A-35 Free Communication/Poster - Epidemiology - Disease Prevention/Treament - Youth: JUNE 1, 2011 7:30 AM - 12:30 PM: ROOM: Hall B
Recent work has demonstrated decreased activity levels in boys with Duchenne muscular dystrophy (DMD) compared to healthy children, but we could find no investigations examining the change in activity level over time due to the natural course of disease progression.
PURPOSE: The purpose of this study was to determine the extent of reduction in activity level in boys with DMD and to explore the relationship of physical activity to muscle composition and functional ability.
METHODS: Six ambulatory boys with DMD (8.7+/-1.2 yrs) participated. Testing was done on two occasions with 16+/-5 mo between sessions. Activity was assessed for 7 days with an ActiGraph monitor, and activity levels were subsequently divided by intensity into light (500-1999 counts/min), moderate (2000-3000 counts/min), and hard (>3000 counts/min). Muscle composition was determined by localized 1H magnetic resonance spectroscopy of the soleus muscle at 3T. Relative concentrations of water and lipid were determined, and lipid:water ratios were calculated. Subjects also completed timed functional tests of 30ft walk and ascending 4 steps. Relationships were examined by correlation coefficients at each testing session.
RESULTS: Activity intensity decreased (light 7%, moderate 32%, hard 19%), and lipid:water ratios increased 81% between testing sessions. Relationships were found at baseline between: 1) moderate activity with 30ft walk (r=-.33) and 4steps (r=-.36); and 2) heavy activity with muscle composition (r=-.28), 30ft walk (r=-.33), and 4 steps (r=-.31). Relationships at the follow-up time session included: 1) moderate activity with muscle composition (r=-.59), 30ft walk (r=-.34), and 4 steps (r=-.59); and heavy activity with muscle composition (r=-.66), 30ft walk (r=-.35), and 4 steps (r=-.58).
CONCLUSIONS: The data from this pilot study provide information regarding the extent of activity level decline and muscle fatty infiltration in boys with DMD. The findings also demonstrate a relationship between activity level with both muscle composition and functional ability. With disease progression, these relationships appear to become even more pronounced. Further research is warranted to better understand the correlations between these variables and how they are impacted with therapeutic interventions for patients with DMD.