Physical fitness is linked to brain health in young adults, but the effects differ by sex

A small study of university students in Spain found that better cardiorespiratory fitness is associated with better cognitive processing speed and a smaller volume of the cingulate cortex of the brain. However, brain volume differences did not explain the links between cardiorespiratory fitness and cognition. The paper was published in Physiology & Behavior.

Cardiovascular fitness is the ability of a person’s heart, lungs, and blood vessels to supply oxygen-rich blood to muscles during sustained physical activity. A person with good cardiovascular fitness can walk fast, run, cycle, swim, or do other continuous activities for longer periods without becoming exhausted quickly. It is often called aerobic fitness because it depends heavily on oxygen-based energy production, and it is an important component of overall physical fitness.

A common scientific measure of cardiorespiratory fitness is VO₂ max, which estimates the maximum amount of oxygen the body can use during intense exercise. Cardiorespiratory fitness can be improved through regular aerobic activities such as brisk walking, jogging, cycling, swimming, dancing, or rowing.

Better cardiorespiratory fitness is associated with a lower risk of cardiovascular disease, type 2 diabetes, high blood pressure, and early death. It can also improve everyday functioning, mood, sleep, and general energy levels. Low cardiorespiratory fitness means the body has more difficulty sustaining activity that requires a continuous oxygen supply.

Study author Neus Camins-Vila and her colleagues note that neuroimaging studies indicate that certain physical fitness components, primarily cardiorespiratory fitness and muscular strength, are associated with larger volumes in specific brain structures.

For example, among young adults, previous studies found that higher cardiorespiratory fitness is associated with larger volumes in several regions of the brain. The researchers conducted a study examining the associations between cardiorespiratory fitness, strength, flexibility, and balance in relation to the volumes of specific brain regions and the participants’ overall neuropsychological profiles. They also sought to determine if sex differences moderated any of these relationships.

Study participants were 94 undergraduate and graduate university students from Barcelona, Spain, and its surroundings, recruited through social media and posters. To be included, participants were required to be between 18 and 25 years of age, to be sufficiently proficient in either Spanish or Catalan to follow instructions, and to have self-reported a regular level of physical activity over the past six months. There was also a list of medical conditions that would exclude prospective participants from the study.

After joining the study, participants first completed an online questionnaire covering demographics and medical history. This was followed by three face-to-face sessions involving a cognitive assessment, an evaluation of physical fitness, and magnetic resonance imaging (MRI) of the brain.

The cognitive assessment lasted 60 to 90 minutes. During this time, participants took a series of neuropsychological tests covering attention and cognitive processing speed (i.e., attention-speed), executive functioning, memory, and visuospatial function. The physical fitness assessment focused on cardiorespiratory fitness, strength, flexibility, and balance.

Results showed that students with higher cardiorespiratory fitness tended to have better processing speed and a smaller volume in the cingulate cortex region of the brain. The researchers theorize that a smaller cingulate cortex in this age group may actually be a sign of advanced, healthy brain maturation rather than a negative outcome, as the brain naturally prunes connections to become more efficient during early adulthood.

When analyzing the data by sex, different patterns emerged. In men, flexibility (the ability of joints and muscles to move through their full range of motion without pain or excessive stiffness) was associated with higher processing speed. In contrast, higher flexibility was associated with lower processing speed in women. The researchers suggest that very high flexibility in women may be linked to joint hypermobility, a condition that can cause pain or fatigue, which could negatively impact cognitive test speeds.

In women, better visual memory was associated with higher strength, and better verbal memory was associated with better cardiorespiratory fitness. Furthermore, lower volume of the hippocampus region of the brain in women was associated with higher flexibility but worse balance.

“Different physical fitness components were associated with cognitive functions and brain volumes in young adults, and some associations—particularly those involving physical flexibility and attention/processing speed—varied by sex at birth. Brain volumes did not explain the observed fitness–cognition associations,” the study authors concluded.

The study contributes to the scientific understanding of the links between cognitive abilities and physical fitness. However, it should be noted that the study authors carried out a large number of statistical tests, but only a few of them returned statistically significant results. They did this without applying any correction for multiple comparisons—procedures routinely used in research studies to mitigate the risk that statistical tests might return statistically significant results purely due to chance. This means that many of the reported findings might simply be products of random variations in the data, rather than real systematic associations between the observed characteristics.

The paper, “Associations between fitness components and brain health in young adults: A cognitive and brain volume MRI study exploring sex differences. The YoungFit study,” was authored by Neus Camins-Vila, Adrià Bermudo-Gallaguet, Samira Rostami, Rosalia Dacosta-Aguayo, Judit Escarré-Grifell, Blai Ferrer-Uris, Albert Busquets, Louis Bherer, and Maria Mataró.