Scores For The Limit Of Stability Physical Education Essay

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Balance is the ability to maintain the body's center of gravity (COG) within the base of support. Balance normative values in adults were reported by the use of the Pro Balance Master® system. Up to the author's knowledge, no population-based reference material of standing balance has been presented in the literature for healthy young adults in Kuwait. Aim: to report the scores of two balance tests; Limits of Stability (LOS), and the modified Sensory Organization Test (mSOT) in young adults. Methods: Eighteen volunteers with 9 males and9 females (x̄ age= 21.4 years, SD= 1.04) were recruited for this study. The variables reported for LOS included: movement velocity (MVL) in deg/sec, reaction time (RT) in sec, percentages of end point excursions (EPE) and maximum excursions (MXE), and directional control (DCL). For the mSOT, the equilibrium scores for four conditions were reported: (1) eyes open/fixed support, (2) eyes closed/fixed support, (3) eyes open/sway-referenced support, (4) eyes closed/sway-referenced support . Results: the LOS variables were as follows: x̄ MVL= 3.51 deg/sec SD=1.182, x̄ RT= 0.85 sec SD= 0.23, x̄ EPE= 75.5% SD=12.18, x̄ MXE= 88.2% SD= 7.15. The results for mSOT were: x̄ C1= 93.11 SD= 2.955, x̄ C2= 91.20 SD=2.425, x̄ C3=87.611 SD= 4.412, x̄ C4= 68.77 SD= 8.812. Conclusion: healthy young adults living in Kuwait were able to complete the balance tests without slipping, stepping, or falling. This finding could provide reference measures for balance scores for healthy young adults aged 20-30 years old living in Kuwait. This information can be used to provide future comparisons with scores of adults with balance problems.


Till date, no population-based reference material of postural sway has been presented in the literature for Kuwaiti adults. Objective assessment of the function of the equilibrium system has applications for the monitoring of the rehabilitation process in patient groups experiencing balance problems (Karlberg et al., 1996; Levine et al., 1996; Luoto et al., 1998; Benvenuti et al., 1999; Gustafson et al., 2000; Carter et al., 2001; Kammerlind et al., 2001; Preisinger et al., 2001). In biomechanics, balance is an ability to maintain the center of gravity of a body within the base of support with minimal postural sway. When exercising the ability to balance, one is said to be balancing. Balancing requires concurrent processing of inputs from multiple senses, including equilibrioception (from the vestibular system), vision, and perception of pressure and proprioception (from the somatosensory system), while the motor system simultaneously controls muscle actions. The senses must detect changes of body position with respect to the base, regardless of whether the body moves or the base moves. In the case of an individual standing quietly upright, the limit of stability is defined as the amount of postural sway at which balance is lost and corrective action is required. The limit of stability may be described by an irregular conical envelope above the support base. A balance board-which is an unstable standing surface that moves in different planes of motion-is commonly used to train balance. In humans, equilibrioception is mainly sensed by the detection of acceleration, which occurs in the vestibular system.

Other senses play roles as well, e.g. the visual system and proprioception. The importance of visual input for balance is illustrated by its being harder to stand on one foot with eyes closed than with eyes open. The sense of balance, usually, deteriorates in the process of aging of a person. However, it can be improved considerably with the help of special training. When the sense of balance is interrupted it causes dizziness, disorientation and nausea. Balance can be impaired by Ménière's disease, superior canal dehiscence syndrome, an inner ear infection, by a bad common cold affecting the head or a number of other medical conditions. It can also be temporarily disturbed by quick or prolonged acceleration, for example riding on a merry-go-round.

There are many approaches in determining if a person has balance problems and disturbances. Two accurate tests that were used in this study were the modified sensory organization test (mSOT) and limits of stability (LOS).The mSOT protocol provides information about the interaction of the three sensory systems that contribute to postural control: somatosensory, visual and vestibular. During the assessment, inaccurate information is delivered to the patient's feet and joints through controlled, calibrated "sway referencing" of the support surface, which tilts to directly follow the patient's anteroposterior body sway.

Operational Definitions

The mSOT measures how well a patient can maintain their postural stability under four sensory conditions (Appendix 1). The functional implications of this test are that accurate organization of sensory information is critical to maintaining balance within the variety of environments encountered in daily life. An inability to organize sensory information appropriately can result in instability in environments where visual cues are diminished (darkness, lack of contrast/depth cues), or the surface is unstable or compliant (sandy beach, gravel driveway, boat deck). Inability to appropriately organize sensory information can lead to or be exacerbated by impairments in COG alignment and/or selection of movement strategies.

The LOS quantifies the maximum distance a person can intentionally displace their Center of Gravity (COG) i.e. to lean their body in a given direction without losing balance, stepping, or reaching for assistance. The measured parameters are reaction time, COG movement velocity, directional control, end point excursion, and maximum excursion. Ability to voluntarily outmove the COG to positions within the LOS is fundamental to mobility tasks such as reaching for objects, transitioning from sitting to standing, or vice versa, and walking.

Reaction time delays are commonly associated with difficulties in cognitive processing and/or motor diseases. Reduced movement velocities are indicative of high-level central nervous system deficits such as Parkinson's disease and age-related disorders. Inability to reach targets in single movements (reduced endpoint excursions or

excessively larger maximum excursions) and poor directional control are indicators of motor control abnormalities. Excursions may be restricted by biomechanical limitations (i.e. range). Dizzy and/or unsteady patients and those fearful of falling may artificially restrict their excursions, while the strength of those with lower extremity weakness may be insufficient to attain and/or maintain stable target positions. Limitations in a subject's LOS may correlate with the risk of falling or instability during weight shifting activities such as leaning forward to take objects from a shelf, leaning back for hair washing in the shower, opening the refrigerator door, etc.

Research Questions:

What are the mSOT scores for healthy young adults in Kuwait?

What are the LOS scores for healthy young adults in Kuwait?


Healthy young adults in Kuwait will be able to complete the mSOT without slipping, stepping, or falling.

Healthy young adults in Kuwait will be able to complete the LOS test without slipping, stepping or falling.

Literature review

Nolan L. et al have investigated sex and age differences in standing balance. Movement of the centre of pressure (COP) was calculated from ground reaction force data collected from a force platform during bipedal stance with eyes open and eyes closed. Age-related 'improvements' in sway occurred in boys, thus some aspects of postural control are still developing after 9 to 10 years of age. As very little age-related difference was seen in girls, boys may lag behind somewhat in terms of developing postural control. (Nolan L. et al, 2005)

A study was done by H.Rogind. et al to evaluate postural control by measuring posturographic parameters, with the aim of establishing useful standards with regard to gender, age, body weight, cigarette smoking, alcohol consumption and articular hypermobility. Measurement of postural sway was performed by the Balance Master Pro®. The influence of individual parameters is similar to what has been found by others; there are little, if any, differences between the genders and age is associated with an increase in postural sway (Gill et al., 2001).

Data on postural balance were collected from a representative nationwide sample of a Finnish population aged more than 30 years. Postural balance was measured with the help of a force platform system. In addition, balance abilities were also evaluated by a non-instrumented field test. The results of the study provided normative values for force platform balance tests at an age of 30 years and above. Deterioration in balance function clearly starts at relatively young ages and further accelerates from at about 60 years upwards. Due to systematic differences between males and females, separate normative values for both genders are needed. Due to marked ceiling effects the field test can only be recommended for older individuals; aged 60 years and more. (P. Era et al, 2006)

A study was done by, Clark S, et al to establish the reliability of the LOS test, and to determine the relative variants contributions from identified sources of measurement error. This study included thirty-eight community-dwelling older adults with no recent history of falls. This study found that the LOS tests are reliable tests of dynamic balance when administered to healthy older adults with no history of recent falls, and dynamic balance measures were generally consistent across multiple evaluations. (Clark S et al, 1997)

Another study was done by, Chaudhry H, et al by using the standard Sensory Organization Test (SOT). They tested for the biomechanically based measure of postural stability that utilizes both vertical and horizontal force data rather than simply the minimum and maximum sway values. The authors of this study concluded that there is a need to establish normative assumptions about sway limits to provide a more biomechanically sound measure of postural stability that may have good clinical utility.



Twenty participants were recruited for this study. Two participants were excluded due to inner ear and balance problems. Nine females and nine males (mean age= 21.4 SD=1) participated in this study. Participants mean height = 1.65 SD= 0.06 and mean weight= 62.44 and SD= 11.4. All participants were free from any condition affecting their gait or standing balance. They did not have any range of motion restrictions at the ankle, knee or hip. They had normal or corrected to normal vision. None of the participants had a history of orthopedic or neurological diseases, balance disorders, falls, or were using medications that may affect standing balance.

Experimental procedures were approved by Kuwait University Health Sciences center institutional review board. All participants signed an inform consent form prior to participation in the experiment. Participants were also asked to fill out a screening form to make sure they have no problems that would exclude them from this study (Appendix 2). Each participant was tested individually in a laboratory setting.


Balance test scores were collected by using the Pro Balance Master®. It is comprised of two 9``x18`` dual force plates connected at the midline by the anteroposterior axis by a pin joint. Each force plate is mounted on a pair of symmetrically positioned force transducers. The four transducers measure vertical and horizontal pressure, which form the basis of subsequent calculations of the COP and COG sway angles. A separate differential amplifier with separate control of gain and zero settings conditioned each force transducer. The data from the force platform are sampled at a 50 Hz and carried to an electrical controller that interfaced with a computer. The reliability and validity of the Pro Balance Master® was established to be moderate to high with ICC of 0.8 (Ford-Smith, Wyman, Elswick, Fernandez, and Newton, 1995)


All participants were asked to remove their shoes and socks upon arrival to the lab. Their heights and weights were measured. One two- minutes practice trial was administered prior to data collection for each test. The practice took place on the Pro Balance Master® located in the neuro-rehab lab at the Health Sciences Center, Department of Physical Therapy. After the practice trials, subjects stood on the force platform for data collection. During the actual data collection for the LOS test, subjects were asked to stand on the force platform with their arms alongside their body and try to move the cursor on the screen from the center box to the target box for each trial, totaling eight trials. For the mSOT test, subjects were asked to stand still as much as possible on the force platform with their arms alongside their body under four conditions: (1) standing with eyes open on a fixed force platform, (2) standing with eyes closed on a fixed force platform, (3) standing with eyes open on a sway-referenced force platform, (4) standing with eyes closed on a sway-referenced force platform. There were no risks involved in these testing procedures. Subjects were in the lab for one 30 minutes testing session.

Statistical Analysis

In this descriptive study, the mean and standard deviation of each variable were reported. For the LOS, the variables recorded were: reaction time (RT) in seconds, movement velocity (MVL) in degrees/ seconds, percentages of end point excursions (EPE) and maximum excursions (MXE) , and directional control (DCL). For the mSOT, the variable recorded was the equilibrium score (ES) for conditions 1 through 4.


Limits of Stability


Healthy young adults living in Kuwait were able to complete the balance tests without slipping, stepping, or falling. This finding could provide reference measures for balance scores for healthy young adults aged 20-30 years old living in Kuwait. This information can be used to provide future comparisons with scores of adults with balance problems.

Appendix 1

Appendix 2

Screening Form

1. Did you have any injuries to your ankles in last 12 months?

O Yes O No

2. Did you have any injuries to your knees in the last 12 months?

O Yes O No

3. Did you have any injuries to your hips in the last 12 months?

O Yes O No

4. Did you have any injuries to your back in the last 12 months?

O Yes O No

5. Do you have any balance problems?

O Yes O No

6. Do you have an inner ear problem?

O Yes O No

7. Do you have vision problem?

O Yes O No

If yes, is it corrected? \

O Yes O No

What is your name?

What is your age?

What is your gender? O Male O Female

Height _m

Weight kg