Thorsten Rudroff, Nathaniel B Ketelhut, John H Kindred

This mini-review focuses on selected, noninvasive imaging techniques that have been used in the study of exercise physiology. These imaging modalities can be roughly divided into two categories: tracer based and non-tracer based. Tracer based methods use radio-labeled substrates whose location and quantity can subsequently be imaged once they are incorporated into metabolic processes. Non-tracer based imaging modalities rely on specific properties of substrates to identify metabolites and determine their concentrations. Identification and quantification of metabolites is usually based on magnetic properties or on differences in light absorption. In this review we will highlight two tracer based imaging modalities, posititron emission tomography (PET) and single photon emission computed tomography (SPECT), as well as two non-tracer based methods, magnetic resonance spectroscopy (MRS) and near-infrared spectroscopy (NIRS). Some of the recent findings each technique has provided on cerebral and skeletal muscle metabolism during exercise, as well as the strengths and limitations of each technique, will be discussed.