To develop the strength of an athlete, it is important to work on the 3 types of strength (general, maximum and explosive) knowing that there are four types of contractions : isometric, concentric, eccentric and plyometrics contraction.
As its name suggests, it is a contraction without joint movement and therefore does not cause any change in muscle length. The Roman chair is the best example of this. Your muscles (especially in the thighs) are well contracted but there is no joint movement. This type of contraction does not develop muscle mass and is not dangerous.
The extremities of the muscle are getting closer together. With our example of the Roman chair, imagine that you make a jump once the time is over. Your quadriceps will contract as they shorten and unfold to jump. Climbing stairs is important to practice this.
This type of contraction develops more strength than isometric and is not dangerous.
In opposition to concentric contraction, eccentric contraction is characterized by a distance from the ends of the muscle. With our roman chair exercise, you are in the air after your jump and then you will fall to the ground. Your legs (especially your quadriceps) will apply resistance to avoid falling. Your legs will initially be stretched (but not 100%, otherwise beware of the knees), the strenght (gravity + your weight) will make your lower limbs bend with a muscular movement that will slow down as much as possible this imposed flexion. You’re doing an eccentric contraction. A second simple example: an eccentric contraction is when you run downhill!
This type of contraction is very effective but dangerous for muscle injuries. The post-exercise recovery phase must be very well managed and the stiffness during the first workouts will be significant.
It is the combination of concentric contraction immediately followed by eccentric contraction. The notion of immediacy is essential vs. isolated contraction. This kind of contraction is reached with bouncing strides, skipping rope, jumping over small hedges (see exercises on explosive force).
This is the most effective but also the most dangerous contraction.
The Prepa Physique Team