*4.2. Sample*

Participants were considered eligible if they fulfilled the following criteria: (1) Healthy and (2) aged 18 to 30 years. Exclusion criteria comprised (1) severe psychiatric, neurological, or cardiovascular diseases; (2) acute orthopedic disorders; (3) pregnancy; (4) muscle soreness; and (5) intake of painkillers, analgesics, or muscle relaxants within the previous 48 hours.

### *4.3. Experimental Design*

The experimental design incorporated three arms. Each participant performed each of the three conditions once (on three different days with a washout of at least 7 days in between) in a randomized, balanced sequence. Before the first exercise intervention, blood flow velocity to validate the BFR application and the individual 1RM from the knee extensor and knee flexor were determined. During each training intervention, loading-associated outcomes were monitored. Acute effects were determined using pre- and post-intervention measurements.

### *4.4. Blood Flow Velocity Measurement*

The arterial blood flow velocity in the popliteal artery was measured in one leg (side randomly chosen, in the prone position) with and without external blood flow restriction caused/provoked by the BFR cuff (7 cm wide; nylon pneumatic cuff) at 300 mm Hg. Doppler sonography (Siemens Acuson X300, Munich, Germany) was used with spectral analysis, and data were gathered about components of the flow profile. The procedure is reliable [35].

### *4.5. RM Determination*

Prior to the 1RM determination, participants warmed up by cycling for 5 min on a stationary bicycle. After a one-minute rest, an individualized starting load (~80% of estimated the 1RM, estimation based on sex, weight, and strength training experience) was moved through the full range of motion in sagittal plane (knee extension and flexion). After each successful performance, the weight increased until an attempt failed. One-minute rests were given between each attempt, and the 1RM was attained within a maximum of 5 attempts.
