An evaluation of the heel strike transient in obese young adults during walking gait

Highlights

• Obese individuals have a greater incidence of heelstrike transient during walking.

• Heelstrike transient dichotomously identifies individuals with high loading rates.

• Walking speed influences heelstrike transient detection.

Abstract

Background

Obesity is considered a risk factor for knee osteoarthritis (OA) in part due to its influence on gait biomechanics. The heel strike transient (HST) is a characteristic of the ground reaction force that is indicative of a high rate of loading, but has not been evaluated in obese adults.

Objective

To compare the incidence of HST in obese compared to normal weight adults.

Methods

15 normal-weight (males = 7, age = 20.4 ± 2.1 years, body mass index = 21.6 ± 1.3 kg/m²) and 15 obese (males = 7, age = 21.2 ± 1.9 years, body mass index = 33.5 ± 4.3 kg/m²) young adults completed 10 walking trials at a standardized speed and 10 trials at a self-selected speed while ground reaction force data were sampled. HST incidence was evaluated using a dichotomous method previously identified in the literature, and compared between groups using χ² analyses.

Results

The number of individuals classified as possessing the HST differed between the obese and normal-weight groups (8/15 vs. 3/15, p = 0.047). Evaluation of the standardized residuals indicated a significantly greater than expected incidence of the HST in the obese group when walking at a standardized speed.

Conclusion

Our findings indicate that a greater proportion of obese compared to normal weight participants displayed a HST. The HST may provide a dichotomous method for identifying individuals with aberrant gait biomechanics.

Introduction

Knee osteoarthritis (OA) is a cause ofdisability that contributes an economic burden of $51 billion annually in the United States [1]. Knee OA contributes to comorbidities such as diabetes and cardiovascular disease [2], and obesity is a risk factor for knee OA development [3]. Obesity is common among young adults, and may reduce the age of onset for knee OA in young obese individuals, thus elevating the lifetime physical and financial burden. Therefore, it is essential to understand the influence of obesity on risk factors for knee OA in young adults.

The cause of knee OA is multifactorial involving mechanical and biochemical processes that result in inflammation and a gradual breakdown of articular cartilage [3]. Body mass index is associated with greater tibiofemoral compression during gait [4], vertical ground reaction forces, (vGRF) and loading rates in obese individuals with OA [5]. A prior study indicates that vGRF loading rate, but not vGRF peak magnitude, is greater in obese compared to normal weight young adults without knee OA [6]. Animal models indicate that repetitive loads applied at higher rates results in rapid breakdown of articular cartilage, irrespective of load magnitude [7]. The heel strike transient (HST) refers to a rapid rise in the vGRF immediately following ground contact, and is an indicator of high rate loading [8], [9]. The HST may provide a dichotomous method for identifying individuals with high loading rates. However, the HST has not been evaluated in obese individuals who may experience a greater incidence of HST.

The purpose of this study was to evaluate the influence of obesity on the incidence of the HST during walking gait in obese compared to normal-weight young adults. We hypothesized that obese individuals would have a greater incidence of HST compared to normal weight adults.