Sex-Based Differences in Oxygen Cost of Walking and Energy Equivalents in Minimally Disabled Individuals With Multiple Sclerosis and Controls.

Background: Elevated oxygen cost of walking and energy equivalents are reported for highly and moderately disabled individuals with multiple sclerosis (MS). However, less is known about minimally impaired individuals. Moreover, no sex-based data on the metabolic rates of individuals with MS are available. In this cross-sectional study, the metabolic rates and temporospatial parameters of gait during overground walking in minimally disabled individuals with MS versus matched controls were quantified and whether sex-based differences occur was examined.

Methods: Sixty-nine minimally impaired adults with MS (37, relapsing-remitting MS [RRMS]; 32, clinically isolated syndrome [CIS]) and 25 matched controls completed two 6-minute walking bouts at comfortable and fast speeds. The oxygen cost of walking, energy equivalents, and respiratory exchange ratio were recorded through breath-by-breath open-circuit spirometry. Gait analysis was performed via a portable electronic walkway.

Results: At comfortable but not at fast speed, men with RRMS showed higher oxygen cost of walking than men with CIS (+17.9%, = .04) and male controls (+21.3%, = .03). In the RRMS group, men showed higher oxygen cost of walking (+19.2%, = .04) and energy equivalents (+19.2%, = .02) than women. Elevated oxygen cost of walking and energy equivalents in men were paralleled by significantly larger base of support and step time asymmetry during walking.

Conclusions: Metabolic demands are elevated while walking in minimally disabled individuals with RRMS. Furthermore, higher energy demands occur in men, probably due to increased step symmetry and base of support. Clinicians are advised to follow energy expenditure metrics collected while walking because they can indicate a decrease in fitness, even in the early phase of MS.