HANDGRIP STRENGTH IN AUTISM SPECTRUM DISORDER COMPARED WITH CONTROLS JANET K. KERN, 1,2 DAVID A. GEIER, 1,3 JAMES B. ADAMS, 4 MELISSA R. TROUTMAN, 5 GEORGIA A. DAVIS, 5 PAUL G. KING, 3 AND MARK R. GEIER 5 1 Institute of Chronic Illnesses, Inc., Silver Spring, Maryland; 2 Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas; 3 CoMeD, Inc., Silver Spring, Maryland; 4 School of Materials, Arizona State University, Tempe, Arizona; and 5 ASD Centers, LLC, Silver Spring, Maryland ABSTRACT Kern, JK, Geier, DA, Adams, JB, Troutman, MR, Davis, GA, King, PG, and Geier, MR. Handgrip strength in autism spectrum disorder compared with controls. J Strength Cond Res 27(8): 2277–2281, 2013—The study examined handgrip strength in participants diagnosed with an autism spectrum dis- order (ASD) as compared with neurotypical children. Thirty-three children, aged 2–17 years, with an ASD and 33 gender-, race-, and age-matched neurotypical controls were tested using a handgrip dynamometer. The handgrip strength in participants with an ASD was significantly (p , 0.0001) lower than the neurotypical controls. The mean handgrip strength was 39.4 6 17.7 kPa in children with ASD and 65.1 6 26.7 kPa in con- trols. The results support the hypothesis that children with an ASD have significantly poorer handgrip strength as compared with neurotypical children. Because the handheld dynamometer has been shown to be a valid tool for measuring overall muscle strength, the results suggest that children with ASD have muscle weakness. Future studies are needed to determine the extent of muscle weakness in ASD, its ramifications, and the possible benefits of muscle strengthening. The present study provides support for the use of handgrip strength as a tool for the assess- ment of targeted treatment in ASD. KEY WORDS muscle strength, handgrip dynamometer, physical condition INTRODUCTION A utism spectrum disorder (ASD) is defined by its core features (1). According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text-Revision (DSM-IV-TR), the core features include (a) qualitative impairments in social interaction, (b) qualitative impairments in communication, and (c) restricted repetitive and stereotyped patterns of behavior, interests, and activities. Although an ASD diagnosis is defined by these 3 core features, other issues, more physical or health related, are associated with an ASD diagnosis (9,25). Examples of physi- cal impairments include fine and gross motor problems (22), movement/motor skills deficits (11), balance problems (19), gait pattern differences (5), dysfunctional posture and muscle tone (7), and hypotonia (18). Another aspect that may be reflective of issues in general physical condition is muscle weakness in ASD (12). Anecdotal reports and limited research suggest that children with ASD are weaker than typically developing children. Hardan et al. (12), for example, examined grip strength in 40 individuals diagnosed with autism without intellectual disabilities and 41 healthy controls. These inves- tigators found that grip strength in participants diagnosed with an ASD was significantly weaker than in the controls. According to Bhat et al., muscle weakness and abnormal muscle tone in ASD may play a role in the limitations in daily activities, such as locomotion and reaching. They also stated that one of the earliest motor signs of an ASD may be weakness in pronation and supination as in turning a door- knob or twisting a bottle cap (3). Studies examining motor impairments in children with ASDs suggest the presence of low muscle tone (3). It is possible that the functional effects of muscle weakness in ASD could be widespread. A study by Kern et al. (14) found that handgrip strength in participants diagnosed with an ASD was related to the severity of the disorder. In that study, 37 children with ASD were evaluated using the Childhood Autism Rating Scale (CARS) (26) and then tested for hand muscle strength using a handgrip dynamometer. The results showed that the more severely affected the child was based on the child’s CARS score, the weaker the handgrip strength. Importantly, studies have shown that the handheld dynamometer is a valid tool for measuring overall muscle strength and for the assessment of muscle mass (8,16). In addition, Theou et al. (27) found that handgrip strength correlates with an overall frailty index. There is a paucity of research in muscle strength in children with ASD, even though muscle weakness may be a factor in Address correspondence to Dr. Janet K. Kern, jkern@dfwair.net. 27(8)/2277–2281 Journal of Strength and Conditioning Research Ó 2013 National Strength and Conditioning Association VOLUME 27 | NUMBER 8 | AUGUST 2013 | 2277 Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.