Blood Flow Restriction (BFR) training, also known as occlusion training or Kaatsu training (originating from Japan), is a strength training method that involves the use of bands or cuffs placed around a limb to partially restrict venous blood flow return while still allowing arterial blood flow into the muscle. The idea is to create a condition of reduced oxygen availability to the muscles being trained, leading to an increase in the production of various growth and repair-related hormones.

Method:

1. BFR is typically used in conjunction with low-intensity resistance training (usually around 20-50% of one's 1-repetition maximum).
2. The cuffs or bands are tightly wrapped around the top of the limbs (either arms or legs), and then the exercise is performed.
3. The level of tightness and pressure from the bands should be significant enough to restrict venous return but not completely occlude arterial inflow.

Benefits:

1. Muscle Hypertrophy: BFR training can lead to muscle size gains similar to traditional high-load resistance training but with the use of much lighter weights. This is believed to be due to a buildup of metabolites and an increase in muscle fiber activation.
2. Strength Gains: While BFR training mainly uses lighter weights, it can still lead to significant strength gains, especially when combined with traditional strength training.
3. Rehabilitation: BFR is especially beneficial in rehabilitation settings. For those who cannot lift heavy weights due to injury or surgery, BFR allows them to still achieve muscle hypertrophy and strength gains with lighter loads, aiding in faster recovery.
4. Increased Growth Hormone Production: The buildup of metabolic waste products due to restricted blood flow can stimulate the release of growth hormone, which has benefits for muscle growth and repair.
5. Improved Vascular Function: Some studies suggest that BFR training can enhance capillary density and vascularity, which can be beneficial for cardiovascular health.

In summary, BFR training offers a unique method of gaining muscle and strength, especially in situations where traditional heavy lifting isn't feasible. However, its application needs to be applied with proper technique and guidance by trained healthcare providers.