Measured variable resistance tiltboard

An apparatus for the objective analysis of human balance reactions involving a pivotable platform with selectively variable resistance to platform rotation which provides for instantaneous measurement of the resistance applied against platform movement at any time during a balance test. Two devices to accomplish the measurement of resistance include use of an exercise dynamometer and use of strain gauges.

FIELD OF THE INVENTION 
The present invention relates generally to evaluating and teaching human 
balance skill, and relates more specifically to a tiltboard having a 
selectively variable and instantaneously measured resistance to platform 
movement. 
DESCRIPTION OF THE PRIOR ART 
Balance boards have traditionally involved a platform upon which a subject 
stands or sits which will rock or rotate according to movement of the 
gravity line of the subject. Large gravity line displacements lead to 
rapid platform movement and relatively smaller gravity line movements 
result in less rapid or no platform movement. 
The "Variable Resistance Tiltboard", U.S. Pat. No. 4,548,289, provides 
resistance against platform rotation that can be adjusted to be relatively 
large, thus providing a stable surface, or the resistance can be adjusted 
to be relatively small so as to provide a less stable surface. Stated in 
other terms, by selecting the degree of resistance to be applied against 
platform rotation, the user of this tiltboard determines the platform 
angular velocity which will accompany a given subject gravity line 
placement on one side of the platform's pivotal axis. 
The changing of the relative stability of the platform of the variable 
resistance tiltboard allows subjects of differing balance skill to 
practice maintaining stable posture at their given skill level. A greater 
degree of resistance to platform movement allows the subject more gravity 
line movement while remaining stable. The subject is aware of these 
changes in gravity line movement through sensations of muscle tension, 
joint motion, and skin pressure detection. The more steady platform allows 
the subject a greater degree of the above sensations while they are 
maintaining stable posture. The less stable platform will start to rotate 
and thereby provide a falling sensation detected with aid from the eyes 
and inner ears if a subject allows large gravity line movements. 
In a variable resistance tiltboard as described in U.S. Pat. No. 4,548,289 
the resistance to platform rotation is provided by a resistance element 
which has no associated means for instantaneously measuring the resistance 
that is applied against the platform. Therefore, although the user knows 
the platform angular velocity which will accompany a given subject gravity 
line placement, the user has no way of directly determining the resistance 
being applied against platform movement at any given time during the 
balance task. This resistance must be deduced by placing differential 
weight in foot pounds on one side of the platform axis of rotation and 
recording the resulting angular velocity at different resistance settings. 
These calibrations are compared to recorded platform angular velocities 
during subject use in order to calculate the differential weight in foot 
pounds on one side of the platform axis of rotation as the subject's 
gravity line moves. 
The above mentioned variable resistance tiltboard provides useful balance 
practice. However, the requirement that the resistance applied against 
platform rotation as the subject shifts their weight be deduced from 
observed platform angular velocities causes delays and inaccuracies. The 
angular velocity must be accurately observed and recorded, and then it 
must be compared to a calibration chart. After completing this conversion 
process, the tester has obtained only one resistance measurement which 
applies only to the time period over which the angular velocity was 
observed. This conversion process presents a barrier to quick, efficient, 
and accurate measurement of the many changes in resistance as the subject 
shifts their gravity line during a balance task. Such a conversion process 
also removes the tester from the immediate and precise data that can be 
used to give the subject prompt feedback on their performance and can be 
used to observe subtle changes in performance throughout a balance task. A 
variable resistance tilt-board is needed which has the ability to 
instantaneously measure and record resistance being applied against 
platform movement such that a resistance-over-time graph can be generated 
to aid in the analysis of balance skill. 
SUMMARY OF THE INVENTION 
The present invention provides a variable resistance tiltboard that is 
designed to satisfy the aforementioned need. The invention embodies a 
tiltboard whose rotation about its axis is opposed by a resistance which 
is measured instantaneously. The present invention provides a force 
measurement apparatus that operates in conjunction with the resistance 
element such that the instantaneous force imparted by the resistance 
element against platform movement can be determined and recorded. 
A preferred embodiment of this device involves using an exercise 
dynamometer to resist platform rotation. This can be accomplished by 
clamping the resistance arm of a dynamometer to a rod which is in turn 
clamped to the platform on one side of the pivot. Adjusting the 
dynamometer control to provide comparatively large resistance to movement 
of the dynamometer lever arm provides a relatively stable platform. 
Likewise, adjusting the dynamometer control to provide a comparatively 
small resistance against movement of the dynamometer lever arm will result 
in a relatively unstable platform. In both cases the force of the 
resistance applied against platform rotation is measured by the 
dynamometer. A recorder or computer that interfaces with the dynamometer 
can be used to record the exact resistance throughout the period of the 
balance task. 
Another preferred embodiment that meets the need for instantaneous 
measurement of the resistance that is applied against platform rotation 
involves the use of a viscous damping device similar to the resistance 
element in referenced U.S. Pat. No. 4,548,289. In this embodiment, strain 
gauges can be attached to a rod which connects the damping device to the 
platform. This strain gauge placement allows instantaneous measurement of 
the resistance being provided through the connecting rod. In this case the 
connecting rod undergoes stress and deformation in proportion with the 
given level of resistance imparted to it by the damping device. This 
stress, and the corresponding resistance, can be recorded by a computer 
associated with the strain gauge circuitry to generate a 
resistance-over-time graph for the period of a balance test. 
Accordingly, it is an object of the present invention to provide an 
improved variable resistance tiltboard for the objective analysis of human 
balance reactions. 
It is another object of the present invention to provide an improved 
variable resistance tiltboard which provides instantaneous measurement of 
the resistance applied against platform rotation. 
It is another object of the present invention to provide an improved 
variable resistance tiltboard which provides ease of recording the 
resistance applied against platform rotation as that resistance varies 
during a subject balance task.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings in which like numbers indicate like elements 
in both drawings, FIG. 1 shows a measured variable resistance tiltboard 10 
constructed in accordance with the present invention. The measured 
variable resistance tiltboard 10 includes a platform 6 pivotably supported 
above a base 5 and a resistive device in the form of a conventional 
automotive shock absorber 7, which is attached to both support base 5 and 
platform 6. 
The tiltboard 10 further comprises a support rod 9 which is attached to 
base 5. Brackets 11, which contain bearings 12, are mounted on the bottom 
of platform 6 such that support rod 9 passes through the bearings 12 and 
allows rotation of platform 6 relative to base 5 about the axis described 
by support rod 9. 
In FIG. 1 the shock absorber 7 has upper and lower connecting bolts 13U and 
13L passing through upper and lower shock absorber eyelets 14U and 14L. 
Lower connecting bolt 13L is parallel to the support rod 9 and is attached 
to lower sliding rail 15L. Upper connecting bolt 13U is perpendicular to 
support rod 9 and is attached to upper sliding collar 16U. Upper and lower 
sliding collars 16U and 16L can be moved along upper and lower sliding 
rails 15U and 15L to be positioned differing distances along an axis which 
is perpendicular to the axis of rotation of platform 6. Upper and lower 
lock keys 17U and 17L may be tightened at any given distance from support 
rod 9 to hold upper and lower sliding collars 16U and 16L at the selected 
distances from the support rod 9. 
It will be understood that movement of upper and lower sliding collars 16U 
and 16L will cause a corresponding movement of shock absorber 7 along the 
upper and lower sliding rails 15U and 15L and along the axis that is 
perpendicular to support rod 9. This differential positioning of shock 
absorber 7 will allow the resistance provided by shock absorber 7 to be 
expressed through different lever arms and therefore apply more or less 
resistance against platform 6 movement. 
Upper sliding collar 16U has two collar extensions 18 which are in planes 
parallel to the axis described by support rod 9. Upper connecting bolt 13U 
is attached to collar extensions 18 at both ends. Upper and lower strain 
gauges 21U and 21L are affixed to top and bottom of upper connecting bolt 
13U with collar extensions 18. 
It will be understood that application of resistance against platform 6 by 
shock absorber 7 will create stress and deformation of upper connecting 
bolt 13U. Resistance applied by the shock absorber 7 to platform 6 as the 
shock absorber 7 is shortening will deform upper connecting bolt 13U such 
that its middle is bent upward. Conversely, resistance applied by the 
shock absorber 7 to platform 6 as the shock absorber 7 is lengthening will 
deform upper connecting bolt 13U such that its middle will be bent 
downward. The upward or downward bending of upper connecting bolt 13U will 
result in deformation of strain gauges 21U and 21L. Such strain gauge 
deformation causes instantaneous changes in electrical inputs to strain 
gauge circuitry which can be used to measure the forces applied against 
platform 6 by shock absorber 7. 
FIG. 2 illustrates a second embodiment 10' employing a platform 6' which is 
pivotably supported above a base 5'. In this case there is a connecting 
rod 22' which has platform connecting rod clamps 24' and 28' on both ends. 
The lower of the connecting rod clamps 24' is tightened around platform 
6'. This second embodiment also includes a resistive exercise dynamometer 
8' which is comprised of a dynamometer base 25', a dynamometer module 26' 
which provides resistance and force measurement, and a dynamometer lever 
arm 27'. The higher of the connecting rod clamps 28' is tightened about 
dynamometer lever arm 27' thus allowing platform connecting rod 22' to 
require that platform 6' and dynamometer lever arm 27' move synchronously. 
Dynamometer 8' is positioned such that the axis of lever arm 27' rotation 
is perpendicular to the axis of platform 6' rotation. 
There are base connecting rods 23' which are attached to the dynamometer 
base 25' and to the tiltboard base 5' thus allowing no relative movement 
between dynamometer module 26' and tiltboard base 5'. Base connecting rods 
23' between dynamometer base 25' and tiltboard base 5' further ensure that 
all movement of platform 6' is associated with movement of dynamometer 
lever arm 27'. Platform connecting rod clamps 24' and 28' are attached to 
connecting rod 22' with clamp connecting bolts 29' and 30' which are 
perpendicular to the axis of rotation of platform 6' and which allow for 
rotation of platform connecting rod 22' about the axis of clamp connecting 
bolts 29' and 30'. 
Resistive exercise dynamometers are designed to allow a subject to push 
against the lever arm during active exercise while providing a measured 
resistance against such exercise. It will be understood that in this case 
rotational forces applied to the surface of the platform 6' will attempt 
to move platform connecting rod 22' as the platform 6' rotates, and that 
platform connecting rod 22' movement will attempt to rotate dynamometer 
lever arm about its axis of rotation. The dynamometer module 26' will 
provide an instantaneously measured resistance against the above mentioned 
rotation of platform 6'. The level of resistance applied against a given 
angular velocity of platform 6' can be altered by adjusting the resistance 
which dynamometer module 26' provides against the rotation of the 
dynamometer lever arm 27'. 
In both preferred embodiments 10 and 10', differential weight that is 
placed on one side of the pivotal axis of platform 6 and 6' will apply a 
rotational force to the platform. This rotational force will be opposed by 
a resistance which is proportional to and in the opposite direction of the 
rotational force. In both embodiments the resistance against the rotation 
of platform 6 and 6' can be adjusted to differing levels. In both 
embodiments the resistance applied against the rotation of platform 6 and 
6' is measured instantaneously and could be recorded as a 
resistance-over-time graph on associated recorders or computers. 
The preferred embodiments of the present invention have been disclosed by 
way of example and it will be apparent that various changes may be made in 
the form, construction, and arrangement of parts without departing from 
the spirit and scope of the appended claims.