**2. Gait analysis**

Walking and running are natural ways of human locomotion which are shaped during phylogenetic development. According to Zembaty (1987) the walking cycle involves "activities and movements performed by a walking person between the contact of one of the heels with the ground and its subsequent contact with the ground", another definition assumes that gait means "locomotion consisting in moving the body weight, focused at the centre of gravity, in space, along a rout requiring the least energy expenditure" (Basmajian, 1976).

There are a lot of more definitions which have been devised over several dozen years when thorough research over the methods of human movement was started. First reports on this issue date back to the 1830s when the Weber brothers performed an analysis of time and space parameters of gait, while the locomotion pattern was first determined by means of a photographic technique by Marey and Muybridge (Andriacchi et al. 2000).

On the basis of these long-term and numerous studies individual gait phases were distinguished, their duration was determined and dependencies between gait phases and their mutual changes induced by changing conditions under which motion is executed.
