I'm always a bit sceptical about such claims which are trotted out rote fashion by UK military.
Two experiments are reported that compared younger and older adults on their performance of two bimanual temporal coordination tasks at varying movement speeds. In many cases, older adults performed as well as younger adults at all speeds of an in-phase coordination pattern and at slow speeds of an anti-phase pattern for both coordination accuracy and stability. Age differences tended to emerge most prominently at high speeds for the anti-phase pattern. These findings are consistent with the aging literature regarding automatic and effortful processing distinctions, suggesting that relative age differences become magnified when effortful resources are required for motor performance.
Laurie R. Wishart, Timothy D. Lee, Jason E. Murdoch, and Nicola J. Hodges
Effects of Aging on Automatic and Effortful Processes in Bimanual Coordination J Gerontol B Psychol Sci Soc Sci (2000) 55(2): P85-P94