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ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Metabolic and vascular support for the role of myoglobin in humans: a multiparametric NMR study

¹NMR Laboratory, AFM and CEA, IFR 14, Institute of Myology, Pitié-Salpêtrière University Hospital, 75013 Paris; ²Center of Sport Medecine of Ecole Interarmées des Sports, 77300 Fontainebleau; ⁴Institut de Médecine Aéronautique du Service de Santé des Armées, 91220 Brétigny/Orge, France; and ³Department of Medicine, University of California, San Diego, La Jolla, California 90293-0623

Submitted 9 April 2004 ; accepted in final form 6 August 2004

In human muscle the role of myoglobin (Mb) and its relationship to factors such as muscle perfusion and metabolic capacity are not well understood. We utilized nuclear magnetic resonance (NMR) to simultaneously study the Mb concentration ([Mb]), perfusion, and metabolic characteristics in calf muscles of athletes trained long term for either sprint or endurance running after plantar flexion exercise and cuff ischemia. The acquisitions for ¹H assessment of Mb desaturation and concentration, arterial spin labeling measurement of muscle perfusion, and ³¹P spectroscopy to monitor high-energy phosphate metabolites were interleaved in a 4-T magnet. The endurance-trained runners had a significantly elevated [Mb] (0.28 ± 0.06 vs. 0.20 ± 0.03 mmol/kg). The time constant of creatine rephosphorylation (PCr), an indicator of oxidative capacity, was both shorter in the endurance-trained group (34 ± 6 vs. 64 ± 20 s) and negatively correlated with [Mb] across all subjects (r = 0.58). The time to reach maximal perfusion after cuff release was also both shorter in the endurance-trained group (306 ± 74 vs. 560 ± 240 s) and negatively correlated with [Mb] (r = 0.56). Finally, Mb reoxygenation rate tended to be higher in the endurance-trained group and was positively correlated with PCr (r = 0.75). In summary, these NMR data reveal that [Mb] is increased in human muscle with a high oxidative capacity and a highly responsive vasculature, and the rate at which Mb resaturates is well correlated with the rephosphorylation rate of Cr, each of which support a teleological role for Mb in O₂ transport within highly oxidative human skeletal muscle.

postexercise hyperemia; skeletal muscle; perfusion; oxygenation; phosphocreatine

This article has been cited by other articles:

				P. G. Carlier and D. Bertoldi In vivo functional NMR imaging of resistance artery control Am J Physiol Heart Circ Physiol, March 1, 2005; 288(3): H1028 - H1036. [Abstract] [Full Text] [PDF]

				R. A. Meyer Aerobic performance and the function of myoglobin in human skeletal muscle Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2004; 287(6): R1304 - R1305. [Full Text] [PDF]