I can't access the full text but from the summary it looks as if blood was taken only once. So the difference between one and the other group was not measured b

I can't access the full text but from the summary it looks as if blood was taken only once. So the difference between one and the other group was not measured before-after and then the change compared, rather a simple comparison was made between the groups at the end. If that's true the whole thing is just bollocks - run it often enough and you'll find a group with this effect.