Thyroid Hormone Responses to Repeated Wingate Exercise Versus a Non-Exercising Comparison Group

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, and most previous reports lack any non-exercising comparison condition, so observed changes cannot be separated from time of day, posture, repeated venipuncture, or routine analytical variation.

This two-group non-randomized study was designed to compare the acute effects of repeated Wingate exercise on free thyroid hormone concentrations against a non-exercising comparison group. Twenty healthy male amateur soccer players completed a standardized repeated Wingate exercise protocol under controlled laboratory conditions, consisting of six 30-second maximal bouts at 7.5% of body mass separated by 4 minutes of passive recovery. A comparison group of twenty male amateur soccer players provided two venous blood samples on one morning without performing any exercise between them. Venous blood samples were collected immediately before and immediately after the exercise session or the resting interval to determine free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) concentrations. Hormone analyses were performed using standardized laboratory procedures.

The two groups were recruited and sampled in different periods rather than concurrently, and participants were therefore not randomly allocated. The primary objective was to determine whether the change in circulating free thyroid hormone concentrations around a repeated Wingate session differs from the change observed across a comparable resting interval.

Inclusion criteria

• Male amateur soccer players.
• Age between 18 and 25 years.
• At least 6 years of licensed soccer experience.
• Actively participating in amateur soccer training.
• Apparently healthy and free from acute or chronic disease on medical history review.
• Willingness to participate and provision of written informed consent.

Exclusion criteria

• Acute illness or musculoskeletal injury at the time of testing.
• Neurological, auditory, visual or vestibular disorder.
• Reduced physical capacity due to injury, or a sedentary lifestyle.
• History of nutritional or pharmacological ergogenic aid use.
• Failure to complete the study procedures or all required blood sample collections.