Effects of shoes on children’s fundamental motor skills performance

Abstract

Progression or impediment of fundamental motor skills performance (FMSP) in children depends on internal and environmental factors. Shoes as an environmental constraint are believed to affect these movements as children showed to perform qualitatively better with sports shoes than flip-flop sandals. However, locomotor performance assessments based on biomechanical variables are limited. Therefore, the objective of this experiment was to assess the biomechanical effects of wearing shoes while performing fundamental motor skills in children. Barefoot and shod conditions were tested in healthy children between the age of 4 and 7 years. They were asked to perform basic and advanced motor skills including double-leg stance, horizontal jumps, walking as well as counter-movement jumps, single-leg stance and sprinting. Postural control and ground reaction data were measured with two embedded force plates. A 3D motion capture system was used to analyse the spatiotemporal parameters of walking and sprinting. Findings showed that the parameters of single- and double-leg stance, horizontal and counter-movement jump did not differ between barefoot and shod conditions. Most of the spatiotemporal variables including cadence, stride length, stride time, and contact time of walking and sprinting were statistically different between the barefoot and shod conditions. Consequently, tested shoes did not change performance and biomechanics of postural control and jumping tasks; however, the spatiotemporal gait parameters indicate changes in walking and sprinting characteristics with shoes in children.

Keywords:

• Spatiotemporal
• kinetics
• jumping
• stability
• gait

Introduction

Fundamental motor skills are the basic movements involved in daily routines and physical activities. Locomotor, object control, and stability skills compose fundamental motor skills, which include movements like walking, running, hopping, catching, throwing, single-leg stance, and twisting (Lubans, Morgan, Cliff, Barnett, & Okely, 2010). Mastery in fundamental motor skills performance (FMSP) is defined as the independent contribution of children in physical and social interactions (Hardy, King, Farrell, Macniven, & Howlett, 2010; Lubans et al., 2010; Rudd et al., 2015; Sun, Zhu, Shih, Lin, & Wu, 2010). Robinson et al. (2011) explained that among factors which influence FMSP, environmental constraints play an important role in children. Footwear as an external factor can either positively or negatively influence children’s feet and consequently FMSP, as the lower body is mostly involved. Foot health can also be influenced by shoes because the structure of the foot is not consolidated in children (Medina-Alcantara et al., 2019). On the other hand, it was shown that children wearing athletic shoes performed better on the TGMD-2 locomotor subscale compared to flip-flop sandals (Robinson et al., 2011) therefore, well-fitted shoes appear to be essential for children’s motor performance.

It has been shown that growing up barefoot, or shod can influence the structure of the foot and the motor performance (D’Août, Pataky, De Clercq, & Aerts, 2009; Hollander, Heidt, Zwaard, Braumann, & Zech, 2017; Zech et al., 2018). The lower foot arch is related to footwear use and its incidence is higher when children wear footwear earlier (Hollander et al.). On the other hand, the performance of some movements like running seems affected by the height of the foot arch (Ker, Bennett, Bibby, Kestert, & Alexander, 1986). Also, FMSP of jumping, balancing and sprinting was assessed by some field tests (Zech et al., 2018). Zech et al. (2018) found that habitually shod participants had a faster sprint, however, scores on jumping and balance tests were higher in habitually barefoot children and adolescents (Zech et al., 2018). Typically, research in this area has focussed on anthropometric variables whereby studies from a biomechanical perspective are sparse.

A few studies have been investigated the short-term effects of wearing shoes on the biomechanics of walking and running in children. However, results were contradicting for spatiotemporal outcomes. Lythgo, Wilson, and Galea (2009) and Wegener et al. (2015) reported that velocity and stride length increased significantly in a barefoot child in comparison with shod walking. However, other studies showed that there were no differences in these variables between barefoot and shod conditions (Chen, Chung, Wu, Cheng, & Wang, 2015). This discrepancy has also been seen in other spatiotemporal parameters of walking, such as single and double support phases of the gait cycle, in a way that Lythgo et al. (2009) reported a significant difference between barefoot and shod conditions while Chen et al. (2015) found none. Furthermore, the influence of footwear on the functional biomechanics of postural control and jumping tasks also needs to be considered, including single- and double-leg stance, as well as horizontal and counter-movement, jumps as crucial parts of FMSP in children (Hardy et al., 2010; LaPorta et al., 2013; Robinson et al., 2011).

Therefore, the purpose of this investigation was, to examine the acute biomechanical effects of wearing shoes on the FMSP of double-leg stance and single-leg stance, horizontal jump and counter-movement jump as well as walking and sprinting in children. Based on the current evidence, it was hypothesised that shoes would alter the biomechanics of fundamental motor skills.

Materials and methods

Participants

14 healthy children from a convenience sample between the ages of 4 and 7 years participated in this study (9 girls and 5 boys, age: 5.6 ± 1.1 years, height: 117.8 ± 7.4 cm, weight: 21.1 ± 4.1 kg, and shoe size: 30 ± 2 EU, data given as mean ± SD). A prerequisite for study participation was the ability to walk independently. Participants with previous surgeries or fractures to the musculoskeletal structures, neurological disorders, any acute injury to the musculoskeletal structures of the legs, as well as pain and acute infection were excluded. The study was approved by the institutional review board of Potsdam University and followed the declaration of Helsinki. All parents/guardians were informed about the content of the experiment and provided their written informed consent.

Shoes

Children were given a well-fitted shoe which was measured with a WMS Scale (Offenbach, Germany). Shoes were evaluated with a footwear assessment tool (Barton, Bonanno, & Menz, 2009) and categorised as walking shoes. They were made of synthetic material for the upper portion and rubber for the outsole. Heel height, forefoot height and longitudinal profile (heel-forefoot difference) were 2.0, 3.0 and 1.5 cm, respectively. The shape of the last was measured with a goniometer at 50% of shoe length and shown to have a straight shape (<5°). The upper part of the shoes was slip-lasted to the sole, and the forefoot sole fixation point was distal to 1st metatarsophalangeal joints. Moreover, shoes were designed with single density and Velcro fixation. The stiffness of the heel counter and midsole sagittal stability were minimal (>45°) and midfoot frontal stability (torsional) was moderate (Figure 1).

Figure 1. The shoes worn by children in the present study.

Instrumentation

Ground reaction forces (GRF) were recorded at 1000 Hz with two force plates (AMTI, Watertown, MA) and were calculated by MATLAB 9.1 (The MathWorks Inc., Natick). A 12 camera motion analysis system (VICON, Nexus 2.6, Oxford, UK) with a sampling rate of 500 Hz was used to capture three-dimensional (3D) movements of the feet by reflective markers attached to them. A total of 6 reflective markers were placed on the participant’s feet according to the ‘plug-in gait model’, including heel, lateral malleoli, and the head of the second metatarsal in barefoot condition and at the same positions on the shoes. The spatiotemporal parameters of walking and sprinting were analysed using the ProCalc software 1.1 (VICON Motion Systems, Oxford, UK).

Test procedures

Initially, height, weight and shoe size (WMS Scale, Offenbach, Germany) were collected. Subsequently, each subject performed three basic locomotor skills, including double-leg stance (DLS), horizontal jump (HJ) and walking. If subjects could correctly perform single-leg stance (OLS), counter-movement jump (CMJ), and sprinting, these movements were also included for further analysis as more advanced skills. Movements were demonstrated to the subject, and between one and three test runs were performed to ensure that they could perform the movements correctly. Subjects started with the barefoot condition and markers were attached to the body for measuring the spatiotemporal data before walking and sprinting tasks. DLS was performed on a force plate for 15 s while subjects kept their hands on their hips. Two trials were recorded for each subject. For the OLS, children needed to keep their balance on one leg for 15 s while keeping their hands on their hips. The order of the leg (right/left) was randomised and two trials were measured for each side. For the HJ, subjects stood on the edge of the force plate and jumped to the front with swinging arms and maximum power. CMJ was tested as the subject stood in the middle of the force plate with hands on the hips and jumped vertically with maximum power and landed on the force plate with both feet. Three correct trials were recorded for each jumping task and a 1-min rest was given after performing each stability and jumping task. Children were asked to walk at a self-selected speed on a 10 m walkway. A 30 s rest between trials was designated in addition to the time they needed to go back to the starting position. Trials were considered successful if only one foot at a time was entirely on either of the force plates. Sprinting was tested the same as walking, but subjects were asked to run as fast as they could. A total of 6 (3 right/3 left) successful trials each were recorded for walking and sprinting.

Data analysis

The total path length of the centre of pressure (CoP, mm) was calculated for postural control skills in both DLS and OLS. The calculation was for the first 10 s of standing minus the first second. The length of the HJ (cm), flight time (ms) in CMJ, and peak vertical ground reaction force (VGRF) (N) was measured. Flight time was calculated by the assessment of measurement time points (frames per sec) between leaving the force plate and landing on it again. The threshold for leaving and landing was set to <10 N. Additionally, the vertical takeoff and landing impulses (N ms) were calculated for both HJ and CMJ as the area under the force-time curve. Takeoff impulse was measured for half a second before foot was lifted from the force plate in the propulsive phase of the jumping. Whereas, the landing impulse (N ms) was calculated as the moment the subject touched the force plate until half a second after landing. The spatiotemporal parameters of walking and sprinting included cadence, single support, double support, velocity, stride length, step width, stride time, and contact time. Measured kinetics variables were first and second peak vertical ground reaction force (FZ1, FZ2), first and second peak anterior-posterior ground reaction force (FX1, FX2), and braking and propulsive impulses. Spatiotemporal and kinetics parameters and their definitions are shown in Table 1.

Table 1. Parameters for walking and sprinting as well as their description.

Item	Unit	Definition
Spatiotemporal
Cadence	Step/min	Frequency of step per minute
Single support	%	Percentage of gait cycle that one foot is on the ground
Double support	%	Percentage of gait cycle that both feet are on the ground
Velocity	m/s	Speed of initial contact of one foot to the next initial contact of the same foot
Stride length	cm	The distance of initial contact of one foot to the next initial contact of the same foot
Step width	cm	The average distance between the centre lines of the two feet
Stride time	ms	Time of initial contact of one foot to the next initial contact of the same foot
Contact time	ms	Time for whole rolling movement of the foot
Kinetics
FZ1	N	First vertical GRF peak
FZ2	N	Second vertical GRF peak
FX1	N	First medio-lateral GRF peak
FX2	N	Second medio-lateral GRF peak
Braking impulse	N ms	The area under the force-time curve from the foot contact the force plate until the midstance phase
Propulsive impulse	N ms	The area under the force-time curve from the midstance phase until foot was lifted from the force plate

Statistical analysis

A Shapiro–Wilk test was applied to check the normality of the data. The mean and standard deviation (SD) of the parametric values, as well as the median of non-parametric data, were calculated for all outcome parameters. Paired t-tests and Wilcoxon matched-pair signed-rank tests were used to compare FMSP changes between the shod and barefoot conditions. Bonferroni correction was applied to account for multiple testing based on each movement task. (DLS and OLS: p < 0.05, HJ and CMJ: p < 0.017, walking and sprinting: p < 0.007)

Results

Locomotor tasks performed by individual participants are shown in Table 2. No statistically significant CoP excursion of DLS (p = 0.147) and OLS (p = 0.825) have been found between barefoot and shod conditions (Figure 2). Overall, no significant differences were observed for CMJ in barefoot versus shod (Table 3). Length of the jump in barefoot condition was not different from wearing shoes (p = 0.967) (Figure 3). There was no difference in the VGRF (p = 0.522) and vertical takeoff impulse (p = 0.878) of HJ between barefoot and the shod conditions (Table 3).

Figure 2. Mean ± SD of centre of pressure (CoP) in (A) double-leg stance and (B) single-leg stance during barefoot and shod conditions.

Figure 3. Mean ± SD of (A) length of horizontal jump and (B) flight time of counter-movement jump in barefoot and shod conditions.

Table 2. Performed fundamental motor skills by individual participants.

Subjects	Age (years)	Double-leg stance	Single-leg stance	Horizontal jump	Counter-movement jump	Walking	Sprinting
1	5.3	*	–	*	*	*	*
2	4.9	*	*	*	*	*	*
3	6.3	*	*	*	*	*	*
4	7.1	*	*	*	*	*	*
5	4.2	*	–	*	*	*	*
6	6.8	*	*	*	*	*	*
7	4.9	*	*	*	*	*	*
8	6.5	*	*	*	*	*	*
9	5.7	*	–	*	*	*	*
10	4.1	*	–	*	*	*	*
11	4.2	*	–	*	*	*	*
12	5.3	*	*	*	*	*	*
13	7.3	*	*	*	*	*	*
14	5.5	*	–	*	*	*	*

‘*’ symbol signifies performed; ‘—’ symbol signifies not able to perform.

Table 3. Kinetics variables during the horizontal jump, counter-movement jump, walking and sprinting.

	Barefoot	Shoes	p-Value
Horizontal jump
VGRF	404.8 ± 102.8	402.4 ± 89.8	0.699
Vertical takeoff impulse	1398.8 ± 627.7	1582.5 ± 784.9	0.313
Counter-movement jump
VGRF	429.2 ± 97.2	438.4 ± 80.3	0.459
Vertical takeoff impulse	71704.6 ± 16954.9	72133.5 ± 16737.3	0.528
Vertical landing impulse	70548.9 ± 15227.3	70661.6 ± 14157.7	0.921
Walking
FZ1 (N)	256.8 ± 51.5	272.9 ± 42.6	0.118
FZ2 (N)	216.1 (197.1–271.8)^†	231.1 (214.1–293.2)^†	0.003*
FX1 (N)	48.9 (12.1–135.4)^†	55.1 (30.9–123.2)^†	0.124
FX2 (N)	48.8 (19.4–118.0)^†	47.3 (11.4–138.3)^†	0.944
Braking impulse (N ms)	42372.3 ± 10291.9	47845.3 ± 14029.7	0.008
Propulsive impulse (N ms)	39900.4 ± 10580.0	44301.6 ± 10503.4	0.002*
Sprinting
FZ1 (N)	741.1 ± 323.2	650.6 ± 99.6	0.227
FZ2 (N)	458.1 ± 101.0	477.1 ± 81.4	0.116
FX1 (N)	224.1 (−1.3 to 703.6)^†	194.2 (112.5–377.6)^†	0.331
FX2 (N)	104.0 (40.0–244.2)^†	85.3 (10.0–269.8)^†	0.060
Braking impulse (N ms)	26153.3 ± 7652.0	29906.3 ± 6884.1	0.084
Propulsive impulse (N ms)	22836.0 ± 5521.9	25386.7 ± 4912.9	0.005*

VGRF: vertical ground reaction force; FZ1: first vertical GRF; FZ2: second vertical GRF; FX1: first anterior-posterior GRF; FX2: second anterior-posterior GRF. ^†Median and 95% confidence interval reported. *Statistically significant difference between barefoot and shod condition (p < 0.007).

However, there were some differences in the spatiotemporal parameters of both walking and sprinting including cadence, stride length, stride time, and contact time (p < 0.007). Table 4 summarises the spatiotemporal parameters for both barefoot and shod condition during walking and sprinting. Kinetic variables of HJ, CMJ, walking and sprinting were shown in Table 3.

Table 4. Spatiotemporal variables during walking and sprinting.

	Barefoot	Shoes	p-Value
Walking
Cadence (step/min)	149.8 ± 11.5	137.6 ± 14.3	0.002*
Single support (%)	43.5 ± 1.9	43.7 ± 3.2	0.724
Double support (%)	13.1 ± 3.8	11.9 ± 5.7	0.349
Velocity (m/s)	1.2 ± 0.2	1.2 ± 0.2	0.089
Stride length (cm)	108.3 ± 13.6	93.3 ± 10.9	<0.001*
Step width (cm)	14.3 ± 0.9	15.0 ± 1.6	0.071
Stride time (ms)	883.6 ± 87.5	813.3 ± 68.7	0.002*
Contact time (ms)	469.2 ± 36.4	525.4 ± 58.8	<0.001*
Sprinting
Cadence (1/min)	253.2 ± 22.5	225.6 ± 12.3	<0.001*
Single support (%)	27.6 ± 2.9	26.8 ± 2.9	0.375
Velocity (ms)	4.0 ± 0.4	3.8 ± 0.3	0.033
Stride length (cm)	190.4 ± 25.0	204.5 ± 16.6	0.001*
Step width (cm)	14.8 ± 1.3	16.1 ± 1.8	0.004*
Stride time (ms)	481.9 ± 46.2	539.5 ± 29.6	<0.001*
Contact time (ms)	149.1 ± 10.8	168.6 ± 10.7	<0.001*

*Statistically significant difference between barefoot and shod condition (p < 0.007).

Discussion

The main finding of this study was that wearing shoes had some effect on children’s gait, with no influence on double- and single-leg stance as well as horizontal and counter-movement jump. In the shod condition, the CoP excursion of the DLS was increased by 14.8%, but not significantly. This outcome is in line with previous studies (Brenton-Rule, Bassett, Walsh, & Rome, 2011; Romkes 2007). However, participants in these studies were older adults. Greater CoP excursion in older adults (22%) in comparison to children in the current study might be associated with a decline in visual and/or vestibular systems (Brenton-Rule et al., 2011). Moreover, postural control during OLS did not change between barefoot and shod conditions. Similarly, Romkes (2007) found no differences in balance while barefoot standing compared to unstable (MBT) shoes. Contrary to that, CoP was higher while being barefoot in OLS and caused more instability than wearing shoes in adults (Germano, Schlee, & Milani, 2012).

Assessment of jump performance, VGRF, and vertical impulses in CMJ and HJ showed no statistically significant differences between barefoot and shod conditions. Similar findings were shown for vertical jump performance of children aged 8 to 12 years (Wegener et al., 2013). These results were also found in Harry et al. (2015) investigation, that adults’ vertical jump and standing long jump were compared in barefoot and in two different kinds of shoes. Displacement of both jumps did not differ among all three conditions (Harry et al., 2015). VGRF, counter-movement, and propulsive phase duration, as well as their impulses, remained unchanged in above study (Harry et al., 2015). By contrast, LaPorta et al. (2013) reported greater vertical jump height while wearing shoes in men but not in women. However, other GRF parameters including relative peak power and relative ground reaction force were not different barefoot, minimalistic and tennis shoes. This dissimilarity could be due to performing jumps on separate days for each condition.

Our findings for the spatiotemporal parameters demonstrated that children’s gait velocity remained unchanged, but cadence decreased. These results are in line with Oeffinger et al. (1999), Wolf et al. (2008), Hollander, Riebe, Campe, Braumann, and Zech (2014) and Chen et al. (2015). However, Lythgo et al. (2009) and Wegener et al. (2015) reported an increase in walking velocity while wearing shoes. Generally, it seems that children are able to take longer steps and consequently increase their speed. However, the reason that the velocity in our experiment and those of Wolf et al. (2008) and Chen et al. (2015) were not significant different might be due to the use of commercial and experimental shoes in comparison to athletic or running shoes in the experiments of Lythgo et al. (2009) and Wegener et al. (2015).

Furthermore, there was no difference between conditions in phases of the gait cycle, which is in agreement with Wegener et al. (2015) and in contrast with the study of Lythgo et al. (2009) where double support increased 1.6% in the shod condition. It is speculated that wearing shoes provides less proprioceptive input; thus, with increasing double support, children try to maintain a stable posture. On the other hand, as changes in the double support and single support variables of gait were negligible in the above-mentioned study, differences between the barefoot and shod conditions should be considered with caution.

In the current study, contact time increased significantly during walking (56 ms) and sprinting (20 ms) while wearing shoes. A 30 ms and 10 ms increase in the contact time while walking and running was also observed with sports shoes in a similar study (Wegener et al., 2015). Increase in the surface area on which the foot contacts the ground while wearing shoes might be responsible for the increase in contact time. The discrepancy between Wegener et al. (2015) and the present study might be due to testing different age groups, as the present study included children 4–7 years of age and in Wegener et al. (2015) children between 8 and 10 years of age. Younger children needed more contact time than older ones in order to keep their balance while walking or running (Wegener, Hunt, Vanwanseele, Burns, & Smith, 2011).

First and second peak GRF in vertical and anterior-posterior were not significantly different in walking and sprinting with regard to footwear, unlike the experiments by Chen et al. (2015) and Hollander et al. (2014), where peak force was statistically different between the shod and unshod conditions. In fact, shoes in the Chen et al. (2015) experiment were designed to correct foot pronation, and in Hollander et al. (2014) running tasks were performed on a treadmill, which might explain differences in GRF data (Nigg, Boer, & Fisher, 1995; Rozumalski, Novacheck, Griffith, Walt, & Schwartz, 2015; Schache et al., 2001; Wegener et al., 2011). Differences in vertical impulses of the braking and propulsive phase during gait reached statistical significance. Considering all impulses in the barefoot and shod condition, impulses were higher while wearing shoes. This additional force could be a result of the weight of the shoes (Swain, Kelleran, Graves, & Morrison, 2016). Limited data are available on this issue, as prior literature on children and shoe function has focussed mostly on the spatiotemporal parameters of walking and running rather than kinetic variables.

To our knowledge, this is the first study that tested the effect of shoes on FMSP of children based on biomechanical parameters. However, there are some limitations in the current study that has to be considered. First, the small sample size included in this experiment might reduce the power of some measured variables like gait velocity. Although children were given an adequate number of familiarisation trials, still the learning effect might be influential because the conditions were not randomised. Additionally, although parents were asked about known lower extremity pathology, children were not examined for delayed motor development. Therefore, future studies should focus on examination prior to the experiment, as only eight subjects were able to perform the single-leg stance task. This study examined the acute effect of wearing shoes on locomotor skills in children; however, further research is needed to assess the long-term effects of footwear on FMSP in children.

In conclusion, postural control and jumping tasks were not affected by footwear use in children. However, there were some spatiotemporal changes, including cadence and stride time in children’s gait, which might influence their walking and sprinting performance. Therefore, the impact of footwear needs to be considered more comprehensively as changes in gait have been shown.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The present study was partially funded by ISA-Traesko GmbH.