Abstact:Introduction to impact force and muscle turning

Researcher's such as Dekel and Weissman, 1978; Radin et al., 1973, 1978 and Serink et al., 1977) state that If the joints are regularly submitted to such high-frequency impact force peaks, subchondral bone and articular cartilage begin to degenerate with speculation that these ‘impact force peaks’ are the causative factors in the development of lower back pain and running injuries in runners (Clement et al., 1981; James et al., 1978).

In an attempt to minimise these impact forces, changing the foot and leg geometry along with ankle and knee joint stiffness have been described by Lafortune, Hennig and Lake (1995) as being important developmentally both individually as well as collectively. Nigg (1997) suggested that the strategy of changing the coupling between the soft and rigid structures of the individuals’ leg termed ''Muscle Tuning'', may also be of much importance.

Nigg (1997) spoke of the muscle turning as a concept suggesting that the impact forces during heel strike should be considered as an input signal, characterized by amplitude and frequency. This impact force signal could produce bone vibrations at high frequencies and soft tissue vibrations of the human leg (e.g., triceps surae, quadriceps, or hamstrings muscles) at frequencies that might concur with the frequencies of the input signal.