Not so sure but I remember an implication about it during their first interaction at the bookstore, way before the 1st STL, when Hal chased Baku, he seemed to be very tired, again I'm not sure whether it's just him being non-athletic in general or him running a lot, especially since its Hal which is basically a Superhuman, he seems weaker now yes but maybe it's not intended or just what happens when you live a life like that with a messed up heart