From the publication:

The low-pH environment induced by the metabolic accumulations is known to stimulate growth hormone (GH) secretion, which is known to possibly have an interactive effect toward MPS [muscle protein synthesis]. There is continual debate over the direct hypertrophic actions of GH toward overall MPS. […] The implementation of BFR training in 1 study has been found to elevate GH levels to ∼290. Another study has found that skeletal muscle ischemia coupled with low-intensity resistance exercise through knee extensions acutely increased GH levels, whereas reducing the maximal voluntary contraction. It is known that the implementation of Kaatsu training [blood flow–restricted training] increased the postexercise GH levels 10-fold above the control group with no blood flow–restriction.

[…]

According to the literature, it is also known that a single bout of low-intensity resistance exercise with blood flow restriction can result in both an upregulation of the anabolic cell signaling mTOR pathway within 3 hours after exercise and a downregulation of the proteolytic transcripts for skeletal muscle at 8 hours after exercise.

[…]

In accordance with occlusion training, it is known that compared with slow-twitch (ST) muscle fibers, the fast-twitch (FT) fibers are recruited quickly, although the intensity is low. In other words, BFR training can recruit FT fibers without regards to the widely accepted size principle in which ST fibers are recruited first with FT fibers being recruited as intensity progresses. The rationale presented throughout the literature may be due to the hypoxia conditions created by the vascular occlusion through which the additional recruitment of more motor units may take place to compensate for the deficit in overall force development. In addition, the metabolite accumulations throughout the BFR training session may also induce the increased recruitment of FT or higher threshold motor units. Several studies show through the utilization of electromyography (EMG) that during Kaatsu training, there was an increase in the recruitment of FT muscle fibers. Another study that implemented low-intensity vascular occlusion training showed early fatigue of type I fibers due to the lack of delivery in oxygen, thus showing a greater increase in the CSA [ross-sectional area] of type II fibers by 27.6% compared with type I muscle fibers increase of 5.9% during a 2-week training program at 20% of 1RM.