Low back pain (LBP) is one of the conditions that affect many people around the world, and it is considered one of the problems that affect health and economic life through absenteeism from work and disability [1, 2]. LBP is classified as specific or non-specific back pain and most people suffer from it; if the specific source of the pain cannot be identified, so it is classified as non-specific LBP [3]. When the back pain arises from the spine, intervertebral disks, or surrounding soft tissues, it is called mechanical low back pain (MLBP) [4]. The diagnosis of CMLBP is solely clinical; however, imaging studies may show degenerative spondylosis, asymptomatic lumbar disc herniation, and spinal stenosis. Some imaging abnormalities are consistent with the dynamic flexion/extension movements, but there are no clinical symptoms associated with these abnormalities [5]. Balance is essential for proper daily activities [6]. Balance disturbance and impairment of postural control may affect persons’ participation in many sports and physical activities. In addition, it can hinder the development of motor skills, reduce motor skills performance and increase the risk of falls [7]. Moreover, back pain with its various causes is always associated with poor balance and a high risk of falls [8, 9]. As many as 9% of patients experience balance changes due to back pain, and age is the main determinant [10].
Balance control is achieved through the interaction between the vestibular, visual, and somatosensory systems, as they provide information about the position of the body in space, the forces acting on it, acceleration, and any other factors in the surrounding environment [11]. Impairment of one of them stimulates the nervous system to rely more on other equilibrium systems to maintain balance, according to the sensory reweighting theory [12]. Therefore, impaired proprioception can lead to increased demand for visual and vestibular input. However, this response may not fully explain deficiencies in proprioception [12].
Deficits in lumbar proprioception, decreased range of motion and altered muscle density are always associated with chronic low back pain (CLBP), because impaired proprioception will cause defective muscular responses, which can lead to a deficit in posture control and trunk balance [13,14,15]. Impaired lumbar proprioception is thought to reduce the ability to obtain and maintain a neutral spine posture and properly coordinate muscle activation. This impairs spinal control and increases trunk muscle activity as well as spinal pressure and strain, which may prolong LBP and cause further deterioration of proprioception [16].
The employment of emerging technologies like smartphones and tablets offers researchers and coach’s opportunities to assess physical performance in the field, instead of science lab sports. Current smartphone technologies include advanced computing capabilities, inertial sensors, global positioning systems, and high-speed video capture [17]. The benefits of these devices are being financially suitable, portable, and need only a software application to access the data outputs of the installed sensors [18]. Smart mobile phones and tablets are used in the assessment of balance due to their containing of triaxial accelerometer [17, 19]. Measurements are taken by a simplified approach from the location of the center of mass (COM) which is typically described by a random single point where the sensor is placed [20, 21].
Many smartphone motion accelerometer programs can be found in Android Play stores such as Balance Y-medical, Balance Test, Gwangju, Korea. These programs use the instantaneous acceleration of the smartphone and use the built-in accelerometer based on the x, y, and z axes for evaluation. It scores one point every 60 ms and 1000 points per minute. The data process is done by dividing the horizontal plane into eight levels and the data is processed at each level. The data process includes the sum of the data points distributed from each level, the distance between the origin point and the farthest data point, and the percentage of points in a given plane [22].
One developed application for assessing balance is the balance Y-MED smartphone application. Balance Y-MED is a smartphone application that uses a motion accelerometer sensor that has its base in a smartphone which has been tested for its reliability and suitability for use as a convenient tool for assessing the postural balance in everyday life [22]. Due to the large number of LBP patients, we need a practical and simple way to easily and quickly measure the balance in the clinic to determine the effectiveness of the treatment methods used to treat the patients. Therefore, we chose to measure the validity and reliability of an easy and fast application on the phone that enables us to take the required data, and therefore, we compared the efficiency of the results extracted from it compared to the HUMAC balance board. Compared with the HUMAC balance board, is the balance Y-MED smartphone app reliable and effective in measuring the static balance of patients with mechanical chronic low back pain? The aims of the current study were (1) to determine the concurrent validity of the balance Y-MED smartphone application in comparison to the HUMAC balance board in chronic mechanical low back pain CMLBP patients and (2) to assess the test-retest reliability of the balance Y-MED smartphone application for measurement of balance in CMLBP patients.
