I am no scientist or athletic trainer, but I do coach a Jr. Olympic track team and have taken classes that have taught me about the science behind training. If a player goes three days (72 hours) without training, the muscle memory and mass begins to break down a bit and then the players slowly loses what they have gained. That is why often times if you are sick for three or more days, suddenly things seem to be a bit tougher than they should be despite being back to full health.
If a player works hard during spring ball and then takes two months off in the summer, that player is going to lose all if not more than all they gained during that practice time.
At the same time, there is also a peak or a breaking point of players. If a player trains hard for enough time without break there is a natural breaking point for them and they get injured and begin to perform bad. For that reason, sometimes you will see a runner in cross country post a time slower at the beginning of the season than they did at the end of the previous season. They are training to peak at the end of the season and that results in common running fans questioning why a runner got “worse”.
With that muscle background we can now get into a bit more of the routine of current players.