Question

When jogging for a while, some parts of the body fell pain due to vibration. Explain how vibration  resonance is related to the pain.

Answer 1

While jogging for long periods of time, we tend to acquire a constant speed. With every step, the impact with the ground delivers some vibration through the legs up to the entire body. This impact, due to constant speed, is seen to come in equal intervals of time i.e. the frequency of impact is constant.

The natural frequency of the human body when standing is about 7.5Hz, which reduces further on the motion. If the frequency of impact comes closer to the natural frequency of the body, then resonance occurs, and the displacements in the joints increase further with each impact. So, the pain in the joints increases with each step, until he/she reduces his speed or stops. If running is continued even after the pain, it could lead to severe injuries.