Exercise as it relates to Disease/The effect of acute physical activity on executive functions in children with ADHD

The following is a critique of the scientific report Acute physical activity enhances executive functions in children with ADHD, published in the Journal of Scientific Reports, 2018.

What is the background to this research?
|Attention Attention Deficit Hyperactivity Disorder(ADHD) is the most prevalent neurobehavioral disorder globally, with 7.2% children under 18 diagnosed. ADHD is characterised by symptoms of inattention, hyperactivity and impulsiveness. ADHD’s symptomology is also associated with executive function (higher-order cognitive function) deficiencies, which are responsible for self-regulation and behaviour.

ADHD can lead to serious individual problems including academic performance, poor social relationships, and lower occupational status. It also causes family stress and has serious economic implications.

Studies have found exercise interventions to have a positive effect on executive functions in healthy children, however, the research is limited and contradictory for children with ADHD.

The aim of this particular study was to investigate whether acute physical activity selectively affects three core executive functions (EF) – inhibition, switching and working memory – in children with ADHD.

Where is the research from?
The research was authored by Valentin Benzing, Mirko Schimidt and Dr. Yu-Kai Chang, who have published 11, 44 and 137 articles respectively, in relation to exercise psychology.

Benzing, a PhD fellow, is a researcher at the Institute of Sport Science (ISPW), University of Bern, Switzerland, where Schimidt is an assistant professor. Chang is a professor in the Department of Physical Education at National Taiwan Normal University, and VP of the Society for Sport and Exercise Psychology of Taiwan.

The research was funded by the Suzanne and Hans Biäsch Foundation for the Promotion of Applied Psychology.

The study was conducted in the canton of Bern, Switzerland, and the study protocol was approved by the cantonal ethics committee. All authors declared they had no competing interests.

What kind of research was this?
This research was conducted using a randomised controlled trail (RCT). RCT’s randomly assign participants into either an experimental group which receives the intervention being tested, or a control group which receives a placebo, standard or no intervention. RCT’s are therefore able to determine whether a cause-effect relationship exists between the intervention and outcome.

RCT’s are considered the gold standard of research designs. They have the highest quality of evidence. The randomisation of patients’ group selection eliminates selection bias and balances confounding factors between both groups.

In this study, information about patient assignment was concealed from participants and researchers (blinding) to further reduce bias. Participants were also blinded with regard to the study aims and conditions.

What did the research involve?
46 participants (ages 8-12), diagnosed with ADHD under the International Classification of Disease, were randomly split into two groups – 24 into the group (EG) and 22 into the control group (CG).

Each participant was assessed twice. The sessions followed the routines below:

Despite using an RCT, there were limitations with the design.


 * 1) Sample Size – The small sample size did not allow analysis of sub-groups – ADHD symptoms, social economic status, pubertal development status, etc.
 * 2) Sample Diversity – 82.6% of the sample population were boys, therefore there was insufficient statistical power to confirm the results are true for girls.
 * 3) Heart Rate Estimations – The study used the formula 208-(0.7 x age) which only provides a rough estimate of participants maximal heart rate and used that estimation to set heart rate cut-offs for exercise intensity.
 * 4) Medication – 79.2% of the EG and 77.3% of the CG were on medication so the effects of the acute exercise alone is inconclusive.
 * 5) Physical Activity Modality – The exergaming condition required non-automated movements making it cognitively challenging, therefore the EF results could be due to the physical activity or the cognitive activity or a combination.
 * 6) EF Assessment – The aim was to separately assess all three core EF’s however the modified flanker test was used to assess both inhibition and switching.

What were the basic results?
The results showed that the Exergaming Group displayed significantly shorter reaction times than the Control Group in post-tests for inhibition and switching, but no significant difference in accuracy scores or working memory.

Results Summary:

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The authors suggest that acute cognitively engaging exercise at moderate to vigorous intensity for 14-15 minutes enhances inhibition and switching reaction times. The authors proposed that the mechanism responsible for these improvements is neuroelectric adjustments.

The authors also believe the reason there was no improved accuracy was due to the increased catecholamine concentrations in the brain which might have different sensitivities for speed of processing and accuracy.

What conclusions can we take from this research?
This study provides evidence supporting that following cognitively challenging acute physical activity at moderate to vigorous intensity for 14 minutes, ADHD diagnosed children can see significant beneficial improvements in inhibition and switching reaction times, but not in accuracy or working memory performance.

The results for this study were consistent with findings from similar studies that found that acute moderate intensity exercise bouts led to increased inhibition reaction time and processes and no significant effect on working memory in ADHD children.

One contradictory study conducted by Piepmeier et al. found similar exercise to have no significant effect on switching. This suggests that the effect of exercise on inhibition is stronger than on switching, which is supported by this present study.

Therefore, although the authors claim that the evidence suggests that physical activity may have specific beneficial effects on ADHD children, further research investigating acute exercise and cognitive challenging games (without exercise) in isolation is required to determine which is the cause for these EF benefits.

Practical advice
Current literature and reports from parents, teachers and scholars suggests that single bouts of exercise at moderate to vigorous intensity produces the most optimal results.

Although the duration-exercise relationship is unknown, Chang et al. found short bouts of 20-minute exercise conditions to exhibit the greatest EF performance.

Exercise has also been shown to improve social, emotional, and motor development and behaviour as well as EF and cognitive performance in ADHD children.

In terms of frequency, the National Association for Sport and Physical Education states that short bouts of exercise should be incorporated during the school day (recess, lunch, P.E class).

Most ADHD diagnosed children consider conventional physical activity programs tiring and boring, so it is important to use complex activities that challenge their cognition as well as body. Exercise modalities such as exergaming, rock climbing, gymnastics, martial arts, mountain biking have all shown greater positive impacts and higher arousal ratings than autonomous exercises.

ADHD children should be pre-screened to ensure they are fit for acute bouts of exercise.

Further information/resources

 * https://www.helpguide.org/articles/add-adhd/attention-deficit-disorder-adhd-in-children.htm
 * https://www.mayoclinic.org/diseases-conditions/adhd/symptoms-causes/syc-20350889#:~:text=The%20primary%20features%20of%20ADHD,they%20may%20continue%20into%20adulthood.
 * https://childmind.org/article/adhd-and-exercise/#:~:text=The%20notion%20that%20physical%20activity,as%20a%20treatment%20for%20ADHD.
 * https://adhd-institute.com/disease-management/non-pharmacological-therapy/exercise-and-diet/
 * https://www.cdc.gov/ncbddd/adhd/treatment.html#:~:text=For%20children%206%20years%20of,of%20the%20treatment%20as%20well.