Science News: Physical Strain of Walking in People With Neuromuscular Diseases Is High and Relates To Step Activity in Daily Life

Summary: The goal of the study was to determine the physical strain of walking based on actual measured oxygen consumption during walking (VO2walk) and peak oxygen consumption (VO2peak) in individuals with neuromuscular disease (NMD), and to assess the relationship between daily physical activity, expressed as daily step count and time spent in moderate to vigorous physical activity (MVPA), and physical strain of walking. Recruited from I’M FINE study in the Netherlands, inclusion criteria: Main inclusion criteria were: Diagnosed with Charcot-Marie-Tooth disease, post-polio syndrome, or other slowly progressive NMD; aged ≥ 18 years; and motivated to follow a physical activity programmed to improve aerobic capacity. Participants were excluded if they had contraindications for physical activity according to the American College of Sports Medicine guidelines; were unable to follow verbal or written instructions; had insufficient understanding of the Dutch language; or had participated in an exercise program for more than 4 weeks in the past 6 months. Only ambulatory participants with complete and valid baseline data for all variables of interest, as defined below, were included in the analyses of the current study. Manual muscle testing was performed. A walking energy cost test at a comfortable speed to assess VO2walk and walking speed, then an incremental increase in exercise to assess VO2peak, were performed. Daily physical activity during walking hours was measured for 7 consecutive days. This was measured using an accelerometer and a heart rate belt. Sixty-one subjects enrolled from the I’M FINE study completed the study. Analysis showed an inverse relationship between daily step count and physical strain of walking. No association between MVPA and physical strain of walking. NMD patients with high physical strain took fewer steps per day. However, time spent in MVPA was not related to physical strain of walking, which may indicate that despite a reduction in step count, strenuous daily activities are still being performed. 

Overall, the study showed that physical strain of comfortable walking was severely increased in NMD. The physical strain was 73%, compared to 34-49% of able-bodied individuals. High physical strain of walking was associated with lower steps taken, while intensity of daily activity was not related. Authors suggest reducing VO2peak with aerobic exercise and potentially reducing VO2walk with lower limb orthoses as possible clinical applications.