Noncontact of the unilateral hallux with the ground reduces forward limits of stability while standing

[Purpose] Although hallux function is fundamental in maintaining forward leaning standing posture, the insight into whether noncontact of the hallux with the ground alters the forward limit of stability (LoS) remains unclear. Thus, we aimed to determine the effects of the unilateral hallux noncontact on the forward LoS while standing. [Participants and Methods] This study included 17 healthy young and 17 community-dwelling older adults. The position of the center of pressure during the forward, forward-left, and forward-right LoS was measured using a force platform under two toe conditions: noncontact or contact of the right hallux with the ground. To ensure the noncontact condition, we positioned the right hallux on the second toe by taping. [Results] The forward and forward-right LoS were significantly displaced in the left and backward directions (p<0.032, η²>0.14), while the forward-left LoS was significantly displaced in the backward direction (p<0.001, η²=0.52). In the noncontact condition, the forward-right LoS exhibited a greater degree of the backward shift than the forward-left LoS (p<0.001, η²=0.42). [Conclusion] Noncontact of the unilateral hallux with the ground reduced the LoS in the forward and oblique-forward directions and induced LoS asymmetry.