Abstract #0861

Exercise Protocol and Muscular Fiber Type Composition Dependent Phosphocreatine Recovery in Health and Disease

Marco Jauslin¹, Anke Henning¹, Ulrike Dydak², Haiko Sprott³, Dieter Meier¹, Hans H. Jung⁴, Peter S. Sndor⁴, Peter Boesiger¹

¹Institute for Biomedical Engineering, ETH and University Zrich, Zrich, Switzerland; ²School of Health Sciences, Purdue University, West Lafayette, IN, United States; ³Department of Rheumatology and Institute of Physical Medicine, University Hospital Zrich, Zrich, Switzerland; ⁴Department of Neurology, University Hospital Zrich, Zrich, Switzerland

Differences in phosphocreatine recovery (represented by its time constant, normalized for pH_min) between controls and patients with mitochondrial encephalomyopathies (and migraine with aura) have been detected with ³¹P-MRS exercise protocols of both low and increasing intensity at low contraction frequency. By employing a protocol of high intensity and high contraction frequency these differences vanish, which may be explained by higher fractions of activated fast twitch fibers and interindividual variations in muscle fiber type composition in controls. Our observations therefore challenge the notion of absolute workload independence of PCr recovery due to different recovery characteristics of fast and slow twitch fibers.