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Introduction
If you ever find yourself in a neurology meeting and notice a group of individuals scrutinising the way people walk, they are likely to be movement disorder enthusiasts. Their passion to screen for abnormal walking patterns may extend to examining YouTube footage, where remarkable discoveries can be made. 1 We were struck to find several consecutive YouTube recordings of Russia's president, Vladimir Putin, manifesting a clearly reduced right-sided arm swing (video 1, segments 1 and 2). Putin's distinctive walk has been debated previously, and different theories emerged, ranging from Erb's palsy to intrauterine stroke. 2 For movement disorders experts such as ourselves, the first, and admittedly biased, diagnosis that comes to mind is Parkinson's disease, in which an asymmetrically reduced arm swing is a distinct feature. 3 In fact, it can be the earliest presenting sign of Parkinson's disease, as was demonstrated by video reviews of football games played by the legendary English midfielder Ray Kennedy. 4 Original footage showed an asymmetrically reduced arm swing even when Kennedy played elite football; only later this proved to be the presenting sign of his Parkinson's disease. 4
The topic of early "preclinical" Parkinson's disease is the subject of a lively debate. 2 5 6 It is now clear that many symptoms and signs (such as constipation or reduced smell) can precede overt Parkinson's disease. This preclinical phase includes a reduced arm swing on one side. Indeed, an asymmetrically reduced arm swing can present in otherwise clinically intact subjects with a predisposition to later develop Parkinson's disease. 7 Such observations raised a debate among us whether President Putin might possibly be in an early stage of Parkinson's disease, even in the absence of other obviously suggestive features.
However, further review of YouTube footage revealed an alternative and more likely explanation, which we present here as a new cause of a reduced arm swing during walking.
Methods
Searching for possible explanations, we encountered a training manual of the former Russian KGB. 8 According to this manual, KGB operatives were instructed to keep their weapon in their right hand close to their chest and to move forward with one side, usually the left, presumably allowing subjects to draw the gun as quickly as possible when confronted with a foe....