Research On The Fall Related Postrual Control Ability In The Lower Extremities Of The Female Elderly

Purpose:The present study was to investigate the fall related factors and the methods to assess fall risk among the female elderly, in order to provide a theoretical foundation for prediction of fall risk and preventive exercise.Method:The variables affecting posture on the lower extremities were firstly indentified from the theories of postural control and motor control & learning. Then, an intensive literatures review was conducted to analyze the findings and unsolved questions with regards to the factors of fall risk for each variable. In the present experiment,51 active female elderly aged 65-80 from Beijing were grouped into fallers and non-fallers based on a fall history survey. Each participant was quantitatively measured with deep squat strength, neuromuscular activities, position kinesthesia on the knee and ankle, plantar tactile sensibility, and static balance. The differences were statistically determined between the groups. Finally, a principal component analysis was conducted to reveal main factors derived from all the possible factors of fall risk.Results:1. In theory, postural control in lower extremities is a complex sensori-motor procedure which is a serious contribution to fall risk of female elderly.2. Compared to non-fallers, fallers showed obviously lower extension peak strength/body weight and larger peak strength asymmetry between two legs in the fast deep squat, lower accuracy on the active & passive kinesthesia position in the knee and on the passive position in the ankle, lower tactile sensitivity of the metatarsal plantar skin, slower reaction time for the neuromuscular response to body perturbation, and larger average speed and displacement of the COP (center of pressure) in the horizontal direction for tandem stance and in the lateral direction for single leg stance. It indicated that all these abilities in postural control of the lower extremities were the fall related factors for the female elderly. They could be effectively used as predictors for fall risk. 3. A regressive analysis found that the main factors affecting fall risk from high to low contribution were COP lateral control ability, tactile sensitivity of the metatarsal plantar skin. In the model of the regressive analysis, Fall Risk Index (FRI)= 0.518*COP lateral sway speed in single leg stance + 0.331* threshold of two-point discrimination.4. The analyses with repeated practice demonstrated that the non-fallers produced more improvement in accuracy of the target angle reproduction on the knee & ankle and the speed of the neuromuscular reaction to body perturbation related to fallers.Conclusions:Theoretically, postural control in lower extremities is a complex sensori-motor procedure which is one of the most serious contributions to fall risk of female elderly. To the active female aged between 65-81, we concluded that:1. Extension peak strength of left leg and strength asymmetry between two legs in the fast deep squat, the accuracy on the active & passive kinesthesia position in the knee and on the passive position in the ankle, tactile sensitivity of the metatarsal plantar skin, reaction speed for the neuromuscular response to body perturbation, and balance control ability in the horizontal direction for tandem stance and in the lateral direction for single leg stance were the fall related factors in postural control of the lower extremities for the female elderly. The related indexes could be effectively used as predictors for fall risk.2. The main factors affecting fall risk from high to low contribution were serious functional decline of lateral balance control, sensitivity of plantar skin tactile, and the model of Fall Risk Index (FRI) = 0.518*COP lateral sway speed in single leg stance + 0.331*two point threshold of plantar skin in metatarsus position can be effectively used to predict fall risk. 3. Fast deep squat is an effective method to evaluate the fall related strength deterioration of the lower extremities in the elderly. Static balance test with some difficult stance postures is sensitive to balance deterioration and fall risk.4. The functional decline in motor learning was one of the important contributors to the deterioration of the joint kinesthesia position and neuromuscular reaction speed. And Repeated exercises using target joint angle reproduction with feedback and adaptation to body perturbation appears effective to improve the functions of joint kinesthesia position and neuromuscular reaction speed, respectively. Key words:Fall Risk; Postural Control; Female Elderly...