Influence of age, gender and obesity on pressure discomfort threshold of the foot: A cross-sectional study.

Highlights

• It shows a pattern for Pressure Discomfort Threshold in the foot plantar surface.

• This discomfort pattern changes due to aging, gender and body mass index.

• The findings can have important implications on orthosis and footwear design.

Abstract

Background

Foot pain is a highly prevalent health problem for which measures such as a pattern of Pressure Discomfort Threshold of the foot plantar surface can provide valuable information for orthosis design. This study aimed to describe such pattern as a tool for the assessment of painful conditions of the feet and to analyse how it modifies according to age, gender and obesity.

Methods

A cross-sectional study was performed with participants allocated in: Group 1 people aged 20 to 35 years, Group 2 aged 50 to 65 years and Group 3 aged over 65. Pressure Discomfort Threshold on twelve points of the foot plantar surface was measured with an adapted manual dynamometer. Inferential analyses of the data were performed using one-way analysis of variance (ANOVA) considering foot areas, age group, gender and obesity.

Findings

36 participants were analysed. The pattern of Pressure Discomfort Threshold for all individuals showed a significantly higher threshold on the heel and external foot (P < 0.001, η² = 0.124) and was statistical significantly influenced by age (P < 0.001, η² = 0.17), especially in participants aged over 65; by gender, with women having higher values (P < 0.001, η² = 0.13), and by obesity (P < 0.001, η² = 0.19).

Interpretation

A Pressure Discomfort Threshold pattern exists in the foot plantar surface. The characteristics of the discomfort pattern of the foot and its association with aging, gender and obesity may have considerable implications for orthosis and footwear design.

Introduction

Foot pain is a highly prevalent health problem, 29% of women and 19% of men suffer from it.(Awale et al., 2016) The existence of high plantar pressures in certain areas of the foot has been associated to pain and discomfort(Mickle et al., 2010) even leading to hyperkeratosis(Barlow et al., 1990) and, subsequently, metatarsal and heel pain, especially in older people.(Akdemir et al., 2011; Hill et al., 2008) In addition, alteration of foot function in one area can instigate unfavourable outcomes such as high pressure onto a new area, imbalance and/or injury when walking.(Mickle et al., 2010)

Foot pressure has different effects, thus depending on its magnitude the resulting sensation can vary from superficial touch to pain, previously passing through discomfort.(Hong et al., 2005) Whereas superficial touch provides the sensory feed-back necessary for balance and locomotion, discomfort and pain are mechanisms that warn of potentially harmful situations.(Xiong et al., 2010)

The most frequent treatment options are advice acquiring appropriate fit shoes, plantar orthosis or footwear modifications.(van der Zwaard et al., 2011) Therefore, minimising foot pain and discomfort due to pressure generated during human locomotion is an important user requirement for plantar orthosis or shoes.

Pressure pain threshold (PPT), understood as the minimum pressure that induces pain, has been evaluated at selected locations or through a full plantar surface map.(Weerasinghe et al., 2017) It is generally accepted that discomfort is a precursor of pain. Thus, pressure discomfort threshold (PDT) understood as the minimum pressure that produces discomfort(Johansson et al., 1999) is presented as a more suitable standard in product design.(Goonetilleke, 2006) A foot plantar PDT pattern can provide valuable information for footwear and orthosis design, aid in preventing pain and identify individuals who may be at risk of developing or worsening an injury due to high pressure. It could also be useful in order to detect patients with loss of hypersensitivity and to evaluate the effects of treatments on various pathological conditions. But before studying the different conditions, the existence of normal patterns in healthy subjects are needed. However, few studies have focused on it.(Gonzalez et al., n.d.; Johansson et al., 1999; Weerasinghe et al., 2017; Xiong et al., 2010)

In addition, there are several potential risk factors for foot pain and discomfort that have been identified from cross-sectional studies, and should be taken in consideration: increased age with a prevalence between 14.9 and 41.9% of adults aged over 50 years,(Gorter et al., 2000) gender, with women having higher prevalence of foot pathologies(Dufour et al., 2009) and obesity, with obese people possibly being more sensitive to pain.(Okifuji et al., 2009) Unfortunately, there is limited knowledge on how foot discomfort relates to age, gender or body mass index (BMI).

In the present study it was hypothesized that there are different PDT depending on different areas of the foot plantar surface and that it modifies with age, gender and increase of BMI. Therefore, the main purpose of this study is to describe a pattern of PDT as a tool for the assessment of painful conditions of the foot.