Introduction

The body of research studies evaluating the potential for physical activity (PA) to improve ADHD symptoms and functioning, especially those employing well-controlled designs, is quite limited. This review gives evidence for the potential benefits of promising research in this field, as well as five key points that researchers and practitioners should keep in mind while reading and evaluating this evidence.

Point I: From neuroscience and developmental perspectives, there is reason to be optimistic about the potential of PA for improving ADHD symptoms and functioning

From a brain science perspective, research shows that PA may promote more adaptive functioning in individuals with ADHD (e.g. changes in neurotransmitter levels, enhanced cerebral capillary growth and blood flow to the brain, promotion of neurogenesis, and growth in brain tissue volume). PA may have a corrective effect on neurodevelopment for those at risk for ADHD, potentially preventing or altering the course of the
disorder.

Point II: Despite this optimism, the amount of actual wellcontrolled research employing designs that meet strict research standards is quite limited

In discussing the PA intervention literature, an important distinction is made between acute and chronic applications of PA. As the goal of the review is to consider the evidence for the use of PA to manage ADHD symptoms over the long term, the discussion is restricted to studies of chronic effects of PA. Unfortunately, the literature is quite limited.

Current status of the literature 

The current status of literature show limitations, that include small sample sizes, nonrandom assignment to conditions, insufficient control groups to rule out competing interpretations of results, raters not blind to condition, and biased analyses that only consider treatment completers.These limitations reflect the level of difficulty associated with fitting chronic PA studies into the rigid confines of well-controlled research.

Point III: The limited amount of research conducted to date reflects the difficulties associated with venturing beyond the ivory tower to conduct the type of research that is needed

Studies of chronic PA, administered multiple times per week, are most likely to succeed in the settings where children live their daily lives. Three key challenges are particularly daunting in research conducted in natural settings:

1. Random assignment to condition
2. Blinded raters
3. Adequate control groups

Point IV: Despite these limitations, the current literature shows promise

For all categories of outcomes, in order to consider PA as beneficial, either (1) a statistically significant between-groups effect or time by treatment interaction or (2) a reported between-groups or simple effect size (Cohen’s d) of at least .20 favoring PA is required.

What we know:

1. In most studies, aerobic PA shows beneficial effects on parent- or teacher-rated ADHD symptoms
2. PA shows benefit on a variety of cognitive capacities, measured primarily using neuropsychological or executive function (EF) tasks.
3. Systematic PA appears to benefit additional functional domains in ADHD (social functioning, motor skills, behavior, and the affective/emotional domain)
4. The benefits noted above are derived from studies using unmedicated participants, medicated (for ADHD) participants, and studies where medication is not systematically considered
5. In at least one study, beneficial effects of PA are associated with measurable changes in brain activity

Point V: What we do not know is just as important as what we know

What we do not know about PA as a symptom management strategy for ADHD:

1. What is the optimal “dose” in terms of individual session length and frequency, and program length, for obtaining PA effects in children with ADHD?
2. Is there an age when the effects of PA are optimized?
3. How does PA perform when compared directly to established treatments for ADHD?
4. Do the effects of PA persist beyond the period of time when PA is actively administered?

Conclusion

Much more is unknown than is known about PA as a management strategy for ADHD. However, preliminary work suggests beneficial impact in multiple areas of dysfunction, with none of the available studies reporting adverse effects. There is currently insufficient research to warrant recommending PA as a sole intervention; an adequate body of well-designed research studies is greatly needed.