The aim of the current study was to examine the effects of 3-session repeated sprint training performed in a normobaric hypoxic condition with 48-hour rest intervals on sprint performance indices, arterial oxygen saturation (SpO2) and rating of perceived exertion (RPE) scores. Twenty-four moderately-trained males participated in this study voluntarily basis. This study was conducted on single-blind placebo-controlled design. Participants were divided into three groups as follows; normobaric hypoxia (3420 m; HYP), normobaric normoxia (162 m; PLA) and control group (CON). HYP and PLA groups subjected to 3 repeated sprint training session (4 set x 5 x 5 s sprints with 30 s recovery and 5 min rest between the sets) in normobaric hypoxia or normoxia condition. Pre- and pos-test were conducted 72 hours before and after the training intervention period. All the training and testing sessions performed in cycle ergometer. There were no detected significant time and condition interaction in the variables; relative peak power output (PPO), mean power output (MPO), percentage of sprint decrement score (Sdec%) and RPE observed in the scope of pre- and post-test.

This single-blind placebo-controlled designed study was approved by Ankara University Human Research Ethics Committee (2020/277) and conducted in accordance with the Declaration of Helsinki. The participants in normobaric hypoxia (HYP) and placebo (PLA) groups visited the laboratory six times and the control (CON) group visited three times. At the first visit of participants, the aim and the possible outcomes of the research was explained, the familiarization process for cycle ergometer and test/training protocol was performed, and the informed consent forms were obtained. The participants were divided randomly into three groups after the anthropometric measurements and baseline tests were completed so as part of the second visit. The groups were divided as follows; HYP group (n=9) which were exposed to normobaric hypoxia equal to 3420 m (FiO2: 13.5-13.6 %), PLA (n=7) that were exposed to normobaric normoxia equal to 162 m (FiO2: 20.9 %) through wearing the altitude generator mask, and the control group (CON; n=8) which was subjected to only pre and post-test. The determined hypoxic dose for HYP group was directly implemented (setting 9 was equal to 3420 m on used hypoxia generator), and no correction was made for the actual altitude (900 m, Golbasi, Ankara, Türkiye). The normobaric hypoxia and placebo condition was provided by Everest Summit II-Altitude Generator (Hypoxico Hypoxicator, New York, USA). At the 3rd-5th visits, HYP and PLA groups performed 3 repeated sprint training sessions under normobaric hypoxia or normoxia exposure with 48-hour intervals. And the participants visited the laboratory last time for post-test measurements. Each participant visited the laboratory for training sessions and test trials at the same time in the day. In the scope of pre and post-test repeated sprint indices, SpO2 and RPE data were collected. Pre-test and post-test were conducted 72 hours before and 72 hours after the training intervention period in normobaric normoxia condition. Including the testing days, the intervention period lasted 11 days in November 2022. All the experimental processes were conducted in Ankara University Performance Laboratory.

Inclusion Criteria:

• non-smokers,
• male gender,
• those who do not have any chronic disease,
• do not use any medication,
• do not any training or accommodate above 1500 m altitude within the past 3 months,
• do not have any musculoskeletal injuries within the past 6 months and,
• train at least 3 days in a week.

Exclusion Criteria:

• Having a chronic or acute condition/disease during the intervention period
• Occurrence of acute respiratory illness or musculoskeletal injury during the intervention period
• Leaving the study voluntarily/on his own account

In this study, blinding was provided in practice by using the simulation device for the normoxia condition.