In the case of runners, there is often talk of little tension, which is expected to improve economic running and thus performance. The mobility and flexibility of the core and lower limbs are in a special position. The tension of the core, which limits the rotation and thus the rotation of the leg from the hip, improves economic running. Similarly, lower back, hip, and ankle tensions shift running biomechanics in a more economical direction. So, while a certain degree of tension may be beneficial from a running performance perspective, consideration must be given to how to determine the appropriate tension.
what excessive stiffness can cause?
Excessive “stiffness,” or in other words, a lack of mobility and flexibility, can increase the risk of injury and tendonitis. For example, your hamstring that crosses two joints; the knee and hip joint greatly affects performance in runners. When the hamstring is at maximum length, the hip is bent and the knee is extended. In the run just before initial contact, the hip flexion is about 25° angle and the knee about 10-20° angle. If this does not happen, the biomechanics will change, the stride length will shorten, and the strain on the lower back will increase as the pelvis turns forward.
Even at the end of the flight phase, when the knee needs to be stretched, your front thigh has to work harder. If your hamstrings are tight and it brakes the movement, a two-way pull is created, which creates a strain on the knee. In the long run, this can lead to patellofemoral pain syndrome or patellar tendinopathy, i.e., the jumper’s knee.
What you can do?
Balancing the good movement and economical running is not that simple. But saying that runners don’t need flexibility or in the better word mobility is not true. That is not mean you need to start stretching like a mad. Focus more dynamic stretching and movement which is increasing the active range of movement as well as mobility.
Excellent movements are a different kind of leg swings. Also, basic hamstring stretchings are good but avoid perform them before the main exercise. Any static stretching should not be done before the exercise. Whereas dynamic stretching and exercises that involve movement can be done before the exercise, together with warm-up routine.