The use of near infrared spectroscopy in sports medicine

In the last 15 years the study of the human muscle energetics in sports medicine underwent a radical change thanks to the progressive introduction of non-invasive techniques, including near infrared (NIR) spectroscopy (NIRS). NIR light (700-1000 nm) penetrates skin, subcutaneous fat and underlying muscle, and is either absorbed (by oxy- and deoxy-haemoglobin) or scattered within the tissue. NIRS is a non-invasive and relatively low cost optical technique that is becoming a widely used instrument for measuring muscle O(2) saturation and changes in haemoglobin volume. Muscle O(2) saturation represents a dynamic balance between O(2) supply and O(2) consumption in the small vessels such as the capillary, arteriolar and venular bed. NIRS offers the advantage of being less restrictive than (31)P-magnetic resonance spectroscopy with regard to muscle performance and more comfortable and suitable for the monitoring, with high temporal resolution (up to 10 Hz), of multiple muscle groups. The aim of this review is to summarise the NIRS instrumentation and the measurable parameters, the role of NIRS in muscle exercise physiology, and the applications in sports medicine. The advantages and the problems of NIRS measurements, in resting and exercising skeletal muscles, are reported. The results of several studies suggest that NIRS is a powerful tool for being applied successfully in sports medicine. NIRS can objectively evaluate muscle oxidative metabolism in athletes and its modifications following potential therapeutic strategies and specific training programs.