A "lost secret" of old-time physical culture, this involves static, maximal-effort contractions to build exceptional density and strength.
The abs are viewed as a source of explosive power for striking and lifting.
Pavel Tsatsouline’s Hardstyle Abs is a definitive guide to developing high-tension core strength, moving away from high-repetition endurance exercises toward "iron body armor" and explosive power. The Philosophy of Hardstyle Core Training
If you find this methodology useful and want the specific programming, diagrams, and advanced variations (like using the kettlebell for these drills), it is highly recommended you purchase the official source.
Training the abs to withstand impact and high pressure.
Pavel Tsatsouline, the man who brought kettlebells to the West, treats the abs as a link in a chain. In Hardstyle training, the core's job is to protect the spine and transmit power between the legs and the arms.
Tsatsouline introduces several unique "secret" methods to achieve this level of iron-clad strength: