System for assessing postural sway and human motion

Abstract

There is provided herein a system and method for performing a balance evaluation that utilizes a hand held accelerometer that measures upper body compensatory and correctional movement. Instead of testing movement in the waist or lower extremity as is commonly done, the instant invention measures thoracic trunk sway to estimate an individual's balance via positional change algorithms. By holding the measuring device to the chest and performing one or a variety of balance tests, the instant invention can determine the amount of sway in the trunk without attached or fixed monitors, which presents a novel approach to assessing postural sway above the center of mass.

1 - 8 . (canceled) 
     
     
         9 . A system for assessing a subject's postural stability, comprising:
 (a) a handheld computing device, comprising:
 (1) a three-axis accelerometer, 
 (2) memory, 
 (3) a screen, and, 
 (4) a CPU in electronic communication with said screen, said three-axis accelerometer and with said memory, said CPU at least for executing a plurality of program instructions stored in said memory, said plurality of program instructions comprising the steps of:
 (i) instructing a subject to clasp a three-component accelerometer against an upper torso of the subject; 
 (ii) instructing the subject to perform a task while the three-component accelerometer is so clasped; 
 (iii) continuously recording an output of said accelerometer during the subject's performance of said task, thereby obtaining a plurality of three-component accelerometer measurements during the performance of said task; 
 (iv) determining from at least a portion of said plurality of three-component accelerometer measurements an indicium representative of the subject's postural stability; 
 (v) using at least said indicium to determine whether the subject's postural stability is within a normal range; 
 (vi) if the subject's postural stability is within said normal range, displaying on said screen an indication that the subject's postural stability is within said normal range and taking no further action with respect to the subject; and, 
 (vii) if the subject's postural stability is not within said normal range, displaying on said screen an indication that the subject's postural stability is not within said normal range. 
 
   
     
     
         10 . The system for assessing a subject's postural stability according to  claim 9  wherein said handheld computer is selected from the group consisting of an iPhone®, an iPod®, an iPod Touch®, an Andriod® cell phone, and a Blackberry® cell phone. 
     
     
         11 . The system according to  claim 9 , wherein said task is selected from the group consisting of a single leg stance test, a tandem stance test, a tandem gait test, a stationary stance test, a static postural sway test, a dynamic squat test, a single leg squat test, a step up test, an up and go test, and a jump stability test. 
     
     
         12 . The system according to  claim 9 , wherein said normal range is determined from at least one previous performance of the task by the subject. 
     
     
         13 . The system according to  claim 9 , wherein said normal range is determined from a plurality of performances of the task by a plurality of comparable subjects. 
     
     
         14 - 18 . (canceled) 
     
     
         19 . A system for assessing a subject's postural stability, comprising:
 (a) a handheld computing device, comprising:
 (1) a three-axis accelerometer, 
 (2) memory, 
 (3) a screen, and, 
 (4) a CPU in electronic communication with said screen, said three-axis accelerometer and with said memory, said CPU at least for executing a plurality of program instructions stored in said memory, said plurality of program instructions comprising the steps of:
 (i) instructing a subject to clasp said handheld computing device against an upper torso of the subject; 
 (ii) instructing the subject to perform a task while the handheld computing device is so clasped; 
 (iii) continuously recording an output of said accelerometer during the subject's performance of said task, thereby obtaining a plurality of three-component accelerometer measurements during the performance of said task; 
 (iv) determining from at least a portion of said plurality of three-component accelerometer measurements a JERK score indicium representative of the subject's postural stability, wherein said JERK score is calculated according to the equation: 
 
   
       
         
           
             
               
                 JERK 
                 = 
                 
                   0.1 
                   * 
                   
                     [ 
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           2 
                         
                         N 
                       
                        
                       
                          
                         
                           
                             X 
                             i 
                           
                           - 
                           
                             X 
                             
                               i 
                               - 
                               1 
                             
                           
                         
                          
                       
                     
                     ] 
                   
                 
               
               , 
             
           
         
         
           
             
               where X i  is an instantaneous acceleration recorded from said three-component accelerometer at time point “i”, 
               where X i-1  is an instantaneous acceleration recorded from said three-component accelerometer at time point “i−1”, and, 
               where “N” is the total number of instantaneous accelerations recorded during said task; 
             
             (v) using at least said indicium to determine whether the subject's postural stability is within a normal range; 
             (vi) if the subject's postural stability is within said normal range, taking no further action with respect to the subject; and, 
             (vii) if the subject's postural stability is not within said normal range, staging an intervention with respect to the subject.