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R. Mizuta1, Y. Urabe1, M. Komiya1, M. Morikawa1, A. Hirota1, N. Maeda1
1Hiroshima University, Department of Sport Rehabilitation Graduate School of Biomedical and Health Science, Hiroshima, Japan
Background: Medial longitudinal arch (MLA) is composed of many factors including muscles, bones, and tendons. Recently, planter intrinsic muscle training has been common to increase MLA height. The training of intrinsic muscle improved abductor hallucis (AbH) of the foot activities (Juntip et al., 2019) and significantly decreased navicular drop (Edward et al., 2013). Meanwhile, the training focused on this motion might be effective since the essential function of AbH is hallux abduction. We hypothesized that navicular drop was decreased when AbH was more activated by the short-term toe spread training.
Purpose: This study aimed to clarify the acute effect of short-term toe spread training on AbH muscle activity and MLA height.
Methods: Ten healthy subjects (7 men, 3 women) participated in this study. The surface electromyography (Oisaka Electronic Equipment Ltd.) was used to measure the AbH muscle activity pre and post training. First, the maximal voluntary isometric contraction of the AbH muscle was measured through manual muscle testing for 3 times to normalize the EMG data. Second, AbH muscle activity of active hallux abduction was measured before the training for 3 times. The active toe spread training was performed 10 repetitions in the sitting position and participants hold each repetition for 5 seconds. Then, we measured the muscle activity of AbH during active toe spread again. Root mean square values were calculated. For measurement of the height of MLA, the navicular height was measured in sitting and standing positions using a ruler before and after training. The navicular drop was calculated to make subtraction of Navicular height sitting - standing. The mean changes in AbH muscle activity of active toe spread and navicular drop at pre and post intervention were compared using the Student t-test. Statistical significance was set at 0.05.
Results: Muscle activity of AbH was no significant difference post training (pre: 81.5 ± 50.7%, post: 93.4 ± 53.1%, p = 0.20). The navicular drop was significant decreased between pre and post training (pre: 7.6 ± 1.7mm, post: 6.2 ± 3.0mm, p = 0.02). Navicular height was almost no change in sitting but increase standing (standing pre: 35.4 ± 6.0mm, post: 36.8 ± 5.6mm, p = 0.003).
Conclusion(s): Our results showed that the toe spread training could reduce the navicular drop. A previous study reported that the muscle activity of the AbH was important for reducing the navicular drop (Okamura et al., 2019). Thus, the toe spread training may be able to assist AbH in reinforcing the MLA. However, the muscle activity of AbH pre and post training did not change in this study. This result indicated that the toe spread training did not increase the muscle activity of AbH when bearing weight. Further study, therefore, is required to examine the effect of toe spread training in loaded and non-loaded positions.
Implications: This investigation could confirm the acute effect of toe spread training and show the way to decrease navicular drop.
Funding, acknowledgements: We have no funding acknowledgement in this study.
Keywords: toe spread training, acute effect, navicular drop
Topic: Musculoskeletal
Did this work require ethics approval? Yes
Institution: Hiroshima university hospital
Committee: Hiroshima University Committee on Ethics in Research
Ethics number: E-2090
All authors, affiliations and abstracts have been published as submitted.
