Beam walking can detect differences in walking balance proficiency across a range of sensorimotor abilities

Highlights

• Most balance assessments are of insufficient difficulty to evoke balance failures.

• Beam walking may provide a simple and stringent assessment of balance failures.

• Beam walking was used to probe balance proficiency across sensorimotor abilities.

• Beam walking discriminated between expert, novice and impaired balance proficiency.

• Beam walking may prove useful as a clinical and research tool.

Abstract

The ability to quantify differences in walking balance proficiency is critical to curbing the rising health and financial costs of falls. Current laboratory-based approaches typically focus on successful recovery of balance while clinical instruments often pose little difficulty for all but the most impaired patients. Rarely do they test motor behaviors of sufficient difficulty to evoke failures in balance control limiting their ability to quantify balance proficiency. Our objective was to test whether a simple beam-walking task could quantify differences in walking balance proficiency across a range of sensorimotor abilities. Ten experts, ten novices, and five individuals with transtibial limb loss performed six walking trials across three different width beams. Walking balance proficiency was quantified as the ratio of distance walked to total possible distance. Balance proficiency was not significantly different between cohorts on the wide-beam, but clear differences between cohorts on the mid and narrow-beams were identified. Experts walked a greater distance than novices on the mid-beam (average of 3.63 ± 0.04 m verus 2.70 ± 0.21 m out of 3.66 m; p = 0.009), and novices walked further than amputees (1.52 ± 0.20 m; p = 0.03). Amputees were unable to walk on the narrow-beam, while experts walked further (3.07 ± 0.14 m) than novices (1.55 ± 0.26 m; p = 0.0005). A simple beam-walking task and an easily collected measure of distance traveled detected differences in walking balance proficiency across sensorimotor abilities. This approach provides a means to safely study and evaluate successes and failures in walking balance in the clinic or lab. It may prove useful in identifying mechanisms underlying falls versus fall recoveries.

Introduction

There is an urgent need for a quick, simple, and low-cost physical performance measure that can detect differences in balance performance over a broad range of sensorimotor abilities; from individuals with motor impairment to elite athletes recovering from a concussion [1]. Balance ability while walking is a critical factor in determining quality of life [2] yet it is especially difficult to assess. Currently there is no accepted laboratory-based approach to evaluate and study balance ability during walking [3]. Moreover there are no specific tests that reliably assess walking balance impairment or fall risk in a clinical setting [4]. These gaps may be attributable to the scarcity of easily implemented clinically feasible techniques, metrics, and analyses that probe for and quantify failures in human balance performance [5], [6]. This limits the identification of neuromechanical principles that govern better walking balance and the determination of fall risk in patients.

Current laboratory-based biomechanical approaches used to study walking balance typically focus on movements or measures during successful performance. Many laboratory studies characterize the challenge to balance control during walking [7], the strategies used to maintain balance while walking [8], or the strategies used to restore balance after a perturbation to walking [5], [9], [10]. However, the relationship between these strategies or metrics to balance proficiency is unclear.

Clinical balance instruments such as the Berg Balance Scale, the Activities-specific Balance Confidence Scale, the Fullerton Advanced Balance Scale, and the Dynamic Gait Index require little in the way of specialized equipment and are relatively quick and inexpensive to administer. Yet they are not without their limitations. Many of these tools provide a nonspecific evaluation of balance rather than an assessment that specifically targets walking, the behavior when most falls occur [11]. For example they often pool static and dynamic [12], as well as standing and walking [13] balance tasks. However, there is little correlation between such elements [9], [14]. Many of these clinical balance tests show ceiling effects and are usually not sensitive enough to small improvements or decreases in balance ability [15].

The inability of laboratory and clinically based measures to quantify balance proficiency may stem from the use of motor behaviors that are of insufficient difficulty to evoke failures in balance control. If successful balance is defined by the absence of falls [16] then experimental conditions should be of sufficient difficulty to result in a loss of balance. Without conditions that allow for the identification of failures establishing the proficiency with which someone can maintain their balance is speculative. It depends on previously established statistical relationships between a given metric and a self-reported history of falls [17] rather than a direct assessment of walking balance proficiency.

Beam walking has been used to examine the effects of age [14], [18] on walking balance, as well as physical guidance and error augmentation on motor learning [19]. More recently beam walking has been used in attempts to identify cortical events that precede a loss of balance [20]. However its capacity to differentiate levels of walking balance proficiency across a range of sensorimotor abilities and specifically individuals with mild balance impairment remains unknown. Therefore the objective of this study was to test whether a simple and low-cost beam-walking task along with an easily interpreted metric could discriminate across the spectrum of walking balance proficiency (i.e. expert to impaired). Beam walking (Fig. 1) presents a challenge to balance control and provides a simple and stringent assessment of balance failures; individuals are either on or off the beam.