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Completed

NCT Number: NCT07689487

Effects of Cyclical Blood Flow Restriction Exercise on Muscle Hypertrophy and Capillaries in Older Adults

The purpose of this study was to learn if low-load resistance exercise combined with cyclical blood flow restriction (BFR) could improve small blood vessel structure and muscle size in older adults.

Skeletal muscle thinning and the loss of tiny blood vessels (capillaries) commonly happen as people age. While lifting heavy weights can help stop this, heavy loads are often not suitable for older adults with joint pain or other health conditions. Low-load exercise with BFR involves wearing inflatable cuffs on the upper arms that temporarily slow down blood flow, which can trigger positive changes in muscles and blood vessels without needing heavy weights.

Researchers compared three groups of older adults:

* One group performed low-load upper-body exercises while wearing cyclical BFR cuffs. * A second group performed the exact same exercises at the same low load but without wearing cuffs. * A third group maintained their normal daily activities without participating in any structured exercise program.

Participants in the exercise groups trained 3 days a week for 8 weeks. Researchers used video capillaroscopy (a specialized camera at the fingernail base) to examine changes in tiny blood vessels and ultrasound imaging to measure arm muscle thickness before and after the 8-week period.

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Key information

Conditions

Sarcopenia in Elderly Aging Atrophy Muscle Atrophy Muscular Atrophy Nervous System Diseases Neurologic Manifestations Neuromuscular Manifestations Pathological Conditions, Anatomical Pathological Conditions, Signs and Symptoms Sarcopenia Signs and Symptoms

Age range

50 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Akdeniz University, Faculty of Sport Sciences

Antalya, 07058, Turkey (Türkiye)

About this study

The goal of this parallel-group randomized controlled trial was to determine the chronic physiological effects of an 8-week cyclical blood flow restriction (BFR) training protocol on microvascular geometry and structural muscle hypertrophy in older adults.

Heavy mechanical resistance training is a primary countermeasure against age-related sarcopenia, yet joint pathologies or cardiovascular comorbidities frequently limit its application in older populations. Low-load resistance training combined with BFR offers a load-sparing alternative by creating localized hypoxia and metabolite accumulation, which stimulate vascular endothelial growth factor (VEGF) and downstream angiogenic pathways. A cyclical BFR approach, where cuff pressure was systematically inflated and deflated, was used to optimize these adaptations via oscillatory shear stress while improving cardiovascular tolerability compared to continuous occlusion protocols.

Participants were stratified by sex, age, baseline strength, and height, and then randomized into one of three arms:

  • Cyclical BFR Group: Low-load resistance training (20-40% 1RM) across four upper-body exercises with automated pneumatic cuffs delivering 8 cycles of 30 seconds inflation and 5 seconds deflation.
  • TRAINING Group: Identical low-load resistance training protocol performed without vascular restriction.
  • CONTROL Group: Non-exercise control maintaining habitual lifestyle activities.

The intervention spanned 8 weeks with a training frequency of 3 sessions per week. Co-primary structural adaptations were tracked using non-invasive surrogates: nailfold video capillaroscopy to record arterial, apical, and venous capillary diameters, and B-mode ultrasonography to assess structural changes in biceps brachii and triceps brachii muscle thickness. Linear mixed models were utilized to analyze Group x Time interactions to verify if cyclical BFR demonstrated an adaptive superiority over standard low-load protocols.

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Age 50 years or older.
  • Recreationally active, defined as participating in light-to-moderate physical activity 2 or more days per week.
  • No structured resistance training within the preceding six months.
  • Free from cardiovascular disease, neurological conditions, or musculoskeletal injury contraindicating resistance exercise.
  • Able to provide written informed consent before enrollment.

Exclusion criteria

  • Current use of anticoagulant or vasoactive medication.
  • History of deep vein thrombosis (DVT).
  • Resting systolic blood pressure greater than 160 mmHg.

Treatment and study plan

Blood flow restriction (BFR)

Device

Vascular restriction administered using an automated cyclical pneumatic device (KAATSU Cycle 2.0) with 40 mm cuffs placed proximally on both arms. Protocol consists of 8 cycles of 30 seconds of inflation followed by 5 seconds of deflation per cycle, individually calibrated by capillary refill time and verified by Doppler ultrasound.

Conventional Low-Load Resistance Exercise

Behavioral

Upper-body resistance exercise training encompassing four movements: biceps curl, triceps pushdown, lat pulldown, and chest press. Executed under a controlled 4x12 repetition scheme at an intensity of 20-40% 1RM, performed 3 days per week for a duration of 8 weeks.

Primary outcomes

  1. Nailfold Capillary Diameter

    Time frame: Baseline and post-intervention (at the end of week 8)

    Microvascular morphology changes measured at three anatomical regions: the arterial (afferent) limb, the apical portion, and the venous (efferent) limb using nailfold video capillaroscopy.

  2. Upper-Arm Muscle Thickness

    Time frame: Baseline and post-intervention (at the end of week 8).

    Structural muscle hypertrophy of the biceps brachii and triceps brachii muscles of the dominant arm, assessed via B-mode ultrasonography.

Secondary outcomes

  1. Total Body Mass

    Time frame: Baseline and post-intervention (at the end of week 8)

    Changes in total body mass measured via bioelectrical impedance analysis.

  2. Body Fat Percentage

    Time frame: Baseline and post-intervention (at the end of week 8)

    Changes in body fat percentage measured via bioelectrical impedance analysis.

  3. Fat Mass

    Time frame: Baseline and post-intervention (at the end of week 8)

    Changes in fat mass measured via bioelectrical impedance analysis.

Sponsors and collaborators

Lead sponsor

Akdeniz University

Other

Collaborators

  • Akdeniz University, Scientific Research Projects Coordination Unit

Registry information

Official study title

Eight Weeks of Cyclical Blood Flow Restriction Exercise Induces Regional Microvascular Remodeling and Muscle Hypertrophy in Older Adults: A Three-Arm Randomized Controlled Trial

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Jul 8, 2026
Registry last updated
Jul 8, 2026

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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