Footwear should allow dynamic activity
By Greg Gargiulo
A recent study of the metabolic costs of barefoot versus shod walking found walking in shoes required a higher energy expenditure and had a poorer economy than barefoot walking. These outcomes suggest going barefoot may be preferable for children whenever it is deemed safe and appropriate, and highlights the need for practitioners to recommend properly fitted shoes designed for dynamic activity to minimize any negative impact on foot development.
“Previous adult data has shown a similar result, but our study does seem to solidify the sports science findings that shoes change our walking dynamic, which alters economy,” said lead author Sarah Shultz, PhD, a senior lecturer in the School of Sport and Exercise at Massey University in Wellington, New Zealand.
For example, a 2011 study published in Gait & Posture found walking in industry-recommended athletic footwear was associated with increases in knee and hip net joint moments compared to barefoot walking, including a 9.7% increase in the first peak knee varus moment.
The 25 healthy participants (aged 8-12 years, 14 girls) completed two five-minute trials on a treadmill at a self-selected speed (1 ± .13 m/s), doing one trial barefoot and the other shod in a standardized lace-up athletic shoe with an elevated heel, rounded toe, arch support, and stiff midsole (total weight, 248 g ± 28 g).
Investigators sampled force plate data in each trial in 20-second intervals (120, 180, and 240 seconds) and used data collected at the 240-second time point to calculate vertical center of mass displacement (vCoM). They used a portable gas analyzer to collect expired gases and measure oxygen consumption and then calculated energy expenditure, walking economy, and substrate utilization.
The children’s oxygen consumption and energy expenditure were significantly higher and economy significantly decreased while wearing shoes compared with barefoot walking. Barefoot walking also elicited significantly less vCoM than the shod condition. Children weren’t given time to get used to the study shoes, but Schultz said all were familiar with the shoe type and had time to accommodate to walking on the treadmill.
Researchers proposed several factors potentially responsible for shod walking’s poorer economy. The footwear’s added mass may have increased energy costs during gait. A 2015 study by Shultz and colleagues evaluated a subset of the current cohort and found an increased stride length in the shod condition (1.03 ± .14 m) versus the barefoot condition (1 ± .13 m). These longer stride lengths could have had a similar effect to the added mass and changed vCoM, both of which are believed to increase the metabolic cost of walking.
Data from the 2015 subset study also suggested the two modes of walking require unique mechanical demands, with shod walking recruiting more hip musculature, and barefoot depending more on the ankle and generating greater plantar flexor energy. These specific features may have also led to differences in elastic energy storage and affected overall walking economy.
“I do not think that any one factor is more significant than another [in contributing to poorer economy], mainly because there are multiple and overlapping relationships between them,” Shultz said. “For instance, you cannot discriminate between effects on walking economy as a result of changes in stride length and changes in vCoM because there is an existing relationship between stride length and vCoM.”
The International Journal of Sports Medicine published the study in May 2016.
“This study nicely complements the existing literature that shod and barefoot gait are significantly different and that footwear has a substantial impact on the kinematics, kinetics, and physiology of children’s gait,” said Caleb Wegener, PhD, the footwear research and innovation developer for Sydney, Australia-based Mack Boots and honorary research associate at the University of Sydney.
Consequently, the decreased energy cost of barefoot walking found here should further guide clinicians’ footwear recommendations for children.
“Although we didn’t measure shoe fit in this study, properly fitted shoes that minimize any negative impact on foot development are very important, and I recommend allowing kids to go barefoot whenever it is safe and appropriate—most likely around the home—to help strengthen the foot and promote positive development. Playing sports will probably require shoes,” Shultz said.
Wegener also noted why children’s habitual behaviors need to be considered.
“Since the clinical effect required is to minimize the biomechanical and physiological effect of footwear, very flexible shoes are required,” he said. “Clinically, I have tended to recommend the requirements for the foot, and then the activity, and the nature of children’s play throughout the day means that all footwear worn by children should be designed for dynamic activity.”
Still, Shultz believes future research will help to explore the specific factors at play in this study.
“Since this is a descriptive study and can only suggest possible reasons, further investigations using more of an intervention approach could help to determine the importance of any one factor that we identified,” she said.
Greg Gargiulo is a freelance medical writer based in San Francisco.
Shultz SP, Houltham SD, Kung SM et al. Metabolic differences between shod and barefoot walking in children. Int J Sports Med 2016;37(5):401-404.
Keenan GS, Franz JR, Dicharry J et al. Lower limb joint kinetics in walking: The role of industry recommended footwear. Gait Posture 2011;33(3):350-355.
Kung SM, Fink PW, Hume P, Shultz SP. Kinematic and kinetic differences between barefoot and shod walking in children. Footwear Science 2015;7(2):95-105.