Influence of Children's Foot Type on Their Physical Motor Performance

Abstract

Background: This cross-sectional study aimed to determine whether normal, flat, or high-arched feet corresponded to better performance of certain motor tests in children. Methods: One hundred eighty-seven children (mean ± SD age, 11.15 ± 1.24 years) were recruited and divided into three groups: 96 with normal feet, 54 with high-arched feet, and 37 with low-arched feet. Nine motor trials were selected to assess motor performance: standing long jump, standing triple jump from each foot, standing vertical jump, shuttle run 10 × 5 m, standing-start 20-m sprint, static balance, dynamic balance on a beam of an inverted gym bench, and agility circuit. Results: There were no significant differences in the trial results between groups, although in eight of the nine trials participants in the high-arched group tended to perform better. Boys performed better than girls in all of the trials except those of balance. Conclusions: These results suggest that children with a certain foot type did not achieve better motor performance in the nine trials tested.

Physical activity is important in the prevention of sedentary habits that may lead to future health problems. That is why today exercise is encouraged from childhood. The foot is considered to be of fundamental importance in sports and other physical activities because it constitutes the support base for the rest of the body's movements. Biomechanically, it is reasonable to consider that small alterations in foot and ankle structure or alignment could influence sports performance.

Few attempts have been made to evaluate foot function for motor skills using physical motor trials in children. However, differences in the gait cycle depending on foot type have been observed in adults.[1-4] The research literature indicates that the forces and plantar pressures of the foot present differences during certain physical activities according to the longitudinal plantar arch height.[5-8] Sometimes these differences have even allowed a functional classification by foot type to be established for a particular activity, as is the case for jogging.[9] Also, during physical activity there may be alterations in the amplitude of ankle joint mobility[10] and in the activity of some lower-limb muscle groups.[11,12]

It is known that different foot types may have an influence on the kinematics, plantar pressure, and electromyographic activity of certain sporting activities. However, no studies have been conducted reporting the results of physical motor trials in children aged 10 to 12 years according to their foot type. Queen et al[5] examined the plantar pressures of different tasks in athletes with normal feet and low-arched feet and showed that the latter moved more load to the medial part of the foot. Chuckpaiwong et al[6] reported that peak pressures on the lateral forefoot were significantly greater in athletes with normal feet than in those with low arches. Nigg et al[13] reported that arch height had a substantial (27%) influence on transfer of the movement of rearfoot eversion to internal leg rotation, that other factors were clearly involved as well, and that this transfer could be a risk factor for injuries. Burns and Crosbie[10] found a significant decrease in ankle dorsiflexion movement under load in individuals with pes cavus. Murley et al[14] described increases in the electromyographic activity of the foot invertors and decreases in that of the foot evertors during the gait cycle in low-arched feet.

However, there are fewer studies that include children.[15-20] The objective of the present study was to determine whether any particular foot type (normal, low arched, or high arched) corresponded to better performance of certain physical tests. This is of particular concern for children because any short-term detrimental effects, such as low athletic performance, are likely to manifest as long-term health consequences (injuries) to foot mechanics and barriers to an active lifestyle. The null hypothesis is that low-arched children will obtain significantly different results (ie, worse values) than the other participants.

Methods

A cross-sectional study was performed in three primary schools in Seville, Spain, during 2007 and 2008. The G*POWER version 3.0.10 software package (Franz Faul, Universität Kiel, Kiel, Germany) was used to calculate the a priori required sample size, assuming a type I error of 5% (α = 0.05), a power of 95% (1 - β = 0.95), and a large effect size (0.40), for an analysis of variance of three groups of participants (normal feet, low-arched feet, and high-arched feet). The result was that at least 102 individuals were needed, ie, 34 per group. During the data acquisition period, 302 children were examined, of whom 187 met the inclusion criteria. These criteria were no foot or lower-limb pathologic abnormality or any other underlying condition, both feet of the same type, asymptomatic feet, body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) of 15 to 20 (mean ± SD BMI, 18.55 ± 1.92), and never having surgery of the feet or legs. The final sample, therefore, comprised these 187 children attending the fourth through sixth years of primary education: 96 with normal feet, 54 with high-arched feet, and 37 with low-arched feet.

An attempt was made for the foot-type groups to be as anthropometrically homogeneous as possible, and age, height, weight, BMI, and hip height (height above the floor) were similar between groups. Arch height is known to be strongly influenced by age[21] and obesity.[22] The reason why participants of similar ages and BMIs were included in the present study was to make the groups homogenous. This way, the results obtained on the motor tests might have been related to their foot type.

Detailed explanations of the procedure were given to the parents and the school headmasters, and consent forms were sent to the parents. Only children with the written consent of their parents were included in the study. The study was approved by the Experimentation Ethics Committee of the University of Seville.

The participants were assigned to the normal, high-arched, and low-arched foot-type groups by measuring the Harris index of their plantar ink footprint, a technique used previously.[23] Despite being a measurement from a two-dimensional print, the plantar footprint has been shown to be useful for detecting arch height[24] and, thus, for classifying the foot as normal, low arched, or high arched. Leg length was determined with a measuring tape, with the participant barefoot and supine, with the feet at right angles to the leg, from the outer edge of the foot to the greater trochanter of the femur.[25]

Motor Tests

To assess motor performance, nine motor trials were selected from the literature in accordance with their objectivity and standardization and because the importance of the type of foot support in their performance and outcome is emphasized. These trials were performed according to the following protocol:

Standing Long Jump (T1)

This test evaluates the explosive strength of the lower-limb extensors. The participant stood behind a line with both feet together. He or she performed deep knee flexion and then leaped to land as far forward as possible. The distance, in centimeters, was measured from the starting line to the landing heel mark.

Standing Triple Jump from Each Foot (T2 and T3)

This test evaluates the explosive strength of the lower limbs. The participant stood behind a line with the starting foot forward and then leaped to land on that same foot, followed by a leap to land on the other foot, and finally a leap to land on both feet. The distance, in centimeters, was measured from the starting line to the landing heel mark.

Standing Vertical Jump (T4)

This test measures the explosive power of the lower-limb extensors. With chalk-smeared fingers, the participant stood straight, feet together and flat on the floor, facing a wall marked with reference lines; with arms stretched up, he or she marked the maximum height reached. The participant then stood sideways to the wall (choosing one side or the other according to their individual preference, usually depending on their left- or right-handedness), feet apart at shoulder width, approximately 20 cm from the wall. The participant then jumped to reach up and touch the wall as high as possible, in any way they wanted, allowing arm swing to gain impulse. The distance, in centimeters, was measured from the standing height to the height reached in the jump.

Shuttle Run 10 × 5 m (T5)

This test measures agility and speed of movement. A smooth track had two parallel lines marked at a distance of 5 m apart. The participant started behind one of the lines and ran as fast as possible to step on the other line 5 m away, then back to the starting line, repeating this cycle five times (in total, ten times the distance of 5 m).

Standing-Start 20-m Sprint (T6)

This test evaluates reaction time and speed of movement. The participant stood behind the line, and, at an acoustic signal, set off to run 20 m in the shortest time possible.

Static Balance (T7)

This test measures static corporal balance. The participant stood on the preferred foot placed longitudinally on a bar 3 cm wide and 20 cm above the floor for as long as possible up to 1 min. The test was interrupted every time the participant lost balance and touched the floor and then was resumed until completion of the minute. If the participant fell 15 times in the first 30 sec, the test was considered completed.

Dynamic Balance on a Beam of an Inverted Gym Bench (T8)

This test measures dynamic balance. The participant stood barefoot on one of the beams of an inverted gym bench. This beam had two markers placed 2 m apart. The participant stood behind one of the markers, using the examiner for support. When the trial began, the participant had to walk to the marker at the other end of the bench and then turn around and return to the starting point. This distance was repeated as many times as possible in 1 min, scoring the number of lengths completed. The trial ended if the participant lost balance and fell from the bench, touched some other part of the bench, touched the floor, or in 45 sec did not complete a length.

Agility Circuit (T9)

This test evaluates agility and speed of movement. A circle measuring 9.15 m in diameter was laid out on a court, and five 1.20-m-high indoor training posts were set out in the form of the points of a compass, with one in the center and the others equidistant from each other around the circle. The participant stood in the ready position behind one of the four posts. At an acoustic signal, he or she ran to the center post and around it, then back to the starting post and around it, heading to the next post, and so on, to complete the circle.

For all of the tests, after a practice trial, the better results of two attempts were recorded. The trials were conducted on 3 consecutive days as follows: day 1—T1, T2, T3, and T5; day 2—T4 and T9; and day 3—T6, T7, and T8. Before performing the trials, the children engaged in specific 10-min physical warm-up exercises.

Statistical Analysis

The data were analyzed with a statistical software package (IBM SPSS Version 23 Statistics for Windows; IBM Corp, Armonk, New York). The descriptive statistics of sex and foot type for the total sample and foot type for girls and boys separately are given. The mean ± SD values and 95% confidence intervals of the variables age, hip height, height, weight, and BMI, as well as of the nine physical trials, are also given for the total sample and for boys and girls separately.

After verifying that the data of the quantitative variables were normally distributed using the Kolmogorov-Smirnov test, comparisons and correlations were made between the variables using parametric tests. A P value of less than 0.05 was considered significant. One-way analyses of variance were used to make comparisons of the physical trial results between the different foot types, by foot type between boys and girls, between boys and girls, and between the different age groups (10, 11, and 12 years old). When significant differences were found, multiple comparisons were made using the Bonferroni post hoc test. This test also showed that the BMI was indistinguishable between participants with the three foot types. A χ² test showed whether there were differences in foot type among the three age groups. The relationship between age and the physical trial results was also examined with the Pearson correlation coefficient.

Results

The general descriptive parameters of the sample are as follows: mean ± SD age, 11.15 ± 1.24 years (range, 10–12 years); hip height, 76.42 ± 6.78 cm; height, 1.48 ± 0.09 m; weight, 40.6 ± 6.9 kg; and BMI, 18.55 ± 1.92. The data in Table 1 suggest that the participants in the three foot-type groups were homogeneous in terms of age, lower-limb length, BMI, and sex.

Table 1. Exploratory Analysis Before the Physical Trials Showing That the Three Groups of Participants Were Similar in Age, Hip Height, BMI, and Distribution by Sex.

Table 1. Exploratory Analysis Before the Physical Trials Showing That the Three Groups of Participants Were Similar in Age, Hip Height, BMI, and Distribution by Sex.

There were no significant differences in the trial results when the three foot-type groups were compared, although in eight of the nine trials there was a tendency for high-arched foot participants to perform better. The dynamic balance trial was the exception, in which the best performances corresponded to the low-arched group.

Boys performed better than girls in all of the trials except those of balance (T7 and T8) (Table 2). The results of analyzing boys and girls separately according to foot type are presented in Tables 3 and 4, respectively. In girls, the high-arched foot group showed a tendency to perform better except for T7, for which the best results corresponded to the low-arched foot group (P = .062). In T9, the difference observed between the results of the group of normal feet and the group of high-arched feet was significant (P = .048), with the latter group performing better. In boys, there was no clear dominance of any foot type performing better in the trials.

Table 2. The Student t Test Comparing the Physical Trial Scores Between Boys and Girls.

Table 2. The Student t Test Comparing the Physical Trial Scores Between Boys and Girls.

Table 3. Comparison of the Trial Results in Boys According to Foot Type.

Table 3. Comparison of the Trial Results in Boys According to Foot Type.

Table 4. Comparison of the Trial Results in Girls According to Foot Type.

Table 4. Comparison of the Trial Results in Girls According to Foot Type.

Discussion

The present study reported the results of nine physical motor trials, none of them involving resistance, in a sample of children aged 10 to 12 years who were divided into three groups according to foot type: normal, high-arched, and low-arched feet. In general, there were no significant differences in the trial results among the three groups, although the individuals with high-arched feet presented a slight tendency to obtain the best scores.

Note that the motor tests were selected to involve relatively little influence of the children's physical qualities (although some such influence seems inevitable). These trials demanded more strength, balance, and agility than other physical conditions, such as resistance. The aim was to form homogeneous groups of children, where the most substantial difference was their foot type, to examine whether children with a certain foot type were more effective at performing this kind of physical trial. Another potential limitation is that any influence of previous or current sports participation on performance of the motor tasks was not considered. Finally, it must be considered that arch type was classified with the children in a barefoot condition; the children then wore shoes to complete all of the motor tasks, which could have been an influence on performance.

Foot type did not seem to influence the results of the trials performed by the participants in this study. These results are in concordance with previous studies, such as that by Tudor et al.[17] They studied how the foot types of 218 children categorized according to arch height affected their performance of 17 motor skills. They found that low-arched and normal-arched children were equally successful at accomplishing the motor tests, and they concluded that flatfoot was not a disadvantage in sports performance in children aged 11 to 15 years. There have been other studies comparing foot and lower-limb function in children with flat feet and normal feet, but these studies considered the gait cycle instead of motor skills tests. Twomey et al[18] evaluated 25 normal-arched feet and 27 low-arched feet in children aged 9 to 12 years. They observed similar patterns and ranges of motion of the rearfoot in the two groups but significantly less forefoot pronation throughout the gait cycle in the group with low-arched feet. Shih et al[19] studied the three-dimensional kinematics of the calcaneus, knee, and hip joints in 20 Taiwanese elementary school children with flexible flat feet and ten without this condition. They observed that the two groups exhibited similar patterns of movement around these joints.

On the other hand, Lin et al[15] found significant differences in some physical test results, with the moderate and severe flexible flatfoot group of preschool children being significantly slower. Twomey and McIntosh[20] observed increased external hip rotation and greater external foot progression angle in the low-arched foot relative to the normal-arched foot in children, although their work studied children walking, not performing physical trials.

In eight of the nine trials in the present study, the high-arched participants showed a tendency to get better scores than the others, but the differences were not significant. These results are similar to those reported by Zurita[26] in a study with 1,413 schoolchildren aged 7 to 9 years. He found that the children with pes cavus performed better on the vertical jump trial. However, Negrín[27] argued that the structure and functionality of the normal foot gives it advantages in preventing injuries and trauma in children and adolescents. The only trial in the present study in which this trend was not observed was that of dynamic balance (T8), with best scores in participants with low-arched feet. These findings are similar to those reported by Lin et al,[16] which indicated that the sway area of the center of mass increases with increasing arch height and decreasing plantar support area in children 4 to 5 years old. These authors attributed this result to the greater area of the support surface in the lower-arched feet. In particular, this means that primarily there are more cutaneous somatosensory inputs available for neuromuscular postural control and that secondarily the changes in joint angles and muscular strategies help maintain a stable base of support.[28]

In the present study, boys performed better than girls in most of the trials (the exceptions being T7 and T8). A publication of the Spanish Institute of Quality and Evaluation on the Eurofit physical test battery with 12-year-olds reported that the boys studied were stronger, faster, and more agile and had greater resistance than the girls but that the girls were more flexible.[29]

Conclusions

There were no significant differences in the trial results when the three foot-type groups participating in this study were compared. However, in eight of the nine trials there was a tendency for the high-arched foot participants to perform better. Only the low-arched group did better in dynamic balance (T8). Boys performed better than girls in all of the trials except those of balance (T7 and T8).