Oxygen Cost During Mobility Tasks and Its Relationship to Fatigue in Progressive Multiple Sclerosis

Objective: To compare the oxygen costs of mobility tasks between individuals with progressive multiple sclerosis (MS) using walking aids and matched controls and to determine whether oxygen cost predicted fatigue.

Design: Cross-sectional descriptive.

Setting: A rehabilitation research laboratory.

Participants: A total of 14 adults with progressive MS (mean age ± SD [y], 54.07±8.46) using walking aids and 8 age- and sex-matched controls without MS (N=22).

Interventions: Participants performed 5 mobility tasks (rolling in bed, lying to sitting, sitting to standing, walking, climbing steps) wearing a portable metabolic cart.

Main outcome measures: Oxygen consumption (V˙o₂) during mobility tasks, maximal V˙o₂ during graded maximal exercise test, perceived exertion, and task-induced fatigue were measured on a visual analog scale before and after mobility tasks.

Results: People with progressive MS had significantly higher oxygen cost in all tasks compared to controls (P<.05): climbing steps (3.60 times more in MS), rolling in bed (3.53), walking (3.10), lying to sitting (2.50), and sitting to standing (1.82). There was a strong, positive correlation between task-induced fatigue and oxygen cost of walking, (ρ [13]=0.626, P=.022).

Conclusions: People with progressive MS used 2.81 times more energy on average for mobility tasks compared to controls. People with progressive MS experienced accumulation of oxygen cost, fatigue, and exertion when repeating tasks and higher oxygen cost during walking was related to greater perception of fatigue. Our findings suggest that rehabilitation interventions that increase endurance during functional tasks could help reduce fatigue in people with progressive MS who use walking aids.