It is well known that exercise benefits both brain and body health; a lack of exercise not only leads to obesity and a series of metabolic health issues, but it is also a major risk factor for cognitive impairment and mental disorders.
However, in this fast-paced era, finding large amounts of time to exercise every day has become an almost impossible task for the vast majority of people, and the tedious and lengthy exercise process may not bring joy. Therefore, High-Intensity Interval Training (HIIT) has emerged.
HIIT is a training method that allows you to perform all-out, fast, explosive exercise in a short amount of time. It rapidly depletes muscle glycogen, thereby increasing the number and activity of mitochondria in the muscles to meet the energy demands of exercise. HIIT is characterized by alternating between intense exercise for a short duration and rest or light exercise. Because it saves time, it has been gaining more attention.
So, can this mode of exercise reduce the risk of cognitive impairment and mental disorders?
A recent study published in Cerebral Cortex, led by a research team from Tsukuba University in Japan, found that although the amount of exercise in HIIT is only about one-third of that in endurance training, both forms of training have similar improvements in exercise capacity and brain function.
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Previously, some studies have shown that High-Intensity Interval Training (HIIT) is considered to be a more enjoyable training program than Moderate-Intensity Continuous Training (MICT), and it has better compliance. Additionally, numerous studies have shown that the physiological adaptations induced by HIIT are similar to or superior to those of MICT. For example, HIIT increases maximal oxygen uptake, enhances the activity of citrate synthase in skeletal muscle, and increases the gene expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), indicating that HIIT also enhances mitochondrial aerobic metabolism. Although the amount of exercise in HIIT is lower than that of traditional MICT, it can enhance peripheral tissues just like MICT.
In the brain, the hippocampus is a highly plastic region involved in learning and memory performance. Numerous studies have shown that exercise can improve hippocampal function. However, little is known about whether the lower volume of exercise in HIIT can also enhance hippocampal function and plasticity.
In this study, researchers examined the muscles and brains of rats, specifically observing how the brain regions involved in spatial learning adapted to different types of exercise and how the animals learned and remembered maze navigation.
In the experiment, ten-week-old rats were randomly divided into three groups: a resting group (control group), a Moderate-Intensity Continuous Training (MICT) group, or a HIIT group. They trained on a treadmill five days a week for four weeks.
Researchers found that compared to the control group, the rats in the MICT and HIIT groups lost weight, gained muscle mass, and exercised for longer durations. They also observed increased aerobic capacity in the soleus and plantaris muscles of the mice in both the MICT and HIIT groups.
The soleus is a muscle primarily composed of slow-twitch fibers, well-suited for endurance activities; while the plantaris is a muscle primarily composed of fast-twitch fibers, used to meet high energy functional demands.
Moreover, both groups of rats showed better memory performance in a spatial learning experiment in a water maze where they searched for an escape platform. In the hippocampal region, both forms of exercise increased cell development and neurogenesis; however, the level of Brain-Derived Neurotrophic Factor (BDNF) signaling protein increased in the HIIT group but did not increase in the MICT group, although its receptor (TrkB) levels increased in both groups.
Brain-Derived Neurotrophic Factor (BDNF), as a member of the neurotrophic factor family, not only promotes the proliferation, migration, and differentiation of neural stem cells, the survival and growth of various neurons, but it also facilitates synaptic plasticity, alters the morphology of neurons in the brain, and promotes the growth of dendrites and axons. Additionally, studies have shown that BDNF is involved in the plasticity mechanisms of learning and long-term potentiation. Therefore, it plays an important role in learning and memory functions.
If BDNF expression is influenced by exercise, then why doesn’t moderate-intensity continuous training increase BDNF expression?
Researchers believe the reason may lie in the regulatory effect of stress on BDNF expression, as exercise also induces stress. However, stress indicators in both groups were found to be similar, so this clue remains to be clarified in future research.
Overall, the researchers believe that HIIT is a time-efficient exercise program that can enhance hippocampal memory and neurogenesis in rats, and is associated with hippocampal BDNF signaling.
The corresponding author of the study, Professor Hideaki Soya from the Laboratory of Exercise Biochemistry and Neuroendocrinology at Tsukuba University, stated: “In this study, we found that the low-volume HIIT program can still improve spatial memory, and we demonstrate that these improvements are supported by changes in neuronal plasticity in the hippocampus. In previous studies, we found that continuous light training also has similar beneficial effects, while continuous high-intensity training does not. Therefore, the benefits of exercise may actually depend on the balance between exercise duration and intensity. In the future, customized exercise programs could improve both physical and cognitive functions, which may soon become a reality.”
Paper Link:
https://doi.org/10.1093/cercor/bhab093
Source: China Biotechnology Network
