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Background: Most middle- aged women, even the healthy ones, have
some impairments, such as muscle weakness and loss of balance. This increases
the likelihood of falling, which causes serious complications, deteriorates the
overall health status, impaires their day-to-day functioning, and increases
their physical dependency and hospitalizations. Purpose: To investigate the
relationship between muscle strength of the lower extremities and balance in
healthy middle-aged women. Methods: Muscle strength will be measured using
hand-held dynamometer. While balance will be measured by one-leg standing test
and timed Get-Up and Go test (GUG). Data analysis: Statistical analysis will be
carried out using SPSS software. Pearson correlation coefficient test will be
used to investigate the relationship between muscle strength and balance and
interaction between participants’ characteristics (Age, BMI). The spearman
correlation coefficient test will be used to investigate the relationship
between other participants’ characteristics, muscle strength and balance. The
values will be considered statistically significant at P ? 0.05.

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??????? ??? ????? ??????? ??? P ? 0.05.



Aging is a normal process that all people pass through within their
lifespan, but it may differs between individuals due to genetic and
environmental factors (P1 et al., 2014). When a person gets older, there is an overall gradual decrease of
physical capacity, muscle power, sensation, and coordination, which leads to
balance deficits) Oliveira et al., 2014). An adequate level of balance is required in middle-aged
people to successfully perform everyday normal activities) Muehlbauer et al., 2012). Researchers define balance as the preservation of ideal body
posture during dynamic and static states by producing suitable motor responses
to facilitate voluntary movements and recover equilibrium) Lord, 2008; Mancini & Horak, 2010). For instance, isometric and dynamic muscle strength reaches its
peak around age 20-29 years old and deteriorates in persons 50-59 years old due
to a reduction in individual muscle fiber counts, particularly among fast
twitch fibers type II, that reduces overall skeletal muscle size (P1 et al., 2014).  As a result, elderly  people are more prone to depend on others to
maintain their balance and protect themselves from falling )Liu CJ 1,  2017; Muehlbauer, 2015).

In this context, the other factor that needs to be considered is
muscle strength. “Muscle strength should be distinguished from muscle power:
muscle strength is defined as the maximal force that a muscle can produce
against a given resistance, while muscle power (force × velocity) is defined as
the product of force and speed.” Thus, to prevent falling, interventions should
focus on muscle power enhancement instead of muscle strength (Winzenberg, 2016(. For more stability, the muscle power of middle-aged people
should be equal between the right and left lower extremities. Differential
muscle power between the left and right sides leads to instability) Kim MK 1, 2015(.

Balance and muscle power are critical for good health and physical
strength and should be improved or maintained adequately throughout one’s
lifespan to be able to play sports and conduct everyday activities without
accidents like falling (Muehlbauer, 2015(. Physical fitness is an effective strategy to enhance
equilibrium and decrease sarcopenia (Oliveira et al., 2014). The lower limb muscle strength evaluation is commonly used to
study balance in middle age. Accordingly, this study will regard muscle
strength as a measurement tool for balance (Wang H1,  2016) .

Middle-aged people with reduced physical capacity are more likely
to depend on others to conduct everyday activies. Liu CJ et al. (2017) studied
the effects of physical exercise with reduced physical capacity in elderly with
age 75 years or older people and their risk of progression to care dependency.
Using a meta-analysis study, their findings showed that multimodal exercises
are effective in reducing falls, improving muscle strength, balance and
physical function of the lower extremities.

Two recent studies have reported that physical exercise directly
affects muscle power and the ability to maintain balance. Hyo-Cheol Lee et al.
(2015) examined the effect of physical exercise by elderly women on balance and
muscle function in 20 healthy elderly women aged 60 and over by dividing them
into control group and exercise group. The exercise group subjects participated
in an elastic band exercise program lasting for 8 weeks, exercising for 40
minutes four days a week with resting periods of 60 seconds. They measured
sit-to-stand capacity to evaluate muscle strength, knees-up exercises for two
minutes to measure muscle endurance and standing on one leg with eyes open to
test balance. They found that leg muscular strength and endurance of the
quadriceps femoris muscle significantly increased in the exercise group after
the intervention. The ability to balance significantly improved in the exercise
group, showing that the intervention is effective at improving balance, muscle
strength and muscle endurance of middle age women. The other study was
conducted by Eckardt (2016) as a randomized control trial on 75 healthy
community-dwelling elders aged 65-80 years to detect if lower-extremity
resistance training on unstable surfaces will improve muscle strength and
balance. The author assigned them to three intervention groups: machine-based
stable resistance training M-SRT, machine-based unstable resistance training
M-URT and free-weight unstable resistance training F-URT. Over a period of
ten weeks, all participants exercised two times per week with each session
lasting ~60 min. Tests included assessment of leg muscle strength (e.g.,
maximal isometric leg extension strength), power (e.g., chair rise test) and
balance (e.g., functional reach test), carried out before and after the
training period. The results showed that lower-extremity resistance training
conducted on even and uneven surfaces meaningfully improved proxies of
strength, power and balance in all groups. M-URT produced the greatest
improvements in leg extension strength and F-URT in the chair rise test and
functional reach test.

Aging correlates with changes in body musculature. Thus, Castro et
al. (2014) studied the relationship between muscle mass, muscle strength and
physical ability in 100 physically independent healthy elderly women aged ? 65
years old. Bone mass and body composition were assessed by dual-energy x-ray
absorptiometry (DXA). Knee extension and flexion strength was assessed by
isokinetic dynamometry, and physical ability was measured by timed Get Up and
Go test (TUG), Berg Balance test (BBT) and dynamic Gait index (DGI). Age and
muscle strength showed a significant association even without a significant
effect of age on muscle mass.

Middle-aged individuals, even the healthy ones, may suffer from
instability and impaired balance. Weirich et al (2010) studied the predictors
of balance in young, middle-aged, and late middle-aged women in eighty-five
subjects between the ages of 18 and 64 years in knee extension, leg press and
knee flexion. Evaluation with maximal muscular strength for the lower
extremities (knee extension, leg press, and knee flexion), lower extremity
flexibility (plantar flexion, dorsiflexion, hip flexion, and sit and reach) and
total bone mineral density (BMD) and bone mineral content (BMC), total and
regional body composition (lean body mass and fat mass), balance and postural
stability. The results showed a significant relationship between balance and

Most middle-age are face health problems. One of the main problems
is falling. Therefore, Ding Li et al. (2016) investigated the relationship
between muscle weakness and slip-initiated falls among community-dwelling in
Thirty-six healthy older male adults of age 71.3±4.7 years, in knee extensors
and flexors muscles. Evaluation of muscle strength and slip perturbation muscle
strength (torque) was assessed for the right knee under maximum voluntary
isometric (flexion and extension) contractions. They were then moved to a
special treadmill. The authors reported a significant relationship between
muscle weakness and slip-initiated falls among community-dwelling middle-aged

Other studies have also reported the relationship between balance
and muscle strength. For instance, F. Wu and his colleagues (2016) examined the
association between lower limb muscle strength and its association with poor
balance in middle-aged women. The study examined strength in quadriceps and hip
extensor muscles sample for this cross-sectional analysis comprised of among
345 women of age 36–57. There was a significant association between lower limb
muscle strength and poor balance in middle aged women. In
another study, Chandak and his colleagues (2014) examined balance performance
and lower limb isometric muscle strength, particularly in the hip flexors,
extensors, abductors and adductors, knee flexors and extensors, ankle plantar-flexors
and dorsi-flexors in 100 community-dwelling middle-aged women of ages 60 and more
by using the Fullerton Advanced Balance (FAB) scale and handheld dynamometer.
They found that knee extensor strength correlated better with balance as
compared to other muscles, while the hip adductors weakly correlated with
balance. That is, women with higher knee extensor strength have better balance.
In addition, Abd El- Kader and Ashmawy (2014) investigated the relationship
between ankle dorsi-flexors strength and balance performance improvement in
fifty healthy middle age male subjects with age range of  65 to 75 years. Twenty-five subjects
(training group) were trained with resisted exercises plus electrical nerve
stimulation of ankle dorsiflexors muscles three times a week for 8 weeks. The
control group, which included twenty-five subjects, received no treatment
intervention except encouragement for performing their usual daily activities
over the 8 weeks of the study. The ankle dorsi-flexors muscles force was
measured by handheld dynamometer in kilograms, and the balance control was
measured by the Berg Balance Scale (BBS), and timed Get-Up and -Go test (GUG).
The Pearson’s correlation coefficients test for the relationship between BBS
scores and ankle dorsi-flexor muscles strength in both groups showed a strong
direct relationship. Conversely, there was an inverse direct relationship
between GUG and ankle dorsi-flexor muscles strength in both groups.

The Most researchers who have researched the relationship between
lower extremity muscle strength and balance in healthy middle-aged individuals
studied subjects ages 60 years old and above, did not examine females, and/or
they did not cover all lower extremity muscle groups in their studies. The
existing literature is deficient in these respects and requires further
investigations to determine the relationship between lower extremity muscle
strength and balance in healthy middle-aged women, as it has been reported that
the likelihood of  falling for
middle-aged people increases from the age of 50 and onwards years old (P1 et al. , 2014). Therefore, this study aims to cover, first, all lower extremity
muscle groups, and, second, to include healthy middle-aged women of age between
45 and 60 years old . The null hypothesis for the proposed study is: there is
no relationship between balance and lower extremity strength in middle-aged
healthy women. The alternative hypothesis is: there is a relationship between
balance and lower extremity strength in middle-aged healthy women.  Accordingly, the question of this study will
be: is there a relationship between balance and lower extremity strength in
middle-aged healthy women?

Materials and
Study design: Cross-sectional correlation study.

Participants: Forty healthy middle-aged
women of age from 45 to 60 years old will be covered in this study. They will
be recruited from the community. Participant information sheet will be
distributed in malls of the eastern region and women’s gathering places with
contact details of the researcher. If they are willing to take part in the
study, they will contact the research team. They will then be invited to the
university and measurement tests will be carried out. Participants will be
excluded if they have neurological disorders, any musculoskeletal problems,
cognitive deficits, any cardiopulmonary diseases, or if they consume
medications that affect balance, as these factors may
affect balance outcomes. They will be included only if they are healthy, if
they are women, and if they are 45 – 60 years old.


The subjects will come to a
clinical lab in Imam Abdulrahman Bin Faisal University. They will be educated
about the entire process and will be required to sign a consent form.
Furthermore, they will be required to complete a personal information form.

The therapist will then perform the
following steps with the subjects:

1-      Measerment of muscle strength of both lower limbs using the
hand-held dynamometer. This step will take 5 -10 minutes.

2-      Measurement of balance by one-leg-stand test and Time up-and-go
test. These will take 5 -10 minutes.

3-      Rest between the two steps and a snack will be provided.

4-      Transportation will be provided to the subjects to and from the
university lab.


To test muscle strength, the following
procedure will be employed:

The therapist will put the participant in a
proper comfortable position, then measure muscle strength in both lower limbs
with a hand-held dynamometer to see how vigorously the participants can
contract their (hip flexors, extensors, abductors, adductors, external
rotators, internal rotators, knee flexors and extensors, ankle dorsiflexors and
planter flexors). Then therapist will place the device in a proper position and
lean over the participant’s leg to provide the appropriate resistance and gain
an accurate reading, while asking the participant to try as hard as she can to
move the tested joint as the practitioner exerts force in the opposite
direction with the muscle testing device pressed against the patient’s
limb. Once the muscle testing device is in place, the therapist will
instruct the participant to press back against the device as hard as possible
for 4-5 seconds. The participant will take approximately one to two seconds to
exert maximum muscle force.

To test balance, the following procedure will
be employed:

1)One leg stands:

The therapist will instruct the
participant to stand on one leg for as long as she can, or until tell her to
stop. Chair/table/counter will be used for initial support. The participant can
choose either foot to stand on, hold her foot anywhere, put not brace free leg
on the standing leg. The participant arms should be at each sides while try not
to move her feet or grab a support unless she need to regain her balance. The
therapist will start timing when participant’s hand leaves the chair/table, and
stop timing when participant’s free foot touches the ground, their hand
contacts the chair/table, their foot moved, or 30 seconds have passed. Other
therapist must be close enough to guard the participant. The time must record
to a tenth of a second. Less than 10 seconds indicate balance impairment and
less than 5 seconds indicate fall risks.

 2) time up-and-go test:

therapist will instruct the participant to sit correctly in a chair with arm
rests. The chair should be stable and positioned such
that it will not move when the subject moves from sit to stand position. The therapist will place a piece of tape or other
marker on the floor 3 meters away from the chair so that it is easily seen by
the participant. Then instruct the participant to
stand when hear the word GO, walk to the line on the floor, turn around, walk
back to chair and sit down. The time will started on the word “GO”
and stop when the participant is seated again correctly in the chair with her
back resting on the back of the chair. Normal healthy middle-aged people
usually complete the task in ten seconds or less and the very frail or weak
middle-aged people with poor mobility, may take 2 minutes or more.

Significance of the study:

If the findings of the study show
a relationship between muscle strength and Balance, educational courses will be
sugested to be delivered to educate healthy women the importance of
strengthening their lower limb muscles to maitain balnce .


The sample size is 40
participants, therefore, the findings of this study will be limited and can not
be generalized to all population  in the
eastern region of Saudi Arabia.

Outcome measures:

Muscle Strength: Many tools are reported in the literature to measure
muscle strength such as myometer, sit to stand ex, maximum isometric leg
extension strength, isokinetic dynamometry and one repetition maximum
assessment (1RM). However, hand-held dynamometer will be used in this study
because it is small, accurate, time efficient, provides a quantified
measurement of force and is relatively inexpensive compared with isokinetic
dynamometry. It is easy to use and has a convenient size which may justify
widespread clinical use) M 
2014; Timothy  Stark  BS, 2011(.

Procedure of data collection: Participants will be instructed to
come to the university’s Lab.
Researcher will do the measurements in approximately 20 minutes, with 5 minutes
rest between each test. Soft drinks will be provided and transportation will be
available for the subjects.

Ethical considerations: Ethical approval will be obtained from the
ethics community within Imam Abdulrahman bin Faisal University. A participation
information sheet will be distributed among healthy middle-aged women
explaining all phases of the study. All participants will sign a consent form
before commencing data collection. Safety of all participants will be ensured
throughout the study. Data will be kept in hard paper format in secure storage
and in digital files, saved on desktop computers accessible only to the primary
investigator and the research team.   

Data analysis:

 Statistical analysis will be carried out using
SPSS software. Participants’ characteristics will be analyzed using descriptive
analysis. Pearsons’ correlation coefficient test will be used to investigate
the relationship between muscle strength and balance. In addition, it will be
used to investigate the relationship between participants’ characteristics
(Age, BMI), strength and balance. The Spearman correlation coefficient test will
be used to investigate the relationship between participants’ other
characteristics, muscle strength and balance. The values will be considered
statistically significant at P ? 0.05.



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