Illustrative thigh muscle oxygenation responses throughout fatiguing exercise in (a) a subject with fibromyalgia (FM) and (b) a healthy control. The oxygenation responses include oxy- and deoxyhemoglobin concentration ([HbO2] and [Hb]), total hemoglobin concentration (THC) and oxygen saturation (StO2), all presented in absolute values. The first two vertical lines indicate the beginning and the end of fatiguing exercise respectively, and the last four vertical lines indicate the time points 3, 6, 9 and 12 minutes after exercise. The arrow indicates the time points immediately post-exercise (over 6 seconds). Note that the muscle motion artifacts during exercise and during maximal voluntary isometric contraction (MVIC) tests at time points 3, 6, 9 and 12 minute post-exercise may contaminate optical measurements, as seen from the peaks in the figure.