 With regard to concurrent validity of the Medtronic Patient Activity measurement, the Pearson correlation coefficient will be calculated between the daily Patient Activity minutes per day and two Actigraph parameters: daily activity count and steps per day. Correlation coefficients will be calculated for the baseline, 3-month, and 9-month monitoring periods to provide a greater number of sampling days. Correlation coefficients will also be calculated for changes in daily activity measurements between baseline and 3 months and baseline and 9 months to determine concurrent validity of change in daily activity measurements. 