stability using stable and
rectangular areas and is strongly correlated with the Berg
Balance Scale (11). This index is calculated by summing
the average rectangular area in each position and the area
of the stability limits, divided by the average rectangular
area to obtain the logarithmic value (11). Stability limits
are obtained by multiplying the movement of the center
of gravity in the anterior-posterior and lateral directions
as well.
The physical characteristics of the participants were
obtained in the interviews and based on the results,
periodic medical examinations were performed in the
second or third trimester . The interview items were
related to the height, weight at the time of measurement,
and abdominal circumference. All the measurements were
duplicated in the second and the third trimesters.
To assess the effect of squat exercises on the muscles,
the toe grip force acting was measured on postural control
in the anterior direction and the muscle force of the
quadriceps, which is an antigravity muscle. Toe grip force
was calculated using a toe grip dynamometer (TKK3364,
Takei Scientific Instruments, Niigata, Japan). The
participants were instructed to maintain 90° knee flexion
and 0° ankle dorsiflexion while sitting. The muscular
strength of the toe in each participant was then measured
by getting them to use their toes to grasp the dynamometer
with maximum voluntary effort (Figure 1A).
Takeda et al
International Journal of Women’s Health and Reproduction Sciences, Vol. 7, No. 1, January 2019
12
The strength of the quadriceps muscle was determined
applying a handheld dynamometer (HHD) (µTAS MF-
01, Anima Co., Ltd., Tokyo, Japan) according to the
method employed by Kato et al (12). The starting limb
position was seated with the knee joint at 90° flexion.
The maximum isometric muscle force of the quadriceps
femoris was calculated twice on the right and left legs with
the sensor part of the HHD placed at the distal part of the
lower leg and fixed to the strut of the treatment bed with a
belt (Figure 1B). Muscle force was duplicated in both legs,
and the mean of the maximum values was adopted.
The control group comprised 20 randomly selected
pregnant women in their 20s and 30s. Measurement data
in this group were selected applying a random number
generator. All the data were used only after obtaining
approval by telephone from those who did not have
regular exercise habits.
This study was implemented following the approval of
the Ethics Committee at the Kansai University of Welfare
Science (under the approval number 16-10). The SPSS
(statistical package for the social sciences) software, version
24 (IBM, Tokyo, Japan) was used for statistical analysis
including: 1) a comparison of physical characteristics
between the squat intervention and control groups, and
of muscle strength in the squat intervention group before
and after the intervention and 2) a comparison of postural
control parameters and time points between both groups.
The Wilcoxon signed-rank sum test was used to analyze
1) the level of significance (P < 0.05). Moreover, two-way
repeated-measures analysis of variance (ANOVA) was
employed to examine 2) the level of significance (P < 0.05)
through using the Bonferroni correction for further
analysis.
Results
The physical characteristics of each group are shown in
Table 1. After excluding the dropouts and those who chose
not to participate because of a poor physical condition,
20 women participated in the squat intervention group.
No significant differences were observed in either
group respecting age, height, weight, or abdominal
circumference.
Changes in the IPS, representative and stability areas,
and the rectangular area in each direction for both groups
are shown in Table 2. Based on the results of two-way
ANOVA, an interaction was observed for the IPS (F (1,
78) = 69.26, P < 0.05). In a subsequent simple primary
effect test, the IPS was significantly higher in the control
group in the second trimester (P = 0.02) and in the squat
intervention group in the third trimester (P = 0.01). In
addition, the IPS decreased significantly (4.5%) with
pregnancy progression in the control group (P = 0.01)
while it increased significantly (6.1%) in the squat
intervention group (P = 0.01). Besides, an interaction
was observed in the mean rectangular area (F (1, 78) =
Figure 1. (A) Measurement method of toe grip force. Subjects
are instructed to grasp the instrument bar with the maximum
force with the toes. (B) Measurement method of knee extension
muscle. Fixed to the legs of the chair with a belt not stretchable.
Instructs to knee extension to tension the belt. Knee extension
strength is extracted from the sensor.
(A) (B)
43.70, P < 0.05). In a subsequent simple main effect test,
no significant difference was found between the groups in
the second trimester (P = 0.49). However, the mean area
in the control group was significantly higher in the third
trimester (P = 0.01). Furthermore, in the control group, the
mean area enhanced significantly (26%) with pregnancy
progression (P = 0.01) while decreasing significantly
(18%) in the squat intervention group (P = 0.01). An
interaction was observed in the stability limits (F (1, 78)
= 4.35, P < 0.05) as well. In addition, in a subsequent
simple primary effect test, significantly larger stability
limits were detected in the control group in the second
trimester (P = 0.01). Nonetheless, there were no significant
differences in either group in the third trimester (P = 0.37).
Moreover, although no significant changes were seen in
the control group (P = 0.77), significant increases (11%)
were found in the squat intervention group (P = 0.01).
Despite these changes in the rectangular area, there
were no interactions in timing and intervention, main
effect, the standing position rectangular area, and the
anterior rectangular area. Nevertheless, an interaction
was observed in the posterior rectangular area (F (1, 78)
Table 1. Comparison of Physical Characteristics Between Control and
Squat Groups
Control Group Squat Group P Value
Age 32.3 ± 3.2 31.7 ± 3.4 0.92
Height (cm) 159.7 ± 5.3 159.3 ± 4.4 0.89
BMI
2nd trimester 21.8 22.2 0.30
3rd trimester 23.0 23.5 0.26
Weight (kg)
2nd trimester 55.6 ± 6.1 56.5 ± 6.6 0.36
3rd trimester 58.7 ± 5.6 59.7 ± 6.9 0.32
Abdominal circumference (cm)
2nd trimester 86.6± 5.2 86.2 ± 4.6 0.79
3rd trimester 92.1 ± 4.6 91.2 ± 9.6 0.47
*P < 0.05.
Takeda et al
International Journal of Women’s Health and Reproduction Sciences, Vol. 7, No. 1, January 2019 13
= 17.68, P < 0.05). Meanwhile, in the subsequent simple
main effect test, no significant differences were found in
the rectangular area in the second trimester (P = 0.60).
Nonetheless, it was significantly smaller in the squat
intervention group in the third trimester (P = 0.01). In the
control group, there was a significant increase (30%) in
the rectangular area with pregnancy progression (P = 0.01)
whereas it decreased significantly (27%) in the squat
intervention group (P = 0.01). Besides, an interaction was
observed in the right rectangular area (F (1, 78) = 13.68,
P < 0.05). Moreover, in the subsequent simple main effect
test, no significant differences were seen between the
groups in the second trimester (P = 0.25). However, it was
significantly smaller in the squat intervention group in
the third trimester (P = 0.01). In addition, a significant
increase (28%) whereas a significant decrease (24%) were
observed in the control (P = 0.01) and squat intervention
(P = 0.02) groups with pregnancy progression,
respectively. An interaction was also observed in the left
rectangular area (F (1, 78) = 22.47, P < 0.05). Furthermore,
in the subsequent simple main effect test, no significant
differences were seen between the groups in the second
trimester (P = 0.43). However, it was significantly smaller
in the squat intervention group in the third trimester (P
= 0.01). Moreover, it was significantly larger (37%) in the
control group (P = 0.01) while being significantly smaller
(14%) in the squat intervention group (P = 0.01) with
pregnancy progression.
Changes in muscle force before and after the intervention
in the squat intervention group are shown in Table 3.
Although toe grip force increased significantly after the
squat intervention (P < 0.05), no significant differences
were found in the quadriceps femoris.
Discussion
The current study sought to investigate the effect of
squat exercises with weight shift on muscle strength and
postural control during pregnancy.
The IPS and stability area were higher in the second
trimester in the control group than in the squat intervention
group. In addition, the control group had better balance
ability as compared to the squat intervention group in the
second trimester.
Likewise, in the squat intervention group, both the IPS
Table 2. Comparison of Posture Control Abilities Between Control and Squat Groups
2nd Trimester 3rd Trimester Time Main Eect Intervenon Interacon
IPS 13.0*1.54*69.26*
Control group 2.15 ± 0.14 2.05 ± 0.17
Squat group 2.05 ± 0.17 2.18 ± 0.14
Average Rectangle area (mm2) 6.19*8.45*43.70*
Control group 153.10 ± 65.15 193.63 ± 76.09
Squat group 164.13 ± 63.13 135.00 ± 44.40
Stability limits (mm2) 13.19*5.04*4.35*
Control group 20076.32 ± 4382.09 20243.95 ± 3636.21
Squat group 17615.93 ± 4037.59 19516.57 ± 3943.49
Rectangular Stasc area (mm2) standing 2.05 2.57 0.00
Control group 86.32 ± 35.98 99.37 ± 41.79
Squat group 87.68 ± 47.15 89.85 ± 49.70
Front 0.01 0.33 0.30
Control group 136.51 ± 74.80 153.20 ± 85.49
Squat group 126.85 ± 81.90 114.38 ± 53.23
Back 0.75 8.47*17.68*
Control group 191.90 ± 98.72 250.18 ± 161.45
Squat group 208.03 ± 136.18 151.61 ± 68.94
Right 5.60*8.04*13.68*
Control group 181.29 ± 106.47 232.61 ± 122.24
Squat group 2013.28 ± 120.80 160.81 ± 68.28
Le 5.78* 13.63*22.47*
Control group 169.50 ± 119.41 232.78 ± 127.00
Squat group 184.80 ± 78.16 158.33 ± 78.60
Note. IPS: Index of postural stability; Control group (n=20); Squat group (n=20); *P < 0.05.
Takeda et al
International Journal of Women’s Health and Reproduction Sciences, Vol. 7, No. 1, January 2019
14
and stability area increased with pregnancy progression
and were significantly higher compared with the control
group in the third trimester. Conversely, the mean
rectangular area decreased significantly in the squat
intervention group and was considerably smaller in the
third trimester compared with that of the control group.
These findings suggest that squat exercises improved
postural control. Conversely, however, in the control
group, the IPS decreased with pregnancy progression
and was smaller in the third trimester. These findings
indicated that a lack of exercise in normal pregnancies led
to a decrease in postural control ability.
In the present study, the IPS was used to evaluate
postural control. The IPS has reportedly been applied in
cases of the neurological medical disease, cerebrovascular
disorders, and cardiovascular disease, and also providing
elderly support treatment. For example, in a study, a 67-
year old man and a 71-year old woman were found to
have IPSs of 1.90 and 1.73, respectively, which both were
lower than 2.00 (13). In the control group, the IPS was
2.15 in the second trimester decreasing to 2.05 in the
third trimester. This means that at the end of a normal
pregnancy, the IPS decreased to a level similar to that in
the elderly. Conversely, the IPS increased with pregnancy
progression in the squat intervention group and was equal
to 2.17 at the end of the pregnancy. The IPS value can thus
be interpreted as being larger than that of healthy people
aged 21–54 years, suggesting improved postural control
ability.
In the squat intervention group, the rectangular area
in the posterior, right, and left directions decreased after
the intervention. In the down phase of the squat, flexion
of the hip joint, knee joint, ankle joint, and trunk must
have been coordinated so that the center of gravity did
not deviate from the stability area. It is considered that
during pregnancy, the center of gravity line was displaced
posteriorly and likely to deviate from the stability area.
Squatting with a posterior weight shift so as not to deviate
from the center of gravity was necessary to achieve
control by proprioception and muscle force at the ankle
dorsiflexors.
The intervention in this study was involved performing
two sets of 10 repetitions of squat exercises per day.
After the intervention, toe grip strength rather than the
quadriceps muscle strength increased significantly. It
seems that the number of occurrences (4 to 6 times per
direction) was not sufficient for the muscle activity until
the muscle strength of the quadriceps muscle increased.
Continuous information from the sensory system
regarding changes in the position of the body’s center of
gravity was important for maintaining the balance during
standing. This information was reportedly obtained from
the contact area between the toes, the sole, and the floor
(14). Furthermore, squat exercises are found to stimulate
a proprioceptive sensation and improve coordination in
the lower limbs (8). Interventions that stimulate plantar
sensation are thought to activate the mechanoreceptor of
the plantar, which increases somatosensory information
and improves balance ability (15-17). Therefore, squat
exercises accompanied by changes in the center of gravity
were thought to stimulate plantar sensation, which led to
decreases in the posterior, right, and left rectangular areas
in the squat intervention group.
Regarding the variation in both groups in static
standing and the anterior rectangular area, in a previous
study, body sway was reported to increase in the anterior-
posterior direction during static standing in the third
trimester (4,5). However, foot width was not specified,
especially in the static standing position. In the present
study, foot width was measured while standing with
feet 100 mm apart (2). The reason for the change in the
rectangular area at standing was not identified, but it
was likely because foot width in this study was believed
to be set wider than that in the prior research. It seems
that there may have been no changes owing to pregnancy
progression. Since, the task of the squat intervention
group was to perform squat exercises with a displaced
center of gravity. Meanwhile, squatting in the normal
standing position was not included as a condition.
Therefore, it was considered that there was no change in
the rectangular area of standing in the squat intervention
group. The anterior rectangular area was measured while
the participant moved the center of gravity line as far
forward as possible holding the sit. Takeda et al. reported
that compared with non-pregnant women, the posterior
component of the floor reaction force in pregnant women
decreased at the maximum functional reach test (FRT)
with pregnancy progression. Conversely, the vertical
component increased (18). This shows that non-pregnant
women controlled their anterior postural attitude in such
a way that the floor surface was pushed posterior whereas
pregnant women seemed to have hardly any force to push
the floor posterior. In other words, it can be inferred that
anterior movement tasks did not involve postural control
with trunk flexion during pregnancy but rather moved
the center of gravity horizontally forward with trunk
extension and ankle dorsiflexion. Normally, in forwarding
the weight shift tasks, the toe grip force is said to be related
to stability in the standing position and the forward
movement of the center of gravity (19,20). Although the
toe grip force increased in the squat intervention group
after the intervention, the forward mass movement
caused by the trunk extension during early gestation and
ankle dorsiflexion may have not resulted in a load on the
Table 3. Comparison of Muscle Strength Before and After Intervention
Before Aer P Value
Foot grip strength (kg) 6.51 ± 2.47 8.18 ± 2.67 0.00*
Quadriceps femoris muscle (N) 15.10 ± 5.29 14.87 ± 5.79 0.80
*P < 0.05.
Takeda et al
International Journal of Women’s Health and Reproduction Sciences, Vol. 7, No. 1, January 2019 15
forefoot. It is supposed that despite the increase in the
toe grip force in the squat intervention group, the front
rectangular area did not change due to postural control
because the forefoot was not loaded in the forward center
of gravity task.
Conclusions
In the squat intervention group, decreases were observed
in the rectangular area in the posterior and lateral
directions. Meanwhile, there were some increases in
the stability limits, resulting in postural control ability
similar to that in the elderly level. This intervention effect
was not thought to be due to muscle enhancement but
rather to the maintenance of proprioception. Maintaining
proprioception may have prevented the deviation of the
body schema promoting the prevention of falls. The
risks of inappropriate and over-exercise predominantly
affect the fetus (21). It is considered desirable to conduct
such movements under strict medical supervision. It was
suggested that the use of a smart-phone application would
encourage regular exercise and enable a better physical
condition management. The results of this study indicated
that squat exercises with weight shifting are effective for
maintaining postural control, which in turn leads to a
reduced risk of falls.
This study did have some limitations which need to be
acknowledged. The number of people in the intervention
group was small. Therefore, the results may be generalized
with caution.
Besides, the muscles which were examined to assess the
effect of the intervention were localized. As a result, other
body muscles are required to be investigated in order to
evaluate the impact of such interventions.
In addition, the effect of the intervention on
proprioception remained unclear. In the future, additional
muscle groups in a larger sample should be investigated,
and proprioception should be evaluated both before and
after the intervention.
Conflict of Interests
Authors declare that they have no conflict of interests.
Ethical Issues
The ethical committee of Kansai University of Welfare
Sciences approved the study(Approval number 16-10).
Financial Support
This research was conducted with the aid of a MEXT 2011
research grant (#23593327).
Acknowledgments
The authors wish to thank all the pregnant participants
and the instructors in the Departments of Midwifery and
Obstetrics and Gynecology for their cooperation. This
research was conducted in part thanks to aMEXT 2011
research grant (under the issue number 23593327).
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... In two of the articles conducting an endurance handgrip test, 118 119 a hand-grip sphygmomanometer was used instead of dynamometry. On the other hand, one used a hand-held dynamometer fixed to a chair to assess quadriceps strength 116 and one used a toe-grip dynamometer. 116 Moreover, two ad hoc isometric tests were used to assess maximal voluntary hip extension and back flexors endurance in the same article. ...
... On the other hand, one used a hand-held dynamometer fixed to a chair to assess quadriceps strength 116 and one used a toe-grip dynamometer. 116 Moreover, two ad hoc isometric tests were used to assess maximal voluntary hip extension and back flexors endurance in the same article. 174 Finally, 13 dynamic endurance tests were found, 9 were listed as ad hoc tests 12 112 122 and another 3 (30 s Chair Stand Test, 5 Times Sit to Stand test, Trendelenburg's test) were classified as 'other' dynamic tests. ...
... However, standing position varied between articles. Ten articles maintained a standing posture with feet separated, 116 131 132 147 158 159 162 165 Open access one with feet together, 129 two used mixed protocols, 128 160 one with medial malleoli separated 130 and four did not mention the standing posture. 138 149 163 164 Moreover, three articles used protocols with eyes open 132 149 162 exclusively, eight articles used mixed protocols with eyes open and closed, one used visual target and visual tasks 164 and six did not specify whether participants kept their eyes closed or opened. ...
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... About half of the studies (54%) reported the instructions, i.e. "to stand quietly or motionless", or "to maintain a stationary standing position" [24,36,[38][39][40][41][42]. Finally, four studies (31%) described standardizing the position of the feet between trials [23][24][25]40]. ...
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... Thus, anti-gravity and muscle strength exercises are essential for improving control during pregnancy. Squat exercise has been cited as an anti-gravity and resistance exercise [18]. ...
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Change of stability limits in the third trimester
  • K Takeda
  • K Shimizu
  • M Imura
Takeda K, Shimizu K, Imura M. Change of stability limits in the third trimester. Journal of Human Life Engineering. 2014;15(1):58-64.