There are many experts and articles on the many long term benefits of sports and activities for our youth. There are also many opinions as to what players should do (and when) to better develop their talents. Attached / linked are two good articles worth reading on this issue, in particular for “pre-teens”.
One point I took away is that players should do roughly as many hours per week of physical activity as they are old (ten hours for a ten year old). Football skills are definitely developed at a younger age and some specialisation is encouraged during this golden period of learning.
Importantly, however, this should not exclude involvement in other sports and activities. These significantly benefit all players – including in their chosen sport – and reduce the likelihood of injuries. The ten hours therefore should not be limited to just football.
P2P FA strongly recommend footballers engage in other activities which (also) develop agility, core strength, flexibility and related physical attributes. These include martial arts, other sports, gymnastics, pilates, yoga etc etc.