Previously, in this month’s focus on the effect of exercise on mental energy, we have looked at both the short- and long-term effects of movement and exercise.

And, a small tendency have appeared, suggesting that moderate-intensity exercise might actually be more advantageous.

Today, we’re looking closer into this.

What type of exercise is best for our mental energy and why?

Today’s insights are mainly drawn from this scientific article:

“The effect of exercise on cerebral blood flow and executive function among young adults: a double-blinded randomized controlled trial” Jianxiu Liu et al, 2023

Today's newsletter

• Takeaways:

• In a nutshell:

• What they did:

• What they found out:

• Why is this relevant in terms of mental energy?

Takeaways:

🥇 Moderate exercise might boosts mental energy

Steady, moderate-intensity training improved blood flow to the brain and executive function, more that high intensity interval training.

🧠 Better blood flow, sharper thinking

Across all groups, participants with the biggest boosts in brain blood flow scored higher on executive function tests.

This suggests that the improved circulation from moderate exercise may be an important reason for the improved cognitive performance.

In a nutshell:

Today’s study looked at how two common exercise styles impact brain functioning in a way very relevant to mental energy.

The study looked at moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT).

Over 12 weeks, 93 sedentary participants (ages 20–30) were split into MICT, HIIT, or a control group.

The researchers measured executive function (skills like focus and mental flexibility) using the Trail Making Test and tracked cerebral blood flow (CBF) with ultrasound.

The results showed that both exercise types improved mental performance, but MICT delivered the strongest benefits.

Only the MICT group had significant increases in blood flow indicators.

This suggests that steady aerobic exercise may enhance brain health and cognition more that high intensity exercise. 

And that it may be because this type of exercise boosts circulation more that HIIT.

What they did:

This study used a double-blind randomized controlled design. This is one of the strongest setups in science because it reduces bias.

The researchers followed 93 healthy but sedentary young adults (aged 20–30) over 12 weeks, and compared the effects of moderate-intensity continuous training, high-intensity interval training, and a control group.

The researchers made sure participants didn’t know about the other groups (everyone trained on different days) and that the people measuring brain blood flow and cognitive tests had no idea which group anyone was in.

That way, neither expectations or cues could affect the results. This setup gives us solid confidence in the findings.

The three groups where as follows:

• MICT group: Ran for 20 minutes at 70–75% of their individual maximum oxygen uptake (VO₂ max), with warm-up and cool-down for a total session length of 40 minutes.
  
  

• HIIT group: Completed 10 cycles of 1-minute sprints at 100% VO₂ max, each followed by 1 minute of active recovery at 50% VO₂ max, also totaling 40 minutes per session including warm-up and cool-down.
  
  

• Control group: Attended health education sessions without exercise.

All groups met three times per week for 12 weeks.

Measures:

Executive function was assessed before and after the intervention using the Trail Making Test.

This test is a bit like the Stroop test, which you can try on the resource site. 

However, while the Stroop test focuses on inhibition and conflict resolution, the Trail Making Test evaluates speed and accuracy in connecting numbers and letters in sequence.

It’s more about visual scanning and task-switching than inhibition.

Cerebral blood flow (CBF) was measured via transcranial Doppler ultrasound, capturing blood flow velocity in the middle cerebral artery and key indicators of vascular health.

What they found out:

Starting point:

All three groups were similar in age, body composition, education, fitness (VO₂ max), and executive function performance on the Trail Making Test (TMT).

Executive Function:

After 12 weeks, both exercise groups improved on the TMT.

However, the MICT-group where better than both HIIT and the control-group.

Cerebral Blood Flow (CBF)

Only the MICT-group showed significant improvements in three key indicators of brain blood flow circulation:

• Pulsatility Index (PI) – shows how strongly blood pulses through the brain’s vessels.

• Resistance Index (RI) – reflects how easily blood can flow through the vessels.

• Systolic/Diastolic velocity ratio (S/D) – compares blood speed during the heartbeat’s pump phase (systolic) versus its rest phase (diastolic).

Increases in these measures indicate healthier, more adaptable blood vessels and better overall brain blood flow.

The interesting thing is, that neither the HIIT nor the control-group showed meaningful changes in these indicators.

Link between CBF and cognition:

Across all participants, higher PI, RI, and S/D values correlated with better executive function scores.

This is extremely interesting, as it suggests that improved blood flow may help explain the cognitive benefits observed with MICT, and therefore give is a meaningful explanation for why the MICT seemed to be the best training form for cognitive functioning.

Why is this relevant in terms of mental energy?

The reason why I really find these results interesting is, that it might be very relevant in terms of mental energy.

Mental energy reflects the brain’s ability to sustain executive control.

The top-down guidance from the frontal regions that keeps us focused and limits drifting into Default Mode Network activity, where mind-wandering takes over.

👉Read more about mental energy here.

This study didn’t directly measure frontal cortex activity, but the improved executive function and increased cerebral blood flow suggest stronger support for the brain’s “control center.”

Better circulation could potentially mean more fuel and oxygen to the brain, helping its cells make ATP, which is the energy they need to function.

And importantly, is could mean better recycling neurotransmitters like glutamate, which is extremely important in terms of mental energy,
 
This could help the brain replenish energy faster, so focus and executive control can be sustained for longer before mental fatigue sets in.

The fact that moderate exercise might be the most relevant in terms of mental energy, is also one that we have seen in the previous newsletters of this month.

_{Disclaimer: The above is mainly based on the 4 articles mentioned in the beginning of this newsletter, and aims to provide key takeaways and a condensed overview of its content. While the essence is drawn from the original articles, some parts have been simplified or rephrased to enhance understanding. Please note that we at, OptiMindInsights or any other potential writers or contributors to our summaries, do not accept responsibility for any consequences arising from the use of these summaries and/or newsletters as a whole. The information provided should not be considered a substitute for personal research or professional advice. Readers are encouraged to consult the original articles for detailed insights and references. The summary does not include references, but they can typically be found within the original publication. Always exercise due diligence and consider your unique circumstances before applying any information in your personal or professional life. We refer to the creative commons for reproducibility rights.}