Do other people struggle with the conventional terminology for describing the phases of the gait cycle? I’m not sure how this arose but the earliest reference I know of is the first edition of Jacquelin Perry’s book .
The first phase is initial contact and lasts for just 2% of the gait cycle. It should really be described as an instant in the gait cycle not a phase. Loading response is also a misnomer. Any response is what happens after an event and even the most cursory glance at the vertical component of the ground reaction shows that loading is not complete until well after the end of the loading response phase.
Mid stance isn’t in the middle of stance – as Perry describes it it is the phase leading up to the middle of stance. Terminal stance isn’t at the end of stance – it ends at opposite foot contact. I quite like the term pre-swing as it emphasizes the continuity of the gait cycle and how the final requirement of stance is to prepare for swing. Following this logic, however, there is a much stronger case for labelling the phase prior to foot contact as pre-stance as preparing the limb for loading is extremely important in late swing.
Another puzzle is why single support and swing, which are the same phases of gait but viewed from the perspective of one limb or the other are divided into a different number of sub-phases. Single support is divided into two phases whereas swing is divided into three. This makes any attempt to describe gait taking into accounting for the interaction between the limbs is unnecessarily complicated.
Some of the technical delineations for the phases are also based on the characteristics of normal walking and it may not be clear how to delineate the phases for different types of pathological gait. Terminal stance, for example, starts with heel rise. Where does terminal stance start for a patient who walks on their toes and never has their heel down in the first place. Mid-swing is defined as ending when the tibia is vertical. Patients walking with a crouched gait pattern, however, may not have a vertical tibia at any stage of the gait cycle.
I’m not really a fan of trying to re-define the terms to be more logical. This only leads to confusion. Try looking at the literature on crouch gait. There are at least four well accepted definitions of crouch gait and thus, unless there is additional clarification, it is actually impossible to know what any given individual is referring to when they use the term.
The terminology I prefer is illustrated above. Single support and swing are both divided into three or equal duration phases. The terms early, middle and late are different to the original initial, mid and terminal which helps avoid confusion. The three letter abbreviations can be useful where brevity is an asset.
1. Perry, J., Gait Analysis1992, Thorofare: SLACK.