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Completed

NCT Number: NCT07114835

Low-Intensity BFR Cycling: Impact on VO₂Max and Muscle Adaptations

This study aims to investigate the effects of low-intensity cycling exercise combined with blood flow restriction (BFR) on maximal oxygen consumption (VO₂max), muscle strength, and muscle thickness in sedentary adult males. Participants will be randomly assigned to three groups: (1) a cycling exercise group performing 40 minutes of cycling at 40% VO₂max, (2) a cycling with blood flow restriction group performing 15 minutes of cycling at 40% VO₂max with limb occlusion pressure at 60-80%, and (3) a control group following a shorter cycling protocol. Muscle thickness, isokinetic knee strength, and VO₂max will be measured before and after the 9-week intervention. The study is designed to evaluate whether short-duration, low-intensity cycling with BFR can induce physiological adaptations comparable to traditional longer-duration cycling protocols.

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Key information

Conditions

Aerobic Capacity Blood Flow Restriction (BFR) Training Effects Blood Flow Restriction Exercise Isokinetic Muscle Strengh VO2max

Age range

18 year–24 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Faculty of Sport Science

Kahramanmaraş, Onikişubat, 46050, Turkey (Türkiye)

About this study

This study is designed to examine the effects of low-intensity cycling exercise combined with blood flow restriction (BFR) on aerobic capacity (VO₂max), isokinetic knee strength, and muscle thickness in sedentary male adults. Traditional methods for improving aerobic capacity and muscle strength often involve high-intensity or long-duration training protocols. However, such protocols may not be feasible for all individuals, particularly during rehabilitation, periods of detraining, or in populations with limited exercise tolerance.

Blood flow restriction training has gained attention as a promising strategy to elicit muscular and cardiovascular adaptations using lower intensities. The technique involves applying individualized limb occlusion pressure (LOP) via pneumatic cuffs during exercise to partially restrict arterial inflow and fully restrict venous outflow. This restriction is thought to create a hypoxic environment and increase metabolic stress, which may enhance the recruitment of fast-twitch muscle fibers and stimulate physiological adaptations.

In this randomized controlled trial, participants are allocated to one of three groups: a standard cycling exercise group (40 minutes at 40% VO₂max), a BFR cycling group (15 minutes at 40% VO₂max with 60-80% LOP), and a control group (15 minutes at 40% VO₂max without BFR). All exercise sessions are performed three times per week for nine weeks. The LOP is adjusted across the training period to progressively increase the stimulus in the BFR group.

Baseline and post-intervention assessments include measurements of body height and weight, ultrasound-based muscle thickness, isokinetic knee strength testing, and graded exercise testing for VO₂max. The goal is to determine whether low-intensity, short-duration cycling with BFR can serve as a practical and effective alternative to longer-duration exercise programs.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Individuals aged between 18-24 years,
  • Individuals without any health problems,
  • Individuals who do not actively participate in sports,
  • Individuals who marked all items as no on the H+cuff participant information form,
  • Individuals who have not had a sports injury that would prevent them from participating in sports in the last 6 months,

Exclusion criteria

  • history of lower extremity injury, respiratory disorders and refusal to participate

Treatment and study plan

Cycling with Blood Flow Restriction (15 min at 40% VO₂max with 60-80% LOP)

Procedure

This intervention involves low-intensity cycling exercise at 40% of VO₂max performed on an electronically braked Astrand cycle ergometer for 15 minutes per session. During each session, pneumatic cuffs (10 cm wide, manually adjustable) are applied to the upper thighs to restrict blood flow. Individualized limb occlusion pressure (LOP) is determined via Doppler ultrasound and set progressively at 60% (weeks 1-4), 70% (weeks 5-7), and 80% (weeks 8-9). Sessions are conducted three times per week over a 9-week period. The aim is to simulate the physiological effects of high-intensity training using a low-intensity protocol.

Other names: BFR Cycling, Low-Intensity Cycling + BFR, CBFR

Cycling Exercise (40 min at 40% VO₂max)

Procedure

This intervention involves standard low-intensity cycling exercise at 40% of the participant's VO₂max, performed for 40 minutes per session on an electronically braked Astrand cycle ergometer. Sessions are conducted three times per week for a total duration of 9 weeks. This group does not receive any blood flow restriction or external loading. The aim is to observe the effects of traditional low-intensity, long-duration aerobic exercise on VO₂max, muscle strength, and muscle thickness.

Other names: CEG, Standard Low-Intensity Cycling, Long-duration Cycling

Short-Duration Cycling Control (15 min at 40% VO₂max)

Procedure

This intervention involves low-intensity cycling exercise at 40% of VO₂max performed for 15 minutes per session, using an electronically braked Astrand cycle ergometer. Participants exercise three times per week for 9 weeks. No blood flow restriction is applied. The aim of this control condition is to match the duration of the BFR intervention while omitting the occlusion component, to isolate the effect of BFR.

Other names: Control Group Cycling, CG Short Cycling, No BFR

Primary outcomes

  1. Change in Maximal Oxygen Consumption (VO₂max, L/min)

    Time frame: Baseline and Post-test (Week 9)

    Absolute VO₂max will be measured during a graded cycling exercise test using a breath-by-breath gas analyzer.

  2. Change in Relative VO₂max (ml/kg/min)

    Time frame: Baseline and Post-test (Week 9)

    VO₂max will also be reported relative to body weight using standard calculation: (VO₂max ÷ body weight).

Secondary outcomes

  1. Change in Muscle Thickness (Rectus Femoris, Vastus Lateralis, Biceps Femoris)

    Time frame: Baseline and Post-test (Week 9)

    Muscle thickness will be measured using B-mode ultrasonography with linear probe at specified anatomical landmarks.

  2. Change in Peak Torque (Isokinetic Knee Strength, 60°/s and 180°/s)

    Time frame: Baseline and Post-test (Week 9)

    Isokinetic knee extension and flexion strength will be measured using an isokinetic dynamometer at angular velocities of 60°/s and 180°/s.

  3. Change in Respiratory Exchange Ratio (RER)

    Time frame: Baseline and Post-test (Week 9)

    RER will be recorded during the maximal exercise test as the ratio of carbon dioxide output to oxygen uptake (VCO₂/VO₂).

  4. Change in Maximal Heart Rate (MHR)

    Time frame: Baseline and Post-test (Week 9)

    Maximal heart rate will be recorded during the graded exercise test.

Sponsors and collaborators

Lead sponsor

Kahramanmaras Sutcu Imam University

Other

Registry information

Official study title

Investigation of the Effects of Low-Intensity Cycling Exercise Combined With Blood Flow Restriction on VO2max, Muscle Strength, and Muscle Thickness in Physically Active Individuals

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Aug 11, 2025
Registry last updated
Aug 11, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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