## 1 Introduction  
In sports, lower limb disorders include a variety of disorders such as medial tibial stress syndrome, tibial overtired fatigue fractures, and chronic exercise compartment syndrome [1]. These are known to occur more frequently, particularly in long-distance runners [1]. Reduced intrinsic foot muscle (IFM) function is one of the contributing factors. A decrease in the medial longitudinal arch height (navicular drop) due to reduced IFM causes malalignment [2], which in turn leads to reduced dynamic balance and is associated with disability [3]. IFM exercises have been shown to reduce the incidence of disability [4], and improve vertical and horizontal jump performance [5]. The IFM strength is important not only for disability prevention but also for performance improvement. Concerning the IFMs, the abductor hallucis (AbH), flexor hallucis brevis (FHB), and flexor digitorum brevis (FDB) muscles play an important role in toe flexion [6] and their muscle size has been reported to correlate with toe strength [7]. Runners with smaller cross-sectional areas of the AbH have also been reported to have a history of injuries such as medial tibial stress syndrome, patellofemoral pain, and plantar fascitits [8]. In runners, the toe strength is an important factor in injury prevention and competitive performance. A well-known conventional IFM exercise is the short foot exercise (SF-ex) [6, 7, 9, 10], which has been shown to be effective in supporting the medial longitudinal arch [2]. However, challenges include the difficulty of learning the movement itself, the inability to adjust the load, and the lack of ankle joint movement. SF-ex is an exercise in which the foot is moved in a 'foot-shortening' manner without flexing the toes, but the movement itself is difficult to learn as it is not something we are normally aware of. Since SF-ex is difficult to teach and learn, a step-by-step training program is recommended. First, the therapist moves the athlete's foot to experience the short foot movement in 'passive mode', and then the athlete progresses to 'active support mode', where they contract the IFMs to achieve the short foot position. Finally, the athlete moves to 'active mode', where they perform the exercise independently. These steps are effective, but time-consuming [10]. Load regulation in SF-ex is restricted to sitting or standing. Usually, when the IFMs are mobilized, this is accompanied by movement and therefore ankle joint movement, but SF-ex does not involve ankle joint movement. Conventional exercises such as SF-ex are IFM-specific and there are no functional toe exercises that involve ankle joint and toe movement and are combined with extrinsic muscles. Evidence on effective toe exercises is considered necessary. On the other hand, the usefulness of elastic resistance (tubing or bands) for non-IFM exercises using the lower limbs is widely recognized [11; 12]. This method has been widely used in rehabilitation medicine and the health and fitness industry for muscle strengthening purposes and has become a staple of training due to its low cost, simplicity, portability, and versatility of use [13]. The load can be adjusted by selecting the type of tubing and adjusting the resistance. The elastic tubing can be simply hooked to the target area of the body to be trained, and exercises with joint movements in any direction can be performed. If the tube is placed between the toes, it is easy to learn how to train the IFMs with ankle joint movement. This is the type of toe tube training that we examined in this study. It has been reported that IFMs can be trained particularly effectively with toe flexion exercises in the plantar flexed position of the ankle joint [14]. The research suggests that in maximum plantar flexion of the ankle joint, the extrinsic muscles are relaxed, but the IFMs are not affected in length by the ankle joint position, so IFM activity is increased. During running, ankle joint plantar dorsiflexion moves from approximately 10 degrees of dorsiflexion to 20 degrees of plantar flexion [15].