Skeletal Muscle Abnormalities in Girls and Adolescents With Turner Syndrome
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CONTEXT: Turner syndrome (TS) is a chromosomal disorder occurring in approximately 1 in 2500 live births. Individuals with TS report lower levels of physical activity than healthy control (HC) subjects. Cardiorespiratory limitations may contribute to the observed reduction in physical activity. OBJECTIVE: The objective of this study was to compare muscle metabolism of patients with TS vs HC subjects before and after exercise using exercise testing, magnetic resonance imaging, and magnetic resonance spectroscopy techniques. DESIGN: We hypothesized that girls and adolescents with TS would have muscle metabolic abnormalities not present in the HC population. SETTING: The research was conducted at the Hospital for Sick Children in Toronto, Ontario, Canada. PARTICIPANTS: Fifteen participants with TS were age-, activity-, and body mass index Z-score-matched with 16 HC subjects. MAIN OUTCOME MEASURES: (31)P magnetic resonance spectroscopy was used to characterize muscle metabolism at rest and after 30 seconds of high-intensity exercise, 60 seconds of moderate-intensity exercise, and 5 minutes of low-intensity exercise. RESULTS: While achieving the same workloads, participants with TS exhibited a greater difference between rest and end-exercise pH compared with HC subjects after 30 seconds (TS, 0.29 ± 0.04; HC, 0.21 ± 0.08; P = .03) and 90 seconds (TS, 0.47 ± 0.22; HC, 0.32 ± 0.13; P = .02) of exercise. During the 5-minute exercise test, similar workloads were achieved between groups; however, ATP production was greater in participants with TS vs the HC subjects via all 3 bioenergetic pathways (total ATP: TS, 0.90 ± 0.34; HC, 0.60 ± 0.25; P = .01). CONCLUSIONS: The results of this study suggest that patients with TS exhibit greater anaerobic stress during exercise than HC subjects, which may lead to symptoms of increased muscle fatigue with short bursts of activity. Recovery metabolism after exercise appears to be similar between participants with TS and HC subjects, which is suggestive of normal mitochondrial metabolism and oxygen transport.
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