referring to the drawings and initially to fig1 there is shown an apparatus for evaluating manual dexterity and object manipulation in humans indicated generally by the reference numeral 1 . the apparatus 1 comprises a hand held unit 2 and a control unit 3 . the control unit 3 is connected to the hand held unit 2 by electrical cable 4 . the hand held unit 2 comprises a pair of handles 5 and a joining member 6 . the handle 5 on the left hand side of the unit 2 has parallel grip surfaces 7 and the handle 5 on the right hand side of the hand held unit 2 has tapered grip surfaces 8 . transducers ( not shown ) are fitted to the grip surfaces 7 and 8 and additionally on or about the connection between the handles 5 and the joining member 6 . straight and curved arrows indicate examples of directions of forces and torques measured by fitted transducers . the control unit 3 comprises a computer 9 having a monitor 10 and speakers ( not shown ). referring now to fig2 there is shown a handle 5 of the hand held unit 2 . the grip surfaces 12 of the handle 5 are provided by longitudinally extending hemi - cylindrical ridges 11 . the ridges 11 are co - axial with the longitudinal axis of the joining member 6 when the handle 5 is mounted on said member 6 . the handle 5 is pinched on grip surfaces 12 between a thumb 13 and an index finger 14 of a subject &# 39 ; s hand 15 . the distance between grip surfaces 12 is typically between 10 mm and 40 mm . in fig3 there is shown a hand held unit 31 having a pair of handles 32 , a joining member 33 and a display screen 34 . the handles 32 have parallel grip surfaces 35 and the display screen 34 is mounted on the joining member 33 of the hand held unit 31 . referring now to fig4 there is shown a hand held unit 41 having a pair of handles 42 and a joining member 43 . the joining member 43 has two sections 44 and 45 and a coupling 46 mounted between the two sections 44 and 45 . the two sections 44 , 45 are inter - engaged to allow compression and extension of the hand held unit 41 about the longitudinal axis of the joining member 43 . the coupling 46 is designed to oppose the extension and compression of the hand held unit 41 and is also designed to allow a momentary removal of the opposing force and subsequent latching . fig5 shows a further embodiment of the invention wherein a hand held unit 51 has a pair of handles 52 , a joining member 53 , a display screen 54 and a shield 55 . in this example , the shield 55 is mounted between the hand held unit 51 and the display screen 54 in order to prevent a subject from seeing the shape of the handles 52 on the hand held unit 51 . fig6 to 9 each show a hand held unit indicated generally by the reference numeral 61 . the units 61 each have a joining member 62 and a pair of handles with various geometries . fig6 shows a hand held unit 61 with both the left handle and the right handle having parallel grip surfaces 64 . fig7 shows a hand held unit 61 with the left handle having grip surfaces 74 tapered at 30 ° to the horizontal and the right handle having parallel grip surfaces 75 . fig8 shows a hand held unit 61 with the right handle having grip surfaces 84 tapered at 30 ° to the horizontal and the left handle having parallel grip surfaces 85 . fig9 shows a hand held unit 61 with both the left handle and the right handle having grip surfaces 94 tapered at an angle of 30 ° to the horizontal . referring to the drawings and now to fig1 there is shown a representative graph of pull force on the x - axis versus grip force on the y - axis . line 101 represents a handle with parallel grip surfaces and line 102 represents a handle with tapered grip surfaces . finally , fig1 shows one possible visual display generated by the computer 9 when configured by the control program and output via a display screen 111 . an image of an electronic stick - man 112 holding a hand held unit 113 demonstrates what a subject is required to do . a visual display of a scale 114 is marked with vertical lines 115 and displays force . this scale 114 shows a subject the zero force marker 116 and the target force marker 117 by highlighting the relevant line 115 along the scale 114 . the dot 118 shows the current force . a target for maximum pull force 119 is located at the right end of the scale . in use , a subject or an examiner starts a test by striking any key on a keyboard of the computer 9 . this initiates the demonstration on the display screen 34 , 54 , 111 or initiates an audible demonstration . the audible demonstration includes a list of verbal instructions output via speakers connected to the computer 9 and is useful for a subject with impaired vision or blindness . when a visual demonstration is used , a pull or push prompt is displayed on the computer screen 34 , 35 , 111 and in response the stick man 112 stretches or compresses the electronic hand held unit 113 in order to show a subject the correct action to take in response to a specific prompt . within the same display screen 34 , 54 , 111 , the scale 114 shows the effect of the stick man 112 stretching or compressing the electronic units 113 by simultaneously moving the current force marker 118 between the zero force marker 116 and the target force marker 117 . once a subject is satisfied with the demonstration , they can proceed with the test by striking any key on the keyboard of the computer 9 . the hand held unit 2 , 31 , 41 , 51 , 61 is held by a subject by the grip surfaces 7 , 8 , 12 , 35 , 64 , 74 , 75 , 84 , 85 and 94 between digits of their hands . the subject then follows a list of prompts displayed on the display screen 34 , 54 , 111 or a list of verbal instructions output via speakers which are connected to the computer 9 . the display also includes the scale 114 which shows the effect of the subject stretching or compressing the hand held unit 2 , 31 , 41 , 51 , 61 by simultaneously moving the current force marker 118 between the zero force marker 116 and the target force marker 117 . the visual display may also include a prompt for the subject to maintain the target force for a predetermined period of time . once the target force has been attained , the computer 9 monitors the quality of the data received from the transducers ( not shown ) comparing it with control data . the computer 9 outputs a signal to the display screen 34 , 54 , 111 informing the subject to release the applied force if the data received is acceptable . alternatively , these prompts can be output via the speakers . the subject follows the audible or visual instructions until completion of the test . in order to prevent the subject using their vision to alter grip - load force co - ordination a shield 55 is placed between the hand held unit 2 , 31 , 41 , 51 , 61 and the subject for certain parts of the test . the hand held unit 2 , 31 , 41 , 51 , 61 is grasped bimanually and manipulated according to a pre - defined ( standardized ) protocol . an automated test protocol combined with automated data analysis allows efficient assessment of the subject &# 39 ; s manual status based on the data obtained from the force / torque transducers of units 2 , 31 , 41 , 51 or 61 . there now follows a detailed description of an example of a test protocol and data analysis . 1 . the subject familiarizes themselves with the apparatus 1 by doing a few ramp - and - hold pull forces and push forces to certain target forces ( e . g . + 4 newtons ( n ), − 4n ). before the action , the task is demonstrated on the display screen 34 , 54 , 111 by the icon stickman 112 performing the task . the subject &# 39 ; s task is to copy the demonstration . 2 . the subject performs a series of ramp - and - hold pull forces of different magnitudes according to the predetermined protocol ( e . g ., 1 , 4 , 2 , 8 newtons ( n )) three times followed by a series of push forces ( e . g . 4 , 4 , 4 n ). these tests are repeated for the different geometric configurations of the handles , shown in the drawings . quality control of the data occurs on - line and is dependent upon the subject maintaining the target push / pull force ( within a predefined tolerance ) for two seconds . in response to successful completion of the task by the subject , the target marker 118 on the display screen 34 , 54 , 111 is turned off . an audible signal indicating that this section of the test has been successfully completed could also be generated . analysis : the computer 9 configured by the control program automatically reads and stores the measured variables during a 2 second epoch while the subject maintains the target force . the coordination between grip force and the load at each hand ( and at the level of the individual &# 39 ; s digits ) is automatically analyzed . the subject &# 39 ; s capacity to scale the grip force with the load force and to adjust the balance between the grip force and load with changes in geometry of grip surfaces 7 , 8 , 12 , 35 , 64 , 74 , 75 , 84 , 85 and 94 is assessed for each hand . 3 . the subject makes sinusoidal pull forces at different frequencies . the amplitude ( e . g . 4n with approximately +/− 20 % tolerance ) is guided by the display screen 34 , 54 , 111 . a metronome sound guides the pace . the frequency range to be explored is 0 . 5 - 3 hz . again , quality control of the data occurs on - line . before changing to the next frequency , a certain number of cycles with an accepted amplitude and frequency are collected . ( the grip surfaces 7 , 12 , 35 , 64 , 75 , 85 are parallel on all handles .) analysis : the phase between grip force and the load is analysed ; normally there is no phase lag , which indicates that the grip force predicts adequately the self - generated load forces ( for grip stability ). the depth of grip force modulation is assessed as a function of frequency ; normally there is a steep decrease in the modulation with increased frequency , starting at about 1 . 5 - 2 hz . 4 . the subject makes sinusoidal pull - push forces at different frequencies ( 0 . 5 - 1 . 5 hz ) and at constant push - pull amplitudes ( e . g . − 4n ( push ) to + 4n ( pull )). ( the grip surfaces 7 , 12 , 35 , 64 , 75 , 85 are parallel on all handles .) in this task , the absolute value of the tangential load increases and decreases with twice the frequency of the sinusoidal load . normal subjects respond to this “ frequency doubling ” by generating two grip force increases per load cycle i . e . the grip force predicts the actual load although it does not match the frequency of the load cycles . analysis : the phase between grip force and the absolute value of the load and the depth of grip force modulation is analyzed ( cf . above ). this analysis assesses the subject &# 39 ; s ability to generalize the directional consequences of self - generated fingertip loads in terms of grip force requirements ( and thus grip force predictions ). 5 . the subject produces their maximum bimanual pull force . normally , a subject &# 39 ; s right hand is stronger than their left — yet subjects never allow the left hand to slip off the unit 2 , 31 , 41 , 51 , 61 during bimanual operations because the knowledge of their musculoskeletal system is incorporated as a control constraint in the neural networks of the brain . to assess asymmetries of force generating capacity by the two hands , the maximum grip force is assessed for each hand separately . 6 . finally , by imposing the transient load impact at a few unpredictable points during the test protocol numbered 2 ( see above ) the reflex status of the reactive grip force control of the two hands is assessed . normally , with two healthy hands , the load impact triggers automatic grip force increases at both hands with similar amplitudes and onset latencies . 1 . a weakened or lost capacity of the impaired hand to adjust the balance between the grip forces and the load forces in response to changes in geometry of the grip surfaces 7 , 8 , 12 , 35 , 64 , 74 , 75 , 84 , 85 and 94 . 2 . with sensory impairment of one hand , the accompanying healthy hand also controls the grip - load force coordination of the numb hand . likewise , the healthy hand uses strategies that reflect constraints imposed by the impaired hand during bimanual actions . 3 . the impaired hand generates increased internal forces upon the hand held unit 2 , 31 , 41 , 51 or 61 due to asymmetric grip force applications at the opposing grip surfaces 7 , 8 , 12 , 35 , 64 , 74 , 75 , 84 , 85 and 94 . this causes unnecessary / uneconomical load of the grasp . 1 . a temporal mismatch between the grip and load force changes and is revealed during the test with sinusoidal load changes . 2 . a reduced modulation of grip forces with load force changes compared to healthy conditions . one or several of the following items revealed impaired reactive grip force control : ( 1 ) no response to the transient load impact . ( 2 ) a prolonged onset latency of the reactive grip force increases . ( 3 ) smaller amplitudes than normal of the reactive grip force increases . with unilateral impairments , asymmetries between the hands in these respects are important . with impaired proprioceptive knowledge concerning one diseased hand the healthy contralateral hand shows incompetence in controlling its actions based on constraints imposed by the diseased hand during bimanual tasks . impaired proprioceptive knowledge is assessed in the present protocol by an inability of the healthy hand to limit the application of pull force to the hand - held unit as to match the capacity of the companion diseased hand . this is critically revealed during the test of maximum voluntary bimanual pull along the hand - held unit 2 , 31 , 41 , 51 , 61 . with proprioceptive knowledge the hand - held unit 2 , 31 , 41 , 51 , 61 does not slip at the diseased hand , whereas with loss of proprioceptive knowledge the unit 2 , 31 , 41 , 51 , 61 slips from the subjects grip .
an apparatus for evaluating manual dexterity in humans and in particular to an apparatus for evaluating the manual dexterity of humans with an impaired nervous system and / or musculoskeletal system is provided . manual dexterity and object manipulation is a three dimensional activity and any attempt to evaluate it should take this fact into consideration . a method and apparatus for evaluating manual dexterity and object manipulation in humans comprises a structure to receive a hand and a unit to measure and record omnidirectional forces applied to the hand . additionally , a connection structure to connect two hands is provided , wherein each hand is capable of transmitting a force onto the other hand via the connection structure . the apparatus may also include a unit to measure and record forces applied by each hand .