\u201cExercise pills\u201d still have a long way to go before they can match the benefits of time spent outside. \u201cThat\u2019s one of the dumbest ideas EVER," claims Dr. Michael Merzenich. The idea in question? Exercise pills: the flash pan scientific wonder of 2017 which, based on studies completed on mice, promised a swallow-able alternative for getting some of the physical benefits of exercise. Merzenich, a professor emeritus and neuroscientist at the University of California San Francisco, doesn't share in the excitement. Merzenich has been studying the plasticity of the brain: the tendency of your brain to evolve and fine-tune itself. The brain's plasticity would suffer from so-called exercise pills, especially when compared to time spent outside. The Wonder Drug When Ronald Evans\u2014a biologist at the Salk Institute\u2014and his team rolled out their study on the drug GW501516 (known colloquially as \u201c516\u201d), the headlines read, \u201cExercise pill could deliver benefits of fitness in tablet form\u201d and \u201cScientists Are Working on a Pill to Replace Exercise.\u201d Evans\u2019s experiments involved a pair of lab mice, one named \u201cCouch Potato Mouse\u201d and the other \u201cLance Armstrong Mouse,\u201d both of which had been given an American diet of sugar and fat. One of the mice, which had not been allowed much exercise, had visibly gained weight. The other, also lacking exercise, appeared in much better shape. The only difference: Lance had his diet supplemented with 516. The drug, which simply-put is designed to recreate the same chemical changes that happen in the body after exercise, was heralded as a wonder drug and a futuristic-yet-possible option for everyone, including busy executives without the time to exercise, those with medical issues that prevent them from exercising, truck drivers and others with long sedentary hours on the job, and even elite athletes looking for a boost. In addition to weight loss, blood sugar decreases, and other chemical benefits, the drug allowed mice using it to run longer on a treadmill. But when it comes to completely replacing physical exercise\u2014especially when that exercise comes from hiking or biking or another outdoor activity\u2014the drug might leave a lot to be desired. Hiking for Your Brain While exercise pills might replicate some of the physical benefits of exercise, something as simple as taking a hike still offers a lot that a drug can't, particularly when it comes to the brain, Dr. Merzenich explains. Keeping your brain in top shape requires exercising it, he says, and one of the best ways to do that is by going for a walk in the woods, which Merzenich contrasted with walking on pavement. \u201cEvery footfall is certain, there,\u201d he said, compared to an uneven trail which requires millions of tiny recalculations by the brain, processing vision and other senses, then recalibrating for balance and control. Troubleshooting and navigating, looking for animals and plants, and dealing with the unexpected are all tasks human brains were originally doing constantly, but have since diminished, thanks to artificial aspects of civilization. \u201cWe used to be masters of our environment,\u201d he said. \u201cBut now, you\u2019re depriving yourself of thousands and thousands of exercises by living your life on pavement. Our brains love surprises.\u201d These micro exercises, he says, train our brains to operate at a higher resolution, improve recognition, and speed up its ability to process the environment even more. \u201cIn order to continually grow it, you have to continually challenge it and continually sustain it.\u201d Even working out in gyms, he contends, isn\u2019t exercising the mind like it needs, but the proposition of an exercise pill, he says, would be truly damaging\u2014none of these brain benefits come from 516. There\u2019s an App for That That\u2019s not to say drugs like 516 are useless. Particularly for people who are incapable of exercise\u2014due to disease or injury, the elderly, or any one of a cadre of people who have a difficult time going for a hike\u2014could benefit dramatically from an exercise pill, maintaining their bodies in ways that would have otherwise been impossible. Little progress on 516 has been made public since the initial study, but that one drug isn\u2019t the only one taking advantage of the chemical benefits of exercise, without the exercise. More recently, a different study looked at the hormone irisin, which is naturally released during physical activity and has been linked to fat burning, noting that it could also protect against mental decline and Alzheimers. \u201cAlthough this study was only in mice, it adds to mounting evidence of the relationship between lifestyle factors, like physical fitness, and dementia,\u201d said Dr. James Pickett, Head of Research at Alzheimer\u2019s Society. \u201cWe know that exercise can decrease a person\u2019s risk of developing dementia, but still have lots to learn about its effect on cognitive decline.\u201d The mental benefits lost by an exercise pill can be made up, at least in part, in other ways as well. Merzenich helped found Brain HQ, a web-based brain training and exercise platform designed to provide similar mental stimulation to outdoor exercise. According to Merzenich, it can be especially helpful to people who need to rapidly improve their mental function or those, similar to the target of the exercise pill, who aren\u2019t able to stimulate and train their brain naturally. \u201dThe biggest change we could see from an exercise pill might come in how we define exercise at all, in much the same way as how the concept of food has morphed into a vehicle for nutrients," says Nicola Twilley, author of the 2017 New Yorker story \u201cA Pill to Make Exercise Obsolete." \u201cA morning jog will be reclassified as a good source of beneficial chemicals; sports may be redesigned to optimize their molecular outcomes. A scientific understanding of the parts may well come at the expense of appreciating the immeasurable whole." A true exercise pill is still a long way off, and it's still far from replacing the benefits of exercise. And as Merzenich points out, there already is a ready-made wonder drug accessible to everyone: outside.