Examination of Certain Blood Parameters Following Performance and Acute Exercise at Specific Times of the Day

The purpose of this study is to examine the acute effects of exercise performed at different times of the day on physical performance, hormonal responses, and biochemical markers associated with exercise-induced muscle stress and recovery in healthy young male soccer players.

The study uses a single-group, repeated-measures pre-test/post-test design in which the same participants complete an identical standardized exercise protocol on two separate occasions. One exercise session will be performed in the morning between 08:00 and 09:30, and the other will be performed in the evening between 17:00 and 18:30. The two experimental sessions will be separated by 96 hours (4 days) to reduce the influence of the preceding exercise session on subsequent measurements.

Before each exercise session, participants will undergo anthropometric assessment and provide a resting blood sample. Participants will then complete standardized physical performance assessments, including a vertical jump test and a Yo-Yo shuttle run endurance test. Immediately after completion of the exercise protocol, a second blood sample will be collected. A third blood sample will be collected two hours after exercise to assess the early recovery response.

Blood samples will be analyzed for hormonal and biochemical parameters, including testosterone and cortisol as hormonal markers, and creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and troponin as biochemical markers of exercise-related physiological and metabolic responses.

The primary purpose of the comparison is to determine whether the acute physiological responses to the same exercise stimulus differ according to the time of day. The study will also explore the potential relationship between exercise timing and circadian variation in physical performance, hormonal responses, and biochemical markers.

All participants will complete the same exercise and measurement procedures under standardized conditions. The study population consists of healthy male soccer players who regularly participate in sports. Participants must be physically able to safely complete the exercise and assessment protocols and must not have medical or musculoskeletal conditions that could affect exercise performance or the safety of the study procedures.

This study is designed to provide information about the influence of exercise timing on acute performance and physiological responses and may contribute to the development of time-of-day considerations in exercise programming and sports training.

• Healthy male soccer players.
• Age between 18 and 25 years.
• Regular participation in organized soccer training.
• Free from musculoskeletal injury during the previous 6 months.
• Able and willing to provide written informed consent.