art by Meghan Carlton

The Newly Discovered Benefits of Exercise

by Maggie Brown

It is common knowledge that regular exercise has incredible effects on human health, and research has shown that different forms of exercise have varying health benefits. For example, jogging increases breathing and heart rate, weight-lifting builds stronger muscle and yoga improves balance. However, neurologists have not been able to definitively indicate which types of exercise are most beneficial to the brain’s health—until now.

Researchers at the University of Jyvaskyla in Finland recently studied how three types of exercise—running, weight training and high-intensity interval training—affect the growth of new neurons, a process called neurogenesis. More specifically, the scientists measured this phenomenon in the hippocampus, a horseshoe-shaped structure in the brain that is responsible for memory formation, organization and storage, as well as emotional responses, spatial orientation and navigation.

The researchers began their study by injecting a group of adult male rats with either doublecortin, bromodeoxyuridine, Ki67 or a combination of the three. These are all substances used to mark the presence of new neurons. The rats were then randomly placed in groups, each of which performed a different type of workout, while the control group lived under the same conditions, but remained sedentary.

One experimental group was given running wheels and allowed to run as they pleased; most of these rats jogged several miles every day. The second experimental group climbed up a wall with weights attached to their tails, simulating resistance training. The third experimental group began high-intensity interval training in which they were required to sprint on treadmills at a very fast pace for three minutes and jog for two minutes. They repeated this sequence thrice for their workouts.

After the rats endured six to eight weeks of these exercise regimens, the researchers used immunohistochemistry staining (Figure 1) to visualize newly formed brain cells in tissue from the hippocampus of these rats. The rats that jogged freely on their wheels experienced by far the most abundant levels of neurogenesis. Compared to the control group, the distance runners had significantly more new neurons present. On average, the longer the rat ran on the wheel, the more neurogenesis occurred.

Interestingly, the weight-training group experienced no significant levels of neurogenesis; they expressed approximately equal amounts of neuron growth as the sedentary control group.  The high-intensity interval training group expressed low levels of neurogenesis relative to the runners. These initial studies seem to indicate that high-intensity interval training is more beneficial for neurogenesis than weight lifting.

The hippocampus, where much of this neurogenesis occurs, plays a crucial role in learning and memory. Disruption of the hippocampus has been linked to such cognitive disorders as depression, anxiety, addiction, and various neurodegenerative diseases.  The volume of the hippocampus has also been found to be smaller in patients with depression and other cognitive pathologies. Taken together, the results from their study and our knowledge of the hippocampus lead researchers to speculate that increasing neurogenesis may improve memory capacity and learning processes, as well as provide insight into how to treat cognitive disorders. 

This study can potentially provide information for how exercise impacts human brains since the neurological processes of rats are, in fact, very similar to humans. Lead researcher Miriam Nokia at the University of Jyvaskyla explained that “sustained aerobic exercise might be most beneficial for brain health [. . .] in humans.”  So the next time you plan your workout, consider going out for a run instead of hitting the weights at the gym – it could just help improve your memory!