Karen J. Mickle

The Feet of Overweight and Obese Young Children: Are They Flat or Fat?

Objective: The purpose of this study was to determine whether the flat feet displayed by young obese and overweight children are attributable to the presence of a thicker midfoot plantar fat pad or a lowering of the longitudinal arch relative to that in non‐overweight children.

Foot pain, plantar pressures, and falls in older people: a prospective study.

OBJECTIVES: To determine whether foot pain and plantar pressure are associated with falls in community‐dwelling older adults.

ISB Clinical Biomechanics Award 2009: Toe weakness and deformity increase the risk of falls in older people

BACKGROUND Hallux valgus and lesser toe deformities are highly prevalent foot problems in older people. One factor contributing to the development of these toe deformities is reduced toe flexor strength. As adequate toe flexor strength is also crucial in maintaining balance, it was hypothesised that poor toe flexor strength and toe deformities would increase the risk of falls in community-dwelling older people. METHOD The feet of 312 men and women aged 60-90 years were assessed for the presence of lesser toe deformities and hallux valgus. Hallux and lesser toe flexor strength were assessed using an emed AT-4 pressure platform and novel test protocol. Participants were then followed prospectively to determine their falls incidence over 12 months. FINDINGS During the 12 month follow-up, 107 (35%) participants experienced a fall. Compared to non-fallers, fallers displayed significantly less strength of the hallux (11.6 (SD 6.9) versus 14.8 (SD 7.8)% BW, P<0.01) and lesser toes (8.7 (SD 4.7) versus 10.8 (SD 4.5)% BW, P<0.01), and were more likely to have hallux valgus (relative risk [RR]=2.36; 95% CI=1.03-5.45; P<0.01) and lesser toe deformity (RR=1.32; 95% CI=1.04-1.69; P<0.01). INTERPRETATION Reduced toe flexor strength and the presence of toe deformities increase the risk of falling in older people. To reduce this risk, interventions designed to increase strength of the toe flexor muscles combined with treatment of those older individuals with toe deformities may be beneficial.

Gait, balance and plantar pressures in older people with toe deformities

Older people with toe deformities have been identified as having an increased risk of falling. Little is known, however, about the biomechanical changes that might contribute to this increased risk. Therefore, the purpose of this study was to determine whether older people with hallux valgus and lesser toe deformities displayed different gait, balance and plantar pressure characteristics compared to individuals without toe deformities. The presence of hallux valgus and lesser toe deformities were assessed for 312 community-dwelling older men and women. Spatiotemporal gait parameters were measured using the GAITrite(®) system, postural sway was assessed on two surfaces using a sway-meter and dynamic plantar pressure distribution was measured using an Emed-AT4 pressure plate. The results indicated that, although there were no effects of toe deformities on spatiotemporal gait characteristics or postural sway, older people with hallux valgus (n=36) and lesser toe deformities (n=71) were found to display altered forefoot plantar pressure patterns. These findings suggest that toe deformities alter weight distribution under the foot when walking, but that the relationship between toe deformities and falls may be mediated by factors other than changes in spatiotemporal gait parameters or impaired postural sway.

Adherence to physical activity and electronic media guidelines in Australian pre-school children

The aim of this study was to determine compliance with the National Association for Sport and Physical Education (NASPE) guideline for physical activity and American Academy of Pediatrics (AAP) recommendation for electronic media use among urban pre‐school children in two large cities on the East Coast of Australia. Cross‐sectional data were collected from 266 parents. Time spent using electronic media (watching television, DVDs or on the computer) and in physical activity were parent reported. The proportion who met each guideline was calculated. 56 per cent and 79% of children met the NASPE guideline on weekdays and weekends, respectively, while 73% and 70% met the AAP recommendation on weekdays and weekends, with no difference between boys and girls. A substantial minority do not meet physical activity and electronic media use recommendations, highlighting the need to better understand what factors contribute to physical activity and electronic media use among this group of pre‐schoolers.

Does excess mass affect plantar pressure in young children

OBJECTIVE To determine the effects of overweight and obesity on plantar pressures generated by pre-school children during gait. METHODS Dynamic plantar pressure variables were measured for 17 overweight/obese children (age = 4.4 +/- 10.8 years; height = 1.08 +/- 0.1 m; body mass index (BMI) = 18.5 +/- 1.3 kg x m(-2)) and 17 age, gender and height matched non-overweight peers (age = 4.4 +/- 0.7 years, height = 1.06 +/- 0.1 m, BMI = 15.7 +/- 0.7 kg x m(-2)). RESULTS When walking, the overweight/obese children displayed significantly larger contact areas and generated significantly larger forces on the plantar surface of their total foot, heel, midfoot and forefoot compared to the non-overweight children. Despite generating these higher forces over larger contact areas, the overweight/obese children displayed significantly higher peak pressures, force-time integrals and pressure-time integrals in the midfoot compared to their leaner counterparts. CONCLUSIONS Although the overweight/obese children displayed greater midfoot contact, this increased contact area was not sufficient to compensate for the high forces generated during walking, resulting in them experiencing higher midfoot plantar pressures relative to the non-overweight children. The overweight/obese children also experienced significantly higher force-time and pressure-time integrals than their leaner counterparts, suggesting that their midfoot may be exposed to increased stress and, in turn, vulnerable to bony fatigue and soft tissue damage. The impact of these greater plantar pressure variables on foot discomfort and physical activity levels of these young overweight/obese children as they develop into adults requires further investigation.

Ultrasound evaluation of foot muscles and plantar fascia in pes planus

BACKGROUND Multiple intrinsic and extrinsic soft tissue structures that apply forces and support the medial longitudinal arch have been implicated in pes planus. These structures have common functions but their interaction in pes planus is not fully understood. The aim of this study was to compare the cross-sectional area (CSA) and thickness of the intrinsic and extrinsic foot muscles and plantar fascia thickness between normal and pes planus feet. METHODS Forty-nine adults with a normal foot posture and 49 individuals with pes planus feet were recruited from a university population. Images of the flexor digitorum longus (FDL), flexor hallucis longus (FHL), peroneus longus and brevis (PER), flexor hallucis brevis (FHB), flexor digitorum brevis (FDB) and abductor hallucis (AbH) muscles and the plantar fascia were obtained using a Venue 40 ultrasound system with a 5-13 MHz transducer. RESULTS The CSA and thickness of AbH, FHB and PER muscles were significantly smaller (AbH -12.8% and -6.8%, FHB -8.9% and -7.6%, PER -14.7% and -10%), whilst FDL (28.3% and 15.2%) and FHL (24% and 9.8%) were significantly larger in the pes planus group. The middle (-10.6%) and anterior (-21.7%) portions of the plantar fascia were thinner in pes planus group. CONCLUSION Greater CSA and thickness of the extrinsic muscles might reflect compensatory activity to support the MLA if the intrinsic foot muscle function has been compromised by altered foot structure. A thinner plantar fascia suggests reduced load bearing, and regional variations in structure and function in feet with pes planus.

Toe weakness and deformity increase the risk of falls in older people

BACKGROUND Hallux valgus and lesser toe deformities are highly prevalent foot problems in older people. One factor contributing to the development of these toe deformities is reduced toe flexor strength. As adequate toe flexor strength is also crucial in maintaining balance, it was hypothesised that poor toe flexor strength and toe deformities would increase the risk of falls in community-dwelling older people. METHOD The feet of 312 men and women aged 60-90 years were assessed for the presence of lesser toe deformities and hallux valgus. Hallux and lesser toe flexor strength were assessed using an emed AT-4 pressure platform and novel test protocol. Participants were then followed prospectively to determine their falls incidence over 12 months. FINDINGS During the 12 month follow-up, 107 (35%) participants experienced a fall. Compared to non-fallers, fallers displayed significantly less strength of the hallux (11.6 (SD 6.9) versus 14.8 (SD 7.8)% BW, P<0.01) and lesser toes (8.7 (SD 4.7) versus 10.8 (SD 4.5)% BW, P<0.01), and were more likely to have hallux valgus (relative risk [RR]=2.36; 95% CI=1.03-5.45; P<0.01) and lesser toe deformity (RR=1.32; 95% CI=1.04-1.69; P<0.01). INTERPRETATION Reduced toe flexor strength and the presence of toe deformities increase the risk of falling in older people. To reduce this risk, interventions designed to increase strength of the toe flexor muscles combined with treatment of those older individuals with toe deformities may be beneficial.

Gender and age affect balance performance in primary school-aged children

OBJECTIVES Compromised stability may hinder a childs ability to master fundamental movement skills and, in turn, the capacity to participate in sporting activities. Therefore, the aim of this study was to investigate postural stability of primary school-aged children and to determine how this was moderated by age and gender. DESIGN Cross-sectional. METHOD Static posturography of primary school-aged boys (n=37) and girls (n=47) was assessed while the children were standing feet apart, feet together and in single limb stances for 30s. RESULTS The boys displayed greater sway than the girls for all conditions, although only the single limb stance scores were significantly different between the two groups (boys: 632±323 mm; girls: 456±338 mm; p=0.04). Eight-year-old children displayed significantly greater sway than the older children during the two dual limb stance conditions, whereas the 8-year-old children performed significantly poorer during the single limb condition than the 10-year-old children. CONCLUSIONS This study shows that when postural stability was challenged, boys displayed greater postural sway than girls and, although proficiency in performing dual limb balance tasks appeared achievable by the time children are 9-years of age; the more difficult single limb balance task required a further 12 months to develop. As balance is important for movement skill development and injury prevention, care should be taken to ensure movement tasks are appropriately designed for boys and girls of different ages.

Is the Foot Structure of Preschool Children Moderated by Gender

Objective: Although boys are frequently reported to have flatter feet than girls, there has been little systematic research to confirm or explain this structural difference between the genders. The objective of this study was to determine whether flat-footedness was moderated by gender in Australian preschool children and, if so, to determine the cause of this between-gender difference in structure of the plantar surface of the foot. Methods: Foot anthropometry, Arch Index derived from plantar footprints, and midfoot plantar fat pad thickness measured by ultrasound were obtained for the left and right feet of 52 girls and 36 boys (mean age, 4.2 ± 0.6 years). The children were recruited from 10 randomly selected preschools from the Illawarra region of New South Wales, Australia. Results: In agreement with previous research, the preschool boys displayed significantly flatter feet than the girls (P ≤ 0.04). Although there were no between-gender differences in structural foot dimensions, the boys had a significantly thicker midfoot fat pad than the girls by approximately 0.4 and 0.5 mm on both the right and left feet, respectively. Conclusions: The increased incidence of flat-footedness in boys compared with girls of the same age seems to be caused by a thicker plantar fat pad in the medial midfoot in boys. This suggests that the development of the medial longitudinal arch may be progressing at a slower rate in boys than in girls, and that intervention for a flexible flat foot, particularly for young boys, may be unnecessary.