Near-infrared spectroscopy (NIRS) is a noninvasive opticalmethod for continuous monitoring of oxygen consumptionand hemodynamics in tissue (eg, muscle tissue). Bank andChance1were the first to use NIRS for the investigation ofmetabolic myopathies. They found specific abnormalities ina variety of metabolic myopathies, indicating abnormal oxy-gen utilization. Several other investigators followed, includ-ing our group,2and reported similar abnormalities in mito-chondrial myopathies as compared with normal muscle.However, NIRS is still a relatively new technique, andmethodological constraints have not yet been fully exploited.We have investigated several methodological aspects of invivo NIRS measurements, and one of these concerned theinfluence of adipose tissue thickness (ATT) on in vivo NIRSmeasurements.