2.2. Study Design
hypoxia
HYPOXIA
The experiment consisted of four study series (S1 to S4). S1 involved baseline tests before the start of supplementation and LH–TL training. S2 took place after the fourth day of supplementation and after the first night of exposure to hypoxia. S3 was conducted after the ninth day of supplementation and after the sixth night of the LH–TL protocol. Finally, S4 was performed immediately after the last night of the LH–TL protocol and the last day of supplementation. The study design is shown in During each study series, venous blood samples (10 mL) collected from the basilic vein were obtained from the participants in the morning (7.30 a.m.) under fasting conditions. Two samples of venous blood were then collected at each time point on the 5th, 10th, and 15th day of the experiment, always after an active rest day. Of each pair of samples, one was drawn using an ethylenediaminetetraacetic (EDTA) tube (for morphology analysis); the other was drawn using an anti-coagulant tube and processed for serum for the other biochemical assays (T, fT, C, and LH). Creatine kinase (CK) activity was determined immediately after blood collection (Piccolo Express Chemistry Analyzer, Abaxis, Union City, CA, USA). After 30 min, blood samples were centrifuged at 1500× 