There are climatic constraints. Plantar tactile sensibility declines from anesthesia from cold when temperature approaches freezing of water, therefore this may be to lower temperature limit of barefoot mobility. In addition, human skin tolerates poorly being wet for many hours, therefore wet conditions may limit safe barefoot mobility. Even when climatic conditions are favorable, optimal safe human locomotion is achieved on paths formed from naturally deposited soils. Many urban areas have developed in areas loam soils are plentiful, such as in river valleys on land once used for agriculture. However the chance of running barefoot on naturally deposited ground often unavailable because of urban expansion. Furthermore, once soils are disturbed through excavation, replacing it in the form of naturally deposited ground becomes almost impossible - it often contains man made elements of gravel and stone used for construction formed from crushing large rocks rather than highly weathered components in naturally deposited ground. Man made gravel produce acute plantar deformations that may penetrate plantar skin. Plantar sensory feedback produces discomfort which protects through avoiding discomfort through slowing walking and running so as to attenuate impact.
Because of the unique properties of naturally deposited loam in terms of safe and efficient human locomotion, I can foresee a time where undisturbed lands are preserved for recreational barefoot human locomotion for both health and rehabilitation, rather than simply to maintain plant species and wildlife, which is currently the case. Though few data are available, there is considerable anecdotal information indicating that barefoot on man made outdoor surfaces (concrete and asphalt), when climatic conditions allow, can be safer than locomotion with current running shoes. Yet it seems unlikely that it could be as ideal as barefoot on naturally deposited ground because of lowered plantar tactile sensory feedback and abrasion risk.
Indoor surfaces currently in use probably present a modest constraint on barefoot activity because of low frictional resistance. These surfaces were designed with the objective of cosmetics, ease of cleaning, low cost and durability. Compared to certain atheltic shoes, risk of falling from slips would be higher indoors when barefoot, and performance in sports performed barefoot when indoors would be lower in terms of ability to accelerate and change direction. These disadvantages of being barefoot on these surfaces are countered by advantages offered by impact control and stability from plantar tactile feedback when barefoot.