Acute Endocrine Responses to Aerobic and Anaerobic Exercise in Sedentary Women: A Comparative Analysis of Thyroid Hormones and Cortisol

This interventional study is designed to compare the acute endocrine responses elicited by aerobic and anaerobic exercise in sedentary women. A total of 30 healthy sedentary women aged 18-25 years will voluntarily participate. Individuals who have engaged in regular exercise or sports training, experienced a serious upper- or lower-extremity injury during the previous six months, or had a neurological, auditory, visual, or vestibular disorder during the previous year will not be included. Before participation, all individuals will be informed about the study procedures, provide written informed consent, and undergo medical screening.

Each participant will complete aerobic and anaerobic exercise protocols in separate testing sessions. The aerobic exercise protocol will consist of a progressive 20-meter shuttle run test. Participants will run continuously between two lines positioned 20 meters apart, following prerecorded audio signals. Running speed will progressively increase as the interval between signals decreases. The test will end when a participant fails to reach the designated line before the signal on two consecutive occasions.

The anaerobic exercise protocol will consist of a 30-second Wingate test performed on a Monark cycle ergometer connected to computerized analysis software. Following an unloaded acceleration period of approximately 3-4 seconds, an external resistance equivalent to 65 g/kg of body mass will be applied. Participants will be instructed to pedal against this resistance at maximal effort for 30 seconds.

Four venous blood samples will be collected from each participant: immediately before and after the aerobic exercise protocol and immediately before and after the anaerobic exercise protocol. Each sample will consist of approximately 8 mL of blood collected from an antecubital vein by qualified healthcare professionals under medical supervision. The samples will be centrifuged at 3,500 revolutions per minute to separate serum and plasma. Serum thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), and cortisol concentrations will be measured using chemiluminescence-based laboratory methods.

Exercise testing will be conducted at the Hasan Doğan School of Physical Education and Sports Laboratory at Karabuk University. Laboratory analyses will be performed at the Public Health Laboratory of the Karabuk Provincial Health Directorate. Pre-to-post-exercise changes in hormone concentrations will be evaluated within each exercise condition and compared between the aerobic and anaerobic exercise protocols.