The idea that brain and brawn are mutually exclusive is fairly well embedded in our culture; the popularity of phrases used to describe weightlifting enthusiasts, like “dumb jock” or “meathead,” make its pervasiveness pretty clear. But is it true? In a word, no. Anyone who’s ever heard Mark Rippetoe assess a novice squatter like a master mechanical engineer, Keith Norris wax poetic about the savage grace of physical culture, or Robb Wolf employ a Battlestar Galactica reference to explain the biochemistry of a glutenous assault on your intestinal tract knows it to be false, but the rest of society tends to lag a bit. Luckily, a few recent studies suggest that resistance training actually promotes neurogenesis – the growth of new neurons in the brain – while another links overtraining to impeded cognitive ability later in life. It may be high time to start disseminating the image of the dumb jogger instead.
The first group of researchers, a team of scientists from Brazil, got rats to “lift weights” by tying weighted objects to their tails and having them climb ladders, five sessions a week (sounds a bit like Crossfit, eh?). They measured levels of brain-derived neurotrophic factor, which is thought to increase neurogenesis, and found that the weight lifting rats’ BDNF levels compared favorably with those of rats who just ran on a wheel. Another group was sedentary and showed very low levels of BDNF. In the researchers’ words, both endurance and resistance training increased BDNF levels (although I’m not sure I’d call sprinting on a running wheel “endurance training”).
Another rat study used weighted and unweighted running wheels; one group of rats ran on an unweighted, normal running wheel and one group ran on a heavier wheel (the extra weight amounted to about 30% of a rat’s bodyweight by the end of the study). The rats on the weighted wheel, who packed on a good amount of lean mass, could only run about half as long as the rats on the unweighted wheel, who gained no muscle. The weighted wheel rats also showed higher BDNF levels and greater gene activity in the brain. Sounds like weighted hill sprints and car pushing are worth working into your routine, huh?
But the law of diminishing returns rears its head, as it almost always does. Another recent study received far less fanfare: women’s (excessive) exercise linked to lower cognitive function. Researchers polled ninety healthy, postmenopausal women about their lifelong exercise habits and tested their cognitive skills. Those who reported exercising “strenuously” showed a statistically significant reduction in cognitive skill when compared to women who exercised “moderately.” Questionnaire studies are notoriously unreliable, but it wouldn’t surprise me if this study reflected reality. After all, overtraining is a potent stimulator of the stress hormone cortisol; excessive, unbalanced levels of which have been linked to depression and lower levels of neurogenesis. I’ve certainly been there as an endurance athlete, and giving up the miles in favor of shorter, faster workouts with weights definitely improved my mental well-being. I don’t know if I would have failed a memory test or anything, but it absolutely felt like a fog had lifted. Brings me back to my personal quest: what’s the least amount of “training” I can do to stay lean, fit, happy, healthy and productive…and allow me more time for “play” and “fun”?
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.