Title: Influence of dual-task on sit-to-stand-to-sit postural control in Parkinson’s disease Ângela Fernandes (PhD) Escola Superior da Tecnologia de Saúde do Instituto Politécnico do Porto, Área Científica de Terapia Ocupacional, Centro de Estudo do Movimento e da Atividade Humana, PORTUGAL Faculdade de Engenharia, Universidade do Porto, PORTUGAL E-mail: [email protected] Andreia S. P. Sousa (PhD) Escola Superior da Tecnologia de Saúde do Instituto Politécnico do Porto, Área Científica de Fisioterapia, Centro de Estudo do Movimento e da Atividade Humana, PORTUGAL E-mail: [email protected] Joana Couras (BSc) Escola Superior de Tecnologia da Saúde do Instituto Politécnico do Porto, Área Cientifica de Terapia Ocupacional, PORTUGAL E-mail: [email protected] Nuno Rocha (PhD) Escola Superior da Tecnologia de Saúde do Instituto Politécnico do Porto, Área Científica de Terapia Ocupacional, Laboratório de Reabilitação Psicossocial, Centro de Estudo do Movimento e da Atividade Humana, PORTUGAL 1 E-mail: [email protected] João Manuel R. S. Tavares (PhD) Instituto de Ciência e Inovação em Engenharia Mecânica e Engenharia Industrial, Departamento de Engenharia Mecânica, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, PORTUGAL E-mail: [email protected] Phone: +351 22 508 1487 / FAX: Phone: +351 22 508 1445 (corresponding author) 1 Abstract 2 Postural control deficits are the most disabling aspects of Parkinson's disease (PD), 3 resulting in decreased mobility and functional independence. The aim of this study was 4 to assess the postural control stability, revealed by variables based on the centre of 5 pressure (CoP), in individuals with PD while performing a sit-to-stand-to-sit sequence 6 under single- and dual-task conditions. 7 An observational, analytical and cross-sectional study was performed. The sample 8 consisted of 9 individuals with PD and 9 healthy controls. A force platform was used to 9 measure the CoP displacement and velocity during the sit-to-stand-to-sit sequence. The 10 results were statistically analysed. 11 Individuals with PD required greater durations for the sit-to-stand-to-sit sequence than 12 the controls (p<0.05). The anteroposterior and mediolateral CoP displacement were 13 higher in the individuals with PD (p<0.05). However, only the anteroposterior CoP 14 velocity in the stand-to-sit phase (p=0.006) was lower in the same individuals. 15 Comparing the single- and dual-task conditions in both groups, the duration, the 16 anteroposterior CoP displacement and velocity were higher in the dual-task condition 17 (p<0.05). 18 The individuals with PD presented reduced postural control stability during the sit-to- 19 stand-to-sit sequence, especially when under the dual-task condition. These individuals 20 have deficits not only in motor performance, but also in cognitive performance when 21 performing the sit-to-stand-to-sit sequence in their daily life tasks. Moreover, both 22 deficits tend to be intensified when two tasks are performed simultaneously. 23 24 Keywords: Dual-task; Parkinson's; Postural Control; Sit-to-Stand-to-Sit. 25 1 26 1. INTRODUCTION 27 Parkinson's disease (PD) is considered the second most common neurodegenerative 28 disorder, affecting about 1% of the world's current population (1, 2). Some projections 29 indicate a large increase of this prevalence over the coming decades (2). 30 At the moment, the aetiology is explained by genetic predisposition and the presence of 31 toxic environmental factors (3, 4). The majority of individuals with PD present an 32 inadequate interaction between systems responsible for body balance, including the 33 vestibular, visual and proprioceptive systems. Consequently, these individuals tend to 34 shift their centre of gravity forward, and therefore, have difficulty to perform 35 compensatory movements to require balance (5). The transition from sitting to standing 36 and standing to sitting are components of some everyday functional tasks that are highly 37 demanding from a postural control perspective. In fact, the sit-to-stand-to-sit (STSTS) 38 sequence implies the involvement of anticipatory postural adjustments (APAs) to 39 movement performance (6-8). Hence, the study concerning the STSTS sequence can 40 contribute to clarify postural control requirements during daily activities. The variability 41 and efficiency of functional movements require an appropriate postural control that 42 depends on APAs to maintain stability of internal and external disturbances, taking into 43 account the context and the task (9). The planning of APAs involves various structures 44 of the central nervous system (CNS), such as the pre-motor cortex, supplementary 45 motor area, basal ganglia and cerebellum (10, 11) that, through independent channels, 46 convey information to the reticular formation, such as the pedunculopontine nucleus, 47 which is important to modulate the APAs (12). The neural connection between the basal 48 ganglia and the pedunculopontine nucleus is through the corticostriatal-pallidum- 49 pedunculopontine circuit, which is compromised in individuals with PD leading to 50 postural control deficits. This is manifested in the changes in the activation of postural 2 51 muscles in the form of APAs (10, 13-15). As the CNS is responsible for the motor 52 modulation circuits, which are compromised in individuals with PD, there is a decrease 53 in postural control and consequently, repercussions in the performance of tasks, like 54 STSTS sequences (16-18). This decreased postural control was demonstrated through 55 CoP displacement variables. The CoP displacement reflects the orientation of body 56 segments and corrective responses that control the centre of mass over the base of 57 support (19), resulting from the combination of descending motor commands and the 58 mechanical properties of the surrounding muscles (20). In situations of dual-task, the 59 use of cortical resources to perform motor tasks can affect or influence the performance 60 of one or both tasks (21-23). Despite the importance of the postural control stability for 61 the STSTS sequence performance and the impact of PD on the postural control system, 62 few studies have assessed these issues and only the sit-to-stand sequence has been 63 addressed. Additionally, no study has evaluated this task under high cognitive 64 demanding conditions. Based on these facts, the objective of the present study was to 65 analyse the postural control stability in individuals with PD in single- and dual-task 66 conditions. More specifically, the postural stability was assessed through representative 67 CoP displacement variables in the anteroposterior and mediolateral directions 68 (displacements and velocities), in the five phases of the STSTS sequence in single- and 69 dual-task conditions. Based on the results obtained by Bhatt et al. (16) and on the neural 70 dysfunction involving postural control pathways, a reduced postural control stability in 71 individuals with PD can be hypothesised during the preforming of the STSTS sequence. 72 This reduced stability would be amplified in these individuals when the STSTS 73 sequence is performed in the dual-task condition. 74 75 2. MATERIALS AND METHODS 3 76 2.1. Study Design and Participants 77 A cross-sectional study was implemented using a non-probabilistic (24) sample of 9 78 individuals with PD and 9 healthy controls, aged between 52 and 80 years old. The 79 individuals diagnosed with PD were patients from the Parkinson's Association, Porto, in 80 Portugal, while the healthy controls were community-dwelling volunteers, mainly from 81 Porto. 82 Subjects were excluded if they presented one of the following criteria: severe cognitive 83 impairment (screened using the Montreal Cognitive Assessment (MoCA) test (25)); 84 incapable of performing the sit-to-stand or stand-to-sit sequence independently; and 85 unable to speak. Severely disabled PD patients (> 3 Hoehn and Yahr scale (26)), 86 patients diagnosed with any other neuromuscular disease, and those who had undergone 87 deep brain stimulation through subthalamic surgery or were taking cholinergic 88 medication were also excluded. Healthy controls that had been diagnosed as adults with 89 any neuromuscular disorder or that could not be considered sedentary according to the 90 Centre for Disease Control for the American College of Sports Medicine, were also 91 excluded (27). 92 A trained researcher conducted the data collection based on a structured protocol. The 93 study was approved by the Ethical Review Board of “Escola Superior de Tecnologia da 94 Saúde - Instituto Politécnico do Porto”, in Portugal. Written informed consent, 95 according to the Helsinki Declaration, was obtained from all participants. 96 97 2.2. Instruments 98 The data collected from all participants included the sociodemographic characteristics 99 age, gender, height, weight and level of education, and years of disease, cognitive 100 performance (assessed using the MoCA test), Hoehn and Yahr scale and the CoP data 4 101 acquired using a force platform (model FP4060-8 from Bertec Corporation (USA)) 102 under the single- and dual-task conditions. 103 The scale of Hoehn & Yahr (1967) evaluates the severity of overall dysfunction in 104 individuals with PD. It is a 7-point scale, in which each point represents a different 105 stage of the disease (stages 1 to 5, including 1.5 and 2.5). The scale increases with the 106 severity of dysfunction along with the stage of the disease (26). The MoCA test consists 107 of eight fields: visuospatial, nomination, memory, attention, language, abstraction, 108 deferred evocation and orientation. The performance of an individual is calculated by 109 the addition of the scores obtained in each of the domains, and the maximum that can be 110 reached is equal to 30 points (25, 28). 111 For the evaluation of the postural control, the data from the force platform was acquired 112 at a sampling rate of 1000 Hz (29). The platform was connected to a Bertec AM 6300 113 amplifier (USA) and in turn, this was connected to an analog-digital converter from 114 Biopac Systems, Inc. (USA), and to an analog board of Qualysis Track Manager 115 (Sweden) that can be used for stabilometric analyses. The stabilometric measurements 116 comprise the assessment of balance in the orthostatic position through body movements, 117 taking into account the anteroposterior (Fx), mediolateral (Fy) and vertical (Fz) 118 components of the ground reaction force. For this, it is necessary to monitor the 119 movement of the CoP in the anteroposterior (CoPAP) and mediolateral (CoPML) 120 directions (30). The signal related to the CoP movement was filtered using a fourth- 121 order Butterworth low pass filter with a cut-off frequency of 20 Hz (31). 122 The attention level and consequently, the motor control perturbations were attained 123 through a cognitive secondary task, namely the Stroop colour word test. This test 124 consists in the enunciation of the visual colour instead of the written one. The number 5 125 of errors and the number of named items were used for analysis (32) during a pre- 126 defined time (60 seconds) for both groups. 127 128 2.3. Procedures 129 After an explanation of all the procedures involved, all individuals performed the study 130 with shorts and standard shoes (33). The height of the chair seat was adjusted to 100% 131 of the lower leg length (from the knee joint to the ground), and 2/3 of the femur 132 supported on the seat was used as a reference for the subjects to be considered in the 133 sitting position. In the single-task condition, the subjects were asked to rise from sitting 134 with a self-selected speed without using their upper limbs (34), then remain for 60 135 seconds in the standing position, looking at a point two meters away at eye level. After 136 this interval, subjects were instructed to sit, again without any kind of support and at a 137 self-selected speed. In the dual-task condition, all the previous procedures were 138 repeated; however, the subjects were required to perform the Stroop test during the 139 performing of the STSTS sequence (28). The test words in different colours were 140 projected on a wall at eye level. The subjects were instructed to name the colour instead 141 of reading the word and no other specific instructions were given. The words were 142 present according to each participant’s responses during a pre-defined period of 60 143 seconds. A one minute rest between each trial was allowed, and the necessary 144 repetitions were performed in order to obtain three valid trials for each subject. 145 The CoP displacement variables were analysed over the five phases of the STSTS 146 sequence. For this, the sit-to-stand-to sit sequence was divided into five phases: sitting 147 phase - phase 1, sit-to-stand phase - phase 2, standing phase - phase 3, stand-to-sit phase 148 - phase 4, and sitting phase - phase 5. The procedures used to identify the phases are 149 shown in Table 1. 6 150 < Insert Table 1 about here > 151 152 The data acquisition was always performed by the same investigator to ensure the 153 reproducibility of the procedures. The data analysis was performed using the Matlab 154 software (MathWorks, USA) and Acqknowledge software (Biopac Systems, Inc. USA). 155 156 2.4. Statistical Analysis 157 Descriptive statistical analyses were performed using proportions and measures of 158 central tendency and dispersion. 159 The independent sample t test and Chi square test were performed to examine whether 160 there were significant differences between the groups in terms of the sociodemographic 161 and anthropometric variables. The multiple analysis of variance (MANOVA) test was used 162 to analyse the interaction between the groups (PD and controls) and the conditions 163 (single- and dual-task). The Bonferroni analysis was used as a post-hoc test to 164 determine the differences in single- and dual- task conditions in each group and to 165 determine for each condition the differences between the groups (PD and controls). The 166 number of errors and the number of correctly named items for the Stroop test were used 167 as covariates in the analysis. Two-tailed tests were used in all analyses, and p < 0.05 168 was adopted for statistical significance. All statistical analyses were conducted using 169 IBM SPSS Statistics 22.0 (SPSS, Inc., Chicago, IL, USA). 170 171 3. RESULTS 172 The 9 PD individuals (66.7% male) had a mean age of 66 years old (standard deviation 173 (SD) = 8.2), a mean education of 7.7 years (SD = 5.6) and a mean number of years with 174 PD 10.22 (SD 5.38). Most of these participants were classified in stage 1 and 1.5 of the 7 175 Hoehn and Yahr scale. The 9 healthy controls (44.4% male) had a mean age of 63.9 176 years (SD = 8.1) and a mean education of 7.8 years (SD = 4.6). The Mann-Whitney test 177 and chi-square test showed no significant differences between the two groups studied, 178 Table 2. 179 180 < Insert Table 2 about here > 181 182 The MANOVA test showed that in phase 1, no significant differences were found 183 between the groups (between-subjects) or conditions (within-subjects) and also no 184 significant interaction was found between group and condition, Table 3. 185 186 < Insert Table 3 about here > 187 188 In phase 2, a significant difference between the groups was found. The individuals with 189 PD presented a greater duration (p=0.047) compared to the healthy controls. The Post- 190 hoc analysis showed that these differences occurred only in the dual-task condition 191 (p=0.005). However, no differences between conditions or any significant interaction 192 between groups and conditions were found. 193 In phase 3, the differences between groups were found in terms of the duration and 194 CoPAP displacement. The duration was significantly greater in the PD individuals than 195 in the healthy controls (p<0.001). These differences occurred both under single- 196 (p<0.001) and dual-task (p=0.004) conditions. The CoPAP displacement was 197 significantly higher in the individuals with PD in comparison to the healthy controls 198 (0.015). The Post-hoc analysis showed that these differences occurred under the dual- 8
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