Exercise and Autism: Can There be too Much of a Good Thing?

By Shawn M. Arent, Ph.D., FACSM, CSCS*D, FISSN, and Bridget A. McFadden, MBS, CSCS

Shawn M. Arent, Ph.D., FACSM, CSCS*D, FISSN Bridget A. McFadden, MBS, CSCS
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Shawn M. Arent, Ph.D., FACSM, CSCS*D, FISSN, is an associate professor in the Department of Kinesiology and Health at Rutgers University, Brunswick, New Jersey. He also is director of the IFNH Center for Health and Human Performance and director of the graduate program in the Department of Kinesiology and Applied Physiology. Dr. Arent's research focuses on the relationship between physical activity and stress and the associated implications for health and performance in adolescents, athletes and special populations.

Bridget A. McFadden is a Ph.D. student at Rutgers University studying kinesiology and applied physiology. She received her B.S. degree from Saint Joseph’s University in Philadelphia, Pennsylvania and her Master of Business and Science degree from Rutgers University. Bridget currently works at the IFNH Center for Health and Human Performance under the direction of Dr. Arent. Her research interests include exercise programming and athlete-monitoring to optimize health and performance outcomes, particularly in females.

This commentary presents Dr. Arent’s and Ms. McFadden’s views on the topic of a research article that they and other colleagues authored. Their article appeared in the May 2017 issue of
Medicine & Science in Sports & Exercise® (MSSE).

With a recognized prevalence of one in every 68 children born in the United States and a growing number of children diagnosed each year, Autism Spectrum Disorder (ASD) is a serious health problem in dire need of effective treatment or management methods. Among symptoms of ASD, repetitive and restrictive behaviors (otherwise known as stereotypical or self-stimulatory behaviors) are some of the most notable features of the disorder. These behaviors can include inflexible routines, repetitive speech, and habitual motor movements such as hand flapping, rocking the body or spinning in circles – behaviors which often cause a distraction for others and impair the ability of the child to effectively learn in a classroom setting.

Exercise generally has been shown to reduce these behaviors in children with ASD, with most recommendations gravitating toward “vigorous” activity. However, the efficacy of this approach has rarely been objectively quantified. Not only is this form of treatment inexpensive and potentially easy to administer, it also promotes the added health benefits inherent to physical activity. The question then, which we investigated (see MSSE, May 2017), becomes “How long should the exercise last and what intensity may be needed to see beneficial effects?” In our dose-response study, seven participants diagnosed with ASD participated in five separate days of aerobic exercise at either low/moderate (50%-65% HRmax) or moderate/high (70%-85% HRmax) intensity exercise for either 10 or 20 minutes, and a no-exercise control condition. Exercise was performed on either a treadmill or stationary bicycle with the modality being consistent for each subject across all conditions, which were completed in randomized order. Intensity was measured using the OMNI rating of perceived exertion, as well as continuous heart rate monitoring. Throughout, the exercising subjects’ heart rates were kept within the ACSM recommended guidelines for the assigned intensity. Stereotypical behaviors were unobtrusively assessed for 60 minutes post-exercise within the students’ classroom.

The shorter-duration and less-intense exercise sessions were found to elicit the greatest and longest-lasting reductions in stereotypical behaviors. Surprisingly, the most exhaustive exercise led to an increase in stereotypical behavior from baseline. The 20-minute high-intensity condition was the only session that showed an increase in behaviors from the pre-exercise level and failed to be more effective than the non-exercise control. These findings are contrary to previous research, which suggested that fatigue was a possible cause of the reductions in behavior seen after exercise. Therefore, we concluded there may be a threshold for the efficacy of exercise as a treatment for symptoms of ASD. Perhaps high-intensity exercise may induce an over-arousal of an already hyper-aroused physiological system and, thereby, lead to increases in stereotypical behavior.

Though the root cause of stereotypical behaviors is not certain, some researchers believe they arise because the behavior itself produces a pleasant internal consequence. Exercise may involve similar feelings driven by body mechanics that resemble the stereotyped behavior. Therefore, low intensity exercise may mimic the physical stimulation received from performing stereotypical behaviors. It also may positively impact neurotransmitters.

When prescribing exercise as a treatment or management tool for symptoms of ASD, it is important to consider that not all exercises doses are equally beneficial. However, 10-minute low-moderate intensity sessions have been shown to be advantageous in attenuating these symptoms and could manageably be included within the regular curriculum with minimal interference on other academic activities. Based on our findings, we believe it is reasonable to suggest that multiple short-duration, low/moderate-intensity exercise breaks throughout the day may help improve the daily management and learning environments for individuals with ASD. Designing an exercise program that matches the stereotyped behavior’s motor pattern may be a practical method to encourage greater participation in exercise within this population.