Abstract
BackgroundRoot mean square (RMS) of trunk acceleration is seen frequently in gait analysis research. However, many studies have reported that the RMS value was related to walking speed. Therefore, the relationship between the RMS value and walking speed should be considered when the RMS value is used to assess gait abnormality. We hypothesized that the RMS values in three sensing axes exhibit common proportions for healthy people if they walk at their own preferred speed and that the RMS proportions in abnormal gait deviate from the common proportions. In this study, we proposed the RMS ratio (RMSR) as a gait abnormality measure and verified its ability to discriminate abnormal gait.MethodsForty-seven healthy male subjects (24–49 years) were recruited to examine the relationship between walking speed and the RMSR. To verify its ability to discriminate abnormal gait, twenty age-matched male hemiplegic patients (30–48 years) participated as typical subjects with gait abnormality. A tri-axial accelerometer was attached to their lower back, and they walked along a corridor at their own preferred speed. We defined the RMSR as the ratio between RMS in each direction and the RMS vector magnitude.ResultsIn the healthy subjects, the RMS in all directions related to preferred walking speed. In contrast, RMSR in the mediolateral (ML) direction did not correlate with preferred walking speed (rs = -0.10, p = 0.54) and represented the similar value among the healthy subjects. Moreover, the RMSR in the ML direction for the hemiplegic patients was significantly higher than that for the healthy subjects (p < 0.01).ConclusionsThese results suggest that the RMSR in the ML direction exhibits a common value when healthy subjects walk at their own preferred speed, even if their preferred walking speed were different. For subjects with gait abnormality, the RMSR in the ML direction deviates from the common value of healthy subjects. The RMSR in the ML direction may potentially be a quantitative measure of gait abnormality.
Highlights
Root mean square (RMS) of trunk acceleration is seen frequently in gait analysis research
We hypothesized (1) that the RMS values in three sensing axes exhibit common proportions for healthy people if they walk at their own preferred speed and (2) that the RMS proportions in abnormal gait deviate from the common proportions
As a result of such body movement optimization, it was considered that the RMS ratio (RMSR) in the sagittal plane and the ML direction converged to the common values in normal gait
Summary
Root mean square (RMS) of trunk acceleration is seen frequently in gait analysis research. The benefits of accelerometers are as follows: low cost compared with commonly used motion analysis equipment; measurement not being limited to a laboratory environment; and accelerometers being small in size and lightweight, Root mean square (RMS) of acceleration is seen frequently in gait analysis research [3,4,5,6,7,8,11,12,15,16,17]. This parameter constitutes a statistical measure of the magnitude of acceleration. It is necessary to consider the walking speed when RMS is used to assess gait abnormality
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