Isoinertial refers to a type of resistance used in physical training that maintains a constant inertia throughout the range of movement, which facilitates constant strength and maximum muscle strength in all angles. The term isointertial derives from the words iso (even) and inertial (resistance) which, in a terminology, describes the primary concept of the isointertial system or expresses the same inertia in the concentric and eccentric phases of muscular contraction.
Since the late eighties, during the long-term space travel, has been placed as a problem the ability to maintain the power of astronaut muscles engaged in missions, since the absence of gravity leads to an environment in which they operate ipotrofismo of the musculoskeletal system, is no longer called to bear the load of the body weight, as well as a reduction of the bone mineral density. Studies and research conducted on a solution that has led to the strengthening of astronaut muscles and thereafter, over the years, has become a very useful muscle training method for preservation, prevention and rehabilitation. In practice, a resistance training system was created with a belt and a steering wheel that, driven by the belt, controlled a process that generated movement regardless of the force of gravity.
The isointertial muscular activity follows the muscular action of the sporting gesture or rather what the body or the parts of it are in the duty to practice in the sports, according to which, in variable strength and speed, an inertial load (such as a ball), limb or body itself (such as by accelerating or changing direction) the athlete is obliged to respond at the motor and neuromuscular coordination level very quickly to sudden and non-predetermined motor situations and gestures .
The great utility of the isointertial method and at the same time what differentiates it from the normal isotonic muscular movement lies in the fact that the isotonic action developed in the conventional exercises (machines of force and free weights), the resistance is constant in the all of the movement both in the concentric phase in which the eccentric, which is equivalent to the set load. In the isointertial method, the resistance is adapted at each moment and is proportional to the force developed in the sense that the greater the force expressed by the subject in the concentric phase is greater, the greater will be the acceleration with which the steering wheel reacts.