Bonita J. Sawatzky, PhD;

Heather M. Macdonald, BSc;

Nicola Valentine, BSc*; OT,

Kathryn Duff, BPE

INTRODUCTION

There are several factors that determine the functional level at which children function effectively in their wheelchair. Initially, the type and set-up of the wheelchair should be chosen according to the mobility needs of the child. It has often been observed that a patient has been prescribed a generic type chair that does not allow the child to function to the best of their ability. In other cases where a chair may be fitted specifically for a patient, a lack of instruction and training from therapists, or muscular weakness of the child, may prevent the child from propelling themselves with ease and efficiency. Wheeling efficiency can be measured by energy expenditure. Research regarding comparisons of energy cost during ambulating and wheeling have shown that for those children who use both modes of mobility, wheeling is more energy efficient. However, there is limited information available on energy cost during wheeling and the factors may effect it for those children who rely solely on wheelchairs.

Wheeling efficiency or energy efficiency is the amount of oxygen consumed (mL) per unit of body mass (kg) per unit of distance traveled (mL/kg/m). This analysis requires that the subject reach a steady state of exercise (constant velocity and constant oxygen consumption level), be it slow or fast. Energy efficiency or expenditure (mL/kg/m) is a well-accepted measurement in gait analysis to study the effect of assistive devices such as orthotics, crutches, and protheses, as well as, surgical interventions in children and adults with cerebral palsy, paraplegia or amputations ^1-5. It can be a valuable tool as it incorporates distance traveled and accounts for the physical ability of the individual as well as the effectiveness of the assistive device being used.

Our experience with a multi-disciplinary, outpatient, spina bifida clinic has outlined other concerns in this population. Approximately one-third of the 300 children in our clinic use wheelchairs on either a full, or part-time, basis. Poor wheelchair setup and minimal knowledge of wheelchair skills are common observations made by our therapists. Simple and valuable skills such as mounting curbs are impossible for some children as the placement of their wheels in relation to their centre of mass makes balancing on two wheels difficult and dangerous. Weight gain, low levels of physical activity and poor self-esteem are also critical issues in the health of this population. These factors may all be important in assessing energy expenditure in children with spina bifida.

PURPOSE: The purpose of this study was to examine the wheeling efficiency in children with spina bifida, and to determine what factors affect wheeling performance.

Recruitment: Subjects were recruited from the spina bifida clinic at our provincial tertiary hospital for children. Subjects were included if they met the criteria of; 1) age between 8 and 18 and 2) primary wheelchair user (uses wheelchair for at least 50% of ambulation). This study was approved by our university ethics board and the local hospital review committee.

A majority of the children were able to transfer independently in and out of their wheelchair (n =28). Those children who required assistance for transfers (n =5) showed trends of increased time to ascend the ramp, and higher energy expenditure during the five-minute wheeling test when compared to the children who could transfer independently. The differences noted are not significant. There was no difference between the two groups with regards to self-esteem.

There was a significant difference between the mean % body fat of the boys (21.9 + 4.4, n = 11) when compared to the girls (30.3 + 4.3, n = 16) (p<.0001). When compared to normals both the boys and girls in our study fall in the "moderately high" category for percent body fat. When grouped together, the overall percent body fat for boys and girls correlated significantly with the total score (67.5 + 30.5, n = 33) on the Piers-Harris self-concept scale (r = .25; p<.0001). Girls who participated in physical activity on a daily basis had a lower percent body fat than girls who participated on a monthly basis (p<.05, not significant for the other groups).

BMI was compared to the USA Growth Study results for girls and boys. No significant difference was found between the girls and boys in this study. The average BMI of the boys (19.3 + 4.1, n = 7) corresponded to the 53^rd percentile. The average BMI for the girls (21.3 + 4.7, n =16) fell into the 63^rd percentile. There was no significant difference between the BMI % ile of girls and boys within our study population.

This preliminary study has provided insight into the nature of wheelchair function in a paediatric spina bifida population. The finding that both strength and involvement in physical activity have an effect on a child’s wheeling efficiency is significant in terms of the health and well-being of children with spina bifida. Disabled populations are targets for exercise intervention as increased involvement can prevent further deterioration of the particular disability, and can deter the occurrence of a second disability. In addition, improved cardio-respiratory fitness and muscular strength may enable a wheelchair user to carry out daily activities using basic wheelchair skills with greater ease and independence. This investigation also outlined wheelchair set-up as a worthy target for future studies. The variability in set-up parameters including camber, centre of mass and dump angle was great. It is noted by other groups that wheelchair design is one of the most important factors in determining the level of function for children with disabilities⁷. Therefore we hope to conduct a study where we can control for wheelchair set-up parameters using a within subject study design.