The effects of short foot exercises and arch support insoles on improvement in the medial longitudinal arch and dynamic balance of flexible flatfoot patients (2024)

Abstract

[Purpose] The purpose of the present study is to apply short foot exercises and archsupport insoles in order to improve the medial longitudinal arch of flatfoot and comparethe results to identify the effects of the foregoing exercises on the dynamic balance ofthe feet and the lower limbs. [Subjects and Methods] Fourteen university students withflexible flatfoot were selected by conducting navicular drop tests and randomly assignedto a short foot exercise group of seven subjects and an arch support insoles group ofseven subjects. The intervention in the experiment was implemented for 30 minutes pertime, three times per week for five weeks in total. [Results] In inter-group comparisonconducted through navicular drop tests and Y-balance tests, the short foot exercise groupshowed significant differences. Among intra-group comparisons, in navicular drop tests,the short foot exercise group showed significant decreases. In Y-balance tests, both theshort foot exercise group and the arch support insoles group showed significant increases.[Conclusion] In the present study, it could be seen that to improve flatfoot, applyingshort foot exercises was more effective than applying arch support insoles in terms ofmedial longitudinal arch improvement and dynamic balance ability.

Keywords: Short foot exercise, Arch support insoles, Flatfoot

INTRODUCTION

Although the feet occupy only 5% of the areas of the human body, they control posturesthrough afferent information obtained through the sense of the soles, provide stability formaintenance of balance, and absorb impacts¹⁾.

The deformation into flatfoot is induced when the medial longitudinal arch (MLA) hasdescended because the arch had been excessively relaxed to the extent that the arch cannotbe maintained and causes the feet to be excessively pronated compared to normal feet so thatheel eversion appears and the weight load is shifted inward to compress the MLA^{2, 3)}.When the MLA has descended or has been completely lost leading to structural or functionaldeformation, the ability to absorb impacts will decrease and the sense of balance will belost so that stability decreases during walking or running leading to walking difficultiesand endurance decreases^{4, 5)}.

Foot wedges are clinically applied for correction of diverse foot diseases and formaintenance of balance⁶⁾, and customizedinsoles are used for correction of pronated feet⁷⁾. Insoles widen the contact surface of the sole to improve stabilityduring weight bearing, reduce turning actions when the foot has been pronated or supinated,and can be applied to the medial longitudinal arch of the foot to increase the sensoryinputs of the sole⁸⁾. Study results havebeen reported indicating that the conservative intervention methods of foot orthotics usingsupport for the arch of the foot improve malformations of the foot, are effective for legalignment and pain control, and improve gaits to become normal⁷⁾.

The previous reported that sole stimulation could improve the motor sensation and posturalmovements to maintain proper postures⁹⁾.Sensory-motor training applies the proprioceptive feedback of the body to activate theabductor pollicis muscle and the flexor hallucis brevis muscle, which are the intrinsicmuscles of the feet important for maintenance of the MLA, to help the formation of the archand the maintenance of the balance of the body¹⁰⁾. In addition, sensory-motor training delivers proprioceptivesensory signals to the sensory cortex area of the brain and affects even the motor area toimprove the asymmetric muscle tone of the sole and draw appropriate new movements therebyimproving the motor sensation and postural disturbance to help maintaining the balance andstability of the body^{9, 11)}. Fiolkowski et al. reported that sensory stimulationtraining was helpful for flatfoot patients to form and support the arch¹²⁾.

Among exercise methods to improve flatfoot, toe bending exercises or towel-curl exercisesmainly mobilize the extrinsic muscles of the foot such as the flexor digitorum longusmuscle¹³⁾. However, short foot exercises(SFE) are sensory-motor training that activates the intrinsic muscles of the foot andactively forms the longitudinal arch and the horizontal arch^{14, 15)}. Although studiesutilizing foot orthotics such as therapeutic footwear, wedges, and insoles to improve theMLA of flatfoot have been mainly conducted, studies for improvement of flatfoot thatcompared foot orthotics with sensory-motor training such as SFE are insufficient.

Therefore, the present study is intended to improve the MLA of flatfoot and investigate theeffects of the improvement on the dynamic balance of the feet and the lower limbs toidentify effective application methods.

SUBJECTS AND METHODS

The subjects of the present study were 14 university students (males 10, females 4) aged 21to 26 years sampled from among students in the health college of S University in Asan-si,Chungcheongnam-do and the experiments were conducted from October to December 2015. Beforethe experiments, the overall details of the purpose and procedure of the present study wereexplained to all subjects pursuant to the ethical standard of the Declaration of Helsinkiand the subject voluntarily agreed to participate in the experiments. The subjects thatparticipated in the experiments were randomly assigned to an SFE group of seven subjects andan arch support insoles (ASI) group of seven subjects.

The selection criteria for participating subjects regarded the foot used to kick balls asthe dominant foot to select subjects with flatfoot. Navicular drop tests (NDT) wereconducted to select those that had flexible flatfoot with a 10 cm or larger difference inthe navicular tuberosity heights and those that were performing lower limb exercisesseparately, or had any foot hypoesthesia, fracture, dislocation, skin disease, or vasculardisease were excluded. The dominant foot of all subjects was the right foot. The subjects’general characteristics are as shown in Table1 and the SFE group’s mean age, height, and weight were 24.0 ± 1.9 years, 172.2± 6.9 cm, and 68.2 ± 12.9 kg respectively. The ASI group’s mean age, height, and weight were24.1 ± 1.5 years, 167.0 ± 6.7 cm, and 63.3 ± 17.6 kg respectively.

SFE was implemented as sensory-motor training for improvement in the flatfoot of theexperimental group. Before the intervention, the researcher demonstrated the short footexercises while giving verbal instructions. Thereafter, each subject was instructed to siton a height-adjustable chair and bend the hip joint, knee joints, and ankle joints to 90°and a towel was placed below the feet. Thereafter, the subject was instructed to pull thehead of the first metatarsal bone toward the heel without bending the toes and maintain thestate for 20 sec to form the MLA. During the exercise, to prevent the forefoot and the heelfrom being lifted off the ground and smoothly induce the flexion of the head of themetatarsal bone, the measurer gently held the instep and the heel¹⁵⁾. The posture was maintained for 10 sec followed by 5 secand this process was implemented for 30 minutes per time, three times per week for a totalof five weeks.

As a method for improvement in the flatfoot of the control group, insoles were applied asmedial arch support structures. To make the insoles, the foot shape of each subject wassketched on 3.2 mm thick Aquaplast-T^® (Sammons Preston Rolyan, USA), which is athermoplastic material. Thereafter, the Aquaplast-T^® was cut out using scissors,wetted with 100 °C water, and attached to the sole of the subject to copy the foot and theheight of the arch. Thereafter, the MLA was made with a shore value of 20° and a height ofat least 15 mm¹⁶⁾. The insoles made assuch were given to the subjects and the subjects were instructed to put the insoles intotheir running shoes and walk on flatlands for 30 minutes per time, three times per week fora total of five weeks.

NDTs were conducted to measure changes in the height of the MLA. In the NDT, each subjectwas instructed to sit on a chair with the knee joint bent to 90° and align the second toeand the knee so that the subtalar joint was placed on the neutral position and under anon-weight bearing condition, the distance from the ground to the navicular tuberosity wasmeasured and marked. Thereafter, the distance from the ground to the navicular tuberositywas measured in a standing position with the feet place at shoulder width and weight bearingby the two feet. Using a plastic ruler and a 3×5 index card, the difference in the height ofthe navicular tuberosity between the non-weight bearing(sitting position) position and theweight bearing (standing position) position was measured three times repeatedly and theaverage value was used.

Y-balance tests (YBT) (Move2Perform, Evansville, IN, USA) were conducted to measure thedynamic balance ability of the leg. The Y-balance test (YBT) kit consists of threedirectional (anterior, posteromedial, posterolateral) PVC pipe graduated rulers. Eachsubject stood on the platform located on the center on the YBT kit with the bare foot of theleg to be measured and pushed the reach indicator placed on the PVC pipe graduated rulerwith the other leg and the maximum reached distance was measured. The PVC pipe graduatedruler has 0.5 cm grades and thus the distance was recorded in 0.5 cm units. During themeasurement, considering the reaching ability depending on leg lengths, the leg length ofeach subject was measured and normalized and to minimize learning effects on measurement,reaching was practiced two times in each direction before measurement. The measurement wasperformed in the same order of directions and each distance was measured two times and theaverage value was calculated. Normalized composite reach distance was computed for each legas the sum of the maximum reach distances (in centimeter) in the 3 directions, divided by 3times the limb length, and then multiplied by 100¹⁷⁾.

The measured data were statistically processed using PASW Statistics ver. 18.0. The generalcharacteristics of the subjects were presented as means and standard deviations usingdescriptive statistics (Table 1). Independentt-tests were conducted to compare the amounts of changes between the two groups and Pairedt-tests were used to measure differences before and after experiment in each group. Thestatistical significance level was set to α=0.05 for all data.

RESULTS

Changes in the NDT and YBT of the SFE group and the ASI group are as shown in Table 2. According to the results on inter-group NDT comparisons, the values of theSFE group significantly decreased after intervention compared to the ASI group and accordingto the results of YBT comparisons, the values of the SFE group significantly decreased afterintervention compared to the ASI group (p<0.05). In intra-group NDT comparison betweenbefore and after intervention, whereas the SFE group showed significant decreases, the ASIgroup showed no significant difference and in intra-group YBT comparison, both the SFE groupand the ASI group showed significant increases (p<0.05).

DISCUSSION

In the case of flatfoot, as the pronated state of the heel is maintained, the talus bone ismoved to the inside of the sole leading to the disappearance of the medial longitudinal archso that the ability to accommodate and distribute the weight is reduced compared to normalpersons³⁾. Structural deformation of thefeet leads to lesions in the ankle joint and the feet and problems in lower limb joints,results in early fatigue and pain due to the excessive compensating actions of the intrinsicmuscles and the extrinsic muscles, and causes problems in the stability and balance of thefeet during gaits¹⁸⁾. To improve theseflatfoot conditions, methods that correct the MLA using foot orthotics or therapeuticfootwear are universally used¹⁵⁾. Otherintervention methods include SFE for strengthening the intrinsic muscles and extrinsicmuscles of the foot through sensory-motor training. Synder et al. presented SFE as the mostpositive method among methods of correcting the eversion of the subtalar articulation¹⁹⁾. The SFE induces the head of themetatarsal bone to approach the heel without bending the toes in a state where the weight isborne¹⁵⁾.

In the present study, attempts were made to improve flatfoot conditions through changes inthe height of the MLA by applying SFE for six weeks. According to the results of measurementusing NDT, the descending distance of the navicular bone decreased from 11.4 ± 1.6 mm beforeintervention to 7.7 ± 1.1 mm after intervention indicating that SFE was effective. However,in the ASI group, changes in the medial longitudinal arch were not significant. In a studyconducted by Allen & Glasoe, the mean descending distance of the MLA was shown to be 7.3± 3.8 mm²⁰⁾. This indicates that aflexible flatfoot can form ab arch close to that of normal feet through exercise through SFEfor six weeks. Lynn et al. reported that towel-curl exercises implemented for four weeks asfoot intrinsic muscle strengthening exercises were effective²¹⁾ and Jung et al. reported that when toe curl exercises and archformation exercises were applied, the rear foot angle significantly decreased while footintrinsic muscle strength was improved¹⁵⁾.

Telfer et al. reported that changes in the structure of the arch of the sole affectedbalance ability and gait ability⁷⁾. In thepresent study, when dynamic balance was measured using YBT, both the SFE group and the ASIgroup showed significant improvement between before and after intervention within eachgroup. This is considered attributable to the fact that short foot exercises improved thefunctions and activity of the abductor pollicis muscle that plays the role of bearing theweight and pushing the body forward during push off in gaits and the flexor hallucis brevismuscle that maintains the MLA during the terminal stance in gaits to maintain footstability¹⁰⁾. The reason why dynamicbalance ability was significantly improved in the group applied with arch support insoles isconsidered to be the fact that the support for the medial longitudinal arch reduced maximumload reactions to improve leg stability thereby brining about dynamic biomechanicaleffects¹¹⁾.

In the present study, short foot exercises and arch support insoles were applied to improveflatfoot conditions and it could be seen that as the medial longitudinal arch was improved,dynamic balance ability was improved. In addition, it could be seen that sensory-motortraining such as short foot exercises was more effective than conservative treatment methodssuch as arch support insoles. In addition, it could be seen that the intervention period ofsix weeks was not sufficient to improve the medial longitudinal arch using arch supportinsoles. Detailed comparison studies combining sensory-motor training of the foot and archsupport insoles with more sufficient intervention periods are necessary.

REFERENCES