How to: Set the Activity Monitor Refresh Interval
Setting the refresh interval for Activity Monitor configures how often Activity Monitor obtains new information about instance activity. Activity Monitor runs queries on the monitored instance to obtain information for the Activity Monitor display panes. When the refresh interval is set to less than 10 seconds, the time that is used to run these queries can affect server performance.
To set the refresh interval
Open Activity Monitor. For more information, see How to: Open Activity Monitor (SQL Server Management Studio).
Right-click Overview, select Refresh Interval, and then select the interval in which Activity Monitor should obtain new instance information.