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.

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

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.

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

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.

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

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.

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.