Diminished muscle oxygen uptake and fatigue in spinal muscular atrophy

Objective To estimate muscle oxygen uptake and quantify fatigue during exercise in ambulatory individuals with spinal muscular atrophy (SMA) and healthy controls. Methods Peak aerobic capacity (VO2peak) and workload (Wpeak) were measured by cardiopulmonary exercise test (CPET) in 19 ambulatory SMA patients and 16 healthy controls. Submaximal exercise (SME) at 40% Wpeak was performed for 10 minutes. Change in vastus lateralis deoxygenated hemoglobin, measured by near‐infrared spectroscopy, determined muscle oxygen uptake (ΔHHb) at rest and during CPET and SME. Dual energy X‐ray absorptiometry assessed fat‐free mass (FFM%). Fatigue was determined by percent change in workload or distance in the first compared to the last minute of SME (FatigueSME) and six‐minute walk test (Fatigue6MWT), respectively. Results ΔHHb‐PEAK, ΔHHb‐SME, VO2peak, Wpeak, FFM%, and 6MWT distance were lower (P