TriDot defines an athlete's "Preseason" as the time beginning a few weeks after that athlete’s last triathlon in one season to about four months before their first one in the following season . By contrast, their “In-season” is the time starting about four months before their first race of the season through their last race of that same season.  

“Preseason Training” provides athletes with the best opportunity to improve their functional threshold power/pace for the coming season.  This threshold represents their race potential.  The preseason also gives athletes the unique opportunity to do the training that's optimal for them versus being forced to do the long sessions or high volume necessary to complete the race distance--unless of course these type of sessions benefit their fitness. 

“In-season Training” takes an athlete’s race potential and develops race-specific stamina that is a percent of their functional threshold capacity.  In-season performance is always limited by preseason preparation.