The amount of condition your players lose depends on the drills you select for the training session. Touch a drill to see how intense the drill is and the condition percentage required. You can view the total impact on player condition for all drills in the session as in the following image:
Manage your players' condition levels carefully as you may want to leave enough time for your players to recover and be well rested for upcoming matches. Remember that each player recovers 6% condition every 3hrs.
Note: Keep in mind that some tactics, e.g. the defensive pressing style "High" and marking style "Man-to-man", also consume more condition during a match than some other tactics.