The response to hypoxia is very individual and depending on many aspects, such as the type of training, duration, intensity, or hypoxic stimulus, hypoxia affects the athlete in various ways. This multi-stage study investigated hematological and physiological responses to normobaric Live High-Train Low (LHTL) exposure in elite male rowers from the Polish national rowing team. Stage I evaluated responses during an 18-day LHTL intervention, whereas Stage II evaluated responses during a 14-day LHTL intervention and extended the assessment to 42 days after return to normoxia. The study focused particularly on hematological variables, erythropoietin (EPO), vascular endothelial growth factor (VEGF), and other physiological and biochemical responses associated with hypoxic exposure.
I stage. The Polish national rowing team athletes, 13 males, were randomly divided into two groups: 1. The hypoxic group (H) included 8 rowers participating in sports training and the LHTL intervention, with progressive normobaric hypoxic exposure corresponding to simulated altitudes of 2000, 2500, and 3000 m. 2. The control group (C) consisted of 5 rowers participating only in sports training and living in normoxic rooms at the same sports camp. Rowers were observed during the preparatory period. The hypoxic group lived and slept in hypoxic rooms for at least 8-14 hours per day. During the camp, all rowers followed the same training schedule and diet. All participants' saturation and heart rate were measured daily, morning and evening, throughout the camp period. Venous blood samples were taken four times, at the beginning of the camp (Baseline), after 6 days, after 12 days, and after 18 days of the camp. Body composition parameters such as body mass index, body fat, and free fat mass were estimated using the bioelectrical impedance method of a Tanita BC 418 analyzer (Japan). Data analysis was performed using Statistica. The response to hypoxia is very individual. Depending on many factors, such as training type, duration, intensity, or hypoxic stimulus, hypoxia affects athletes in various ways. The results of this study have shown that the blood parameters did not increase significantly in the hypoxic group compared to the control group. However, reticulocytes, immature red blood cells, have shown significant differences after 18-d LHTL between groups. Further research should be carried out to investigate an optimal hypoxic dose and time, which will raise EPO, VEGF, and morphology variables. II stage. Fourteen elite male rowers from the Polish national rowing team participated in the second stage and were randomly allocated to the LHTL group (n = 8) or the normoxic control group (n = 6). Both groups followed the same standardized training program. The LHTL intervention lasted 14 consecutive days and involved progressive normobaric hypoxic exposure corresponding to 2000-3000 m for approximately 14-16 h/day, while all training sessions were performed under normoxic conditions. Blood samples were collected at baseline, after 7 and 14 days of the intervention, and 8, 14, and 42 days after completion. Hematological variables, EPO, VEGF, iron-related indices, CK activity, and lipid-profile variables were assessed, while SpO₂ and resting HR were monitored throughout the intervention.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
14
Participants lived in normobaric hypoxic rooms for 14-16 h per day while completing their regular training under normoxic conditions. The simulated altitude was progressively increased during the intervention.
Erythropoietin (EPO) mlU/ml
immunoenzymatic assay methods using diagnostic kits
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Vascular endothelial growth factor (VEGF) mlU/ml
immunoenzymatic assay methods using diagnostic kits
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Creatine kinase (CK) ng/ml
was determined using spectrophotometer analysis and diagnostic kits
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Hs C-Reactive Protein (hsCRP) mg/L
was determined by immunoenzymatic assay methods using diagnostic kits
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention.
Hemoglobin (Hb)g/dL
A professional accredited laboratory company determined the Hb level (Poland, ISO 9001:2008).
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Hematocrit (Htc)%
A professional accredited laboratory company determined the Htc level (Poland, ISO 9001:2008).
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Red blood cells (RBC)mln/mm3
A professional accredited laboratory company determined the RBC level (Poland, ISO 9001:2008).
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
White blood cells (WBC)10 3/µL
A professional accredited laboratory company determined the WBC level (Poland, ISO 9001:2008).
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Reticulocytes (Ret)‰
A professional accredited laboratory company determined the Ret level (Poland, ISO 9001:2008).
Time frame: Stage 1: at baseline and on days 6, 12, and 18 of the intervention. Stage 2: at baseline, on days 7 and 14 of the intervention, and at 8, 14, and 42 days after the intervention.
Peripheral oxygen saturation (SpO₂) (%)
Peripheral oxygen saturation (SpO₂) was measured non-invasively using a pulse oximeter (Tech-Med, ISO 13485). Measurements were performed twice daily, in the morning and evening, throughout each sports camp in both study groups.
Time frame: Stage 1: daily from Day 1 through Day 18 of the intervention, in the morning after waking and in the evening before bedtime; Stage 2: daily from Day 1 through Day 14 of the intervention, in the morning after waking and in the evening before bedtime.
Heart rate (HR) (beats/min)
Heart rate (HR) was measured using a pulse oximeter (Tech-Med, ISO 13485). Measurements were performed twice daily, in the morning and evening, throughout each sports camp in both study groups.
Time frame: Stage 1: daily from Day 1 through Day 18 of the intervention; Stage 2: daily from Day 1 through Day 14 of the intervention.
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