It is not a secret that there are two types of failures: the failure when our muscles cannot contract, i.e. we cannot perform a next movement and the failure when we stop exercises because we cannot tolerate burning/pain in our muscles, although we can perform several reps more. First type of failure is common for high loading and small number reps, whereas the second type is associated with small loading and high number reps or long muscle isometric contraction. Both failures are used in training to gain muscles, strength and endurance.
Static-Dynamic Method (SD) is not a very correct name because statics and dynamics exclude each over. SD here means slow, partial reps that are performed with external resistance or with muscle co-contraction inside the full range of movements.
https://www.youtube.com/watch?v=jYIoQmGSA-I
This method is based on the second type of failure. A student keeps tension in his muscles all the time when he performs the partial movements inside the full range of moving. He does not relax muscles in a set. This continuous tension prevents the blood stream to the muscles and creates corresponding anaerobic biochemical background that stimulates the gain of muscles and strength. I think you remember a method when guys wrapped their limbs with bands to prevent the blood stream through their muscles to stimulate hypertrophy. SD method acts similar. An important moment is that, using SD, we should perform 30-45 sec sets (number reps in sets is not important) to get burning/ pain in a working muscle. If after first set we did not get this burning/pain, we should perform the second set after 20-30 sec rest and sometimes even third set to get clear burning/pain feeling. Usually 3 sets are more than enough. Pain in the muscles creates biochemical stress that stimulates secretion of hormones. Hormones, in their turn, move to muscle cells and stimulate their growth. This is a short description of SD method.
Hormones and training: what you need to know rebel-performance.com/hormones-training-need-know/
This is very interesting but long since-like paper; therefore, I make a short quotation that directly devotes to the practical aspects of SD method.
"The stato-dynamic effort method uses loads of approximately 50% or less, and witnesses the participant moving the load at slow velocities. 2 to 4 second eccentric and concentric motions are typically used for this method. The low load and slow tempo makes this approach target the slow twitch fibers due to the very low forces. While the force variable is low, the duration of the set should be large. Slow twitch fibers are easy to recruit, but difficult to fatigue, and the longer duration sets are ideal for setting the stage to turn these slow twitch fibers into target cells. Sets are typically performed for 40 to 60 seconds, and participants can build up to performing multiple rounds of 3 to 5 sets. Typically the rest period is kept in a 1 to 1 ratio with the work duration. The stato-dynamic effort method fits into the broader category of occlusion based training approaches. Occlusion techniques were made popular by the Japanese, Katso approach, also called Blood Flow Restricted Training (BFR). The overall findings from the various protocols that have been used in BFR approaches is that a substantial increase in growth hormone is typically seen, even when loads of approximately 30% 1RM are used. The thought behind this approach is that occlusion of venous vessels prevents the removal of metabolic byproducts from the local tissue area for an extended period of time, creating a larger than normal level of waste products and heat trapped in the blood that cannot escape until the occlusion is released. Once the occlusion is released, the blood that is loaded with waste products ultimately is circulated back to central regions, such as the heart and neck. Chemoreceptors in the carotid body and arch of the aorta register the high concentrations of metabolic byproducts in the blood, send an afferent signal to the nucleus tractus solitarius, which relays the message to the hypothalamus. The hypothalamus perceives the internal environment of the body to be one that would threaten homeostasis. The hypothalamus then begins a signaling cascade to the anterior pituitary that unleashes a potent growth hormone pulse. The stato-dynamic effort method asks the participant to never completely lock out the joints during performance of the tempo based exercise. Such an approach keeps the muscle tissue actively creating tension throughout the time period that the exercise is being performed. When muscle tissue is actively creating tension, it mechanically compresses the blood vessels that supply and drain the tissue, thus creating an occlusal effect. Eventually the set ends, and the occluded blood is sent back into circulation, leading to the mechanism of hormonal signaling described in the previous paragraph. Since only the slow twitch muscle was recruited and fatigued with this approach, only the slow twitch tissue is the target cell for the hormonal cascade."
Interestingly, some authors also report if athletes increase loading during stato-dynamic exercises up to 70-80% RM and decrease time under tension to 30-45 sec, they could also train fast twitch fibers in addition to slow twitch ones.
P.S. I use SD method when I perform co-contraction exercises, and when I train with a stick. I can say that pumping and feelings in muscles are very strong after that. This method can be easily adapted for any self-resistance training. If we can voluntary regulate and keep tension in our muscles, we can perform full range movements in the SD manner.