Age related adaptations in postural control after balance perturbations by simulating a *near fall*.

Falls are one of the greatest concerns among the elderly, because the incidents
are high and they lead to severe consequences. The extent of the problem will
continue to expand as the number of older people is expected to increase
dramatically over the next few decades. An important risk factor for falls in
the elderly is an impaired postural control, which is defined as the act of
maintaining, achieving or restoring a state of balance during any posture or
activity. A growing number of studies show the potential of video games
incorporating training (exergames) to improve postural control. However, scarce
evidence is available that these interventions actually contribute to a
decrease in fall risk. Finding indicators for improved postural control are
needed in order to be able to validate fall risk interventions. By studying age
related postural adaptations to perturbations that challenge balance in a
controlled environment like CAREN (Computer Assisted Rehabilitation
Environment) insight into these indicators can be gained. Eventually these
findings can be used for validating an exergaming training intervention in
terms of reducing fall risk by improving postural control.

To gain insight into factors that indicate an improved postural control by
evaluating balance recovery (in terms of centre of mass (CoM) and centre of
pressure (CoP)) of both young and older adults during a reaching task while
exposed to perturbations of physical, visual or cognitive factors, causing a
near fall.

The present study has a cross-sectional study design. Balance recovery of
different age groups will be measured during experimental sessions. Both young
and older adults will be exposed to three different types of perturbations
(divided in three experiments) during the performance of a weight-shifting
task.

Both young and older participants will perform multiple target-directed weight
shifting movements, i.e. reaching tasks, in three simulated fall risk
situations which are divided in three experiments. The experiments will be
conducted in the CAREN (Computer Assisted Rehabilitation Environment) lab.

• Experiment 1. Mechanical perturbations
Mechanical perturbations will be created by sudden platform translations with
different velocity profiles during the performance of multiple reaching tasks.

• Experiment 2. Visual surround manipulation
Visual surround will be manipulated by applying optic flow patterns on a large
screen in front of the subjects during the performance of multiple reaching
tasks.

• Experiment 3. Cognitive demanding dual task
Participants will perform a continuous cognitive demanding dual task during the
performance of multiple reaching tasks.

Balance is challenged during an everyday standing-reaching task. Participants
are wearing a harness during all trials which is attached with a girdle to the
frame of the CAREN system. During all trials an assistant remains at the side
of the subjects. Time between trials will be enough to let the participants
recover and prepare for upcoming trials.Therefore the risk associated with
participation can be considered negligible and the burden can be considered
minimal.