The restrictive force of the anterior foot portion in a shoe was measured in terms of luminous reflection Y% of pressure-sensitive films as a sensor. Environmental factors which affect the foot were specified with the W values of the restrictive force.
1) The contribution ratio of foot size was high on all toes when the foot was rather wide (maximum, 48.9%) and high on the fibular side of the 5th toe and the 1st and 5th metatarsal heads when the foot was rather narrow (maximum, 40.9%).
2) It was found that the environmental factors which affect the restrictive force were not only foot and shoe sizes, but also shoe material, the presence or absence of stockings, and movements.
3) The restrictive force was high (about 1.0 kg) on the tibial side of the 1st, 2nd and 4th toes, and 5th metatarsal head and especially high (maximum, 3.97 kg) on the fibular side of the 5th toe.
4) Similarity assessment showed mutual influence in terms of restrictive force between the 1st and 2nd toes and between the 3rd and 4th toes but not between the 1st and 5th metatarsal heads and the fibular side of the 5th toe.
