Effects of vibrating insoles on balance in diabetic neuropathy. Research into the optimal characteristics of the applied noise signal.

Patients with neuropathy often show a decreased sensibility at the feet and
therefore a decreased balance control and an increased risk of falling.
Improvement of the tactile feedback from the plantar side of the feet
concerning pressure distribution, is a way to improve balance control.
A new technique that may improve tactile, and possibly proprioceptive feedback,
is the application of mechanical noise (vibration with a randomly varying
frequency) to the plantar surface of the feet. By adding noise to a
subthreshold sensory input, the sensory threshold may be crossed. In this way a
signal that is not detected during normal circumstances can be detected. The
mechanism, by which signal detection is improved by noise, is called stochastic
resonance. A few studies have shown that the application of noise can improve
tactile sensitivity and balance.

The objective of this study is to compare the effects of noise with different
characteristics on balance in patients with diabetic neuropathy

First the degree of neuropathy will be tested with monofilaments. Moreover
vibrotactile sensitivity will be tested with a tuning fork.

Following the patient has to stand on a pair of vibrating insoles placed on a
forceplate. The threshold for the noisy vibration will be determined. Each
measurement consists of standing on the vibrating insoles for one minute during
which the insoles will be turned on and off for 30s. Based on the forceplate
recordings the center of pressure displacements will be determined. Because
balance problem appear mostly with poor vision or when attention is destracted,
balance will be tested under two conditions.
1. Eyes closed, no dual task
2. Eyes closed, dual task

Appliction of mechanical noise at the plantar side of the feet by vibrating
insoles.

Participation takes about an hour, the burden for the patients is minimal and
there is no specific risk for them.