Dynamic physiological function testing apparatus and method

A cart for measuring dynamic physiological forces has a plurality of wheels, a handle, and a brake attached to at least one of the wheels for controlling the amount of force required to move the cart. A directional sensor indicates the direction in which the cart is moving, and a velocity sensor indicates the velocity of the cart. Grip sensors on the handle detect the gripping force applied to the handle. A force sensor between the handle and the cart indicates the amount of force applied to the handle to move the cart. Data loggers connected to sensors record indications from the sensors. A computer is connected to the data loggers for accepting the recorded indications. A method of using the cart for measuring dynamic muscle function includes presetting the brake for a known resistance to movement, having a test subject move the cart along a predetermined course, measuring the force required to move the cart, measuring the velocity of movement of the cart, and measuring the direction of the cart.

BACKGROUND OF THE INVENTION 
This invention relates to apparatus and methods for testing dynamic 
physiological functions. 
Various methods and devices are used to determine a person's physical 
strength and ability to perform certain physical tasks. Such methods and 
devices are used in preemployment testing to determine a person's ability 
to perform certain employment related tasks, in injury evaluation related 
to workman's compensation claims, in rehabilitation exercise, in general 
exercise and physical conditioning, and in general injury evaluation. For 
example, Baltimore Therapeutic Equipment Co., Baltimore, Md., describes a 
stationery device and method which is said to effectively simulate the 
actual job task, or use muscle groups affected by injury, and record the 
subject's performance. 
SUMMARY OF THE INVENTION 
In general, in various aspects, this invention features a cart for 
measuring dynamic physiological forces. The cart includes a movable 
structure having wheels and a handle. A brake is attached to the front 
axle for controlling the amount of force required to move the cart. The 
related aspects include a directional sensor which indicates the direction 
in which the cart is moving; a velocity sensor which indicates the 
velocity of the cart; grip sensors on the handle to detect the gripping 
forces applied to the handle; and a force sensor between the handle and 
the cart which indicates the amount of force applied to the handle to move 
the cart. 
In preferred embodiments of these aspects, the grip sensors are a pair of 
elongated beams spaced from and substantially parallel to the handle with 
a strain gauge attached between one end of the beam and the handle; the 
brake has a rotary portion connected to the axle and an adjacent fixed 
portion connected to the cart for applying a variable resistance to the 
free rotation of the rotary portion (one such brake is an electromagnetic 
brake responsive to the amount of electrical energy supplied to it); and 
the directional sensor includes a wheel contacting the surface on which 
the cart is moved connected by an angled member to the shaft of a 
cart-mounted potentiometer. 
Other preferred embodiments further include data loggers connected to at 
least one, most preferably each, of the force, directional, velocity, and 
grip sensors for recording separately the indications from each of the 
sensors as functions of time; and a computer is connected to the data 
loggers for accepting the recorded indications. 
In general, in various related aspects, the invention features a method of 
using the above-described cart for measuring dynamic muscle function. 
These methods include combinations of the following steps: presetting the 
brake for a known resistance to movement; having a test subject move the 
cart along a predetermined course; measuring the force required to move 
the cart, including individual grip force and overall push; measuring the 
velocity of movement of the cart; and measuring the direction of the cart. 
Moving the cart includes pushing, pulling and pushing while turning. 
In another related aspect, the invention features a method which includes 
measuring the test subject for maximal isometric strength, and presetting 
the above-described resistance of the brake to some fraction of the 
measured maximal isometric strength. Preferably, the fraction is set 
between 20% and 60% of the measured maximal isometric strength. 
In yet another related aspect, the method features a method which includes 
calculating one or more of the dynamic physiological forces required to 
move the cart from one or more of the force, velocity, and directional 
measurements; comparing the calculated dynamic physiological forces with 
prior calculations of the forces from the same or other test subjects; and 
determining the level of physiological function of said test subject from 
said comparison. 
The invention provides a clinical tool and therapy test apparatus for 
measuring forces characteristic of dynamic physiological functions. The 
tool is stable, has variable mobility, is maneuverable, and is adaptable 
to anthropomorphic measurements of human functions. It accurately 
simulates actual pushing, pulling and turning tasks where a force is 
exerted against a constant or even a variable resistance. The mobility of 
the tool requires the user to use several large muscle groups rather than 
smaller isolated muscle groups; thus, providing a better estimate of 
overall muscle function than prior isometric or stationary tests. 
Measurements are not limited to incremental mass units, and fatigue is 
reduced since repeated trials are unnecessary to determine the maximum 
force the subject is able to exert against a given resistance.

STRUCTURE 
Referring to FIGS. 1 and 2, a four-wheeled cart 10 for simulating physical 
work is provided with a horizontal planar base 12 attached substantially 
perpendicular to a vertical frame 14. Frame 14 is formed from two 
substantially parallel hollow vertical tubes 16, 18, each having a 
substantially square cross-section, joined to opposite ends of a 
horizontal lower member 20. A horizontal upper member 22 is attached to 
two substantially parallel vertical tubes 23, 25 each having a 
substantially square cross-section sized to telescopically fit into 
vertical tubes 16, 18 respectively. The telescoping vertical tubes are 
secured by pins 27 which pass through aligned holes 29 in each of the 
telescoping tube pairs. Vertically distributed holes in the vertical tubes 
allow the height of the upper member to be varied by simply pinning those 
holes which align at the desired height. Upper :member 22 has a handle 28 
disposed substantially parallel to the upper member and attached by 
parallel handle guides 30 which slidably ride on ball bushings 33 
(commercially available from Thomson, Thomson, Conn., part number 
A-101824), mounted in upper member apertures 31. The ball bushings assure 
that the handle guides slide freely with respect to the upper member, as 
well as the rest of the cart. 
Cart base 12 is supported on one end by horizontal lower member 20, and 
along its length by a central support beam 48 of substantially rectangular 
cross-section. One end of central support beam 48 is welded to horizontal 
lower member 20, and the other end is supported by a front two-wheel 
assembly 32. Horizontal lower member 20 has a rear wheels 24, 26 mounted 
on each end. The rear wheels are free wheeling and mounted on a swivel 
allowing 360 degrees of directional rotation. A directional wheel assembly 
60 is mounted on horizontal lower member 20 centered between the two rear 
wheels to indicate the direction of the cart, as discussed below. 
An equipment shelf 34 is disposed horizontally and parallel to base 12 and 
is supported on one end by vertical members 16, 18, and on the other end 
by two vertical shelf supports 36 (one shown) between the shelf and the 
base. 
Referring to FIG. 3, front wheel assembly 32 has two wheels 40 fixedly 
mounted on each end of an axle 42 which is rotatably mounted through two 
pillow blocks 44 supported by pillow block supports 46. Pillow block 
supports 46 are rigidly attached to support member 48 connected to the 
bottom surface of cart base 12. Axle 42 also passes through an 
electromagnetic brake assembly 50 disposed between pillow blocks 44. A 
brake mounting plate 52 perpendicularly extends from central support beam 
48 to rigidly support and prevent rotation of the fixed portion of the 
brake assembly. 
Electromagnetic brake assembly 50 (commercially available from Electroid, 
Springfield, N.J., part number EC42B-12) has a rotary brake portion 56 
fixedly attached to axle 42, and an adjacent fixed brake portion 54 
fixedly attached to brake mounting plate 52. Electrical current applied to 
the fixed brake portion creates a magnetic field which inhibits the free 
rotation of the adjacent rotary brake portion attached to the axle, and 
thereby creates resistance to the rotation of front wheels 40. Adjustment 
of the electrical current applied to the fixed brake portion determines 
the amount of force required to rotate the front wheels, and thus 
determines the amount of force required to push the cart. 
A tachometer 58 (commercially available from Electromatic Equipment Co., 
Cedarhurst, N.Y., part number DT 5FV #73028807) is mounted adjacent to one 
of front wheels 40 by means of a tachometer sensor mounting block 59 
attached to base 12. Tachometer 58 senses the rotation of the adjacent 
wheel to produce an electrical output indicative of the velocity of the 
cart. 
Referring to FIG. 4, direction indicator wheel assembly 60 has a wheel 62 
rotatably mounted in a wheel mount 64 attached to one end 65 of an angled 
member 66. The other end 67 of angled member 66 is accepted in a bore 68 
in one end of a cylindrical support member 70 coaxial with the long axis 
72 of the support member. End 67 of angled member 66 passes through a 
spring 74 which is captured between the closed end 76 of the bore and a 
spring pin 78 extending perpendicularly from the angled member. Spring pin 
78 rides in a guide notch 80 adjacent to bore 68 to restrict the travel of 
angled member 66 along long axis 72 and prevent the angled member from 
rotating about the long axis relative to the cylindrical support member, 
thus causing both angled member 66 and cylindrical support member 70 to 
rotate in unison. 
The other end of cylindrical support member 70 has a bore 71 coaxial with 
long axis 72 which accommodates one end of a potentiometer shaft 80. The 
potentiometer shaft is fixedly mounted in the bore by two sets of opposing 
set screws 84 threadably engaged with the cylindrical support member so 
the potentiometer shaft and the cylindrical support member rotate in 
unison about the long axis. The other end of the potentiometer shaft is 
connected to a potentiometer 86 (commercially available from 
Allen-Bradley, Fairfield, N.J., part number JA1N200P-5K) which is fixedly 
mounted in potentiometer block 88 attached to horizontal lower member 20. 
The potentiometer produces an electrical resistance indicative of the 
relative rotational position of the cylindrical support member to the cart 
base. The extent of rotation of the cylindrical support member is limited 
to approximately 180 degrees by a swivel stop 92 extending perpendicularly 
from the support member. Swivel stop 92 contacts travel stops 90 which 
extend from the potentiometer block and positioned at the rotational 
limits, and is thereby prevented from further rotation in each direction. 
Angled member 66 is bent at an angle of approximately 30 degrees with 
respect to long axis 72 which is designed to cause wheel 62 to trail in 
the direction the cart is being turned. This in turn rotates cylindrical 
support member 70 relative to cart base 12 causing potentiometer 86 to 
produce a resistance value indicative of the direction of the cart. Spring 
74 urges the wheel against the surface on which it is riding to help it 
track the surface, especially where the surface is rough, and reduces 
erroneous directional indications from the potentiometer. 
Referring to FIG. 5, handle 28 incorporates grip pressure sensors 100 on 
opposing ends of the handle between the handle and upper horizontal member 
22. Each grip mount 100 has an elastic measurement beam 102 disposed 
substantially parallel to the handle. The beam has one end free and the 
other end attached to a mounting block 104 connected to the handle. A 
strain gauge 103 (commercially available from Baldwin Lyman Hamilton, 
Canton, Mass., FAE-12-25-56) is mounted on the surface of each elastic 
beam 102 so that simultaneous gripping of the handle and the elastic beam 
causes the strain gauge to produce an electrical signal indicative of the 
gripping force applied (i.e., the strain gauge measures the bending of the 
beam which is proportional to the gripping force applied to bend it). 
Handle 28 also incorporates a load cell 106 (commercially available from 
Baldwin Lyman Hamilton, Canton, Mass., part number 461630) attached 
between the handle and upper horizontal member 22. Since parallel handle 
guides 30 are slidably engaged with the upper horizontal member, as 
described with reference to FIGS. 1 and 2, all pushing and pulling forces 
applied to the handle to move the cart are transferred to the upper 
horizontal member through the load cell. The electronic sensor within the 
load cell produces an electrical signal indicative of the pushing or 
pulling force applied to the handle and transferred to the cart. 
Additionally, the electrical signal from the load cell is connected to a 
direct reading digital millivolt meter 107 (commercially available from 
Simpson, Norwood, Mass., part number 24101) attached to horizontal member 
22 to provide visual readback of the pushing and pulling forces applied to 
the handle. 
Referring to FIG. 6, a control panel 150 is attached to vertical member 18 
(see FIG. 1) to provide a user controllable interface to several of the 
electrical devices on the cart. A rheostat 152 (commercially available 
from Allen-Bradley, Fairfield, N.J., part number 1712,) electrically 
connected to the fixed portion 54 of the electromagnetic brake (FIG. 3) 
allows the user to vary the electrical current supplied to the brake, and 
thus set the resistive forces encountered while pushing the cart. A 
battery switch 154 supplies power to the electrical devices on the cart 
from an onboard battery, discussed below. meter switch 156 is electrically 
connected to digital load meter 107 to turn the meter on and off. A grip 
switch 158 is electrically connected to the grip pressure sensors 100 to 
activate or deactivate them. 
Referring again to FIG. 2 a rechargeable battery 200 (commercially 
available from Sears Roebuck and Company, Chicago, Ill., part number 27F) 
supplies power to various electrical devices on the cart. A battery 
charger 202 (commercially available from Sear Roebuck and Company, part 
number 2V-20A), is connected to the battery and may be plugged into 
electrical mains to recharge the battery between cart uses. A direct 
current to alternating current (DC-AC) invertor 204 (commercially 
available from Powerverter, Chicago, Ill., TRIPP LITE, Model-550) is 
connected to the battery and supplies alternating current to those 
electrical devices on the cart requiring it. 
A DC powered data logger 206 (commercially available from Hewlett Packard, 
Palo Alto, Calif., part number 160B) disposed on equipment shelf 34 
accepts electrical signals from the various sensors positioned about the 
cart, specifically, cart velocity tachometer 58, cart direction 
potentiometer 86, both grip sensor strain gauges 104, and push-pull force 
load cell 106. Each signal is applied to a separate data logger input 
channel which is sampled by the data logger approximately once a second 
and collected in the data logger's internal memory. The collected data are 
then downloaded from the data logger to a personal computer 208 through an 
RS232 data link as an ASCII file. The personal computer contains 
"standard" software programs (e.g., Lotus 123, data bases, e.g., DBASE IV, 
for processing, analyzing, comparing and reporting the results of the test 
performed. 
Operation 
Before a test is run and a set of measurements gathered, the cart must be 
configured for the individual subject and the type of test desired. The 
height of handle 28 (FIG. 1) is adjusted using pins 27 to attain the 
desired anthropomorphic conditions (i.e., to simulate job performance 
based on the physical characteristics of the job in relation to the 
physical characteristics of the subject). Battery power switch 154 (FIG. 
6) is turned on to activate the onboard electronic equipment. 
Electromagnetic brake rheostat 152 is adjusted to provide the desired cart 
push and pull resistance. Data logger 206 is activated and the test is 
begun. 
Referring to FIG. 7, a subject 300 of the test grips the handle and pushes 
or pulls the cart through a predetermined sequence of maneuvers over 
straight, inclined, and curved paths along a test track 302. The data 
logger accumulates data samples from the various sensors around the cart 
representing push and pull forces, cart velocity, cart direction and 
handle grip forces. The data logger allows the test operator to mark each 
set of data so that it may be identified and correlated with the test 
conditions incident to that particular data set (i.e., handle height, 
brake resistance, track conditions, maneuver type). After a predetermined 
set of maneuvers is run the data are transferred to the personal computer 
for further analysis. 
Testing Methods 
This invention allows dynamic testing of subjects to quantitatively 
evaluate extremity functions. In particular the cart of this invention 
simultaneously measures dynamic forces characteristic of extremity 
function, including push and pull forces required to move the cart along 
straight paths, turning forces required to move the cart around a curve, 
cart acceleration forces, cart jerk forces (rate of change of 
acceleration), cart velocity, and grip strength. 
A variety of independent variables may be input into the test through 
manipulation of the cart brake parameters and the inclination and path of 
the track. For instance, after measuring a subject's maximal isometric 
effort through traditional means, the cart brake resistance and track 
conditions (i.e., inclination, curves, surface texture) may be adjusted to 
test the subject at some percentage of the measured maximal isometric 
effort (i.e., 25% or 50%). Testing at submaximal isometric effort levels 
help to prevent injury to the subject and make it more difficult for the 
subject to feign a disability. Additionally, the handle can be adjusted to 
simulate a variety of anthropomorphic conditions. 
The various sensors on the cart collect a variety of measurements 
characteristic of a subject's physical ability. These measurements are 
gathered by the data logger and sent to the computer for further analysis 
including comparison of the measurements with normal and abnormal control 
groups, and with the subject's past performance. The measurements provide 
data for calculating a set of dependent variables including peak force, 
average force, velocity, displacement, acceleration, jerk (rate of change 
of acceleration), and endurance for any particular task. 
Of particular interest is the determination of the sincerity of effort of 
the subject during exercise, which may be relevant to evaluating workman's 
compensation and other injury claims. The measurement of grip strength 
during pushing, pulling and turning can be indicative of the sincerity of 
effort since it is difficult for the subject to control. Additionally, it 
may not be apparent to the subject that grip strength measurements are 
being recorded, and thus the subject may not think, or know, to adjust his 
grip to be consistent with the remainder of the test results. 
A typical test protocol involves the subject executing a sequence of 
maneuvers with the cart around a test track. The test subject is first 
measured for isometric strength and the brake on the cart is set to 
provide a pushing resistance of approximately 25% of the maximal isometric 
strength measured From a start point the subject pushes the cart along a 
predetermined path including a straight portion and a curved portion. The 
subject then pulls the cart back along a predetermined straight path The 
brake on the cart is then adjusted to provide a pushing resistance of 
approximately 50% of the maximal isometric strength measured. The subject 
then repeats the same pushing and pulling sequence. The subject is 
measured again for isometric strength and the above test is repeated using 
the new maximal isometric strength measurements. 
Other embodiments are within the following claims.