Running hard on a treadmill might make you smarter, but lifting weights probably won’t, reports Gretchen Reynolds in the New York Times Magazine (9/20/09). Gretchen is citing the results of research at National Cheng Kung University, in which scientists observed two groups of mice — one group that simply ran inside their rodent wheels and another that was forced "to push harder on minitreadmills at a speed and duration controlled by the scientists." (abstract)
The two groups were then tested for "learning skills and memory." In one test, the mice had to swim through a water maze and in the other they had to "endure an unpleasant stimulus to see how quickly they would learn to move away from it." This went on for four weeks and both groups did well on the water maze, which was the easier test. But only the huffing and puffing treadmill runners did better with "the avoidance task, a skill that, according to brain scientists , demands a more complicated cognitive response."
Another study, this one with humans, had a similar result. This study involved "21 students at the University of Illinois." The students were required to memorize a string of letters, and then tested on it after either sitting quietly, running on a treadmill or lifting weights for 30 minutes. Each group was tested a second time after a 30 minute cooldown, and the treadmill runners did best. Henriette van Praag, a neuroscientist, theorizes that "you need a fairly dramatic change in blood flow" to stimulate the brain. Weight lifting kind of just stays in your arms.