This is just a warning message and you will currently always receive this on short runs. Traditionally calculations involving Running Economy and Efficiency are only considered for easy runs of around 40 minutes and upwards. However, we allow the system to calculate them for 'quality' data streams of 10 minutes or more. This often means that runs of less than 15 minutes will receive this message. It only prevents Running Economy analysis (not affecting the many other aspects of analysis) and so can be ignored. It is our intention to improve the user interface with regards to this in the future, to help explain and avoid any potential confusion.