Effects of Low-Intensity Blood Flow Restriction Training in Normoxia and Hypoxia Conditions

Study Overview
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Brief Summary
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One approach to significantly reducing resistance training intensity while maintaining effectiveness in muscle mass and strength development involves conducting training sessions under hypoxic conditions. This is likely due to heightened physiological responses. While sports science research indicates a substantial impact of hypoxic conditions on immediate increases in metabolic stress and augmented hormonal responses, recent findings suggest that the role of their influence on skeletal muscle adaptations post-resistance training under hypoxic conditions remains unknown. Additionally, there is a lack of reports on whether the type of hypoxia applied via blood flow restriction or chamber differentiates the increase in secretion of these catecholamines in both immediate and long-term aspects.

Official Title
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Acute and Chronic Effects of Low-Intensity Blood Flow Restriction Training in Normoxia and Hypoxia Conditions on Muscle Strength, Thickness, Catecholamine, and Inflammatory Responses in Physically Active Adults

Conditions
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Hypoxia, Altitude, Blood Flow Restriction, Resistance Training

Intervention / Treatment
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* Other: low-intensity resistance training
* Other: high-intensity resistance training
* Other: low-intensity resistance training combined with blood flow restriction
* Other: low-intensity resistance training in hypoxia condition
* Other: low-intensity resistance training combined with blood flow restriction in hypoxia condition


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Regularly physically active (at least 30 mins of structured exercise 3 times per week), Sea-level natives, Experienced in resistance training (at least one year of experience in regular resistance exercise) Exclusion Criteria: presence of any medical risk factors to exercise and/or exposure to altitude presence of any medical condition that would make the protocol unreasonably hazardous for the participant smokers

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Low-Intensity Normoxia<br>Participants will be breathing room air, and perform low-intensity lower-body resistance exercise. | Other: low-intensity resistance training<br>* 4 sets of 30/15/15/15 repetitions of leg press exercise with a load of 20-30% of one-repetition maximum (weeks 1-3: 20%, weeks 4-6: 30%) in normoxic conditions performed twice a week for 6 weeks.<br>|
| Active Comparator: High-Intensity Normoxia<br>Participants will be breathing room air, and perform high-intensity lower-body resistance exercise. | Other: high-intensity resistance training<br>* 4 sets of 10 repetitions of leg press exercise at 70-80% one-repetition maximum (weeks 1-3: 70%, weeks 4-6: 80%) in normoxic conditions performed twice a week for 6 weeks.<br>|
| Experimental: Low-Intensity Normoxia with Blood Flow Restriction<br>Participants will be breathing room air, and perform low-intensity lower-body resistance exercise combined with blood flow restriction. | Other: low-intensity resistance training combined with blood flow restriction<br>* 4 sets of 30/15/15/15 repetitions of leg press exercise with a load of 20-30% of one-repetition maximum (weeks 1-3: 20%, weeks 4-6: 30%) in normoxic conditions with lower-limbs blood flow restriction (80% total occlusion pressure) performed twice a week for 6 weeks.<br>|
| Experimental: Low-Intensity Hypoxia<br>Participants will be breathing a 13% oxygen gas mixture, and perform low-intensity lower-body resistance exercise. | Other: low-intensity resistance training in hypoxia condition<br>* 4 sets of 30/15/15/15 repetitions of leg press exercise with a load of 20-30% of one-repetition maximum (weeks 1-3: 20%, weeks 4-6: 30%) in hypoxia conditions (3500 meters above sea) performed twice a week for 6 weeks.<br>|
| Experimental: Low-Intensity Hypoxia with Blood Flow Restriction<br>Participants will be breathing a 13% oxygen gas mixture, and perform low-intensity lower-body resistance exercise combined with blood flow restriction. | Other: low-intensity resistance training combined with blood flow restriction in hypoxia condition<br>* 4 sets of 30/15/15/15 repetitions of leg press exercise with a load of 20-30% of one-repetition maximum (weeks 1-3: 20%, weeks 4-6: 30%) in normobaric hypoxia conditions (3500 meters above sea) with lower-limbs blood flow restriction (80% total occlusion pressure) performed twice a week for 6 weeks.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Force Output | Force plate will be used to quantify maximum absolute (N) and relative force output (body mass divided per force output in N/kg) during maximum voluntary isometric back squat in a 100ms time frame. Participants will be pushing as hard and as fast as they can on an unmoveable barbell while standing on a force plate. | Immediately pre and post first and last training session | 
| One-Repetition Maximum | One-Repetition Maximum test in leg press exercise will be performed to quantify maximum lower body dynamic strength (kg). Participants will be performing single repetitions of leg press exercise with increasing load until volitional failure. | within 5 days from the start and end of training | 
| Maximum Number of Repetitions | A maximum number of repetitions in leg press exercise will be performed to quantify lower body strength endurance (number). Participants will be performing leg press exercise at 50% of one-repetition maximum until volitional failure. | within 5 days from the start and end of training | 
| Countermovement Jump Height | Countermovement jump height will be performed estimated via take-off velocity performed on force plates to Participants will perform 3 trials on force plate. | Immediately pre and post first and last training session | 
| Countermovement Jump Power Output | Countermovement jump performance will be performed to quantify maximum lower body relative and absolute power-output (W/kg and W), and jump height (cm) with concomitant assessment of contraction depth (cm) and contraction time (ms). Participants will perform 3 trials on force plate. | Immediately pre and post first and last training session | 
| Catecholamine Response | A blood sample will be analyzed to quantify changes in epinephrine and norepinephrine level changes. | Immediately pre and post first and last training session | 
| Muscle Stiffness | Myotonometry measure will be used to quantify changes in vastus medialis oblique muscle stiffness in N/m | Immediately pre and post first and last training session | 
| Muscle Thickness | Ultrasonography measure will be used to quantify changes in vastus medialis oblique cross-sectional area. | within 5 days from the start and end of training | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Perception of Pain | A visual analogue scale will be used to quantify the perception of pain (units on a scale). | Immediately pre and post every training session | 
| Perception of Effort | The rate of perceived exertion scale will be used to quantify the perception of effort (units on a scale). | Immediately pre and post every training session | 
| Blood Pressure | Systolic and diastolic blood pressure will be measured to quantify blood pressure responses. | Immediately pre and post first and last training session |