MODULE 3: SELF-ASSESSMENT

LO 3.1: Differentiate between Centre of Gravity and Centre of Mass and their position in upright standing

i     These are fundamentally the same concept in any situation, movement or place and it does not matter which is used

ii     Centre of Mass is the preferable option, as it relates to the amount of matter present in a body

iii    The human body has only a Centre of Mass: the use of the term Centre of Gravity is erroneous

iv    Centre of Mass/Gravity is in a fixed, known and constant position in the human body and needs no differentiation between the two terms

v    The human body has both a Centre of Gravity (best used in relation to static postures) and a Centre of Mass (used when movement is taking place) but clinically the positions can only be estimated

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LO 3.2: Understand the correct use of the projection from the Centre of Gravity

i     The projection is a line passing downwards through the CoG to indicate the relation of the CoG with the body structures below and with the support area and also projecting upwards to indicate the relation with the body structures above. This helps determine a balanced posture.

ii     The projection from the CoG is related to the direction of gravity i.e. downwards and provides information about stability of the body with respect to the support area.

iii    In a single-leg stance static posture, the projection from the CoG has value as it predicts stability when the raised leg is grounded.

iv    As the CoG always lies within the body, the projection from the CoG will always end in a body part, such as a foot, or a hand if doing a handstand.

v    The projection from the CoG is a hypothetical construct and has no practical relevance

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LO 3.3: Explain the practical difference for therapists between Centre of Gravity and Centre of Mass when training upright postural control

i     The Centre of Gravity will lie slightly lower in the body than does the Centre of Mass. This height difference is critical, and you should determine which you wish to influence.

ii     It depends on the height of the place where you are working. If your premises are at the top of a skyscraper building or at the top of a mountain, you should pay attention to the relative heights of the Centre of Gravity and the Centre of Mass as this will influence control training.

iii    There is no practical difference. In the upright posture the position of the CoG and of the CoM cannot be distinguished – or clearly determined – in a clinical environment.

iv    Precision is important when training upright postural control and knowing where the Centre of Gravity and the Centre of Mass are and how they move will positively impact your therapy.

LO 3.4: Evaluate the use of total body Centre of Gravity to assist planning of therapy to promote postural control at the lumbar segments

i      Knowledge of the position of total body CoG is fundamental to effective therapy for promotion of postural control, not only in the lumbar segments but throughout the body.  

ii     The position of the total body CoG is irrelevant when training control at specific segments.  It is the CoG of all segments above the support – and thus the stability relative to the support – that is critical. Training postural control of the lumbar segments means that support will be directly beneath those lumbar segments.

iii    It is essential to know the exact positions of the CoG of the lumbar segments and of the total body to ensure effective control learning so that, therapeutically, these positions can be modified as required.

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LO 3.5: Explain which segments and which support area should be considered when promoting control of the head and trunk in the vertical posture

i The head and trunk are considered as two units i.e. the head and the trunk from Upper Thoracic to Lower Lumbar inclusive. The support area is the pelvis.

ii The head and trunk are considered as two units i.e. the head and the trunk from Upper Thoracic to Lower Lumbar inclusive. The support area is the pelvis in sitting postures, the knees in kneeling postures, and the feet in standing postures

iii Promotion of control of the head and trunk in the vertical posture is a staged and sequential process from the head progressing downwards. It is important that each segment is considered in isolation at all times. This means that training commences with head control and C7 as the support area. The focus then transfers to the Upper Thoracic segment with T3 and associated structures as the support area. Control training proceeds until the Lower Lumbar segment is reached. The Lower Lumbar segment is then the focus and knowing the position of the CoG of this LL segment and its relation to the support area of S1 is critical to a successful outcome.

iv Promotion of control of the head and trunk in the vertical posture is a staged and sequential process from the head progressing downwards. Training commences with head control (if not present) and ensuring the downward projection of the CoG of the head lies within the support area of C7. From there, each segment is added sequentially to the previous i.e. Head + Upper Thoracic, Head + Upper Thoracic + Mid Thoracic and so on. For each addition, the CoG concerned is that of the combined segments, with the relevant support area being the structures directly beneath the lowest segment under discussion.

v The head and trunk are best taken as a single unit, with the support area being the pelvis. This ensures focus on head and trunk movements that are coordinated.

Help improve our teaching.  Please tell us your selected answers by sending an email to [email protected] using the format “LO 3.1 A  LO 3.2 B LO 3.3 C  etc ” (replace A B C etc with the number of your answer to each question).