Pharmacological interventions are the most common treatments in ADHD. However, more recently, clinicians have begun research investigating physical activities and exercise interventions in children with ADHD. Studies have shown that physical exercise can relieve anxiety, depression, aggressive behaviour and social issues in children with ADHD (Zang, 2019). The aim of this meta-analysis was to evaluate the effects of physical exercise on children with ADHD in China and other countries, and provide evidence for use in clinical practice.

Using several key phrases and medical subject headings,* eight Chinese and English databases were searched (CBM, The Cochrane Library, DNKI, Embase, PubMed, Wanfang, Web of Science and Weipu) from their inception to the cutoff date (28 March 2021).

The inclusion criteria were:

• Patients aged 5–15 years (children or adolescents diagnosed with ADHD)
• Randomised controlled trials (RCTs)
• Type of intervention (physical exercise programmes, or increased physical exercise in addition to treatment in the control group)
• Primary outcomes of ADHD symptoms of hyperactivity and inattention, and secondary outcomes of depression, social problems, motor skills and executive function.

Using a standardised form, two researchers extracted information relating to publication (author, country, published year, subject characteristics and trial design) and experimental characteristics (cycle, frequency, movement form and time) and outcome measures. The Cochrane bias risk assessment tools were used to evaluate methodological quality (allocation concealment, blinding, incomplete outcome data, random sequence generation, selective reporting and other biases).

Once duplicate articles were accounted for, a total of 3872 articles were identified in the search, with 17 articles added from alternative sources. Fifteen RCTs from 1984–2019 were included in the final meta-analysis once the process of elimination had been completed. Analysis found that physical exercise significantly improved attention, executive function and motor skills in patients with ADHD:

• Nine studies (N=352) evaluated the intervention effects of physical exercise on attention. The combined effect size (standardised mean difference [SMD] = –0.60; 95% confidence interval [CI] –1.10 to –0.11) indicated that physical exercise can effectively improve attention in children with ADHD compared with the control group (p<0.05).
• Four studies (N=191) evaluated the intervention effects of physical exercise on motor skills. Based on the combined effect size (SMD = 0.67; 95% CI 0.22 to 1.12) physical exercise can effectively improve motor skills in ADHD children compared with the control group (p<0.01).
• Eight studies (N=319) evaluated the intervention effects of physical exercise on executive function. The combined effect size (SMD = 1.22; 95% CI 0.61 to 1.82; p<0.01) demonstrated that physical exercise can effectively improve the executive function of ADHD children compared with the control group. The possible source of heterogeneity was explored further, with executive function analysed in subgroups according to intervention duration, frequency and cycle. It was found that the source of heterogeneity is possibly related to intervention duration and frequency, with 70 minutes of physical exercise twice a week for 12–14 weeks demonstrating a higher effect size.

However, physical exercise was not found to significantly improve hyperactivity (four studies, N=161), depression (four studies, N=98), social problems (four studies, N=117) or aggressive behaviour (three studies, N=78) in patients with ADHD.

The authors identified several limitations. Firstly, the authenticity and reliability of results may be confounded by factors such as variation in intervention programmes, as well as methodological quality. Few studies described blinding and random allocation concealment. There was also a paucity of large-sample, long-term, multicentre RCTs. Finally, different measurements may have led to heterogeneous results.

The authors concluded that physical exercise can effectively improve attention, executive function and motor skills in patients with ADHD. However, physical exercise was found in this meta-analysis to have no effect on hyperactivity symptoms, aggressive behaviour, depression or social problems associated with ADHD. The authors concluded that the meta-analysis provided evidence for the use of long-term physical exercise in patients with ADHD, while also suggesting that future research may also consider time, period, frequency and intervention intensity when developing exercise plans.

Read more about the effects of physical exercise on symptoms of ADHD here

*Search terms were as follows: exercise, sport, fitness, physical activity, Attention Deficit, Hyperactivity, Hyperkinetic Syndrome, Attention Deficit Hyperactivity Disorder, ADHD, ADD, randomised controlled trial

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