It's Saturday, 8pm. Which basically means that Sherlock has left his house and went into the shady park behind the gym to do some illegal fighting. He told his mother he went to the gym but... He just went there and fought with some dudes bigger and stronger than him

It's late and he's been completely beaten up by a guy twice his size, he wipes the blood from his lip as he steps aside. The other bunch of people pushing and yelling as they cheer for the other two fighters as Sherlock tries to step aside to get some air. He shouldn't love this as much as he does.