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. 2023 Oct 6;13(1):16901.
doi: 10.1038/s41598-023-43401-6.

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

Michael Herzog  1   2 , Frieder C Krafft  3   4   5 , Bernd J Stetter  6   7 , Andrea d'Avella  8   9 , Lizeth H Sloot  3   4 , Thorsten Stein  6   3
Affiliations

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

Michael Herzog et al. Sci Rep. .

Abstract

The transitions between sitting and standing have a high physical and coordination demand, frequently causing falls in older individuals. Rollators, or four-wheeled walkers, are often prescribed to reduce lower-limb load and to improve balance but have been found a fall risk. This study investigated how rollator support affects sit-to-stand and stand-to-sit movements. Twenty young participants stood up and sat down under three handle support conditions (unassisted, light touch, and full support). As increasing task demands may affect coordination, a challenging floor condition (balance pads) was included. Full-body kinematics and ground reaction forces were recorded, reduced in dimensionality by principal component analyses, and clustered by k-means into movement strategies. Rollator support caused the participants to switch strategies, especially when their balance was challenged, but did not lead to support-specific strategies, i.e., clusters that only comprise light touch or full support trials. Three strategies for sit-to-stand were found: forward leaning, hybrid, and vertical rise; two in the challenging condition (exaggerated forward and forward leaning). For stand-to-sit, three strategies were found: backward lowering, hybrid, and vertical lowering; two in the challenging condition (exaggerated forward and forward leaning). Hence, young individuals adjust their strategy selection to different conditions. Future studies may apply this methodology to older individuals to recommend safe strategies and ultimately reduce falls.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Experimental setup. Left: Participant stands up from an instrumented chair with the custom-made robot rollator simulator. Full-body passive markers for motion tracking and EMG electrodes (data not included in this article) were placed on the body. Two movements were studied: sit-to-stand and stand-to-sit. Middle column: Three different support conditions were used: unassisted (top, handles not used), light touch (middle, palm on the handles), and full support (bottom, power grip). Right column: Two floor conditions were used: non-challenging (lab floor, top) and challenging (balance pads, bottom).
Figure 2
Figure 2
Process for identifying strategies, performed separately for each of the four combinations of sit-to-stand, stand-to-sit, and non-challenging, challenging floor conditions. For each variable, a matrix (e.g., GRFa/p) served as input for the variable-specific PCA (PCAGRFa/p). The input for the clustering consists of a coordinate system with axes formed by the extracted principal components of all variables, as well as the scores obtained from the PCAs. The extracted clusters constitute the strategies. Pi ith participant, UAi ith unassisted trial, FSi ith full support trial.
Figure 3
Figure 3
Distribution of trials among strategies. One dot represents one trial. The row indicates the strategy to which it belongs. The column shows to which participant it belongs. The support conditions are color coded as indicated by the legend. The labels on the right y-axis show how many trials were associated with the strategy written on the left y-axis.
Figure 4
Figure 4
Strategies of the non-challenging sit-to-stand task. (a) The strategies are given in different colors (see legend) and separated into rows according to the support condition. The CoM is depicted as an asterisk (*). (b) Means and standard deviations of the variables, aggregated by cluster. The gray shaded area illustrates the range of seat-off (mean ± s.d.). The red lines and corresponding p-values indicate significant differences revealed by the post-hoc tests (p < 0.017).
Figure 5
Figure 5
Strategies of the challenging sit-to-stand task. (a) The strategies are given in different colors (see legend) and separated into rows according to the support condition. The CoM is depicted as an asterisk (*). (b) Means and standard deviations of the variables, aggregated by cluster. The gray shaded area illustrates the range of range of seat-off (mean ± s.d.). The red lines and corresponding p-values indicate significant differences (p < 0.05).
Figure 6
Figure 6
Strategies of the non-challenging stand-to-sit task. (a) The strategies are given in different colors (see legend) and separated into rows according to the support condition. The CoM is depicted as an asterisk (*). (b) Means and standard deviations of the variables, aggregated by cluster. The gray shaded area illustrates the range of seat-off (mean ± s.d.). The red lines and corresponding p-values indicate significant differences revealed by the post-hoc tests (p < 0.017).
Figure 7
Figure 7
Strategies of the challenging stand-to-sit task. (a) The strategies are colored in different colors (see legend) and separated into rows according to the support condition. The CoM is depicted as an asterisk (*). (b) Means and standard deviations of the variables, aggregated by cluster. The gray shaded area illustrates the range of seat-off (mean ± s.d.). The red lines and corresponding p-values indicate significant differences revealed by the post-hoc tests (p < 0.017).
Figure 8
Figure 8
Example arm activity for two movements (left: sit-to-stand, right: stand-to-sit). Top: Spatial progression of the CoM and the lateral elbow marker. The black and red lines connecting the points illustrate the spatial progression. The distances between the points illustrate 5% of the total duration in each case. The cross-connections help assess whether the elbow and CoM moved at comparable speeds (as with nearly parallel cross-connections). Bottom: The whole-body movement is shown along with the plots above.
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