RESUMEN
INTRODUCTION: In this study we explored walking activity in a large cohort of boys with Duchenne muscular dystrophy (DMD). METHODS: Step activity (monitored for 7 days), functional ability, and strength were quantified in ambulatory boys (5-12.9 years of age) with DMD and unaffected boys. Ambulatory status was determined 2 years later. RESULTS: Two to 5 days of activity monitoring predicted weekly step activity (adjusted R2 = 0.80-0.95). Age comparisons revealed significant declines for step activity with increasing age, and relationships were found between step activity with both function and strength (P < .01). Our regression model predicted 36.5% of the variance in step activity. Those who were still ambulatory after 2 years demonstrated baseline step activity nearly double that of those who were no longer walking 2 years later (P < .01). DISCUSSION: Step activity for DMD is related to and predictive of functional declines, which may be useful for clinical trials.