This study compared two intensities of a single bout of exercise. It included 64 healthy right-handed adults recruited in Oldenburg. None of the people analyzed had ADHD. They were split into two matched groups of 32. The paper does not say the groups were assigned at random. One person in the high-intensity group was excluded for drug abuse.
One group cycled at a moderate pace for 30 minutes. The other did 30 minutes of high-intensity interval cycling. On a separate day, each person watched a film instead, for comparison.
After moderate exercise, people tended to do better on a Go/No-go task. Activity also rose in several brain areas, including the insula. This edge over the high-intensity group did not hold up under a stricter test. After high-intensity exercise, activity in those areas went down and Go/No-go scores did not change.
Exercise did not change the main score or brain activity on a second test, the flanker task. An exploratory check found faster flanker reactions after high-intensity exercise. People with higher fitness showed more brain activity after moderate exercise and less after intense exercise. The authors report the effects did not last more than 30 minutes.
Fitness was spread unevenly, with only one third of the high-intensity group highly fit. Brain scans came from two different scanners. Task order was not varied.
The numbers Stats and what the terms mean
The statistics behind the plain-language claims above.
- Mehren, 2019: difference between the groups in change in Go/No-go sensitivity, moderate versus high intensity, t 61 = 2.96, p = 0.045, d = 0.43, as printed; this did not survive Bonferroni correction (p ≤ 0.025).
- Mehren, 2019: Go/No-go sensitivity after exercise versus the film in the moderate group (exploratory), t 31 = 2.04, p = 0.025, d = 0.36.
- Mehren, 2019: flanker interference score, group or condition differences, p > 0.025.
- Mehren, 2019: reaction time on congruent flanker trials after exercise versus the film in the high-intensity group (exploratory), t 30 = −2.70, p = 0.011, d = 0.48.
- Mehren, 2019: reaction time on incongruent flanker trials after exercise versus the film in the high-intensity group (exploratory), t 30 = −3.12, p = 0.004, d = 0.56.
- Mehren, 2019: brain activity during hit trials, moderate versus high intensity, in the left superior frontal area, p = 0.020, FWE-corrected.
- Mehren, 2019: brain activity during hit trials, moderate versus high intensity, in the right insula, p = 0.003, FWE-corrected. What the terms mean:
- t is a test score comparing two sets of results; the small number after it reflects how many people were in the comparison.
- p is how likely a result this large would be if there were no real difference; smaller means less likely to be chance.
- d is the size of a difference. Roughly, 0.2 is small, 0.5 is moderate and 0.8 is large. A minus sign shows the direction of the change, not its size.
- Go/No-go sensitivity (d′) is a score for how well people told apart when to respond and when to hold back.
- Bonferroni correction is a stricter cutoff used when several tests are run, to guard against chance findings.
- FWE-corrected means the brain result was adjusted for the many brain areas tested at once.
Source: Aylin Mehren, Cecilia Diaz Luque, Mirko Brandes, et al.. Intensity-Dependent Effects of Acute Exercise on Executive Function. Neural Plasticity (2019). doi:10.1155/2019/8608317