1. From the Pauline and Adolph Weinberger Laboratory for Cardiopulmonary Research, University of Texas Southwestern Medical Center, Dallas, Tex (D.K.M., B.D.L., J.W.W., P.G.S., C.G.B., J.H.M.); Institute for Exercise and Environmental Medicine, Presbyterian Hospital, Dallas, Tex (B.D.L.); and Copenhagen Muscle Research Center, University of Copenhagen, Copenhagen, Denmark (B.S.).