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Research Christmas 2015: Political science

“Gunslinger’s gait”: a new cause of unilaterally reduced arm swing

BMJ 2015; 351 doi: https://doi.org/10.1136/bmj.h6141 (Published 14 December 2015) Cite this as: BMJ 2015;351:h6141

The orator’s gait...?

Dear Madam,

We read with great interest the article in your last Christmas edition by Araújo et al, in which they describe their observations of the left-dominant asymmetric arm swing of Russian dignitaries and attribute this to a posture habituated through military weapons training (1).

Our experience in the analysis of upper body kinematics in a large cohort of healthy subjects has led us to the conclusion that such left-dominant arm swing asymmetry is, in fact, prevalent across all walks of life. Rather than being a purely habituated pattern, arm swing asymmetry is surprisingly dynamic and may provide a fascinating window into lateralised brain functions and gender differences in cognitive control.

We have recently shown that males of all ages and females over 60 demonstrate a significant shift from symmetrical upper limb movements towards left-dominant arm swing asymmetry (i.e. adopt the gunslinger’s gait) when engaged in a Stroop word / colour naming task while walking on a treadmill (2). The degree of asymmetry increases with task difficulty. Reduction in right arm swing, and specifically right shoulder anteversion, underlies the change in symmetry, with left arm swing unaffected. The site of this interference may be the left prefrontal cortex, important for both motor behaviour (3) and cognitive control (4). Tantalisingly, oestrogen-mediated plasticity has been observed in this region (5,6), providing a potential mechanism for the observed resistance of premenopausal women to this effect.

We propose that unilateral alterations in corticospinal drive to the right arm are brought about by engagement of the left cerebral hemisphere in the demanding, verbal Stroop task. With this in mind, the context of the videos used as the key evidence by the authors is worthy of some further consideration. In all cases, the political figures studied in Araújo et al were on camera and preparing to meet peers or address an audience. It is reasonable to believe that they may have been anticipating or mentally practising the speech or greeting they were about to give – Mr Putin in particular is known to be quite deliberate, even strategic, in his choice of phrases (7). Such mental rehearsal activates Wernicke and Broca’s area in the left hemisphere (8) and may lead to cognitive/motor interference (9).

To support this position, we sought video examples of leaders who exhibit upper limb gait asymmetry without having undergone the extensive covert operations training that Mr Putin received during his 15 years with the KGB. Ronald Reagan, US president from 1981 – 89, presumably received little in the way of concealed sidearm instruction during his relatively brief wartime service with the US Army’s First Motion Picture Unit, yet demonstrates considerable left-dominant arm swing while walking and conversing with former British prime minister Margaret Thatcher in this video (from 7:26) (10). Even lawyer and career politician António Costa, prime minister of Portugal, can be seen exhibiting the gunslinger’s gait while walking alongside German chancellor Angela Merkel in this video (from 0:06) (11). Interestingly, and in keeping with our findings that females are resistant to this effect until old age, neither Mrs Merkel nor Mrs Thatcher exhibit any appreciable degree of asymmetry in the videos.

We propose that the effect observantly detected by Dr Araújo and colleagues is not limited to Mr Putin and his inner circle and is instead a rather more interesting and widespread phenomenon. We are inclined to refer to such a gait pattern as the orator’s gait and feel that our interpretation stands on somewhat firmer scientific ground.

References
1. Araújo R, Ferreira JJ, Antonini A, Bloem BR. “Gunslinger’s gait”: a new cause of unilaterally reduced arm swing. Br Med J. 2015;351:1–5.
2. Killeen T, Easthope CS, Filli L, et al. Increasing cognitive load attenuates right arm swing in healthy human walking. R Soc Open Sci. 2017;4:160993.
3. Hausdorff JM, Yogev G, Springer S, Simon ES, Giladi N. Walking is more like catching than tapping: gait in the elderly as a complex cognitive task. Exp Brain Res. 2005;164:541–548.
4. Milham MP, Erickson KI, Banich MT, et al. Attentional Control in the Aging Brain: Insights from an fMRI Study of the Stroop Task. Brain Cogn. 2002;49:277–296.
5. Keenan PA, Ezzat WH, Ginsburg K, Moore GJ. Prefrontal cortex as the site of estrogen’s effect on cognition. Psychoneuroendocrinology. 2001;26:577–590.
6. Hao J, Rapp PR, Leffler AE, et al. Estrogen alters spine number and morphology in prefrontal cortex of aged female rhesus monkeys. J Neurosci. 2006;26:2571–2578.
7. Dougherty J. Trash talk: What Putin’s presidential potty mouth is all about [online]. CNN Online 2015. Available at: http://edition.cnn.com/2015/12/25/europe/vladimir-putin-bad-language/. Accessed January 24th, 2017.
8. Price CJ, Wise RJS, Warburton E a, et al. Hearing and saying: The functional neuro-anatomy of auditory word processing. Brain. 1996;119(Pt 3):919-31.
9. Al-Yahya E, Dawes H, Smith L, Dennis A, Howells K, Cockburn J. Cognitive motor interference while walking: A systematic review and meta-analysis. Neurosci Biobehav Rev. 2011;35:715–728.
10. footagefarm. 1981 Thatcher State Visit to US w/Reagan 250013-01 [online]. youtube.com 2012. Available at: https://www.youtube.com/watch?v=ZHxld-JXjRs. Accessed January 24th, 2017.
11. Martins AE. António Costa oferece solidariedade para resolver problemas da Europa [online]. RTP Not. 2016. Available at: http://www.rtp.pt/noticias/politica/antonio-costa-oferece-solidariedade-.... Accessed January 24th, 2017.

Competing interests: No competing interests

24 January 2017
Tim Killeen
MD-PhD Student
Volker Dietz, Armin Curt, Marc Bolliger
Spinal Cord Injury Center, University Hospital Balgrist
Forchstrasse 340, 8008 Zurich, Switzerland