Skeletal muscle mitochondrial capacity and muscle-specific endurance in persons with Friedreich's ataxia

PURPOSE: Evaluate skeletal muscle mitochondrial capacity and muscle-specific endurance using noninvasive methods in persons with Friedreichs Ataxia (FRDA) and able-bodied controls (AB). METHODS: Participants with FRDA (n=16) and AB controls (n=10) were tested (ages 8-55 yrs). Forearm mitochondrial capacity was measured using the rate of recovery of oxygen consumption after electrical stimulation with near-infrared spectroscopy. Mechanomyography was used to assess muscle-specific endurance after electrical stimulation for 3 minutes at 2Hz, 4Hz, and 6Hz sequentially. RESULTS: There was no difference in mitochondrial capacity (FRDA and AB: 1.8 0.3 1/min). Muscle-specific endurance was significantly impaired by 14% in the FRDA participants in comparison to AB controls (p < 0.001). Correlations show a positive, moderate relationship between these two measurements and a negative, moderate relationship with disease severity in the FRDA group. CONCLUSIONS: Impairments in endurance and relationships between disease severity, endurance and mitochondrial capacity suggest that these measurements can be useful to monitor people with FRDA. The ease of testing and noninvasive nature of these methods also make them appropriate for futures studies.