Niantic is changing the way trainers can train at a friendly Gym. As it stands now, whenever a trainer tries to train at a gym that is controlled by the same team, a limit of one Pokemon is applied. Therefore, when battling the Pokemon of other fellow team members, you fight them all using only one of your Pokemon. Niantic’s future update will change this mechanic to allow a trainer to use a full roster of six Pokemon.
But that’s not all, Niantic also stated that when battling against team member’s Pokemon with higher CP level, the CP level of the gym’s Pokemon will be adjusted to meet the CP levels of your Pokemon. In other words, if you have a CP 1000 Snorlax and the friendly gym you are training at have CP 2000 Lapras then the Lapras’ CP level will adjust to a lower CP that matches your CP1000 Snorlax.
It is important to note that the CP reduction only works when you are training at a friendly gym. It will not work when trying to take over a rival team’s gym.
What are the benefits of this new feature? First, it will allow for lower level trainers to contribute in leveling up friendly gyms quicker. Also, lower level trainers will be able to gain more XP and stardust when leveling up the gyms. I imagine that this is an effort by Niantic to help bridge the gap of trainer levels and pokemon CP levels.