It doesn't matter who said 2+2=5, it remains invalid. See and think for yourself -- the study simply measured correlations on non-randomized samples (namely, the researchers didn't assign randomly half the subjects to the exercise group and and half to non-exercise, but subjects selected themselves for reasons beyond control and largely unknown to researchers).
Claiming causal relation between correlated variables on such samples is a junk science based on a logical fallacy as trivial as 2+2=5, no matter who claims it.
The human body was precision engineered for walking long distances while carrying a weapon. Running is what humans do when they forget their weapon.