an activity that is natural to or the purpose of a person or thing. (Oxford English Dictionary)
The purpose of the foot is to provide a stable base of support to control the direction of the body weight during the stance phase of locomotion [1-3]. Newtonian physics dictates that a wider base of support is more stable than a narrow base. Width and stability of the forefoot is crucial in this regard as the highest forces during mid stance occur at the forefoot [4, 5]. A greater spread of the toes, the great toe in particular, reduces forefoot peak pressures, distributes force more evenly, and stabilises the foot and ankle [6-8]. Toes squashed together by years of wearing narrow shoes that do not respect the natural fan shape of the human foot  are common  and are linked to instability and movement-related pain [11, 12]. Natural function can be restored by regular loading of the feet in footwear that respect natural design of the foot  and permit freedom for the toes to spread and stabilise the foot.
Pain-free movement begins with a stable base of support. A stable foot requires Toe freedom, only functional footwear provides toe freedom. Joe Nimble ‘functional footwear’ is based on this science.
1. Mann R and Inman VT. Phasic Activity of Intrinsic Muscles of the Foot. The Journal of Bone and Joint Surgery 1964 46(3): 469-481. (http://www.ncbi.nlm.nih.gov/pubmed/14131426)
2. Reeser LA, Susman RL, and Stern JT. Electromyographic Studies of the Human Foot: Experimental Approaches to Hominid Evolution. Foot and Ankle 1983 3(6): 391-407. (http://www.ncbi.nlm.nih.gov/pubmed/6409717)
3. Rolian C, et al. Walking, running and the evolution of short toes in humans.
Journal of Experimental Biology 2009 212: 713-721. (http://homepages.ucalgary.ca/~cprolian/pubs/Rol...)
4. Wilkinson M and Saxby L. Form determines function: Forgotten application to the human foot? . Foot and Ankle Online Journal 2016 9(2): 5-8. (https://faoj.org/2016/06/30/form-determines-fun...)
5. Wilkinson M, Stoneham R, and Saxby L. Feet and footwear: Applying biological design and mismatch theory to running injuries. International Journal of Sports and Exercise Medicine.
2018 4(2). (https://clinmedjournals.org/articles/ijsem/inte...)
6. D'Aout K, et al. The effects of habitual footwear use: foot shape and function in ntaive barefoot walkers.Footwear Science 2009 1(2): 81-94. (http://www.tandfonline.com/doi/abs/10.1080/1942...)
7. Mei Q, et al. A comparative biomechanical analysis of habitually unshod and shod runners based on foot morphological difference. Human Movement Science 2015 42: 38-53. (http://www.ncbi.nlm.nih.gov/pubmed/25964998)
8. Shu Y, et al. Dynamic loading and kinematics analysis of vertical jump based on different forefoot morphology. SpringerPlus 2016 5: 1999. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC51...)
9. Munteanu SE, et al. Hallux valgus, by nature or nurture? A twin study. Arthritis Care and Research 2017. (https://www.ncbi.nlm.nih.gov/pubmed/27863158)
10. Nix S, Smith M, and Vicenzino B. Prevalence of hallux valgus in the general population: a systematic review and meta analysis. Journal of Foot and Ankle Research 2010 3: 21. (https://www.ncbi.nlm.nih.gov/pubmed/20868524)
11. Vorobiev G. Evolution of injuries in athletics. New Studies in Athletics 1999 4: 23-26.
12. Travell J and Simons D, Myofascial Pain and Dysfunction: The Trigger Point Manual. 1993: Lippincott Williams & Wilkins
13. Knowles FW. Effects of shoes on foot form: An anatomical experiment. The Medical Journal of Australia 1953 1(17): 579-581. (http://www.ncbi.nlm.nih.gov/pubmed/13062868)