the moment of inertia in these dist

the moment of inertia in these distal areas is less,
allowing the summation of higher velocities. Finally,
by allowing joint force control to be largely
influenced and controlled by pre-programmed muscle
activation patterns and interactive moments developed
through core activation, instead of being
based on local ligament size or feedback-based local
muscle activation, the ligaments can be smaller in
size, and the smaller local muscles can be activated
for precision and control of performance variables.
5. Examples of Failure of Core Stability
Associated with Dysfunction
Weak hip muscles and resulting alteration of hip/
trunk position are a common finding associated with
knee injury. Weak hip abductors and tight hip flexors
are seen in association with anterior knee pain
and chondromalacia.[33,34] Alterations in hip muscle
Fig. 3. ‘Corkscrewing’ – using hip rotators to stabilise the trunk over
the planted leg in the presence of hip abductor weakness.
activity are associated with increased hip varus and
elbow maximal velocity is developed before maxi- hip flexion positioning and increased knee valgus
mal shoulder velocity. However, this general pattern positioning in squatting or landing manoeuvres, all
of force development from the ground through the of which increase load on the anterior cruciate ligacore
to the distal segment has been demonstrated in ment. A recent longitudinal study looked at core
the tennis serve,[23,31] baseball throw[26] and kick.[2] stability parameters and found that weakness in hip
Force control is also maximised through the core. external rotation was correlated with incidence of
The trunk is essential in re-acquiring the forward knee injury.[35] Based on these associations, most
momentum in throwing,[24] and approximately 85% rehabilitation and conditioning programmes for the
of the muscle activation to slow the forward-moving knee now emphasise core stabilisation and hip
strengthening.[33,34,36]
arm is generated in the periscapular and trunk muscles,
rather than the rotator cuff.[32]
4. Advantages of Core Stability
in Function
Core stability creates several advantages for integration
of proximal and distal segments in generating
and controlling forces to maximise athletic function.
The larger, bulkier muscles in the central core
create a rigid cylinder and a large moment of inertia
against body perturbation while still allowing a stable
base for distal mobility. In addition, it places
most of the ‘engine’ of force development in the
central core, allowing small changes in rotation
around the central core to effect large changes in
rotation in the distal segments, similar to the cracking
of the end of a whip. Because of the need for
relatively smaller mass in the peripheral segments,