This is a fantastic training style by the legend Hany Rambod.
Try it for yourself!!!
It stands for Fascia Stretch Training (A fascia is a structure of connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding some structures together, while permitting others to slide smoothly over each other, like a protective sock) the seven refers to 7 sets performed usually as the final exercise of a target body part. Basically you train that body part on any given day as heavy as you normally would, keeping the rep range between 8-12, but the last exercise you perform the seven sets to finish off that particular muscle, with minimal rest in between to get the best pump possible, keep rest intervals between 30-45 seconds and making sure to stay hydrated to push that fluid into the muscle and stretch the fascia even further.
You should refrain from using compound lifts as your “seven set,” because they require balance and the use of ancillary muscles that takes focus off the target muscle. Machines and cables are a good idea and free weights like barbell curls and skull crushers also work well for this “seven set”. Perform your “seven set” at the end of the workout for that muscle group.
The goal is to bring as much vitamins, minerals, amino acids, oxygen etc. into the muscle, and also stretch the fascia surrounding it to help encourage maximal muscle growth. The fascia is the limiting factor in achieving muscle growth because the muscle will grow only as much as there is room for it to do so. This training system is targeted to stretch the fascia and allow more room, instead of limiting muscle growth.
Restricting the “seven sets” as your last exercise is recommended for new users of this training principle. This will allow you to lift heavy for first few exercises before taking the muscle to failure. There are many other variations for advanced users, including “front-loading the seven sets”, to allow creativity in workouts and to shock and further stretch the fascia and enhance muscle growth.