By Hank Black
Young male tennis players prefer a wider shoe with more interior volume, while upper stiffness matters less, according to a new study from France that correlated the players’ perceptions of comfort with measurements taken with innovative textile pressure sensors.
“We found children who play tennis prefer roomier tennis shoes than adults,” said lead author Alexis Herbaut, PhD, a research engineer for Decathlon, a sportswear company based in Villeneuve d’Ascq, who in 2016 investigated optimal inner shoe volume in adult tennis players.
All 16 of the current study participants (all boys, aged 8-12 years) were asked to don prototypes of six commercially available tennis shoes of a style familiar to them. The shoes had narrow, medium, or wide lasts with either a stiff or soft upper construction as determined by a dynamometer-based traction test. All shoes were 10 mm longer than participants’ mean foot lengths.
The researchers’ 2016 study had identified the narrow last as having optimal (most preferred) inner shoe volume for adults; the medium last differed only in having a 7-mm larger metatarsal girth. The wide last was 14 mm larger at that point, 4 mm wider at the metatarsals, and 4 mm wider at the heel than the narrow last.
Researchers measured participants’ foot dimensions in a half-body weightbearing state with a digital caliper and tape measure, the scenario they thought most representative of children’s real-world tennis shoe fitting experience.
—Alexis Herbaut, PhD
The tennis players donned a sock with eight interwoven pressure sensors and stood still while the devices recorded pressure from lateral and medial surfaces at fore-, mid-, and rearfoot locations as well as two dorsal surface positions. To evaluate comfort, players tied their shoes as they normally would for tennis, and researchers recorded static pressure measurements for the six shoes, asking participants about comfort at each sensor location.
The widest shoes produced the lowest pressure on the external side of the first and fifth metatarsal heads, the medial midfoot, and the medial and lateral heel; players perceived them as the most comfortable shoes at the top of third metatarsal head and external side of the fifth metatarsal head, fifth metatarsal base, and the medial and lateral heel. Applied Ergonomics epublished the study in July.
“Child tennis players perceived the shoe with the wide last as more comfortable than those made with thin and medium lasts, both globally and for most sensor locations,” Herbaut said. Asked whether results might differ in girls, he said he thought not, noting, “The children were mostly preadolescents, when boys’ and girls’ feet have the same proportion. It is only later that men have a wider foot. A question that remains is: Do girls have the same [perceptions of comfort] as boys?”
The relative stiffness of the upper had little effect on comfort, with no effects found except at the top of the third metatarsal head, where the soft upper was perceived as more comfortable; pressure in this location, however, wasn’t significantly higher in the stiffer shoes. Herbaut noted, “Tennis requires more frequent braking and displacements than most other sports, but pediatric displacements are less intense than adults’ and require less work from the shoe upper to prevent the foot from moving around inside.”
Herbaut said designing tennis shoes for children is challenging. “Adult and child shoes are proportionally different, with the child’s wider in relation to length,” he said. “And pediatric feet are still growing, more than two sizes a year at certain ages, so for kids, there must be a compromise between too much and not enough space.”
He has observed parents buying shoes for their kids and noted, “They often buy ones big enough for the child to ‘grow into,’ but they usually only put their thumb on the toe to check shoe length, and ignore shoe width.”
The textile sensors were crucial for his study, Herbaut said, and could open new research opportunities. “Since they are woven into the sock, with tiny wires that extend only to the top of the sock, they stay in position. In addition, they are not apparent to the wearer as compared with stick-on sensors.” (See, “Cutting edge: Treatment for kids goes high tech,” page 8.)
That worked well for static measurements, but a later unpublished trial attempting dynamic measurements was partially stymied because of textile stretching. “We await advanced sensors for that step,” he said.
Neeru Jayanthi, MD, associate professor of orthopedics and family medicine at Emory Sports Medicine Center in Atlanta, GA, commented: “While this is a relatively small study, it does bring up an important point regarding decisions about footwear in young tennis players. Decisions should not be solely based on their potential for foot growth but also should include consideration of individual foot type, including width.”
Jayanthi, who is president of the La Grange Park, IL-based Society for Tennis Medicine and Science, said this is important to youth tennis players, especially those playing competitively, because they spend a lot of time on their forefoot.
He said, “That subjects them to more forefoot overload than most sports. Paying attention to the forefoot component, where more pressure is typically found, would be an important consideration when choosing shoe type in a growing child.”
Hank Black is freelance medical writer in Birmingham, AL.
Herbaut A, Roux M, Guéguen N, et al. Determination of optimal shoe fitting for children tennis players: effects of inner-shoe volume and upper stiffness. Appl Ergon 2017 Jun 6. [Epub ahead of print]
Herbaut A, Foissac M, Jurca A, et al. Determination of optimal shoe dimensions for occasional and regular tennis players. J Sports Eng Technol 2016; 230(3):149-157.