Cambridge Study: Body Prioritizes Brain Over Muscles During Exercise

The study, conducted at Cambridge University, employed 62 of Britain’s most elite rowers to complete three separate tasks. John Tlumacki/The Boston Globe via Getty Images

Running, strength training, tennis, basketball; whatever the physical activity, you’ve probably also heard of it described as a mental game. But a fascinating new study suggests that the further you get inside your own head while exercising, the harder it is for your body and brain to function simultaneously. While exercise and brain function were previously viewed as a dynamic duo, scientists are now speculating that mixing intense thought with high-intensity exercise is counterproductive.

Humans have larger brains than other mammals as compared to the size of our bodies. Like any other organ, the brain requires constant blood flow and nutrients to keep it going. The harder the brain works, the higher the demand for caloric fuel, reducing the flow of nutrients that would normally go toward the muscles. In other words, exercise and high levels of cognition send the body a mixed signal, resulting in a disproportionate amount of nutrients in the muscles versus the brain. Muscles and brain tissue both require blood sugar as a main form of nutrition, and it can become unevenly dispersed in moments of high brain and muscle activity.

The study, conducted at Cambridge University, employed 62 of Britain’s most elite rowers to complete three separate tasks: one mental, one physical, and one combining the two. The rowers were first shown words on a screen, asked to memorize them, and write down as many as they could remember afterwards. These memorization exercises are often used by doctors to measure the mental impact of concussions, brain damage, and other cognitive issues. The next day, the rowers were asked to row as intensely as they could for three minutes. The third day, they completed the memorization exercise while rowing. During the simultaneous challenge, memorization ability decreased by 9.7 percent, while physical ability dropped by 12.6 percent. Across all participants in the study, the decrease in physical power was about 29.8 percent greater than the decrease in memorization.

The results were clear: in the faceoff between physical and mental strength, the brain conquered. The rowers performed lower, both in rowing wattage and word retention, when required to complete both tasks together. However, the physical implications were far worse than the mental, meaning that the brain was dominant in receiving more blood sugar than the muscles activated by rowing. The study sheds an interesting light on athletes who persevere through extreme physical and mental conditioning in the world’s most “mental” sports. To excel in a competitive sport is not only to overcome physical and emotional barriers, but the barriers presented when the two intertwine. The findings also support the theory that the human brain surpassed the body from an evolutionary standpoint to aid survival. “A well-fuelled brain may have offered us better survival odds than well-fuelled muscles when facing an environmental challenge,” said Dr. Danny Longman, study leader and research fellow at Cambridge.

With cognition coming out on top, scientists are hoping to further examine how our “selfish brain” dominates other bodily functions, and explore the far-reaching limits of the power of the mind. “For me, the main message of this study is a bit philosophical,” Longman stated, “An enlarged and highly functioning brain is one of the key factors that make us human. This study demonstrated, in a very simple way, this defining characteristic of our species.”

Cambridge Study: Body Prioritizes Brain Over Muscles During Exercise