The goal of this clinical trial is to compare two types of shoulder strength training: low-load training with blood-flow restriction (BFR) and high-load training without BFR. The study includes healthy adults. The main questions it aims to answer are: Are changes in shoulder strength, power, endurance, and muscle mass similar with low-load BFR and high-load training? Researchers will compare strength training with BFR to strength training without BFR to see whether changes in shoulder muscle performance are similar. Participants will: * Provide basic personal details, body measurements (e.g., height and weight), and a brief medical history before starting. * Train in one of the two programs (BFR or no BFR) two times per week for 4 weeks. * Complete tests of shoulder maximum strength, power, endurance, and muscle mass at the start and at the end of the protocol.
All outcome assessments were conducted after a standardized warm-up to minimize measurement variability. The warm-up comprised light aerobic activity, followed by dynamic mobility exercises for the shoulder girdle and upper limbs, and targeted stretching of the shoulder and elbow/forearm muscle groups (two sets of 20-30 seconds per muscle group). Safety procedures included monitoring for adverse symptoms during testing and training; sessions were paused or discontinued according to predefined criteria.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
23
Each session began with a warm-up including mobility and stretching exercises for the shoulders and upper limbs. During the first session, the one-repetition maximum (1RM) for each participant and exercise was determined using a failure-to-repetition method with applied coefficients. Training was performed at 30 percent 1RM, following a standardized sequence of three shoulder-targeted exercises (shoulder abduction, external rotation, Dumbbell Overhead Press), totaling 75 repetition per session (30/15/15/15), 30-second rest intervals per sets. Movements were executed at a controlled 4-sec. tempo (2 seconds concentric, 2 seconds eccentric). BFR was applied using pneumatic cuffs, maintained during each exercise, released for 60 seconds between exercises, and reapplied for the next. Participants rated exercise difficulty, including pain, tension, and numbness, using a 0-10 numeric scale, with protocol adjustments or session cancellation if symptoms exceeded 7/10.
Each session began with a warm-up including mobility and stretching exercises for the shoulders and upper limbs. During the first session, the 1RM for each participant and exercise was determined using a failure-to-repetition method with applied coefficients. Training was performed at 70 percent following a standardized sequence of three shoulder-targeted exercises (shoulder abduction and external rotation, and Dumbbell Overhead Press). Four sets of 8 to 10 repetitions were completed for each exercise, with 2-minutes rest between sets and exercises. Movement speed was moderate (1-second concentric, 2-second eccentric).
Escola Superior de Tecnologias da Saúde do Tâmega e Sousa
Gandra, Paredes, Portugal
Change in Deltoid muscle mass
Arm circumference at the armpit level of the dominant limb, used as a proxy for deltoid muscle mass.
Time frame: Baseline and between 24 hours and 1 week after completion of the 4-week intervention.
Change in shoulder muscle power
Shoulder muscle power, assessed by the Single Arm Seated Shot-Put Test
Time frame: Baseline and between 24 hours and 1 week after completion of the 4-week intervention.
Change in shoulder muscle maximal strength
Maximal isometric muscle strength measured with the Smart Groin Trainer dynamometer (NeuroExcellence, Braga, Portugal) during a vertical lift task.
Time frame: Baseline and between 24 hours and 1 week after completion of the 4-week intervention.
Change in muscle shoulder endurance
Shoulder muscle endurance, assessed by the Shoulder Endurance Test (SET)
Time frame: Baseline and between 24 hours and 1 week after completion of the 4-week intervention.
Change in Numeric Rating Scale
Participants in the Low-load strength training with BFR group rate pain, numbness and tingling in the dominant upper limb on a 0-10 Numeric Rating Scale (NRS) (0 = none; 10 = worst imaginable). Sessions are paused if NRS ≥ 7/10.
Time frame: Continuously from the start to the end of each training session, across all sessions during the 4-week intervention (participants report immediately if symptoms reaches ≥7/10.
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