Employment of near-infrared spectroscopy to assess the physiological determinants of hiking performance in single- handed dinghy sailors

The ability to measure quadriceps muscle blood flow in sailors has implications for understanding the principal factors limiting their capacity to counterbalance the boat in strong winds. Until very recently, it was not feasible to measure quadriceps muscle blood flow during simulated sailing owing to lack of noninvasive techniques. Early measurements of quadriceps muscle oxygen saturation by near-infrared spectroscopy (NIRS) gave indication of restricted local muscle oxygen availability during simulated sailing. Recently, employment of NIRS in combination with indocyanine green dye (ICG), a valid and minimally invasive technique, allowed direct measurement of muscle blood flow during simulated sailing. The findings indicate that in simulated sailing quadriceps muscle, blood flow is threefold lower compared to cycling sustained at similar levels of cardiac output. It is thus suggested that the progressive reduction in quadriceps muscle oxygen availability during sailing is due to reduced blood flow to these muscles; this most likely leads to energy deficits and occurrence of muscle fatigue, thereby limiting sailing performance.