Physical activity capacity in children with myelomeningocele

Thirty-three children (10 to 15 years of age) with myelomeningocele were studied to determine isometric muscle strength of hip and knee extension, range of hip and knee extension, usual and maximal ambulatory velocities, maximal aerobic capacity, and the energy cost (oxygen uptake) of ambulation versus wheelchair usage in subjects who both walked and wheeled. Subjects were placed into one of four groups depending on their level of motor function (those with motor levels at L2 and above, L3-4, L5 to sacral, and without motor deficit). Maximal ambulatory velocity correlated with strength of the hip extensor (r = 0.85) and knee extensor (r = 0.81) muscles. All variables were found highly dependent upon the level of motor function. Subjects with the greatest deficits had the most significant impairments and vice versa. It was found, however, that subjects without motor deficit had impairments in the usual speed of ambulation (9%), maximal running velocity (20%), and VO2 max (13%). These deficits were due to the measured strength deficits in these subjects as compared to normal values. This finding underscores the importance of quantitative assessment of muscle strength as significant deficits in strength can be missed with manual muscle testing. In those subjects who walked and wheeled, wheeling was found much more energy efficient. Wheeling at 4.8 km/hr was 11% more efficient than walking at 33% that velocity.