High-Intensity Intermittent Training Improves Spatial Memory in Rats

There is plenty of evidence to show that exercise improves memory, both very quickly and for a short time following any specific bout of exercise, and over the long term due to regular exercise. The mechanisms involved here are varied, likely a combination of cerebral blood flow changes and signaling molecules such as BDNF that are involved in the regulation of neurogenesis. Neurogenesis, the creation and integration of new neurons into the brain, is vital to memory function.

Researchers found that, despite only covering about one-third of the distance in high-intensity intermittent training (HIIT) compared with that covered in endurance training, similar improvements in exercise capacity and brain function were observed for both forms of exercise. In the experiment, rats were assigned to 1 of 3 groups - resting, endurance running, or alternating intervals (short sprints and rest) - during training sessions on treadmills 5 days/week for 4 weeks.

Both endurance running and HIIT resulted in weight loss, greater muscle mass, and the ability to exercise longer compared with controls; however, increased cellular aerobic capacity was found in the soleus (a muscle with predominantly slow-twitch fibers that makes it functionally well suited to endurance) and in the plantaris (a muscle with predominantly fast-twitch fibers for meeting high-energy functional demands) in the endurance-running and HIIT groups, respectively.

Rats in both groups demonstrated having better memory of spatial learning trials in searching for an escape platform in a water maze. In the hippocampus, increased cell development, neurogenesis, was also observed for both forms of exercise; however, levels of a signaling protein that promotes neurogenesis (BDNF) were increased by HIIT but not by endurance running, whereas the levels of its receptor (TrkB) were increased by both. Given that BDNF expression is known to be affected by exercise, why didn't endurance running increase BDNF expression? The answer may lie in the mediating role of stress on BDNF expression; exercise is a type of stress. While stress indicators in both exercise groups were found to be similar, this line of enquiry may lead to future studies:

Link: https://www.eurekalert.org/pub_releases/2021-05/uot-hit051721.php

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