# RELATIVE AEROBIC LOAD OF WALKING IN PEOPLE WITH MULTIPLE SCLEROSIS

## TL;DR

People with multiple sclerosis use a large portion of their available energy when walking, which can lead to early fatigue and may be improved through exercise or assistive devices.

## Contribution

This study quantifies the relative aerobic load of walking in people with multiple sclerosis using objective measures of energy demand and aerobic capacity.

## Key findings

- Participants walked at a mean relative aerobic load of 60% of peak aerobic capacity and 89% of the first ventilatory threshold.
- 31% of participants walked above the first ventilatory threshold, indicating high energy demand.
- 45% had reduced peak aerobic capacity and 52% had increased energy demands during walking.

## Abstract

To examine the energy demand of walking relative to aerobic capacity in people with multiple sclerosis.

Cross-sectional cohort study.

A total of 45 people with multiple sclerosis (32 females), median disease duration 15 years (interquartile range (IQR) 9; 20), median Expanded Disability Status Scale 4 (min–max range: 2.0; 6.0).

Aerobic capacity, derived from a cardiopulmonary exercise test and gas exchange measurements, assessed during a 6-min overground walk test at comfortable speed, were analysed. The relative aerobic load of walking was determined as the energy demand of walking relative to oxygen uptake at peak and at the first ventilatory threshold. Healthy reference data were used for clinical inference.

People with multiple sclerosis walk at a mean relative aerobic load of 60.0% (standard deviation 12.8%) relative to peak aerobic capacity, and 89.1% (standard deviation 19.9%) relative to the first ventilatory threshold. Fourteen participants walked above the first ventilatory threshold (31%). Peak aerobic capacity was reduced in 45% of participants, and energy demands were increased in 52% of participants.

People with multiple sclerosis walk at a relative aerobic load close to their first ventilatory threshold. A high relative aerobic load can guide clinicians to improve aerobic capacity or reduce the energy demands of walking.

LAY ABSTRACT

People living with multiple sclerosis often experience walking problems, which may be increased by a high energy demand during walking and/or reduced aerobic fitness. In 45 people with multiple sclerosis, this study examined how much of the subject’s total available energy is required during walking; the so-called relative aerobic load of walking. Compared with healthy subjects, those with multiple sclerosis were found to use more energy during walking, while having less energy available. This may result in early exhaustion during walking and can have a negative effect on the daily lives of people with MS. It may be possible to address these effects by appropriate treatment; for example, through aerobic exercise training to improve aerobic fitness or the use of assistive devices to reduce energy demands during walking.