Wearable inertial sensors for centre of mass stability changesduring the incremental shuttle walk test.

Postural stability is the ability to remain stable while the person is standing still, voluntarily moving, changing directions or is subject to external perturbation. Postural stability is retained while the centre of mass (COM) remains over the base of support (BOS) in a stable position (static) or while moving (dynamic).The margin of stability (MOS) can be considered the amount of dynamic stability during gait, measured using the position and velocity of the COM over the BOS. While there has been investigation of the MOS during normal gait, it has not been investigated during increased walking speeds, such as during the incremental shuttle walk test (ISWT).

The incremental shuttle walk test (ISWT) is a standardised and validated walking test used to measure exercise capacity and fitness levels in adults. During the ISWT, the walking distance remains standardised to 10 metres per lap while the walking speed gradually increases from 0.50 m/s at level 1, to 2.37 m/s at level 12. Therefore,as time decreases the walking speed increases with each level.
Given that dynamic stability fluctuates during gait and tends to reduce with increasing age, a reduction in dynamic stability predisposes to near falls and falls. Near falls are momentary losses of balance without falling to the ground.

With the increased exertion and resultant fatigue from increased walking speed in the ISWT, there are likely to be changes in the COM and MOS. Measurement of COM and MOS changes can be captured by triaxial accelerometers and gyroscopes in a wearable inertial sensor worn on the surface closest to the COM, L4.

Aim: The aim of the research is to explore changes to postural stability by measuring the effects of fatigue on the centre of mass (COM) and margin of stability (MOS) using a wearable inertial sensor on L4.