Effects of Body Mass Index on Mechanical Properties of the Plantar Fascia and Heel Pad in Asymptomatic Participants.

BACKGROUND: Musculoskeletal foot disorders have a high incidence among overweight and obese individuals. One of the important factors causing this high incidence may be plantar fascia and heel pad (HP)-related mechanical changes occurring in these individuals. The aim of the present study was to investigate the plantar fascia and HP stiffness and thickness parameters in overweight and obese individuals and compare these values with those of normal-weight individuals.

METHODS: This study was carried out in 87 (52 female, 35 male) healthy sedentary individuals between the ages of 19 and 58 years (34 ± 11 years). Participants were subsequently categorized according to body mass index (BMI) as normal weight (18.5 kg/m2 < BMI < 25 kg/m2 ) or overweight and obese (BMI ≥25 kg/m2 ). Plantar fascia and HP thickness and stiffness were measured with an ultrasonography device using a linear ultrasonography probe.

RESULTS: Overweight and obese individuals had higher HP thickness ( P < .001), plantar fascia thickness ( P = .001), heel pad microchamber layer (MIC) stiffness ( P < .001), and heel pad macrochamber layer (MAC) stiffness ( P < .001), whereas they had lower plantar fascia stiffness ( P < .001) compared with the individuals with normal weight. BMI had a moderate correlation with HP thickness ( P < .001, r = 0.500), plantar fascia thickness ( P = .001, r = 0.536), MIC stiffness ( P < .001, r = 0.496), and MAC stiffness ( P < .001, r = 0.425). A negative and moderate correlation was found between BMI and plantar fascia stiffness ( P < .001, r = -0.439).

CONCLUSION: Increased BMI causes a decrease in the stiffness of plantar fascia and an increase in the thickness of the plantar fascia as well as the thickness and stiffness of HP. Increased body mass could cause changes in the mechanical properties of HP and plantar fascia.

LEVEL OF EVIDENCE: Level 3, comparative study.