An evaluation of the 30-s chair stand test in older adults: frailty detection based on kinematic parameters from a single inertial unit

Abstract

Background: A growing interest in frailty syndrome exists because it is regarded as a major predictor of co-morbidities and mortality in older populations. Nevertheless, frailty assessment has been controversial, particularly when identifying this syndrome in a community setting. Performance tests such as the 30-second chair stand test (30-s CST) are a cornerstone for detecting early declines in functional independence. Additionally, recent advances in body-fixed sensors have enhanced the sensors' ability to automatically and accurately evaluate kinematic parameters related to a specific movement performance. The purpose of this study is to use this new technology to obtain kinematic parameters that can identify frailty in an aged population through the performance the 30-s CST.

Methods: Eighteen adults with a mean age of 54 years, as well as sixteen pre-frail and thirteen frail patients with mean ages of 78 and 85 years, respectively, performed the 30-s CST while their trunk movements were measured by a sensor-unit at vertebra L3. Sit-stand-sit cycles were determined using both acceleration and orientation information to detect failed attempts. Movement-related phases (i.e. impulse, stand-up, and sit-down) were differentiated based on seat off and seat on events. Finally, the kinematic parameters of the impulse, stand-up and sit-down phases were obtained to identify potential differences across the three frailty groups.

Results: For the stand-up and sit-down phases, velocity peaks and "modified impulse" parameters clearly differentiated subjects with different frailty levels (p < 0.001). The trunk orientation range during the impulse phase was also able to classify a subject according to his frail syndrome (p < 0.001). Furthermore, these parameters derived from the inertial units (IUs) are sensitive enough to detect frailty differences not registered by the number of completed cycles which is the standard test outcome.

Conclusions: This study shows that IUs can enhance the information gained from tests currently used in clinical practice, such as the 30-s CST. Parameters such as velocity peaks, impulse, and orientation range are able to differentiate between adults and older populations with different frailty levels. This study indicates that early frailty detection could be possible in clinical environments, and the subsequent interventions to correct these disabilities could be prescribed before further degradation occurs.

Figures

Figure 1

Raw MTx signals during the 30-s CST of one pre-frail subject. The blue line is the X-Orientation signal, the green line is the Z-Acceleration signal and the red line is the Z-Position signal from a signal sit-stand-sit cycle. Impulse, stand-up and sit-down phases are also marked.

Figure 2

Explanation of the impulse (A-D) or body management (1–4) parameters. Numbers 1 to 4 outline the maximum lean backwards and forwards to sit-down and stand up: “TurnB_Sit”, “TurnF_Sit”, “TurnB_Up” and “TurnF_Up”. Capital letters refer to the active and passive impulse to achieve the standing and corresponding sitting positions: “+” and “-“ Up “modified impulses” and “+” and “-“ Down “modified impulses”. Signals are raw MTx ones during the test performed by a pre-frail subject: Z-position (red), Z-acceleration (green) and X-orientation (blue).

Figure 3

Box plots of the accelerometer-derived parameters which differentiate between groups for the pairwise comparisons. (a) represents the time invested for the impulse phase, left side, and the X-orientation range during the impulse phase, right side. (b) represents the Z-acceleration minimum values during the stand-up and sit-down and. (c) represents the Z-acceleration AUC for the negative and positive impulse when standing-up and sitting-down. Finally, (d) represents the maximum and minimum Z-velocity peaks during the stand-up and sit-down.

Figure 4

Movement patterns of raw MTx signals (Z-position, X-orientation, Z-acceleration) for frail (a), pre-frail (b), and healthy subjects (c). The circle outlines the extra forward and backward lean for more frail subjects and the arrows features the time duration and X-orientation range.