Physical fitness and physical behavior in (wheelchair-using) youth with spina bifida

Associations between low physical fitness, unfavorable physical behavior and higher cardiovascular and overall mortality are well known. Children with a physical disability like spina bifida (SB) are at high risk of decreased levels of physical fitness and unfavorable physical behavior. They seem to be prone to a vicious circle of decreased mobility and functional impairment, resulting in an inactive lifestyle, obesity, reduced health related quality of life, lower levels of physical fitness and decreased participation. Even though optimizing physical fitness in youth with disabilities are important goals in rehabilitation, there are no valid and reliable tests available to measure physical fitness in wheelchair-using youth with SB. Furthermore, evidence about physical behavior in this population is lacking. Although we expect that the majority does not comply to physical activity (PA) guidelines, we do not have objective evidence to truly understand the seriousness of physical inactivity problem in this population. The aims of this thesis were to develop valid and reliable physical fitness tests for wheelchair-using youth with SB, to objectively measure physical behavior, analyze facilitators and barriers for participation in PA and evaluate effectiveness of PA interventions. We performed three clinimetric studies. First we found that the Graded Wheelchair Propulsion Test showed significantly higher heart rate peak and higher VO2peak compared to the Graded Armcranking Exercise Test with a good reliability. Therefore, we advised to use wheelchair propulsion for measuring VO2peak in wheelchair-using youth with SB. Secondly, the Shuttle Ride Test (SRiT), a field-based propulsion test, was found to be highly valid and reliable to measure aerobic fitness. In the third study we found that the Muscle Power Sprint Test, the 10x5 Meter Sprint Test and the slalom test were highly valid and reliable for measuring skill-related fitness. We performed two observational studies using objective accelerometers to assess both types of physical activities and intensity. Only 19% (schooldays) – 8% (weekend days) of wheelchair-using youth with SB met the PA guidelines of the American College of Sports Medicine. An older age and the inability to walk influenced physical behavior negatively, gender and VO2peak were not associated with physical behavior. Interestingly, a large percentage of the variance in physical behavior remained unexplained, implicating that there are other important factors. We additionally performed qualitative research and systematic reviews and found that a wide variety of factors were associated with PA in both children with SB and in children with physical disabilities. Overall, competence in skills, sufficient fitness and self-efficacy were important personal factors. Environmental factors associated with PA included contact with and support from others, the use of assistive devices for mobility and care, adequate information regarding sports possibilities and availability and accessibility of playgrounds and sports facilities. Finally, we found that there was no effect of training on PA in children with physical disabilities, conflicting evidence for the effect of interventions with a behavioral component on the short term and no effect on the long term. More research using innovative approaches is needed to develop and investigate interventions for improving physical behavior