Here's a weird one: I think it's almost a semantic mistake. On the one hand, "exertional malaise" was not improved. On the other, "fatigue, muscle aches/cramps, and muscle weakness" were all improved.

So what does exertional malaise mean? You're too tired to move, or you don't feel like moving, because you have muscle weakness or aches. But our subject all were improved in the latter areas.

I'm guessing it's more a response about mentality, not physical improvement -- the "malaise" part. "Anxiety" wasn't positively affected either. I think you have all these beaten-up, depressed LHers and they didn't all just snap out of it mentally, in part because they are so used to being down about their physicality that the head reacts slower than the muscles.