Assisted Six Minute Cycle Test (A6MCT): A Feasible and Valid Measurement of Functional and Fatigue Changes in Individuals with Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) characterized by progressive muscle weakness and atrophy results in loss of function. Most outcomes assess motor function without assessing fatigue, a common clinical feature that may change with treatment. To assess feasibility and effectiveness of a performance-based evaluation using the Assisted 6 Minute Cycle Test (A6MCT) for non-ambulatory patients with SMA and to determine the relationship of A6MCT with the RULM and ATEND measures. Prospective data was collected on patients who were on disease modifying treatments for an average of 3.0 years. Outcomes used for analysis include: A6MCT total revolutions(TR) and % fatigue, RULM, ATEND, Fatigue Severity Score (FSS) and EK2. Analysis included association of A6MCT revolutions and fatigue with disease characteristics and outcomes. Two separate linear mixed models were utilized to analyze the interaction and change over time between visits (Significance ɑlevel of 0.05). Thirty-two participants were recruited (sitters=8.31.8±13.8 yrs; non-sitters=24.28.9±.5 yrs) who had 35 follow up evaluations (avg baseline to follow up=0.92 yrs). No differences in revolutions between functional groups or SMA type was found. No significant correlations with fatigue and RULM, ATEND, FSS; moderate correlations (r-0.6; p>0.05) with functional status and EK2 for both sitters (r=-0.7; p=0.005) and non-sitters (r=0.76; p=0.024). There was a statistically significant positive interaction between time and fatigue (β=7.136, p=0.0127). Sitters showed a statistically significant negative relationship with fatigue (β=-18.647, p=0.0055) showing less fatigue than the non-sitter group. TR showed a significantly positive interaction with time (β=46.455, p=0.0096). These results suggest that both time and functional status are predictors of fatigue, and TR shows change over time. The A6MCT test may be used in clinical settings for patients with SMA to evaluate endurance and fatigability. Spinal muscular atrophy (SMA) characterized by progressive muscle weakness and atrophy results in loss of function. Most outcomes assess motor function without assessing fatigue, a common clinical feature that may change with treatment. To assess feasibility and effectiveness of a performance-based evaluation using the Assisted 6 Minute Cycle Test (A6MCT) for non-ambulatory patients with SMA and to determine the relationship of A6MCT with the RULM and ATEND measures. Prospective data was collected on patients who were on disease modifying treatments for an average of 3.0 years. Outcomes used for analysis include: A6MCT total revolutions(TR) and % fatigue, RULM, ATEND, Fatigue Severity Score (FSS) and EK2. Analysis included association of A6MCT revolutions and fatigue with disease characteristics and outcomes. Two separate linear mixed models were utilized to analyze the interaction and change over time between visits (Significance ɑlevel of 0.05). Thirty-two participants were recruited (sitters=8.31.8±13.8 yrs; non-sitters=24.28.9±.5 yrs) who had 35 follow up evaluations (avg baseline to follow up=0.92 yrs). No differences in revolutions between functional groups or SMA type was found. No significant correlations with fatigue and RULM, ATEND, FSS; moderate correlations (r-0.6; p>0.05) with functional status and EK2 for both sitters (r=-0.7; p=0.005) and non-sitters (r=0.76; p=0.024). There was a statistically significant positive interaction between time and fatigue (β=7.136, p=0.0127). Sitters showed a statistically significant negative relationship with fatigue (β=-18.647, p=0.0055) showing less fatigue than the non-sitter group. TR showed a significantly positive interaction with time (β=46.455, p=0.0096). These results suggest that both time and functional status are predictors of fatigue, and TR shows change over time. The A6MCT test may be used in clinical settings for patients with SMA to evaluate endurance and fatigability.