Summary, in English
Rett syndrome (RTT) is a rare neurodevelopmental disorder usually affecting females. It is associated with multiple disabilities including intellectual disability leading to a high level of dependency in all aspects of daily living including participation in physical activities. The overall aim of this thesis was to investigate physical activity behaviors by developing measures of walking, describing patterns of physical behavior and influencing factors, and evaluating the effects of an intervention that focuses on participation in standing and walking activities (i.e. ‘uptime’ activities) in Danish girls and women with RTT. This thesis comprises four studies. In study I, measurement properties of a modified two-minute walk test (2MWT) and a modified RTT-specific functional mobility scale (FMS-RS) were determined. Forty-two girls and women with RTT aged 2.4–60.9 years were included. Comparison measures were the Clinical Severity Score (CSS), Rett Syndrome Gross Motor Scale (RSGMS) and the mobility domain in the Pediatric Evaluation of Disability Inventory (PEDI-m). In study II, patterns of sedentary behavior and physical activity were described in a population-based sample including 48 girls and women with RTT aged 5.5–60.5 years. Participants wore the activPAL and StepWatch Activity Monitor (SAM) for at least four days. In study III, facilitators and barriers to participation in ‘up-time’ were explored from the perspectives of parents and professionals using focus groups. Data was analyzed using thematic analysis. In study IV, the feasibility and effectiveness of an individualized 12-wk ‘uptime’ participation intervention (U-PART) were evaluated in 14 girls and women with RTT aged 5.6-48.3 years. Each individual program focused on participation in enjoyable activities to promote ‘uptime’ in home, school/day center and community settings. Feasibility was assessed using a study-specific questionnaire. Primary outcomes were sedentary time (activPAL) and daily steps (SAM). Secondary outcomes were gross motor skills (RSGMS), walking capacity (2MWT), quality of life (Quality of Life Inventory-Disability, QI-Disability) and participation-level goals (Goal Attainment Scaling, GAS). Outcomes were evaluated on four occasions: at baseline and after a 6-week interval, immediately following the 12-week intervention program and 12 weeks after the intervention program. Results showed low-moderate and moderate-high correlations between comparison measures and the 2MWT and FMS-RS, respectively. Intraclass correlation coefficients (ICC) were high for both the 2MWT (ICC=0.86-0.98) and FMS-RS (ICC=0.94-0.99) test values. In the 2MWT standard error of measurement (SEM) was 13.8m and minimal detectable difference (MDD) was calculated to be 38m (study I). On average 83.3% (SD 13.9%) of waking hours were spent in sedentary behaviors (n=48) and the median (IQR) daily step count was 5128 (2829–7704) (n=28). Advancing age and poorer walking skills were associated with higher levels of sedentary time (study II). Several facilitators and barriers of ‘uptime’ activities were identified within five subthemes relating to the individual girl/woman and her physical, organizational, social and attitudinal environment. The resources within each of the five areas needed to be balanced to enable optimal participation in ‘uptime’ activities (study III). Stakeholders perceived the U-PART intervention as feasible and significant positive effects were seen after the intervention in sedentary time (-4.1%), daily steps (+708 steps), 2MWT (+18.9m), QI-Disability (+2.8) and for individually determined goals. At follow-up, effects on sedentary time (-3.4%) and 2MWT (+12.4m) were maintained (study IV).In conclusion both walking measures showed good concurrent validity and test-retest reliability and have the potential to be used in both clinical practice and research (study I). High levels of sedentary time and low daily step counts were demonstrated in RTT (study II). Parents and professionals described how opportunity for participation in ‘uptime’ activities depended on a balance of facilitators and barriers within the individual with RTT and the environment (study III). Knowledge from study I-III enabled the planning and implementing of a health-promoting intervention. The U-PART intervention was considered feasible with regards to acceptability and practicality, and positive effects were seen in the outcomes of sedentary time, daily step count, walking capacity, quality of life and participation-level goals, some maintained after a further 12 weeks (study IV).This thesis contributes important knowledge to disability research in Denmark and internationally by focusing on the availability of valid outcome measures and health-promoting strategies in girls and women with RTT.