A Single-Arm Pre-Post Study

High-intensity anaerobic exercise induces acute physiological and endocrine responses that contribute to metabolic regulation and athletic performance. Thyroid hormones, including free triiodothyronine (fT3) and free thyroxine (fT4), play essential roles in energy metabolism, oxygen consumption, and exercise adaptation. However, the immediate effects of repeated supramaximal exercise on thyroid hormone responses remain insufficiently understood.

This single-arm pre-post interventional study was designed to evaluate the acute effects of repeated Wingate exercise on serum free thyroid hormone concentrations in male amateur soccer players. Twenty healthy male amateur soccer players aged 19-22 years participated in the study. Participants completed a standardized repeated Wingate exercise protocol under controlled laboratory conditions. Venous blood samples were collected immediately before and immediately after exercise to determine serum concentrations of free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH). Hormone analyses were performed using standardized laboratory procedures.

The primary objective was to determine whether repeated Wingate exercise produces acute alterations in circulating free thyroid hormone concentrations. The findings of this study are expected to improve the understanding of endocrine responses to repeated high-intensity anaerobic exercise and to contribute to exercise physiology and sports medicine by clarifying the relationship between maximal anaerobic exercise and thyroid function in trained athletes.

Inclusion criteria

- Male amateur soccer players.

• Age between 19 and 22 years.
• Apparently healthy and free from acute or chronic disease.
• Regular participation in amateur soccer training.
• Willingness to participate and provision of written informed consent.

Exclusion criteria

- History of thyroid disease or endocrine disorders.

• Current use of medications or supplements known to affect thyroid function or hormonal responses.
• Acute illness or musculoskeletal injury at the time of testing.
• Failure to complete the repeated Wingate exercise protocol or all required blood sample collections.