Heel lifts made of materials with good support and elastic properties may be more appropriate to improve footwear comfort and medial-lateral motion control, according to study results.
“It is widely believed that heel rise would induce plantar pressure redistribution, and the effects of high-heeled shoes on kinetics and kinematics have been reported extensively. However, the effects of the heel rise caused by heel lifts might be difference from that of high-heeled shoes due to their inherent differences in shape and material,” the researchers wrote. “The purpose of this study was to investigate the effects of height and material of in-shoe heel lifts on plantar pressure and medial-lateral center of pressure motion during walking, which may provide a basis for the in-shoe heel lifts designs that minimize adverse effects.”
Effects of heel lifts
Researchers asked 17 young male adults with normal arches and no history of lower extremity injuries to walk on an 8-m walkway while wearing a high-cut flat shoe with either 16-mm, 25-mm, or 34-mm medium heel lifts, soft heel lifts or hard heel lifts. Using the Pedar in-shoe pressure measurement system (Novel GmbH, Munich, Germany), researchers measured peak pressure (PP), pressure-time integral (PTI) and contact area (CA) for the forefoot, midfoot and heel, while Footscan pressure plate (RSscan International, Belgium) collected range and velocity of medial-lateral center of pressure (ML-COP) during forefoot contact phase (FFCP) and foot flat phase (FFP).
Study results showed the hard insert condition significantly increased the forefoot PP, whereas the soft, 34-mm medium and hard heel lifts significantly increased the forefoot PTI compared with the shoe-only control condition. As the height and hardness of heel lifts increased on the midfoot region, the PP, PTI and CA decreased. Researchers found a significant reduction on PP and PTI under the midfoot in the hard heel lift condition compared with the control and soft heel lift conditions. Except for the 16-mm medium inserts, all heel lifts demonstrated a significant decrease in CA under the midfoot compared with the control condition, according to study results. In heel PP, researchers found a statistically significant decrease with the use of all heel lifts except for the hard one which slightly increased PP.
Hard heel lifts demonstrated a statistically significant larger ML-COP range compared with the control and 34-mm medium lift conditions, as well as a significantly faster velocity during FFCP than the control, soft and 34-mm medium lift conditions.
“There was no significant difference between heel lifts of different height, so approaches to relieving heel peak pressure only by elevating the heel are not practical, at least within 34-mm heel rise,” Xianyi Zhang, a graduate student at Sichuan University in China, told O&P Business News. “The findings from this study suggest that it is advisable to wear thick heel lifts with caution on a daily basis. To decrease peak pressure under heel, insole material should have elastic properties. The range and velocity of medial-lateral COP could be used to assess the medial-lateral control ability during walking.”
Heel lift comfort
According to the researchers, comfort is important when it comes to acceptance of heel lifts for daily use. Among all conditions, participants rated the 16-mm medium heel lift as the most comfortable. As the heel was elevated, ratings decreased and researchers found a significant difference in ML control rating between 16-mm medium and 34-mm medium heel lift conditions. Compared to the control condition, study results showed the ML control ratings of the soft, 34-mm medium and hard heel lifts were significantly lower, according to study results. Although participants rated the soft heel lift as more comfortable vs. 34-mm medium and hard heel lifts, the 34-mm medium lift was rated more stable vs. the soft and hard heel lifts.
“Comfort was assessed by the overall comfort ratings in this study. As to the material properties, the softer material provided better comfort. As to the heel height, higher heel provided less comfort,” Zhang said. “The comfort rating of the lowest heel lifts was the best in this study, even better than the shoe only condition. The rating of medium height heel lifts was the same as that of the shoe only condition.” — by Casey Tingle
Disclosure: Zhang reports no relevant financial disclosures.