**3. Postural deficits and integrated balance performance**

Fear of falling is a major health concern among older adults and has even been reported in those who have no history of falls [24, 25]. The presence of fear of falling was defined as "low perceived self‐efficacy at avoiding falls during essential, nonhazardous activities of daily liv‐ ing" [26]. Fear of falling risk drastically increases with age and is known to affect quality of life in older adults, especially for women who fear that falling contains potentially serious outcomes [27–29]. These studies indicated that fear of falling in older women is a common and persistent complaint that is caused mainly by impairments of balance and mobility. The results for balance problems or fear of falling imply that early intervention might be impor‐ tant in the prevention and rehabilitation of balance deficits.

The development of sensitive tools that can quantify loss of balance is paramount to improv‐ ing quality of life in older adults. It is essential to perform biomechanical and functional anal‐ yses of the most representative kinematic and kinetic variables obtained from specific tasks, including the one‐leg standing test. Since the control of spinal function might include excit‐ ability in the motor pathway with fearful aspects of pain syndromes, the combined kinematic analysis based on spinal regions and kinetic indices from a force plate may provide compre‐ hensive postural integrity strategies to reduce the risk of injury.

Previous studies support the idea that older adults with LBP have reduced proprioceptive sensation on position‐reposition accuracy and have a higher prevalence of balance deficits [30–32]. Several other studies focusing on typical movement patterns in older adults with LBP identified increased postural sway and decreased lumbar spine motion [33, 34]. It has been reported that individuals with LBP demonstrate significantly decreased postural stabil‐ ity during one‐leg standing and other clinical balance tests [7, 8, 14]. However, the results of these studies lacked an understanding of three‐dimensional dynamic variables over time dur‐ ing one‐leg standing. Further, most clinical outcome studies are still not convincing in their measurements, and implications of functional activity need to be further investigated [35, 36]. For example, center of pressure (COP) displacement may provide useful information in quantifying standing postural stability as well as predicting dynamic balance [37]. However, the COP provides limited information, as it is only a two‐dimensional quantity.

Before one can quantify balance deficits, however, one must first understand their origins and the factors that directly or indirectly impact them. The assessment and classification of balance deficits due to spinal disorders have been carried out in different ways. Patients have been classified according to the injured or painful structure using imaging techniques (i.e., magnetic resonance imaging, computed tomography, and myelography). However, a patho‐ logic‐anatomic diagnosis is established in only 10–15% of all patients with disorders of the lumbar region [1]. Additionally, there is great variation in the reported prevalence of bal‐ ance deficits in older adults, which is associated with multiple factors, including poor health characteristics [38, 39]. Gender, age, body mass index (BMI), time since initial pain onset, and quality of life warrant further investigation for a complete understanding of the role of these factors in providing comprehensive tools to prevent fall injuries. Therefore, valid and reliable measurement tools for balance deficits that account for physiological and socioeco‐ nomic factors would be important for clinicians to develop rehabilitation and injury preven‐ tion strategies.

lumbar spine may cause musculoskeletal injuries, and altered coordination of the postural reaction might lead to compensatory responses to prevent injuries [14, 22, 23]. Quantifying postural compensation may lead to a better understanding of spinal movement patterns due to a fear of falling in order to clarify the relationship between kinematic and kinetic changes

The normalized kinematic index of the lumbar spine was calculated based on the three‐ dimensional rotation angle (*Rxyz*) and relative standing index between control and recurrent LBP groups. The ratio between standing duration and requested duration could be compared with the corresponding older adults' *Rxyz* values. The analysis time window excluded the initial transition time (5 s) from standing with bilateral legs to maintaining single, dominant

Fear of falling is a major health concern among older adults and has even been reported in those who have no history of falls [24, 25]. The presence of fear of falling was defined as "low perceived self‐efficacy at avoiding falls during essential, nonhazardous activities of daily liv‐ ing" [26]. Fear of falling risk drastically increases with age and is known to affect quality of life in older adults, especially for women who fear that falling contains potentially serious outcomes [27–29]. These studies indicated that fear of falling in older women is a common and persistent complaint that is caused mainly by impairments of balance and mobility. The results for balance problems or fear of falling imply that early intervention might be impor‐

The development of sensitive tools that can quantify loss of balance is paramount to improv‐ ing quality of life in older adults. It is essential to perform biomechanical and functional anal‐ yses of the most representative kinematic and kinetic variables obtained from specific tasks, including the one‐leg standing test. Since the control of spinal function might include excit‐ ability in the motor pathway with fearful aspects of pain syndromes, the combined kinematic analysis based on spinal regions and kinetic indices from a force plate may provide compre‐

Previous studies support the idea that older adults with LBP have reduced proprioceptive sensation on position‐reposition accuracy and have a higher prevalence of balance deficits [30–32]. Several other studies focusing on typical movement patterns in older adults with LBP identified increased postural sway and decreased lumbar spine motion [33, 34]. It has been reported that individuals with LBP demonstrate significantly decreased postural stabil‐ ity during one‐leg standing and other clinical balance tests [7, 8, 14]. However, the results of these studies lacked an understanding of three‐dimensional dynamic variables over time dur‐ ing one‐leg standing. Further, most clinical outcome studies are still not convincing in their measurements, and implications of functional activity need to be further investigated [35, 36]. For example, center of pressure (COP) displacement may provide useful information in quantifying standing postural stability as well as predicting dynamic balance [37]. However,

the COP provides limited information, as it is only a two‐dimensional quantity.

**3. Postural deficits and integrated balance performance**

tant in the prevention and rehabilitation of balance deficits.

hensive postural integrity strategies to reduce the risk of injury.

in older adults with recurrent LBP.

198 Innovations in Spinal Deformities and Postural Disorders

leg standing.

The quantification of balance deficits based on three‐dimensional kinematic and kinetic indi‐ ces is valuable to a number of populations, including older adults with LBP. It is generally accepted that individuals with LBP possess altered postural control as well as less‐refined proprioception [15, 40, 41]. Previous research has shown that control groups demonstrated significantly longer standing duration in the eyes‐open condition [7, 13]. Due to decreased proprioception, the pain‐avoiding strategies implemented by the LBP group may be more evident. When proprioception is limited, the differences in standing duration may explain the proprioceptive capability between groups [42]. The normalized kinematic index could be utilized to compare postural integration based on visual input as well as proprioceptive responses. This compensatory pattern needs to be further investigated for optimal injury pre‐ vention and the development of effective rehabilitation programs.

Studies have also reported poor coordination of balance performance in individuals with LBP; however, there is a lack of understanding about the individual kinetic and kinematic characteristics of trunk motion in older adults with balance deficits. Recent studies have been performed to evaluate the role of core stability in older adults with LBP [43–45], as kinematic changes of the trunk are compensated for by postural alignment and core spine stability [13, 15]. Further, a comprehensive investigation to determine postural steadiness might be help‐ ful to understand the control of postural segments, including the trunk, pelvis, and lower extremities, during one‐leg standing. The ability to adjust postural steadiness as a function of these regions is critical for activities of daily life, as increased balance sway was related not only to spinal motion but also to dynamic functional capacity in older adults with LBP [46]. Therefore, a change in postural steadiness might be related to an increase in kinetic stability [7], which reduces dynamic functional capacity in the trunk, pelvis, and lower extremities.

Older adults with LBP demonstrated differences in lumbar spine stability, possibly due to a pain avoidance strategy and compensation from the standing limb [7]. However, it is not clear how the kinematic chain reaction might change for whole body control mechanisms during one‐leg standing. Therefore, the normalized kinematic stability index of the body regions (thorax, pelvis, and bilateral thighs, shanks, and feet) and one‐leg standing duration might contribute to an integrated understanding of postural steadiness in older adults with LBP.

Several studies have used the one‐leg standing test to investigate postural control using dif‐ ferent outcome variables [7, 13, 47]. The one‐leg standing test can be divided into two phases: the dynamic phase and the static phase. The dynamic phase is defined as a rapid decrease of force variability during the first 5 seconds (s) of the test. The static phase is defined as the maintenance of a certain level of force variability. One study, which investigated the first 5 s of a 25 s duration test (dynamic phase), concluded that the first few seconds of the one‐leg standing test pose the greatest challenge to postural steadiness [48]. They concluded that if participants were unable to perform one‐leg standing for at least 5 s, they were at an increased risk for injurious falls. Other studies have investigated the static phase. High vari‐ ability during the first 5 s of the static phase of the one‐leg standing test was reported, which could potentially be caused by muscular or postural adjustments [7, 14]. Based on these find‐ ings, it might be possible to analyze the first 5 s increments of the static and dynamic phases of postural stability to discover different aspects of sensorimotor function that older adults with LBP use to enhance pain‐avoiding strategies.

It has been reported that impaired back muscle function may lead to an inability to adopt postural control strategies focused on increasing strength and self‐efficacy in older adults with LBP [49, 50]. These studies suggested that impaired back muscle function may lead to an adaptation of postural control strategies with the primary purpose of preventing pain and decreasing mobility of the painful region. By contrast, longer one‐leg standing duration in the control group can be explained by enhanced motor learning due to greater ability to perform functional activities and implement more functional postural control strategies.

Other studies supported the reorganization of trunk muscle representation at the motor cor‐ tex in individuals with recurrent LBP [51, 52]. Their results suggest that this reorganization is associated with deficits in postural control, which persist after the training effect takes place as LBP becomes chronic or recurrent. Eventually, these learned strategies become automatic defense mechanisms to prevent pain and further injury [15, 52].
