From muscle properties to human performance, using magnetic resonance

Abstract

Our goal is to show how muscle properties can be used to understand the exercise performance limitations of the elderly. We show that magnetic resonance (MR) imaging and spectroscopy are useful for noninvasively characterizing the structural and energetic properties of muscle in vivo. Determination of muscle volume and cross-sectional area is easily and rapidly accomplished by applying quantitative morphometric methods to MR images. New MR spectroscopic techniques provide a noninvasive "biopsy" of the oxidative, glycolytic, and contractile capacities of muscle fibers. We show how the structural and energetic properties measured by MR can be used to define the functional capacity of muscle and the contribution of this capacity to the performance of the whole body (e.g., VO2max). Finally, we relate these laboratory measures of muscle properties and performance to activities meaningful to the functioning of the elderly in everyday life, such as sustained walking and stair climbing.