Endurance sports, fitness training (+++)

For detailed information on endurance sports and strength training for ADHD: Deutsch et al.¹

(Endurance) sports appear to be the most effective non-drug form of treatment for ADHD.²³⁴

For many people with ADHD, especially those with ADHD-HI and ADHD-HI-C, regular intensive sports (burning off excess energy) is essential. As a rule, sports can support ADHD treatment, but are only likely to be sufficient on their own in very mild cases.
In the experience of people with ADHD, weight training, in contrast to endurance sports, is apparently much less suitable for combating ADHD symptoms in the long term.

One study found a 21% reduced propensity for physical activity in children with ADHD.⁵ In terms of excessive sports, however, another study found a 3.23-fold increase in activity in children with ADHD compared to people without ADHD (9.0% of those with ADHD compared to 2.7% of those without ADHD).⁶ On the other hand, one study suggests that increased physical activity in adolescence (16 to 17 years) could lead to reduced ADHD symptoms in young adulthood (19 to 20 years).⁷
The amount of physical activity of children with ADHD was strongly driven by their interest in physical activity and also strongly tracked the amount of physical activity of their parents.⁷

However, not all people with ADHD benefit equally from sports. A dropout rate of 17.5% has been reported, with male people with ADHD having an even higher dropout rate.⁸ Sports therapy is also only effective for depression in around 50% of people with ADHD.⁹

However, sports (or non-sports) have no causal influence on the development or non-development of ADHD.¹⁰

Physical activity differs in several criteria:¹¹

• Type of training
  • Endurance training (cardio training; e.g. running, cycling, dancing, treadmill training)
    • increases heart rate
    • stimulates perspiration
    • gets out of breath
  • non-cardiovascular, calm training (e.g. yoga, tai chi)
• Training duration
  • acute, one-off training
  • long-lasting repeated training
• Duration of effect
  • acute effect (effect can be measured shortly after physical activity)
  • chronic effect (effects last even after a longer rest period)

• 1. ADHD symptoms and sports
• 2. Neurophysiological changes through sports
• 3. Neurophysiological changes through sports: short-term exercise vs. regular training
  • 3.1. Neurophysiological changes due to short-term stress
    • 3.1.1. Studies on the effect of one-off sports exercises on ADHD symptoms in children
    • 3.1.2. Studies on the effect of one-off exercise on ADHD symptoms in adults
  • 3.2. Neurophysiological changes through regular training
    • 3.2.1. Studies on the effect of long-term training on ADHD symptoms in children
    • 3.2.2. Studies on the effect of long-term training on ADHD symptoms in adults

1. ADHD symptoms and sports¶

Studies report improvements through sports training in children with ADHD regarding:

• Attention^{1213 14} , SMD = 0.84¹⁵ to 1.79¹⁶, especially through cognitively demanding physical activity¹⁷, also through exercise therapy¹⁸
  • Memory accuracy¹⁹
  • Selective attention¹⁹²⁰
    • By strengthening the sensorimotor basis²¹
  • Sustained attention²⁰
  • Fewer omission errors¹⁹
  • Reduced interference errors¹⁹
• Cognitive performance^{1422 23} , also through exercise therapy¹⁸
  • Clear²⁴
  • Statistically significant, but small in Effect size²⁵
• Working memory, SMD = 0.37 (meta-analysis, k = 10, n = 526)²⁶
• Orientation behavior improved comparably by sports, MPH and atomoxetine in SHR²⁷
• Academic achievement²⁸
• Hyperactivity^{1213 14} , SMD = 0.56¹⁵
• Impulsivity/inhibition^{1213 28 19 29 14} , repeated sports 1.77 (meta-analysis, k = 8, n = 373):³⁰, SMD = 0.78, meta-analysis³¹, acute sports: 0.65 meta-analysis, k = 8, n = 373):³⁰, SMD = 0.56, meta-analysis¹⁵, SMD = 0.34, meta-analysis (k = 10, n = 526)²⁶
  • Moderate aerobic sports improved inhibition in ADHD just as well as intensive aerobic sports³²
  • Pilates: 2.22³⁰
  • Tai Chi: 2.20³⁰
  • Cycling: 0.67³⁰
  • Vibration training: 0.67³⁰
  • Yoga: 0.01³⁰
• Executive functions³³
  • Through a single 30-minute sports exercise³⁴³⁵²¹
  • After long-term training²¹³⁶ , low to moderate³⁷, SMD = 0.58¹⁵ to 2.19¹⁶
• Neuroplasticity of nerve cells and synaptic connections²¹
• Behavior²⁸
  • Social problems¹⁴
  • Social disorders, SMD = 0.59¹⁵
  • Aggression¹⁴
  • Social behavior comparably improved by sports, MPH and atomoxetine in SHR²⁷
• Sleep quality.³⁶, also through exercise therapy¹⁸
• Motor skills²¹
• Depression
  • Exercise improves your mood
    Even for people who find exercise unpleasant, a half-hour walk has a mood-lifting effect
  • Endurance sport has an antidepressant effect³⁸¹⁴
  • Exercise therapy is helpful¹⁸
• Fear
  • Endurance sport has an anxiolytic (anxiety-relieving) effect³⁹¹⁴ , SMD = 0.66¹⁵
• Emotional dysregulation in ADHD
  • Especially for people with ADHD on medication⁴⁰
  • Improved impulsivity in relation to emotional expression, among other things⁴⁰
• Stress
  • Sports have a regulating effect on stress⁴¹
    • Preventive
      • Sports prevent stress.⁴²⁴³
    • Buffering
      acute and habitual physical activity can buffer the negative effects of stressful events on physical and mental health
      • Strengthening resources
        • If sports are included in options for action, sports themselves are available as a stress-reducing tool
        • Group sport creates social bonding
          • Reduces the stressor of social isolation, especially for mental patients⁴⁴
      • Reaction reduction
        in trained people, negative stress reactions do not occur to the full extent in the first place
        • Cognitive
        • Affective
        • Behavioral
        • Biological
          • Trained men respond to psychological stressors (TSST) in comparison to untrained men⁴⁵
            • Significantly lower cortisol stress response (with the same basal cortisol level)
            • Significantly lower increase in heart rate
            • Significantly greater calmness, better mood and a tendency to react less anxiously to psychological stress
    • Compensating
      negative stress reactions are reduced or balanced out by sports and exercise
      • Sports reduce cortisol
• Social behavior with ASD¹⁸

While sports training showed additional positive effects in certain disorders when it was carried out in nature, cognitive performance did not improve in ADHD. (meta-analysis, k = 14)⁴⁶

2. Neurophysiological changes through sports¶

Sports are said to cause an increase in:

• Dopamine^21474849
  • Sports (as well as MPH) can induce the expression of tyrosine hydroxylase (TH)⁵⁰ and thereby increase TH levels. TH is a precursor for dopamine. Sports can thus support dopamine synthesis.
  • Exercise acutely increases dopamine levels in the ventral striatum by gut microbiome-dependent production of endocannabinoid metabolites stimulating the activity of TRPV1-expressing sensory neurons⁵¹
• Noradrenaline⁵²⁵³ , in the brain regions relevant for ADHD⁵²
• Endocannabinoids
  • One round of aerobic exercise, especially at moderate intensity, increased blood levels of endocannabinoids⁵⁴
    • AEA
    • 2-AG
  • This contributes significantly to mood enhancement and stress reduction in healthy individuals. Moderate and high-intensity aerobic exercise modulates stress through a negative feedback loop on the HPA axis as well as the sympathetic nervous system, which facilitates stress regulation that plays a crucial role in endocannabinoid synthesis⁵⁴
  • Endocannabinoids are very closely linked to the dopamine system. More on this in the chapter Neurological aspects.
• Serotonin^{2152 53}
• Acetylcholine⁵²⁵³
• GABA⁵²⁵³
• BDNF^{2152 53}
• Blood flow in the brain²¹
• Inflammation levels reduced through regular exercise⁵⁵ (increased during sports competitions)
• Oxidative stress reduced by regular exercise⁵⁵ (increased during sports competitions)
• Stress hormones reduced through regular exercise⁵⁵ (increased during sports competitions)
• Telomerase activity in humans and mice increased by regular exercise⁵⁵
  • Counteracts behavioral changes caused by stress-induced telomere shortening
• Calorie consumption
  • Contrary to previous assumptions, sports do not appear to increase total calorie consumption. Among the Hadza people, active hunter-gatherers in Africa, women walk an average of 8 km and men an average of 14 km per day, but do not consume more energy per day than sedentary office workers in the USA.^56575859 Hadza are active and fit up to the age of 70 and 80 and are said to have neither diabetes nor heart disease.
  • However, high calorie consumption through exercise reduces stress systems and inflammatory reactions and thus reduces the calorie consumption that the stress reactions would have caused.⁵⁸ Acute physical stress barely increases cerebral blood flow, but there is a redistribution in brain regions involved in motor control and coordination (e.g. vestibular) and transport systems (respiration, circulation).⁶⁰ This could be the nutritional-physiological equivalent of the long-standing finding that sports have a stress-regulating effect.
  • This sheds a whole new light on the common side effect of stimulants of reduced appetite. We hypothesize that this could be an adaptive response to the body’s decreased energy expenditure due to reduced stress responses. Further, we wonder whether hyperactivity as a symptom of the externalizing ADHD subtypes could possibly be a (misguided) compensatory response of the body, as inflammation is more common in the externalizing stress phenotype than in the internalizing ADHD-I subtype.

One-off training has statistically significant but small Effect size improvements in cognitive performance during, immediately after and delayed after the training session.²⁵ In another study, working memory and inhibition were impaired immediately during exercise in people with ADHD compared to those without ADHD⁶¹
The benefits of acute physical activity can gradually accumulate over time.²¹

A combination of sports training with cognitive tasks for children with ADHD proved to be helpful²¹, but not superior to sports training alone.²⁰

3. Neurophysiological changes through sports: short-term exercise vs. regular training¶

With regard to the effects, a distinction must be made between acute changes caused by short-term exercise and the long-lasting effects of regular training.
This section is largely based on the article by Christiansen et al, 2019.⁶²

3.1. Neurophysiological changes due to short-term stress¶

Basic effects on catecholamines:⁶²
Acute physical activity increases blood plasma levels of catecholamines^{6364 65} and monoamine levels in the brain.

• Noradrenaline: The noradrenaline level in the brain correlates more strongly with the peripheral (physical) adrenaline level than with the noradrenaline level there.
• Dopamine cannot cross the blood-brain barrier. It is possible that the brain’s dopamine level is stimulated by peripheral calcium, which stimulates dopamine synthesis in the brain.⁶⁶⁶⁷
• In rodents, dopamine^{6869 70 71} (different in humans⁷², as well as noradrenaline in the striatum⁶⁸⁷³ and PFC⁷³, increases during physical activity, while noradrenaline decreases in other areas of the brain.
  A very small study of n = 18 children found that the increase in peripheral dopamine induced by acute exercise was much lower in children with ADHD than in non-affected children.⁷⁴

3.1.1. Studies on the effect of one-off sports exercises on ADHD symptoms in children¶

• 30 minutes one-off improved inhibition (treadmill training; n = 40 children, 9 to 11 years)⁷⁵
• 30 minutes once improved processing speed and inhibition (moderate-intensity sports; n = 32 children, 8 to 13 years)⁷⁶
• 30 minutes one-off improved working memory (treadmill training; n = 40 children aged 8 to 12)⁷⁷
• 20 minutes once improved executive functions (moderate-intensity sports; n = 150 children, 6 to 12 years)⁷⁸
• 20 minutes once improved the previously reduced P3 amplitude of ADHD children to the level of non-affected children and improved inhibition (treadmill training; n = 20 children, 8 to 10 years)⁷⁹
• 20 minutes once improved cognitive flexibility in children with ADHD as in non-affected children (ergometer cycling; n = 36 children)⁸⁰
• 15 minutes once accelerated inhibition and task switching, but did not improve accuracy or visual working memory (exergaming; n = 46 children, 8 to 12 years)⁸¹
• 5 minutes once improved inhibition, the error rate in the Go/No Go task and (especially in the case of high hyperactivity) the symptoms of depression (trampolining or running; n = 47 children)⁸²
• 5 minutes once improved performance on tasks, performance on computer game tasks requiring attention by 30 % in people with ADHD and by 40 % in people without ADHD (race without a break; n = 28 children aged 10 to 16)⁸³

3.1.2. Studies on the effect of one-off exercise on ADHD symptoms in adults¶

• Impulsivity: 0.65 Meta-analysis, k = 8, n = 373)³⁰
• 20 minutes once (cycling at moderate intensity; n = 32 adult men aged 18 to 33)
  • improved
    • Vigor (physical/mental strength and energy)
    • Motivation to complete intellectual work
    • Symptoms of depression
    • Tiredness
    • Confusion
  • left unchanged
    • Hyperactivity of the legs
    • Response time
    • Performance in vigilance tasks (accuracy, error or reaction time)
• Adults with ADHD who engage in frequent physical activity report⁸⁴
  • reduced impulsive behavior
  • less worrying and intrusive thoughts
• Passive sitting on a vibrating chair for 2 minutes⁸⁵⁸⁶
  • improved attention in adults with and without ADHD alike
• 30 minutes of one-off aerobic training resulted in⁸⁷
  • for those not affected:
    • significantly increased intracortical facilitation (ICF)
    • reduced short intracortical inhibition (SICI)
  • for people with ADHD
    • significantly increased short intracortical inhibition (SICI)
    • improved inhibition
    • improved motor learning

3.2. Neurophysiological changes through regular training¶

Long-term, regular training (here: treadmill training for weeks) led to long-term adaptations in the monoaminergic system.⁶²

• promotes increased dopamine synthesis and release from midbrain projections through:⁸⁸
  • increased tyrosine hydroxylase expression
  • reduced DRD2 autoreceptor expression in the substantia nigra
• compensates for impaired TH expression in SHR in a dose-dependent manner
  • in the substantia nigra ⁸⁹⁵⁰
  • in the striatum⁵⁰⁹⁰
• increases noradrenaline levels in the brain compared to untrained rats⁹¹⁹²
• causes structural changes in the PFC of juvenile but not adult rats⁹³
• causes symptom improvements:
  • reduced hyperactivity
  • reduced impulsiveness
  • also by a decrease in DRD2 expression in the striatum and substantia nigra⁹⁴
• normalized the orientation behavior mediated by reduced NET levels in the PFC⁹⁵

3.2.1. Studies on the effect of long-term training on ADHD symptoms in children¶

A number of studies provided ample evidence of chronic effects of endurance training on parents’ and teachers’ assessments and observations of a wide range of behavioral and socio-emotional outcomes.¹¹⁹⁶

• 20 minutes a day (?) for 12 weeks for boys aged 7 to 10 years⁹⁷
  • High-intensity interval training (HIIT) had a better effect than moderate-intensity continuous training (MICT) on improving attention deficits
  • Both HIIT and MICT significantly improved impulsivity
  • HIIT showed additional benefits in reducing false responses and improving reaction times in cognitive tasks
• 26 minutes daily over 8 school weeks (moderate to vigorous physical activity, n = 17 children:⁹⁸
  • 0.40 to 0.70 SMD Improvement of social and behavioral functions in everyday school life in the teacher rating
  • 0.78 SMD Improvement regarding interruption
  • 0.40 SMD Improvement in unintentional aggression
  • unchanged: “not speaking nicely”, “deliberate aggression” and “not following adult instructions”
• 50 minutes, 3 x week over 12 weeks improved EEG values and frontal executive functions (rope jumping and ball exercises; n = 12 children, 7 to 9 years)⁹⁹
  -’40 to 50 minutes 3 x / week over 10 weeks significantly improved 3 out of 5 points (attention, motor skills and academic and school behavior) (circuit training and running training, n = 84 students 11 to 16 years); no improvement in the control group¹⁰⁰
• 30 minutes 5 x / week over 3 months improved hyperactivity. Sports of any kind (jogging, cycling, badminton, table tennis, soccer, basketball, aerobics or rope skipping) had a slightly better effect than qigong; n = 120.¹⁰¹
• 30 minutes 3 x / week over 8 weeks improved executive functions (exergaming; n = 51 children, 8 to 12 years)⁸¹
• 90 minutes, 2 x / week over 6 weeks showed improvements in the DuPaul’s ADHD Rating Scale, parent and teacher version (K-ARS-PT) and in cognitive functions in the Digitsymbol and the Trail Making Test Part B (TMT B), in cooperativeness scores as well as positive correlations regarding attention symptoms, cognitive symptoms and social skills (athletics, n = 28 children)¹⁰²
• 85 minutes, 2 x / week over 8 weeks improved inhibition and reaction speed (water gymnastics and motor exercises; n = 27 children, 5 to 10 years)¹⁰³
• 65 minutes, 2 x week over 12 weeks improved executive functions (table tennis; n = 60 children)¹⁰⁴
• 60 minutes 2 x / week over 8 weeks improved executive functions (combination of endurance, perception and coordination training; n = 37 children, 8 to 11 years)¹⁰⁵
• 70 minutes 2 x / week over 12 weeks improved executive functions (table tennis; n = 32 children, 6 to 12 years)¹⁰⁶
• 40 minutes of Teakwando martial arts, 2 x / week over 1 1/2 years improved selective attention compared to the control group who played handball, soccer, basketball twice / week (n = 40 children, 11 to 18 years)¹⁰⁷
• 40 minutes of yoga, 2 x / week over 8 weeks improved executive functions, especially accuracy and reaction time (yoga; n = 49 children, 8 to 12 years)¹⁰⁸
• 60 minutes 1 x / week over 12 weeks improved working memory (various sports; n = 43 children, 7 to 12 years)¹⁰⁹
• 90 minutes 1 x / week over 24 weeks improved cognitive inhibition and behavioral inhibition (sports program; n = 40 children, 7 to 11 years)¹¹⁰

One study found significant differences in the effectiveness of different types of exercise interventions on working memory in children with ADHD (in SMD):¹¹¹
0.72 Cognitive-aerobic training
0.61 Ball games
0.50 Physical exercises
0.40 General aerobic exercises
0.37 Interactive games

3.2.2. Studies on the effect of long-term training on ADHD symptoms in adults¶

There have been barely any studies on the effect of repeated sports on adults with ADHD. A planned RCT has disclosed its protocol.¹¹²

• Impulsivity: 1.77 meta-analysis, k = 8, n = 373):³⁰

One study found no significant effect of sports in adults on ADHD symptoms overall, but an improvement in inattention.¹¹³