Low Load, High Gains: Blood Flow Restriction's Impact on Quadriceps Adaptations

Low-load resistance exercise with blood flow restriction (BFR-RE) presents a compelling alternative to high-load resistance exercise (HL-RE), particularly in scenarios where high loads are not feasible due to various limitations. Blood flow restriction exercise restricts blood flow to the working muscle, creating a state of ischemia. A significant advantage of BFR-RE lies in its capacity to stimulate muscle hypertrophy and strength adaptations using light external loads (20-30% 1RM), comparable to those achieved with high-load (HL) training programs that employ 70-85% 1RM As a result, BFR training has been increasingly adopted in both athletic performance and rehabilitation settings over the past few decades. Quadriceps strength and power are essential factors in both the advancement of athletic performance and the successful return to unrestricted sporting activity following injury. The findings of Culvenor et al.'s review strongly suggest that weakened quadriceps strength is a significant risk factor for symptomatic and functional decline in the knee during both activities of daily living and sport-recreational activities. Numerous electromyographic (EMG) findings suggest that single-joint and multijoint exercises elicit varying muscle activation patterns. For instance, single-joint exercises targeting the quadriceps, such as leg extensions, demonstrate higher EMG amplitudes compared to multijoint lower-extremity exercises like leg presses and squats. Resistance training, characterized by the application of high mechanical tension, remains the cornerstone for promoting muscle hypertrophy, So, research suggests that higher training intensities are associated with greater hypertrophy, up to a certain point. While both light and heavy loads have been shown to elicit similar muscle growth when sets are taken to failure. Studies have reported that high-repetition training with light loads leads to greater central fatigue. Existing literature comparing the effects of BFR-RE and HL-RE primarily focuses on the some quadriceps and hamstring muscle group and its associated exercises. However, none of these studies employed a training protocol in which sets were taken to or near failure.

Study Overview

• Status: Active, not recruiting
• Conditions: Healthy Individuals
• Intervention / Treatment: Other: Low-load resistance exercise with blood flow restriction; Other: High-load resistance exercise

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey
  • Karabuk, Turkey, 78000
    • Karabuk University Faculty of Sports Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• keep healthy
• must be able to attend training regularly

Exclusion Criteria:

• smoking habit
• had orthopedic conditions that hindered lower-body resistance exercise, had hypertension (140/90 mm Hg), or had a BMI exceeding 30 kg/m2

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Muscle thickness; Muscular hypertrophy , or muscle growth, refers to an increase in muscle mass. There are two types of muscular hypertrophy: myofibrillar, which is an increase in myofibrils, and sarcoplasmic, which is an increase in muscle glycogen storage.	Other: Low-load resistance exercise with blood flow restriction; BFR-RE group performed bilateral leg extension exercises to volitional exhaustion (90 seconds rest between sets, 30% 1RM) with BFR cuffs applied at 60% of limb occlusion pressure.; Other Names: (BFR-RE); Other: High-load resistance exercise; The HL-RE group performed the same exercise to volitional exhaustion (90 seconds rest between sets, 70% 1RM) without BFR cuffs.; Other Names: (HL-RE)
Experimental: Muscle stiffness and strength; Muscle and tendon stiffness is defined as an internal resistance to changes in muscle and tendon shape caused by an external force. Muscle strength production takes place with the help of the elastic behavior of the muscles and tendons	Other: Low-load resistance exercise with blood flow restriction; BFR-RE group performed bilateral leg extension exercises to volitional exhaustion (90 seconds rest between sets, 30% 1RM) with BFR cuffs applied at 60% of limb occlusion pressure.; Other Names: (BFR-RE); Other: High-load resistance exercise; The HL-RE group performed the same exercise to volitional exhaustion (90 seconds rest between sets, 70% 1RM) without BFR cuffs.; Other Names: (HL-RE)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Thigh Circumference	Measurement of thigh circumference was performed at a point 33% distal to the inguinal crease, precisely matching the intended cuff application site as verified by a trained investigator. The inguinal crease-to-superior patellar pole distance was also recorded using a standard anthropometric tape measure	2 day
Muscle Strength Test	Prior to commencing the strength assessment, using a Lafayette Manual Muscle Testing System (Lafayette Instrument Company, Lafayette®) a period of familiarization was allowed between the examiner and participant. Subsequently, a trained examiner guided the participant through a series of practice repetitions of leg flexion, and leg extension movements until correct execution was confirmed. The order of movements was randomized. The participant was then verbally instructed to perform three maximal contractions for each movement (3-second hold). A 1-minute rest interval was incorporated between successive contractions, and a 3-minute rest interval was implemented between different movement sets. Measurement of leg extension were obtained with participants in a seated position, while leg flexion measurement were taken with participants in a prone position.	2 day
Muscle Thickness Assessment	Subjects had not engaged in physical activity before the study (48-72 hours), and muscle thickness (MT) was measured at a prone rest position. All muscle thickness measurements were obtained with a single ultrasound device equipped with a 2-9 MHz linear transducer. A researcher (medical doctor, N.K.K) who was blinded to the exercise groups with more than 10 years of experience in musculoskeletal imaging performed all measurement	4 day
Muscle Stiffness and Shear Wave Elastography	After the muscle thickness measurements, the stiffness measurements of quadriceps muscle were obtained using the shear wave elastography (SWE) imaging option of the same ultrasound device with the same linear transducer.	4 day

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Anthropometric Measurements	Height, weight and Body mass index (BMI) were measured using a stadiometer (InBody 270 (Biospace, California, USA), with subjects wearing light clothing and no shoes. Measurements were taken before the exercise program.	One day
Blood Pressure	After a 5-minute supine rest, participants' left brachial blood pressure (BP) was measured twice (1-minute interval). The average of the two closest readings (within 5 mmHg) was recorded in mmHg	One day
Heart Rate	After a 5-minute supine rest	One day

Collaborators and Investigators

• Sponsor: Karabuk University

Study record dates

Study Major Dates

• Study Start (Actual): October 11, 2024
• Primary Completion (Estimated): March 29, 2025
• Study Completion (Estimated): March 29, 2025

Study Registration Dates

• First Submitted: December 11, 2024
• First Submitted That Met QC Criteria: December 20, 2024
• First Posted (Actual): March 25, 2025

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: March 3, 2025
• Last Verified: March 1, 2025

More Information

Terms related to this study

• Keywords: strength; shear wave elastography; muscle stiffness; hypertrophy; vascular occlusion
• Other Study ID Numbers: KarabukUniSportsSciences

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All antropometric and muscle strength, muscle thickness, and muscle stiffness parameters will be shared
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No