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A few further details from the study might be useful:
- The analysis of movement such as gait and mobility is a science which I won't even pretend to understand. You get terms like goniometer fulcrum which probably makes a lot of sense to those in the know, but to me just sounds like a character from Game of Thrones. Suffice to say however that various measures were used to ascertain passive joint mobility - that is suppleness - across fingers, wrist, elbow and ankle. Gait was also analysed based on participants being "videotaped while walking and running barefoot up and down a hallway in the physician's office for 1-2 min".
- Results: as a group, participants with autism showed significantly greater values for maximum passive joint mobility angles across nearly all measured joints than controls. Taking one example, finger extension (or should that be 'finger metacarpo-phalangeal joint extension angle'), the authors present the very stark differences in angles obtained in histogram form between ASD and control participants. The majority of those with autism able to extend 110 degrees or over; such a feat only noted in 1 of the control participants. I might direct you to a post I wrote a while back on joint hypermobility (see here) which I'll talk about it moment.
- When it came to gait, the authors observed: "toe-walking was significantly more prevalent in children with autism" than controls (33% vs 3% observed on video only). I've talked about toe walking and autism in a previous post (see here) and what it may or may not mean for autism when present. Several other features of gait were also observed; 33% of children with autism were described as apraxic (an inability to execute learned purposeful movements) and 20% were described as clumsy. Both of these issues were not noted in any of the control group participants.
I found the Shetreat-Klein paper to be quite an intriguing read. Not only for the results obtained but because nestled in the paper introduction was reference to some of the original descriptions of autism by Leo Kanner, and how he "commented on the motor deficits in many of his patients". I've talked previously on this blog about how the seminal 1943 paper from Kanner  contained so much more than just descriptions of the triad (now dyad) of behaviours which make up the clinical diagnosis of the condition (see here). Aspects which we have perhaps ignored for too long...
The word 'hypotonia' - roughly translated as decreased or low muscle tone - is also a discussion point in the paper: "Our findings that passive joint mobility is on average increased in autism corroborates other studies that report a significantly increased proportion of clinically hypotonic children among those with ASD". Once again, I can't profess to be able to offer any great insight into this issue aside from some light reading around this concept and other uses in the research texts with autism in mind. Hypotonia seems to crop up quite a bit in various case reports detailing often rare genetic conditions with autism as part of presentation. Take for example the paper by Belengeanu and colleagues  reporting on a young child presenting with developmental delay and among other things, hypotonia. The paper by Shuvarikov and colleagues  talking about a potential HERV (human endogenous retrovirus) mediated genetic deletion with hypotonic features is another example; HERVs are another favourite talking point on this blog (see here).
That all being said, I'd also like to go back to the previous mention of joint hypermobility. Shetreat-Klein et al do talk about whether the descriptions of hyptonia in cases of ASD, or at least "joints with ligamentous laxity", might suggest "a disorder of elastin or collagen". Collagen issues immediately brought my mind back to the condition called Ehlers-Danlos syndrome (EDS), a heritable disorder of connective tissue. One of the primary features of EDS - accepting that there are various different presentations - is hyper-flexible joints. The literature looking at any overlap between autism and EDS is currently sparse, very sparse. I did happen upon the paper by Takei and colleagues  (open-access here) detailing a single case where "autistic disorder and EDS were diagnosed" concurrently. Takei et al describe a family history of EDS and as they note: "We speculate that associations exist between connective tissue diseases and autistic disorders, and that connective tissue abnormalities may contribute to autistic symptoms". I do wonder whether this might be an area requiring a little more scientific inspection.
The take home message from this post is that joint mobility and gait issues do seem to be quite apparent across the autism spectrum. Alongside other research in this area, one might start asking further questions about the hows and whys of such findings and whether it may offer further insight into some of the underlying issues potentially associated with at least some of the autisms?
To close, football (soccer). Now knowing that Germany are the 2014 World Cup Champions and this is the first lifting of the Jules Rimet trophy in a reunified Germany, I'm sure David Hasselhoff might have something to say...
 Shetreat-Klein M. et al. Abnormalities of joint mobility and gait in children with autism spectrum disorders. Brain Dev. 2014 Feb;36(2):91-6.
 Kanner L. Autistic disturbances of affective contact. Nervous Child. 1943; 2: 217-250.
 Belengeanu V. et al. A de novo 2.3 Mb deletion in 2q24.2q24.3 in a 20-month-old developmentally delayed girl. Gene. 2014 Apr 10;539(1):168-72.
 Shuvarikov A. et al. Recurrent HERV-H-mediated 3q13.2-q13.31 deletions cause a syndrome of hypotonia and motor, language, and cognitive delays. Hum Mutat. 2013 Oct;34(10):1415-23.
 Takei A. et al. High-functioning autistic disorder with Ehlers-Danlos syndrome. Psychiatry Clin Neurosci. 2011 Oct;65(6):605-6.
Shetreat-Klein M, Shinnar S, & Rapin I (2014). Abnormalities of joint mobility and gait in children with autism spectrum disorders. Brain & development, 36 (2), 91-6 PMID: 22401670