Health Preservation: Exercise Is a Double-Edged Sword—Too Much Can Make You Dumber
"Life lies in movement"—exercise shapes our robust bodies and strengthens resistance to illness. However, there is a limit to how much exercise the human body can handle. Exceeding this limit may bring harm instead of benefit.
American neuroscientist Justin Rhodes found in his research that mice addicted to exercise had slower brain responses compared to mice with normal exercise levels. This report was published in journals such as *Neuroscience* and *Behavioral Neuroscience*. Thus, Rhodes concluded, "Exercise benefits the brain, but moderation is key."
Moderate Exercise Makes You Smarter
On the side of the human brain lies a hippocampus-like structure called the hippocampus, responsible for learning and memory. Researchers at the Salk Institute in La Jolla, California, discovered through animal experiments that mice enjoying running on wheels developed new cells in their hippocampus, whereas mice confined to ordinary cages did not.
Based on this, researchers believe that regular, moderate exercise in humans can stimulate the hippocampus to grow more cells, enhancing thought, sensation, and reaction speed, thus making people smarter.
Excessive Exercise Makes You Dumber
Intense exercise can damage brain function through multiple pathways. Depletion of ATP energy sources during exercise may be the primary reason for reduced central nervous system function. During exercise, blood redistribution in the body, accumulation of free radicals, vascular endothelial damage due to accelerated blood flow, and buildup of local acidic products all reduce cerebral blood and oxygen supply, directly inhibiting neural activity and impairing brain function.
Studies show that short-term intense exercise reduces cortical brain activity, while prolonged intense exercise leads to widespread reduction in brain excitability.
People often feel mentally sluggish and physically uncoordinated after vigorous exercise. This is not only related to the above factors but also due to the body’s own "protective inhibition" mechanism. Overexertion consumes massive energy, triggering protective inhibition to prevent further depletion. People then feel extremely fatigued, weak, and mentally slow. If excessive exercise continues long-term, the body’s protective inhibition becomes less sensitive, damaging brain function. Symptoms include difficulty concentrating, insomnia, forgetfulness, and long-term harm to overall health.
Find the Right Exercise Volume
The standard for determining whether exercise is appropriate is heart rate—ideally 60% to 85% of maximum heart rate. Notably, since everyone’s condition varies widely, the difference from resting heart rate should be 15% to 30%, or even more. Therefore, optimal exercise volume should be determined based on individual factors such as age, gender, occupation, physical condition, health level, athletic background, living environment, and goals.
To check if exercise volume is suitable, observe post-exercise bodily responses. For example, monitor sweat production and comfort level. Also pay attention to appetite, sleep quality, and whether you still feel motivated to exercise the next day.
Generally, older adults should focus on single-hand aerobic exercises under aerobic conditions to enhance coordination. Children should do mechanical activities like stacking blocks—seemingly simple, yet highly beneficial for brain development and hand-eye coordination.
The key is to manage exercise intensity. Besides keeping heart rate within a proper range, maintain a strong sense of time. Generally, aerobic exercise sessions lasting 30 to 60 minutes are ideal. Exceeding this duration offers no benefit and may actually harm bodily functions.