Dynamic balance: relating functional reach tests to falls and impairment

Falls are commonly reported by people with Charcot-Marie-Tooth disease (CMT). This study explores whether dynamic balance tests can predict falls and which impairments relate to performance of these tests. We measured isokinetic lower limb muscle strength, sensory impairment, disease severity (CMT examination Score) and balance confidence (Modified Falls Self Efficacy scale). Falls events were recorded over 6 months using weekly postcards. Dynamic balance was tested in the movement laboratory using kinematic analysis of a forward and lateral reach task. An infrared marker was placed on the right ulnar styloid and participants were asked to maximally reach forward and to the side without stepping. The distance reached was recorded for an average of three trials. Static standing balance was also measured by the velocity and path length of the centre of pressure (COP) using a force plate. Negative binomial regression analysis explored whether forward reach, lateral reach and static balance performance predicted falls. A linear regression analysis explored the impairments that predicted performance of the forward and lateral reach tests. Twenty seven participants completed the reach tests. The negative binomial multiple regression indicated that forward reach and COP velocity significantly predicted falls (R2 =0.14, P<0.001). Performance of forward reach was predicted by knee extensor peak torque (R2 =0.23, P=0.09) and lateral reach by ankle inverter peak torque (R2 =0.34, P<0.001). Dynamic balance testing may indicate potential falls risk in people with CMT, as has also been demonstrated in older people.