COMPARISON OF FOOT MORPHOLOGY AND INTRINSIC FOOT MUSCLE PROPERTY BETWEEN ADOLESCENT SWIMMERS AND OTHER ATHLETES IN JAPAN

K. Kaneda¹, N. Maeda¹, T. Tashiro¹, S. Tsutsumi¹, S. Arima¹, M. Komiya¹, Y. Urabe¹

¹Graduate school of Biomedical & Health Science, Hiroshima University, Department of Sports Rehabilitation, Hiroshima, Japan

Background: Competitive swimmers have more foot flexibility than other athletes due to the general laxity of their joints, and their excessively flexible feet are typically flat-footed. Foot injuries in competitive swimmers often generally during dry land resistance training; however, previous studies have not explicitly discussed swimmers’ foot morphology.

Purpose: This study aimed to investigate the relationship between foot posture and intrinsic foot muscles (IFMs) in competitive adolescent swimmers compared with other athletes in matched age and competitive level.

Methods: The subjects were 32 competitive adolescent swimmers’ group (age: 15.9 ± 2.4 years) and 32 other athletes’ group (age: 15.3 ± 2.4 years), totaling 64 members and 128 feet. All participants were elite adolescent athletes registered by the prefectural sports association who had at least 5 years of experience in the competition. Foot morphology was measured that sitting and standing navicular height by using a 3D foot scanner. Morphologies of IFMs (thickness and cross-sectional area: CSA) were observed using ultrasonography. The following were measured of abductor hallucis (AbH), flexor hallucis brevis (FHB), and flexor digitorum brevis (FDB). The demographics, foot morphology, IFMs thickness and CSA were compared between the two-groups using the unpaired t-test. The relationship of each group between navicular height by posture differences, navicular drop test (NDT) and IFMs property was examined using the Pearson product rate correlation test. Statistical significance was set at p <0.05.

Results: Navicular height in a standing position, the thickness and CSA of AbH and FDB were significantly lower in swimmers than in other athletes (p<0.05). Upon NDT and CSA of FHB were significantly higher in swimmers than in other athletes (p<0.01).
The navicular height of the swimmers in the standing positions was positively correlated with thickness and CSA of FHB (r=0.295, r=0.301, p<0.05), and FDB (r=0.276, r=, 0.284, p<0.05). In addition, NDT was positively correlated with thickness and CSA of AbH (r=0.331, r=0.320, p<0.01).

Conclusions: The flatfoot is decreases with aging due to the development of IFMs and the attainment of foot stiffness by loading response (Kelly et al., 2014). Meanwhile, the adolescent swimmers had a significantly lower navicular height in standing positions than other athletes, and the thickness and CSA of AbH and FDB were smaller. These findings might have been due to their competitive characteristics and less loading opportunity. Moreover, among the IFMs, AbH mainly contributes to the medial longitudinal arch (MLA) formation; thus, the deterioration of AbH function led to an increase in NDT (Wong, 2007).Therefore, FHB, which were larger among adolescent swimmers, and FDB instead of AbH, might compensate for the MLA during sitting and standing.

Implications: This study revealed that the navicular height of adolescent swimmers was lower than that of other athletes in age and competitive level matching. These results provide fundamental data that will aid understanding of foot characteristics among adolescent swimmers.

Funding acknowledgements: We have no funding acknowledgment in this study.

Keywords:
Adolescent competitive swimmer
Foot morphology
Intrinsic foot muscle

Topics:
Sport & sports injuries
Disability & rehabilitation
Orthopaedics

Did this work require ethics approval? Yes

Institution: Hiroshima university hospital

Committee: Ethics Committee for Epidemiology

Ethics number: E-2090