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 < 0.001), and Fatigue6MWT and FatigueSME were higher (P < 0.001) in SMA compared to controls. ΔHHb‐PEAK correlated with FFM% (r = 0.50) and VO2peak (r = 0.41) only in controls. Only in SMA, Fatigue6MWT was inversely correlated with Wpeak (r = −0.69), and FatigueSME was inversely correlated with FFM% (r = −0.55) and VO2peak (r = −0.69). Interpretation This study provides further support for muscle mitochondrial dysfunction in SMA patients. During exercise, we observed diminished muscle oxygen uptake but no correlation with aerobic capacity or body composition. We also observed increased fatigue which correlated with decreased aerobic capacity, workload, and body composition. Understanding the mechanisms underlying diminished muscle oxygen uptake and increased fatigue during exercise in SMA may identify additional therapeutic targets that rescue symptomatic patients and mitigate their residual disease burden.

BACKGROUND: Guidelines recommend exercise for secondary prevention of acute coronary syndrome (ACS), however adherence to guidelines is low. A paucity of data examining factors associated with objectively-measured exercise post-discharge in ACS survivors exists. The purpose of this study was to identify factors associated with exercise during the 5 weeks after ACS discharge. METHODS: A sample of 151 ACS patients treated at a university hospital were enrolled into an observational cohort study and wore an accelerometer for 35 days post-discharge. Days on which participants accumulated ≥30 mins of moderate-to-vigorous physical activity in bouts ≥10 mins were considered exercise days. Participants were categorized as non-exercisers (0 exercise days) or exercisers (≥1 exercise day). A multi-variable logistic regression model was used to examine the association between exercise and socio-demographics, depression, SF-12 physical and mental health scores, disease severity, length of hospitalization, and percutaneous coronary intervention.

Background: Individuals with spinal muscular atrophy (SMA) III walk independently, but experience muscle weakness, gait impairments, and fatigue. Although SMA affects proximal more than distal muscles, the characteristic pattern of selective muscle weakness has not been explained. Two theories have been proposed: 1) location of spinal motor neurons; and 2) differences in segmental innervation. Objective: To identify neuroanatomical models that explain the selective muscle weakness in individuals with SMA and assess the relationship of these models to ambulatory function. Methods: Data from 23 ambulatory SMA participants (78.2% male), ages 10–56 years, enrolled in two clinical studies (NCT01166022, NCT02895789) were included. Strength was assessed using the Medical Research Council (MRC) score; ambulatory function was measured by distance walked on the 6-minute walk test (6 MWT). Three models were identified, and relationships assessed using Pearson correlation coefficients and linear regression. Results: All models demonstrated a positive association between strength and function, (p < 0.02). Linear regression revealed that Model 3B, consisting of muscles innervated by lower lumbar and sacral segments, explained 67% of the variability observed in 6 MWT performance (β= 0.670, p = 0.003). Conclusions: Muscles innervated by lower lumbar and sacral segments, i.e. hip extensors, hip abductors, knee flexors and ankle dorsiflexors, correlated with and predicted greater ambulatory function. The neuroanatomical patterns of muscle weakness may contribute to a better understanding of disease mechanisms and enable delivery of targeted therapies.

Introduction The 6‐minute walk test (6MWT) is a well‐established clinical assessment of functional endurance, validated as a measure of walking ability in spinal muscular atrophy (SMA). The current availability of disease‐modifying therapies for SMA indicates a growing need for normative reference data to compare SMA patients with healthy controls. Methods The literature was searched in two scientific databases. Studies were evaluated and selected based on adherence to American Thoracic Society guidelines for administering the 6MWT. Reference equations from the selected studies were applied to 6MWT data collected from SMA patients to calculate and compare % predicted values. Results Three pediatric and six adult studies were selected for comparison. The % predicted values using the pediatric and adult equations ranged from 47.7 ± 18.2% to 67.6 ± 26.2% and 43.0 ± 17.9% to 59.5 ± 26.2%, respectively, and were significantly different (P < 0.001). Discussion Results suggest significant variability between % predicted values derived from published reference equations in children and adults, despite adherence to 6MWT standardization.