Muscular and Cutaneous Dysfunction in POTS

Patients and Healthy Volunteers will undergo a 14-day endurance training protocol. No study drugs will be administered. Patients and Healthy Volunteers will be instructed regarding their training protocol. Training sessions will be undertaken on days 1, 3, 5, 7, 9 and 11 after the first examination day. Patients and Healthy Volunteers will be asked to contract their TA muscle repeatedly by pulling the right foot towards the head in a standing position while the heel remains on the ground (at 5 second intervals). In order to carry out the training they will also receive a video demonstrating the exercise. On days 1 and 3 they will do the exercise for 5 minutes, on days 5 and 7 for 10 minutes and on days 9 and 11 for 15 minutes.