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Lower extremity reconstruction utilizing free tissue transfer has become a common and safe procedure. Postoperative care and especially timing and duration of dangling however have not yet been extensively studied. We therefore aimed to assess the changes in oxygenation and hemoglobin concentration in lower extremity free flaps during dangling. A total of 19 patients who underwent microsurgical reconstruction of the lower leg (nine parascapular, five latissimus dorsi, and five anterolateral thigh [ALT] flaps) were included in a prospective study. Beginning on the 6th postoperative day (POD), dangling was commenced three times a day for 5 minutes each and gradually increased over time. Oxygenation and concentration of hemoglobin was measured using noninvasive near infrared spectroscopy. A specific pattern of oxygenation and hemoglobin concentration was identified. After beginning of dangling, oxygenation and hemoglobin concentration rises, followed by a rapid decrease. Over the course of training, the predangling saturation values increased steadily, resulting in a 9.5% increase on POD 9. The time needed for the flap to regain its predangling oxygenation level declined over the course of training from 5.1 minutes on POD 6 to 3.8 minutes on POD 9. The ALT flaps showed the highest increase in predangling saturation values (12%) and the most pronounced decrease in recovery time (6.7 minutes on POD 6 vs. 3.5 minutes on POD 9). The type of flap seems to influence behavior during dangling. However, further influencing factors need to be identified to enable reconstructive surgeons to tailor not only the flap but also the aftercare to the individual patient.