Relative Effort While Walking Is Higher Among Women Who Are Obese, and Older Women

Hoda Koushyar; Dennis E. Anderson; Maury A. Nussbaum; Michael L. Madigan

Disclosures

Med Sci Sports Exerc. 2020;52(1):105-111. 

In This Article

Abstract and Introduction

Abstract

Purpose: Individuals who are obese, and older individuals, exhibit gait alterations that may result, in part, from walking with greater effort relative to their maximum strength capacity. The goal of this study was to investigate obesity-related and age-related differences in relative effort during gait.

Methods: Four groups of women completed the study, including 10 younger healthy-weight, 10 younger obese, 10 older healthy-weight, and 9 older obese women. The protocol included strength measurements at the hip, knee, and ankle in both flexion and extension, and gait trials under self-selected and constrained (1.5 m·s−1 gait speed and 0.65-m step length) conditions. Relative effort was calculated as the ratio of joint torques during gait, and strength from a subject-specific model that predicted strength as a function of joint angle.

Results: Relative effort during self-selected gait was higher among women who were obese in knee extension (P = 0.028) and ankle plantar flexion (P = 0.013). Although both joint torques and strength were higher among women who were obese, these increases in relative effort were attributed to greater obesity-related increases in joint torques than strength. Relative effort was also higher among older women in hip flexion (P < 0.001) and knee extension (P = 0.008), and attributed to age-related strength loss. Results were generally similar between self-selected and constrained gait, indicating the greater relative effort among women who were obese and older women was not attributed to differences in gait spatiotemporal characteristics.

Conclusions: Women who were obese, as well as older women, walk with greater relative effort. These results may help explain the compromised walking ability among these individuals.

Introduction

One-third of the adults in the United States are obese.[1] Obesity is linked to a number of gait alterations, including slower gait speed,[2,3] shorter step length,[4] longer duration stance phase and double support,[3,5,6] and difficulty walking long distances.[7] Possible reasons for these gait alterations include range-of-motion limitations,[3,6] knee extensor dysfunction,[8] and neuromuscular adaptations to reduce energy expenditure,[2,4] reduce knee joint loading,[2,5,6] or maintain balance.[3,4]

Another possible reason for obesity-related gait alterations is that individuals who are obese walk with greater relative effort. Relative effort has been calculated by expressing joint torques during an activity as a percentage of strength, or maximum voluntary torque.[9–11] Relative effort during gait may be higher among individuals who are obese because they exhibit higher joint torques at the ankle,[5,6] knee,[5] and hip.[5] Although lower limb strength is also higher among individuals who are obese in knee extension,[12–14] hip flexion,[13] and ankle dorsiflexion,[13] relative effort may still be higher if obesity-related increases in joint torques surpass increases in strength. For example, Browning and Kram[5] reported a 51% obesity-related increase in peak knee extension torque during 1.5 m·s−1 gait, while Koushyar et al.[13] reported a 30% obesity-related increase in knee extension strength, which would together suggest an 11% obesity-related increase in knee extension relative effort during gait. Prior studies have quantified relative effort during sit-to-stand,[9–11] stair ascent and descent,[10,15] and gait.[15–17] However, we are not aware of any studies that have investigated the effects of obesity on relative effort during gait. Identifying any such effects could help clarify the underlying factors by which obesity compromises walking ability and inform interventions to improve walking capacity among individuals who are obese.

Aging has also been associated with gait alterations, including a lower gait speed,[18] shorter step length,[16,18] and smaller ranges of motion at the ankle and hip.[16,18] These alterations have been attributed, in part, to walking with greater relative effort.[15,16] For example, Anderson and Madigan[16] reported relative effort of the ankle plantar flexors to be close to 100% among older adults walking at a hurried speed, indicating that near full effort was being exerted. Older adults who are obese would seem to be particularly susceptible to greater relative effort during gait due to obesity-related increases in joint torques, and age-related loss of strength.[13,19]

The goal of this study was to investigate obesity-related and age-related differences in relative effort during the support phase of gait. We focused on women because they have a higher prevalence of obesity[1] and obesity-related mobility limitations[20] than men. We hypothesized that: 1) relative effort would be higher among women who were obese compared with healthy-weight women, 2) relative effort would be higher among older women compared with young women, and 3) obesity-related differences in relative effort would be larger among older women than young women. We evaluated subjects during self-selected gait, as well as during a constrained gait (fixed speed and step length across all subjects), due to the potential for obesity-related differences in gait characteristics from confounding any obesity-related differences in relative effort.

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