Ergonomic footwear for Sri Lankan primary schoolchildren: A review of the literature

1 Introduction

There are about four million schoolchildren in Sri Lanka [1] and on this basis, it is conjectured that there would be about two million children in primary schools. Supporting this, the Child Activity Survey 2008/2009 [2] has found that there were 2.24 million children in the age group five to eleven attending school. It has been observed that Sri Lankan children grow at about seven centimeters per year in height at age five, slowing down to three centimeters per year at age ten [3]. At these rates of growth, it may be assumed that children will outgrow their shoes rapidly. The relative time spent in different activities such as sitting, standing, walking and running, and the environment in which they need to engage in such activities are also important factors to be considered in footwear design [4]. However, there is a dearth of published information relevant to Sri Lankan schoolchildren. Thus, footwear design for this age group can be challenging.

Studies leading to the classification of foot types of schoolchildren for the purpose of footwear design have been conducted in relation to other populations [5], especially in developed countries. No study appears to have been conducted on these aspects in relation to Sri Lankan children in their period of growth, and Sri Lankan footwear manufacturers usually use the same or similar designs to those based on these studies, even though the existence of environmental, ethnic and geographical differences in foot-shape are well known [6–13].

To provide fitting footwear, on the one hand, Sri Lankan footwear manufacturers lack adequate knowledge on requirements for design and manufacture of footwear [14]. On the other, imported ergonomic footwear is expensive [15]. Even when available, they would not have been designed specifically to suit Sri Lankan conditions, both functional and environmental, which means that they would not be ‘ergonomic’ for Sri Lankan children. Thus, it can be stated that the majority of Sri Lankan schoolchildren do not have access to affordable ergonomically designed footwear.

Ill-designed footwear is harmful for the health, not only for the feet, but also for posture and spinal alignment [16–18]. Given the large number of variables that are reported to affect footwear design, it is imperative that studies of the target population be carried out before an attempt is made to design ergonomic footwear for Sri Lankan primary schoolchildren. However, in order to enable the design of footwear suitable for Sri Lankan primary schoolchildren, aspects of foot anatomy, gait and footwear need to be thoroughly investigated. Thus, a literature survey of requirements for design and manufacture was carried out using the following primary keywords: Biomechanics, foot anatomy, morphology of children’s feet, gait and foot alignment, anatomy of footwear, ill-fitting footwear, foot measurements, materials for footwear and Last design. Even though there is much overlap among some of these phrases, the search results were often different from one another. In many instances, the word ‘child’, ‘children’ or ‘paediatric’ was added to obtain better targeting. The main search engines used were Google Search, Google Scholar and PubMed. The searches themselves directed the search to other search engines such as Science Direct. The initial search yielded 392 publications with relevant titles, and after reading the abstracts, 208 publications were selected to be read in full, 94 of which are referenced in this review. The findings are discussed under the topics foot anatomy and functionality, activities of primary schoolchildren, anatomy of footwear, footwear design and manufacture.

2 Foot anatomy and functionality

A normal foot has a total of 26 bones; (28 bones if the two sesamoid bones near the medial phalange joint are counted), 33 joints and more than 120 muscles, ligaments, and nerves [19]. The bone structure of a foot is illustrated in Fig. 1 and it indicates the complex nature of the human foot, and helps to explain its functionality. According to general classification, talus and calcaneus, five tarsal bones, and phalanges and metatarsal bones constitute the hindfoot, midfoot, and forefoot respectively [20]. The two sesamoid bones are formed within the muscle, and protect the tendon from wear and tear and bear the weight of the body when the toe pushes off in walking or running. The metatarsophalangeal [MTP) joint is known as the ball of the foot and it bears the weight of the body when the heel is raised during walking andrunning [21].

Although a fully grown foot behaves as described above, Magnetic Resonance Imaging has shown that developmental cartilaginous bone changes follow a definite pattern [20]. Thus, growth of feet needs to be studied in order to help design footwear for schoolchildren. Figure 2 shows their chronological development from embryonic period to 20 years. Physeal closure only occurs at about 14 years in boys and slightly earlier in girls [22].

In the age group under discussion (primary schoolchildren, both boys and girls), the bone structure is still evolving and developing. The changing nature of children’s feet means that shoes for children should be designed to encompass changing sizes, but also with changing mechanical characteristics, with softer material for younger children and more rigid material as they grow older, so as to accommodate the stresses that they are subjected to [23].

The foot has an elastic vault-like structure, which enables it to both carry loads passively as well as to actively adjust the relative positions of the bones to accommodate uneven surface conditions while walking, and it helps maintain the body in equilibrium under adverse conditions [24]. The ability to adjust dynamically is important to provide for the acceleration and deceleration of the foot during push-off and landing. The foot is said to be correctly aligned when the axes of the bones are in line and the weight of the body is transferred without undue stress on the joints and muscles [25], further Improper body alignment affects posture and gait [26], and body alignment [at least up to pelvic and lower limb alignment) is affected by foot alignment [27]. These geometries need to be ensured to support stability during different activities that the schoolchildren engage in.

The ankle bone, talus, together with the two lower leg bones tibia and fibula form a stable ankle joint, which allows the foot to bend up and down while the heel bone calcaneus with the ankle bone talus form the subtalar joint that allows the foot to rock from side to side [24]. The bones of the hindfoot form a set of articulated bones, meaning that they are connected together, but can move relative to each other. There are multiple connections between them, and when the foot is twisted in one direction by muscle action, they lock together to form a rigid structure, but when the foot is twisted in the opposite direction, they are unlocked, and the foot is able to follow the contour of the ground [24]. Footwear needs to support these needs, but specific requirements with respect to growing feet needs to be further researched.

It has been hypothesized that children lack neuromuscular maturity, especially at the ankle, to produce an adult-like gait pattern [28]. In a study based on 345 students [29] it has been reported that in almost two thirds of the sample, misalignments or even deformities in feet were present that may result in altered gait patterns. This study has also found that there is no correlation between body weight and body height with leg alignment and foot deformity. However, other researchers have reported contrary evidence; for instance, it has been found that foot pronation is related to the leg-heel alignment [30]. It has also been concluded from a study of 200 children aged nine to twelve years that excessive body mass affects the discrete anthropometric structure of the pre-pubescent foot [31]. In any case, for those that already have fallen arches, being overweight will make it almost impossible to sustain proper foot alignment as the strength required to maintain the integrity of the arches increases with the extra weight on the feet [32]. Moreover, the stress on misaligned joints and its resulting harm is substantially increased by being overweight [25]. Design requirement needs to be derived from such findings to effectively design footwear.

In addition to the bones, the anatomy of the foot has numerous other components. They include muscles, tendons, ligaments, fasciae and nerves [24]. Tendons, ligaments and fasciae are the connecting fibrous tissues that connect the bones and muscles together. The nerves primarily send and receive signals that co-ordinate the functioning of the foot in its task of locomotion, including standing [24]. For example, gait is dependent on sensory feedback [33, 34], and hence, the design of shoes has to ensure that they do not unduly interfere with sensory feedback of environmental conditions [35]. This is an important aspect that needs to be considered especially in material selection for footwear.

The anatomical, biomechanical and sensory requirements for footwear design are related to the activities that the children carryout. The footwear for a sedentary lifestyle may be different from footwear for different activities such as walking, running and jumping. Thus, study of typical activities that the Sri Lankan schoolchildren engage in need to be studied.

3 Activities of primary schoolchildren

Although it was difficult to find any literature relating exclusively to the activities engaged in by Sri Lankan primary schoolchildren, there were a few studies related to Sri Lankan schoolchildren in general, and a few age-specific studies, some covering at least partly the age group of interest. In a study of 1224 urban Sri Lankan schoolchildren in the age group eight to twelve years covering both male and female students and spanning public national, public provincial and private schools, it has been found that a majority of them spent less than two hours a day watching television during weekdays, although almost half of them spent up to four hours a day during weekends [36]. A majority of them spent less than two hours a week in outdoor physical activity. More than half of them attended tuition classes, both during weekdays and weekends. In another study involving a nationally representative sample of 6264 adolescents in the age group ten to fifteen years, a subsample of 1521 children were interviewed on their pattern of physical activity. This study has found that almost 20% of them had not participated in any form of play or games involving physical activity during the preceding week [37]. A further study, also relating to older children, has reported that Grade 11 students [age 16 years) spent an average of 8.6 hours per week on private tuition [38]. The same report stated that 80% of Grade six children received private tuition, while the proportion for Grade 11 children was slightly lower, at 75%.

Distance to school from home is another factor that would influence the manner in which children spend their day. The Sri Lanka Integrated Survey of 1999–2000 [39] has collected data from 7500 households covering 500 communities. This data is used in another report [40] to analyze the reasons why all children in the age group five to fourteen are not in school. Further in this report it shows that the average distance to primary school for the whole country is seven kilometers and for the poorest quintile of the population, it is as high as ten kilometers [40]. Whatever the mode of transport, seven to ten kilometers (14 to 20 km, up and down) is time consuming.

While these studies correspond to a very sedentary lifestyle of schoolchildren, watching television and attending tuition classes can be considered as two of the main activities that compete with physical activity, even though these data relate to an older age group than primary schoolchildren. From this, it is possible to surmise that grade five children also would have spent a considerable time in receiving private tuition. Overall, it may be concluded that a normal school day of a student attending primary school will consist of six hours at school, two hours of watching television and a considerable time receiving tuition and for travel. However, specific studies need to be carried out to determine, among other factors, how the children spend the time during the period that they would be wearing footwear. Even though it was noted that they spend very little time in outdoor sports activity, other activities such as travel especially if it involves walking to school may indicate considerable stress on feet and footwear, especially when undertaken in a hot and humid environment. This makes it necessary to study footwear construction to suit the Sri Lankan context.

4 Anatomy of footwear

A simplified explanation of the anatomy of a shoe consists basically of an upper and a sole [41], as illustrated in Fig. 3 (a) and (b). According to this, the portion of the upper, which fits around the heel, is the counter. The sole is made up of the insole, the outsole, and filler between. The shank area of the sole extends through the mid part of the foot from approximately the middle of the heel to mid metatarsal area. However, modern shoes are more complex. There are two different versions of the components of a shoe, one for athletic shoes and another for non-athletic shoes [42].

Different footwear types have been manufactured over the years and are found in general use. The characteristics of footwear would depend not only on its type, but also on the relationship to the wearer (or foot) and the expected function. In one study [42], seven generic types have been identified into which most modern shoes can be classified: oxford, boot, pump, clog, mule, sandal and moccasin. Another has listed fourteen different basic types of shoes [43]. There are other specialized types of shoes such as orthopedic, ballet, rocker bottom (unstable and stable) [44], minimalist [45] and ethnic shoes. Most modern shoes have a heel, a toe spring, an in-flare and padding under the ball cavity [17]. The attributes of the most common types of footwear in terms of ergonomics, selected from the different classifications are shown in Table 1.

The relationship between the material used and the characteristics of the footwear is complex [42]. The material to be used for an item of footwear would depend on many factors including the expected characteristics of the footwear being considered, its function and style and the physical characteristics of the material from which each component is manufactured [42]. Thus, research is needed to relate footwear types to the activities that the Sri Lankan primary school children engage in. Furthermore, suitable material to facilitate activities and environmental conditions need to be researched.

In general, the most important components of a shoe may be considered to be: Uppers (Quarter, Vamp, Eyelet stay, Tongue, Achilles tendon protector and Collar) [42, 43], Soles (Insoles, Outsoles, Midsoles, Heels and toplifts) [43, 48–50] and Reinforcements (Toe box, Counters, Foxing, Rear-foot stabilizer, Mudguard, Shank and Welt) [42, 48]. All of these may not be present in any particular item of footwear. Therefore, tools have been suggested to evaluate footwear, for instance [43] assesses footwear characteristics, listing the following measures: Fit (e.g. length, width), footwear type, materials (upper and outsole), weight/length ratio, general structure (heel height, forefoot height), normalized longitudinal profile (heel – forefoot difference, or pitch), last shape, fixing of upper to sole, forefoot sole flexion point),motion control properties (multiple density sole, fixation, heel counter stiffness, midfoot sole sagittal stability, midfoot sole torsional stability), cushioning (presence of cushioning system, lateral midsole hardness, medial midsole hardness, heel sole hardness) and wear patterns (upper, midsole, tread pattern, outer sole wear pattern). Such approaches may prove important to improve fit and comfort, and prevent or at least reduce foot problems related to unsuitable footwear.

5 Footwear fit

Shoes were originally worn for the purpose of protection from the environment [42]. It is suggested that a modern shoe should, in addition, provide foot stability and shock attenuation [42]. It should also treat foot deformities and provide a foundation for foot orthoses. However, shoes have evolved as items of fashion [51] ignoring the above, resulting in unintended consequences. Most footwear is designed without giving adequate consideration to morphological differences among human feet [52]). In a study involving 443 males and 297 females, it has been found that foot shape is significantly affected by the skeletal structure of the foot and the pronation of the foot and abduction of talus and calcaneus in relation to the tarsometatarsal part of the foot and that these factors are important in determining the fit between feet and shoes [52].

The literature on the association of footwear with foot health is however confusing, and is littered with contradictory findings. While many recent studies strongly support the position that ill-fitting shoes are a major cause of foot pain and diseases associated with feet, there are also contrary views being expressed. The presidential address to the Section of Orthopaedics of the Royal Society of Medicine in December 1976 states categorically that ‘shoes cannot influence the shape of the foot for better or for worse’ [50]. In this connection, the evidence from practitioners also warrants attention. For instance, a practitioner states: ‘Many patients complain of painful feet. While this problem may seem minor to the physician, it causes the patient considerable distress [53]. Further, a study of 300 Bengali subjects found that foot pain and other associated problems are caused by ill-fitting footwear [54]. Some of these conditions are readily amenable to treatment; others require continuing care. Much foot relief can be given by simple office procedures and by correcting ill-fitting footwear’ [53].

The effects of wearing shoes have been found to be more pronounced in the case of women than men, especially due to the dominance of high-heeled shoes [55]. In ‘The Framingham Foot Study’, data collected from 3378 members were analyzed for association between foot pain and shoe wear. It was found that ‘past shoe wear use in women remained associated with hind-foot pain.’ Those who wore ‘good’ shoes in the past were 67% less likely to report hind-foot pain. In the case of men, such an association could not be discerned as very few men wore ‘bad’ shoes (55). Both radiographic techniques and Magnetic Resonance Imaging have been used in the study of musculoskeletal foot conditions in women, and such studies have found that ‘the altered biomechanics [associated with high-heeled shoes and shoes with a narrowed toe box) has been linked to the genesis of hallux valgus, hammer toe deformity, Haglund syndrome, metatarsal stress fracture, Freiberg infraction, and Morton neuroma’ [56]. The structural and biomechanical differences between the female and the male feet has been studied in view of the higher incidence of foot diseases attributed to footwear in the case of women and the reported effects of ill-fittingshoes [57].

Ill-fitting footwear are known to cause diseases such as Achilles tendonitis [58], Athlete’s Foot/Tineapedis [59], Bunion/Hallux valgus [60–64], Corns and calluses [65, 66], Flatfoot (Pes Planus Foot)/Fallen arches [67], Lesser toe deformities [68], Morton neuroma/Perineuralfibrosis [69], Plantear fasciitis/Heel pain [70] and Rheumatoid arthritis [71]. Therefore, it is imperative that children in particular are shod in proper footwear [67], for the feet of children are still developing [22].

Supporting this notion, a study of 1846 skeletally mature adults noted significantly higher rates of prevalence of flat foot among those who began to wear shoes before the age of six years suggesting an association between wearing of shoes in early childhood and flatfoot [72]. An earlier study of 2000 students by the same team using static footprint had found that ‘flat foot’ was most common in children who wore closed-toe shoes, less common in those who wore sandals or slippers, and least in the unshod [73]. These findings suggest that shoe-wearing in early childhood is detrimental to the development of a normal longitudinal arch. Therefore, improvement in footwear design and construction is essential.

As discussed earlier, the bone structure of children is different from that of adults, as it is not yet fully developed. The strength of the connective tissues and the flexibility of the joints of children reach adult levels only by the age of 15 [23]. Hence, it is reasonable to assume that footwear will play a major role in the foot health of children and in their later life as adults. A review of 11 studies of children below the age of 16 years has concluded that footwear does affect the gait of children [74]. Based on this study, researchers have concluded that children wearing shoes walk faster by taking longer steps with greater ankle and knee motion and increased tibialis anterior activity. They further found that shoes reduce foot motion, increase the support phases of the gait cycle, and during running, shoes reduce swing phase leg speed, attenuate some shock and encourage a rearfoot strike pattern. It is suggested that further research is needed on the long-term effect of these changes on growth and development.

A study comparing barefoot walking with shod walking using 18 healthy children (average age 8.2 years) has also found that footwear does alter the foot motion in children [75] and has concluded that slimmer and more flexible children’s shoes do not change foot motion as much as conventional shoes and therefore should be recommended for all healthy children. It has presented the hypothesis that ‘The increased prevalence for flatfoot and hallux valgus in modern societies may be the consequence of inadequate footwear in childhood.’ In addition, differences have been reported between the morphology of healthy children’s feet depending on many factors. Although there can be reasons other than footwear for these conditions, there is plausible evidence to conclude that footwear causes ailments. Foot ailments, especially among primary schoolchildren, will hinder their growth and also detrimentally affect their performance.

These factors affecting the morphology include the age or the state of development [23]; Body Mass Index [76–79]; gender [80–82]; ethnicity or genetic background [6–12]; geography or physical environment [11, 12] and social environment [13]. As a large number of factors are found to influence the morphology of children’s feet, it is difficult to ensure correct fit between the shoes and feet, unless special care is exercised in designing shoes for children. Relatively little work has been reported on the effect of ill-fitting shoes in children compared to that of adults, although they are reportedly more vulnerable to related effects. Thus it is important to study issues faced by children due to ill-fitting shoes.

The above evidence shows that footwear does have adverse effects on feet, accentuated by the differences in the morphology between the sexes and among individual feet, and the anatomy and structure of the footwear. Thus, proper identification of footwear sizes and their characteristics is essential to avoid foot ailments.

6 Measurements for the manufacture of footwear

Two types of foot measurements have been reported in the literature – morphological measurements and kinetic and kinematic measurements. The latter two, even though distinct from each other, are often considered together.

7 Conclusions

The review emphasizes the importance of considering the changing morphology and activities of schoolchildren in the age group five to ten years to design ergonomic footwear. The factors that will determine their suitability for use in changing foot morphology and environmental conditions are essential to ensure proper design and manufacture of footwear. Thus, adequate design inputs need to be given to footwear designers and manufacturers in order to design footwear suitable for schoolchildren. For this, cost effective methods of foot measurements need to be identified or derived using existing techniques. Information on suitable materials that will provide support and protection for the growing feet while not inhibiting sensory feedback during varying activities and conditions in which the primary schoolchildren perform tasks may prove essential for the design of ergonomic footwear.

Conflict of interest

The authors have no conflict of interest to report.