Physical exercise is widely reported to be beneficial to executive functions (EFs) in children with autism spectrum disorder (ASD). However, the impact of physical exercise on self-regulation (SR) in this population remains unknown. Moreover, very few studies have been done to examine the mechanism(s) that underlie the exercise-EF and exercise-SR relationships. The purposes of the present study were to test whether two types of physical exercise (cognitively engaging vs. non-cognitively engaging) benefited SR, and if the social, emotional and physical needs of an individual mediated the exercise-EF and exercise-SR relationships. Children diagnosed with ASD were randomly assigned into one of three groups: learning to ride a bicycle (n = 23), stationary cycling (n = 19) or an active control with walking (n = 22). Two EFs (flexibility and inhibition), SR and the mediating roles of perceived social support, enjoyment, stress, physical self-efficacy and perceived physical fitness were assessed.

Given the well-evidenced cognitive benefits of physical exercise for executive functions (EFs) in children with typical development (TD), there is growing research interest in whether such benefits could also be translated to children with autism spectrum disorder (ASD). Previously, the investigators examined the effectiveness of a 12-week basketball training intervention on inhibition control and working memory in children with ASD. Results showed that the training improved inhibition control. More recently, Liang and colleagues (2022) conducted a meta-analysis of seven studies examining the effect of physical exercise interventions on EFs in children and adolescents with ASD. They concluded that chronic exercise interventions were beneficial to overall EFs in the population, particularly for cognitive flexibility and inhibitory control. While physical exercise appears to be beneficial in this population, the mechanism by which physical exercise potentially impacts EFs in children with ASD remains a question. It is important to understand the mechanism in order to design an effective physical exercise intervention to promote the development of EFs among children with ASD.

Over the past few decades, most of the studies examining the exercise-cognition relation in the general population have viewed the mediating mechanism via a neurobiological framework, expressed most clearly by the neurotrophic hypothesis. The hypothesis states that physical activity increases metabolic demands and triggers a cascade of biochemical changes, such as enhancing cerebral blood blow and increasing the availability of brain-derived neurotrophic factor, which strengthens brain plasticity for higher-level cognitive activities such as those involved in executive functions. It is not until recently that scientists started questioning whether the exercise-cognition relation could also be mediated by a person's social, emotional, and physical needs. Diamond and Ling (2016) hypothesized that the most successful approaches for improving EFs would address social, emotional and physical needs, and that cognitively engaging physical activity (e.g., martial arts, dance) that enhances social interaction and joy would be more beneficial to EFs than less cognitively engaging physical activity. To the best of our knowledge, no previous studies have examined the possible mediating roles of social support, emotion and physical fitness in the exercise-EF relation.

Also of interest is the impact of physical exercise on self-regulation. Self-regulation (SR) is a psychological construct that encompasses a range of functional behaviors, such as interacting with peers, remembering rules and regulations, controlling emotions and inhibiting inappropriate and aggressive actions. Given these behaviors call upon the higher-order cognitive processes associated with EFs (e.g., shifting attention, working memory, inhibition), and the fact that SR and EFs predict many of the same positive outcomes (e.g., physical health, mental health, academic achievement), SR has long been thought of as the behavioral manifestation of EFs. However, several recent studies provided compelling evidence that SR and EFs are distinguishable and should be treated independently. Confusion may arise when measuring one without the other. Therefore, it is important to investigate whether physical exercise could yield similar benefits in SR as those in EFs, particularly in children with ASD where SR difficulties are common.

Therefore, the purposes of this study were to examine the exercise-SR relation, and to investigate the possible mediating roles of social and emotional experience and physical perception in the exercise-EF and exercise-SR relationships in children with ASD. In the present study, these needs were expressed by individuals' perceived social support, enjoyment, stress, physical self-efficacy and perceived physical fitness. Similar to our previous study, the investigators compared EFs among three groups: 1) learning to ride a bicycle, 2) stationary cycling and 3) active control (walking) before and immediately after the two-week intervention period. Following the suggestion by Diamond and Ling (2016), the active control group with walking (instead of a no-treatment control group) was used to control for potential Hawthorne effects. Walking was chosen because it was a low intensity physical activity that enabled us to assess the same potential mediators as those in the intervention groups. Unlike our previous study, only inhibition and flexibility were measured in this study because exercise interventions were shown effective to improve these two EFs in children with ASD, and to enhance the feasibility of the study (to avoid overburdening participants with the additional mediation assessments compared to our previous study). To examine the mediating effects, perceived social support, enjoyment, stress, physical self-efficacy, and perceived physical fitness were measured during the baseline period, mid-intervention and post-intervention.

Inclusion Criteria:

• age 8 - 12 years
• mild to moderate ASD (i.e., level 1-2 support classification) diagnosis from physicians or psychologists based on the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, (DSM-5) and Autism Diagnostic Observation Schedule, 2nd Edition (ADOS-2)
• non-verbal IQ over 50 using a brief version of the Wechsler Intelligence Scale for Children (Chinese revised) [C-WISC]
• able to follow instructions with the assistance of research staff
• able to perform the requested physical intervention, executive function measures and mediator measures with the assistance of the research staff
• no additional regular participation in physical exercise other than school physical education classes for at least one month prior to the study
• novice at riding a two-wheel bicycle (i.e., cannot ride the bicycle alone for more than 10 consecutive seconds).

Exclusion Criteria:

• other medical conditions that limited physical exercise capacities (e.g., asthma, seizure, cardiac disease)
• a complex neurologic disorder (e.g., epilepsy, phenylketonuria, fragile X syndrome, tuberous sclerosis)
• suffering from obesity (i.e., > 95 percentile of age-gender specific BMI cutoff, such that it would be difficult for research staff to catch them if they began to fall when riding
• self-reported color blindness.

The staff responsible for the cognitive assessments and data analyses were not aware of the participants' group assignments.