Device for monitoring loads exerted on parts of the body

A device suitable for monitoring loads exerted on body parts features a measuring device (1) for acquiring a load parameter and an electronic unit (103). The latter possesses an input device (11) for the purpose of entering a load reference range, an analysis device (16), an indicating device (9, 15), a microprocessor (18) and a data memory (19). Fed into the latter are raw data, analysis data derived herefrom, and reference range data. The microprocessor (18), serves to calculate the relationship between momentary-loading and the reference range; the comparative values thus obtained are also stored. From the stored data, and if necessary temporal values, statistical values can be obtained and stored. Indicating device (9,15) permits data to be displayed and stored synchronously. Stored data relating to a load history can be retrieved by means of a retrieval device (11), which permits improved monitoring of loading activities.

The present invention relates to a device suitable for monitoring loading 
on body members such as the locomotor apparatus of the legs, such device 
having a measuring apparatus for measuring a load parameter and a portable 
cordless electronic unit fed with measurement data from the measuring 
apparatus and comprising an input device for inputting a load reference 
range. Included also are a computing device and an indicating device, 
which is used especially for signalling exceeding of the reference range. 
The partial removal of loads on the body members plays an important role in 
treating orthopaedic patients and accident victims. Contusions and 
compressive injuries to joints, broken bones, injuries to ligaments and 
tendons, inflammation of the locomotor apparatus as well as wearing down 
of such parts, or fitting with artificial joints etc. require in part week 
or month-long partial removal of loading on the affected body part. It is 
necessary in such cases, to maintain a precise partial load range in order 
to expedite healing; while excessive loading must be avoided, a minimum 
load level must be maintained so as to promote the mechanical stimulation 
required for an optimal healing process. Throughout treatment, the 
delimited load reference range can be increased. 
A device of the above-mentioned type is currently on the market and is 
described in the brochure "EDAR Insert with Pressure Sensor and Acoustic 
Feedback" from Harald Haberman Co., Orthopaedic-Technical apparatus, 
Frankfurt am Main. The conventional battery-driven apparatus possesses a 
measuring unit in the form of a sole-insert having a pressure sensor. The 
apparatus emits a low tone when the measured data lie inside the preset 
reference zone and a high tone whenever this reference zone is surpassed. 
The patient on crutches can, for example, be acoustically warned by the 
higher tone should he exert a load upon the locomotor apparatus that is 
greater than that prescribed by his physician; the deeper tone reassures 
him that the proper load is being exerted. 
The object of the present invention is the further development of the 
conventional load monitoring device described, with a view to better 
gauging the loading activity of the patient while permitting continuous 
long-term load monitoring. 
This object is satisfied by the proposed device in that: its data analysis 
unit features a microprocessor and a data storage area, to which data 
acquired by the measurement unit, as well as analysis data forming the 
basis of a load profile, can be fed; analysis data reference values for 
the establishment of a load reference range can be fed into the storage 
area from the input device; the momentary load is compared with the 
reference range and the thus obtained comparative data stored by the 
electronic unit with the aid of a microprocessor; and the indicating 
device is designed to function simultaneously with the storage function 
and/or the stored data relating to a load profile can be retrieved by 
means of a retrieval device. 
The proposed device produces for evaluation not only data relating to the 
measured load parameters, but also analysis data obtained from such raw 
data. This has the practical advantage that the loading history can be 
described more accurately and therefore a more relevant structuring of 
therapy sessions can be devised. A longer period of overloading, for 
example, necessitates a different compensatory decrease in the load than a 
shorter overload interval. On the other hand, the wealth of measurement 
data permits the acquisition of meaningful analytical data so that the 
data to be stored and, if necessary, to be compared with the appropriate 
analysis data reference range, can be reduced in relation to the amount of 
raw data obtained. This arrangement reduces both the requirement for 
memory space and the operating time of the microprocessor. 
The indicating device allows the patient to monitor his own loading 
activities and an acoustic signal can be employed to alert the patient 
should he exceed the load reference zone. This prevents a first feedback 
means. 
The data memory stores the raw data or a portion thereof selected by the 
microprocessor, together with the analysis data prepared in the 
microprocessor, as instantaneous or actual load values, so that the 
relationship of the latter to the appropriate reference zone can be 
established. The data memory can also store the comparative data obtained. 
By retrieving all or only selected portions of the stored data, especially 
the raw and analysis data, as well as the comparative data, the loading 
activities of the patient throughout a given period can be precisely 
documented. This arrangement, which permits the patient to monitor his 
activities during the evening so that he can modify his activities for the 
next few days, constitutes a second feedback system. If the physician is, 
upon first meeting the patient, able to review and evaluate his loading 
behaviour, the patient's chances of recovery are enhanced, therapy 
sessions can be effectively structured and precise forensic documentation 
can be undertaken. Depending on the loading behaviour of the patient, the 
loading reference range can be either raised somewhat or not changed at 
all during the following period. This arrangement represents a third 
feedback system. Thus a graduated feedback system is created, which abets 
optimal therapy structuring. 
The measured load parameter is preferably a load force. Suitable load 
parameters are also an area specific force, i.e. pressure, tensile, shear 
or bending force. The measured load parameter can also be represented as a 
kinetic quantity, more particularly the speed or acceleration of a body 
part, or another physical quantity. 
The choice and disposition of the proposed measurement device depends on 
its use. It is sometimes necessary, for example, to take pressure off the 
leg or portions thereof. It is advisable if in this case the proposed 
measurement device be positioned underneath the sole of the foot, whether 
in the form of an insertable sole, as a therapeutic shoe, or either inside 
or on the outside of a plaster cast--e.g. in the form of a plaster heel. 
This type of measuring device can be constructed from two essentially 
rigid plates, between which are situated three sensors. The presence of 
the latter affords at once even coverage and the assurance that the entire 
force will be acquired by the sensors. It is suggested that such plates 
form an insertable sole, whereby two sensors are arranged near the ball of 
the foot while the other is arranged in the zone of the heel. The sensors 
are capable of measuring force or pressure, and can be provided more 
particularly with strain gauge strips. Such insertable soles could be 
inexpensively produced as disposable articles suitable for one-time use. 
The proposed measuring device can also be fitted to body parts other than 
the foot, such as the palms of the hands of arthritis patients. The 
proposed device can also be connected to joints, bones, tendons and 
ligaments, and is suited for use with artificial joints, bones, tendons, 
ligaments and parts thereof. It is possible, in these cases, to implant 
one or more of the proposed devices in the body in order to measure local 
loading. One or more measuring devices can be positioned between the body 
and the surface of covers or undercovers, used when the patient sits or 
lies. 
It is furthermore possible to attach one or more measuring devices to an 
orthotic device or to a mechanical transportation aid, for example to knee 
braces, underarm crutch supports, axillary crutches or wheelchairs. In 
such cases, either the load exerted on a given body part, or a load 
passing by such parts, can be measured. 
The apparatus can also be applied to other points, for the purpose e.g. of 
avoiding long-term overloading damage caused in strenuous sports such as 
marathons. The device can also be used as a prophylactic against 
overloading where joints have already been affected (e.g., arthritis), and 
a worsening of the condition through overloading must be avoided. 
It is particularly advantageous if analysis data can be obtained from the 
measurement data with the aid of the microprocessor. This additional 
function can be assumed by the microprocessor without great difficulty. 
The data used for analysis is largely related to load conditions; included 
in particular are the maxima of the raw data related to each load cycle. A 
single load value is derived from the set of raw data processed during the 
load cycle by the microprocessor. 
It is especially advantageous if, in the course of constructing analysis 
data, the raw data can be correlated with temporal values. This 
arrangement provides a number of important additional load data. 
In particular, the relevant load times of individual load cycles can be 
used as analysis data. The load time is an important criterion. Should 
this time period extend beyond a load time reference range, the patient is 
obliged to alter his loading pattern. An acoustic alarm sounds when this 
reference range is exceeded. In this connection, the electronic unit, with 
the aid of the microprocessor, can serve to acquire raw data permitting 
the monitoring of the time delay occuring between the overstepping and the 
understepping of a threshold value. 
A further analysis parameter can be the impulse magnitudes of the load 
parameter-time-curve measured in each load cycle. This can be 
accomplished, in particular, in that the electronic unit, with the aid of 
the microprocessor, derives a surface integral from the temporally serial 
raw data. This function can also be assumed with ease by the 
microprocessor. The magnitude of the impulses represents both the 
mechanical and temporal load. 
It is also advantageous to employ as an analysis datum the number of load 
cycles occuring within a predetermined period. Where loads are applied to 
the leg, this parameter is expressed by the number of steps taken. The 
reference range feature enables the patient to establish an optimal 
reference range for the number of steps to be taken per day. Aside from 
the analysis data already mentioned i.e. measurement value maximum, load 
time, impulse magnetically and cycle count, mathematical functions derived 
from the latter, be these in conjunction with (or without) time values 
(such "as per day"), can be employed as analysis data. 
A preferred embodiment of the proposed device enables the electronic unit, 
with the aid of the microprocessor, to produce from the information stored 
in memory and in conjunction if necessary, with temporal values, 
statistical data that can appear on the indicator and/or, for the purpose 
of subsequent retrieval, are fed into memory. Such statistical values 
compress the load history of the patient and permit either patient or 
physician to rapidly review and evaluate such information. Such additional 
work can be handled by the microprocessor without much difficulty. 
For these purposes, it is of great help if the analysis data acquired 
during each load cycle are sorted into classes, of which one is assigned 
to the reference range, one or more are assigned to an upper range above 
the reference range and one or more are assigned to a lower range below 
the reference range. The array of data, thus segregated into classes, is 
much easier to review. 
It is particularly advantageous if a total of five classes be provided, 
wherein upper range and lower range are each divided into two sub-ranges. 
Segregation into five classes as opposed to three classes permits not only 
the determination of the frequency of a patient's either exceeding or 
falling short of the reference zone, but also the extent to which such 
exceeding or falling short has occurred. 
Thus can be obtained statistical values expressed as percentages, that 
describe the relationship between the analysis data count obtained in each 
class and the total number of load cycles over a given period of time. 
Such percentages clearly indicate the extent to which the patient has or 
has not adhered to the prescribed reference-range guidelines. This method 
of interpreting data is particularly suited to indicating raw data maxima, 
but can also be applied to other analysis data. 
Another embodiment permits the maxima of raw data obtained in individual 
load cycles occuring in a predetermined period to be sorted into load 
categories and the relevant mean values of the analysis data to be used as 
statistical values. This arrangement permits certain analysis data such as 
load times or impulse magnitudes to be compared to maximum raw data 
values, which opens up further avenues of interpretation. 
It is also advantageous if statistical values such as mean analysis data 
values from all of the load cycles occurring over a predetermined period, 
are obtained. Such averages aid the doctor considerably in his analysis of 
data. 
It is preferable if both electrical supply and memory have a capacity and a 
size permitting operation to extend beyond one week. The capacity should 
permit the essential variables relating to a two week load history to be 
stored. In order to prevent data loss, the memory should be protected 
against a power failure. 
The indicator advantageously features a viewing window or display, which 
allows the patient to visually review his load condition and permits more 
accurate reading of information than afforded by a acoustic signal. 
Information retrieved from memory can also be displayed in the window, an 
arrangement that permits both doctor and patient to review, either at the 
end of the day or during a visit, prior loading events without exacting 
special knowledge of computer language or hardware. 
Another version of the present invention comprises connecting the 
electronic part to a printer for the purpose of printing out retreived 
data. Such printing also does not require any EDP knowledge. 
The input and/or retrieval device can also feature a device suitable for 
storing a programme medium. Such programme media can be reference range or 
storage retrieval EPROMS. 
The input device can also be embodied as a keypad, whereby values can 
either be entered or retrieved. 
In addition, an auxiliary portable measuring amplifier can be connected to 
the electronic part, in order to process low raw data values, if at the 
outset of the treatment process a low load reference range has been 
selected. 
It is furthermore advantageous for the microprocessor to possess a means of 
calibration, by means of which the measuring device can be calibrated. By 
using the microprocessor, the input device and the display device, it is 
possible to determine whether or not each sensor has transmitted the 
correct information and, if not, to correct this error through a 
correction factor during the evaluation of the raw data. 
Concerning the state of the art regarding the related area of indicating 
the pressure profile of a loaded foot, a measuring system is known that 
also makes use of sensor-sole inserts in many shoe sizes, but that in 
addition comprises a large number of sensors for measuring pressure 
distribution. The evaluation of the information gathered requires 
considerable hardware and software; the operation of the system requires 
EDP knowledge and the system itself is conceived for use by orthopaedic 
surgeons or makers of othopaedic shoes.

The device shown in FIGS. 1 to 3 comprises a measuring device embodied as 
an insertable sole 1, a measurement amplifier 2 as well as an electronic 
unit 3. Leading away from insertable sole 1 is a wire 4 having a 
connection 5, such wire being sufficiently long to connect measuring 
device 1 to the measurement amplifier 2 strapped onto the malleolus. A 
cable 6 having a plug 7 leads from measurement amplifier 2 to electronic 
unit 3 which advantageously held by means of a carrying loop 8 upon the 
patient's chest. 
The electronic unit 3 shown in FIG. 2 comprises a microprocessor, an 
indicating system and a data memory which are not shown in detail. The 
indicating system comprises, in addition to an acoustic indicating device 
(e.g. a piezo-beeper), an optical indicating device 9 on whose face is a 
display window. Electronic unit 3 possesses an input device 10, in which 
can be seen a slot into which a prepared programme medium, such as a 
reference-range EPROM, can be inserted. Electronic unit 3 is furthermore 
fitted with a keypad 11, which serves either to input or retrieve data. 
The insertable sole of FIGS. 3 and 6 comprises two plates 40, 41 joined 
together at the edges, located between which are two force sensors 12, 13, 
in the zone of the ball of the foot, and one force sensor 14 in the zone 
of the heel, whereby each sensor has a strain measurement strip. The 
sensors measure the force F acting on the upper plate 40. The sensors are 
connected to multi-pole plug 5, which serves not only to transfer raw data 
through the cable but also to conduct the required current from 
battery-operated electronic unit 3 or measurement amplifier 2. This 
modular arrangement, coupled with the simplicity and low cost of the 
sensors, permits insertable sole 1 to be used as a disposable item. 
The circuit diagram of FIG. 4 corresponds essentially to FIGS. 1 to 3. The 
measurement amplifier 102, being housed inside electronic unit 103 and not 
separately, requires the electronic unit to be attached at the ankle or 
neccessitates the use of a longer cable 4. Measuring device 101 features 
merely a pressure sensor 112, which is either implanted between two 
superposed parts of an artificial joint or between two parts of a brace. 
The other components are identified by the same reference numbers as in 
the previous figures. 
Electronic unit 103 features, in addition to input device 11, which is 
embodied as a keypad, and to optical indicating device 9, an acoustic 
indicating device 15 and an evaluating device 16, which comprises 
measurement amplifier 102, an A/D converter 17, and a microprocessor 18 
having a data memory 19 and a programme memory 20. Stored in the latter 
are the programmes for the microprocessor-controlled processing cycles. 
Connecting to microprocessor 18 is an I/O interface 21, through which, for 
example, can be connected a printer for printing out stored data or an 
external input device for entering commands and data. 
FIG. 5 shows a load-time curve having a curve constructed from raw data K. 
Used as an example is load force F acquired by measuring device 1, over a 
time (t). A load-reference range S is established on the basis of preset 
boundary values F.sub.1, F.sub.2 Located above reference range S is an 
upper range which is divided by boundary value F.sub.3 into a near upper 
range O1 and a further upper range 02. Beneath load reference range S is 
located a lower range, which is similarly divided by a boundary value 
F.sub.4 into a near lower range U1 and a further lower range U2. A further 
threshold value F.sub.5 is provided in the region of the zero line. The 
predetermined boundary values can be entered into evaluation device 16 by 
means of input device 11. The input step is facilitated if a fixed 
relationship exists e.g. F.sub.2 =0.8 F.sub.1 ; F.sub.3 =1.5 F.sub.1 ; 
F.sub.4 =0.5 F.sub.2 and F.sub.5 =0.1 F.sub.1. One need input only 
F.sub.1. 
The curve from raw data K obtained from adding the output values of sensors 
12, 13, 14 has a continuous path and is tracked over a chronological cycle 
determined by microprocessor 18; the thus acquired raw data are converted 
into digital code in the A/D converter 17 and fed into data memory 19. 
Further analysis data are derived from such raw data with the assistance 
of microprocessor 18. The raw data fed to the data memory does not have to 
be permanently stored. The length of time the data is stored depends on 
the length of time required for analysis or display. 
FIG. 5 shows four methods suitable for obtaining analysis data: 
a) Each of the raw data maximums is obtained, so that the individual 
maximums M1, M2, M3 etc. can be used as analysis data. 
b) Times are determined, at which the raw values exceed or fall short of 
threshold value F5. The intervals d thus obtained can be employed as 
analysis data. 
c) The area below curve K is integrated over loading time t. Impulse 
magnitudes A obtained can also be used as analysis data. 
d) The load cycles are counted during a predetermined time period, e.g. 
during the course of a day. Such cycles are established by observing the 
number of times threshold value F.sub.5 is either exceeded or fallen short 
of. The load cycle count represents another analysis datum. 
The loading history is thus described not only by means of the curve of raw 
values K, but also by means of the derived analysis data. 
The analysis of this loading is described in greater detail in FIG. 5 in 
connection with example (a). The first maximum M1 lies within reference 
range S, the second maximum M2 in the near upper zone 01 and the third 
maximum M3 in the further lower zone U2. In the case of maximum M2, the 
acoustic indicator device 15 is actuated and an acoustic warning signal is 
emitted, since the reference range S has been exceeded. 
Zones S, O1, O2, U1, U2 constitute load classes. The purpose of subsequent 
analysis is served if it is determined to which load class each maximum 
value belongs. It is thus not necessary to know the exact value of the 
maximum figure. It is sufficient to determine only which of boundary 
values F.sub.1 to F.sub.5 was last exceeded. Even this indication can be 
further simplified through statistical values that demonstrate the number 
of maxima occurring, during a predetermined time period, in the individual 
classes, i.e. what percentage of the individual load cycles corresponds to 
the individual classes. This procedure permits a brief overview of the 
load history over a predetermined period of time. 
It is also possible to evaluate other analysis data by comparison with an 
analysis-data reference range and the relevant upper and lower zones. It 
is possible to establish relationships that reveal the mean values of the 
analysis data within individual load classes. 
Concerning the number of load cycles per day, the momentary load value in 
question is reached only at the end of the period, so that comparison with 
the reference range begins only at this juncture. 
The raw data routed from measuring device 1 as well as the analysis data 
obtained therefrom, can be caused to appear at any time, and 
simultaneously with stored data from memory 19, in the optical indication 
device 9. The relevant comparative data can thus also be displayed, which 
permits the patient to know at any time if he can increase the load or 
not, and to what extent this is possible. 
After a period of loading, electronic unit 3 is given to the physician, who 
is able, by means of a retrieval device, e.g. keypad 11, to call up to the 
indicator device 9, or to a printer, the stored data relating to a 
particular load history. The physician can use the information acquired on 
the load history to adjust the load reference range for the following 
period, and more particularly, to reset the reference ranges for the 
above-mentioned analysis data in accordance with an optimal treatment 
regimen. 
In one embodiment example, a reference range delimited by an upper and a 
lower value was input for: the maximum load force; the number of load 
cycles per day (number of steps) and the total energy expended per day 
expressed as the sum of all impulse magnitudes, as well as a reference 
range, delimited only by an upper value, for maximum load duration (step 
duration). A warning signal is produced whenever the reference ranges for 
load force and step duration are exceeded. 
The patient is thus able at anytime, by pressing a button on keypad 11, to 
view on the optical display 9 the momentary load force, the load reference 
ranges (especially for load force and number of steps), the average value 
of the maximum current day load and the current day's step count. The 
patient can review in the morning the overloading occurring on the 
previous day, represented by the number of excesses and the maximum value 
(expressed as a percentage deviation from the reference value), as well as 
the number of steps taken on the previous day, expressed by the step count 
and a deviation in percent. 
The physician can, in a brief interrogation session, review from the 
already entered reference ranges, the daily counts since the last visit, 
the average number of steps taken per day, the average size of the load 
force maximums as well as the three highest individual loads. It is 
furthermore possible to recall the maximum and minimum number of load 
cycles occurring per day and the maximum and minimum average load forces 
per day. Moreover, a special interrogation session can serve to identify 
what percentage of the load cycles reached their maximum values M1, M2, M3 
within the individual load categories, the size of the average duration d 
of all load cycles as well as the durations of the load cycles in each of 
the load categories, and the average value of the total energy (expressed 
as the sum of the impulse magnitudes) expended per day as well as the 
percentage of total energy apportioned to each class. Such information 
affords the physician a good overview of the load history. 
In conclusion, analysis data, obtained from the raw data, not only 
corresponds to the extent, duration, impulse magnitude and number of 
individual loads, but can be mathematical functions derived from one, two 
or three such values, and can be expressed as functions of such values 
measured and/or derived over a period of time (e.g. "per day"), whereby 
such values can be routed to data memory 19 as well, as indicating device 
9. For certain kinds of load, expressible as raw or analysis data, 
reference value ranges can be input through input device 10 or 11. The 
actual value of such loads (momentary loads) are compared, with the aid of 
the microprocessor, with the input reference ranges. Comparative data are 
also fed to data memory 19 and can be routed in real time to indicator 
devices 9, 15. Statistical values are obtained from stored actual values, 
comparative data and other temporal values (e.g. number of days), with the 
aid of microprocessor 18. Such statistical values can be routed in real 
time to both the indicating devices 9, 15 and data memory 19. A certain 
combination of reference range, actual values, temporal values and 
statistical values causes one or more types of acoustical signal to be 
produced by acoustic signal device 15, while certain information is 
displayed in the optical display device. 
The size of the battery or accumulator and that of the data memory 19 
permit electronic apparatus 103 to function for one, two or more weeks, 
which allows storage of the entire load history occurring between two 
serial visits to the doctor. The type of memory system used, or an 
auxiliary battery, ensure the protection of memorized data and the 
continuous running of the clock. 
The calibration of the measuring device entails a calibration routine being 
entered with the aid of keypad 11. In this mode, each force sensor 12, 13, 
14 is loaded with a standard force. This calibration, can be accomplished, 
for example, by subjecting the sensor to loading by a local-area pressure 
body, whereby a weighing scale positioned underneath indicates a 
predetermined reference value. If the latter does not appear in the 
indicating device 9, the display must be altered by keypad manipulation 
until the desired reference value appears. The result of this arrangement 
is that all other data from the sensor in question can be corrected for 
error by an adjustment member employed by the microprocessor. 
Shown in the embodiment examples is that measuring device 1 is connected to 
electronic unit 3 by means of cable 4, 6. Alternatively, a transmitter can 
be integrated in the measuring device and a receiver in the electronic 
unit for the purpose of remote data transfer. 
Commercially-available components are used in the circuitry. The following 
components, for example, have been used: 
Force sensor 12, 13, 14: Type 125 SF sensor with strain gauge 
strip--SK-06-125GF-20C from Measurement Group. 
A/D Transformer 17: MAX 134 from Maxim 
Microcomputer with microprocessor 18, data memory 19 and programme memory 
20:DS 5000 from Dallas Semiconductors. 
FIG. 7 shows an insertable sole 201 which comprises a pair of spaced plates 
240,241. Three displacement sensors 212,213,214 are sandwiched between the 
plates 240,241 and measure the distance x between the latter. 
FIG. 8 illustrates a measuring device 54 serving as an implant in the knee 
joint of a leg 50. The measuring device 54 is disposed between the femur 
51 and the tibia 52 behind the knee cap 53. 
FIG. 9 shows a knee brace 61 which is secured to the thigh 64 and shank 65 
of a leg 60. The knee is bridged by connecting rods 66,67 and measuring 
devices 62,63 are incorporated in the respective rods 66,67. 
The operation of the monitoring device according to the invention is 
described below with reference to the exemplary algorithm of FIG. 10 and 
the exemplary load-time diagram of FIG. 5. 
The algorithm starts with the input of the boundary value F.sub.1 in step 
301. Next, the boundary values F.sub.2,F.sub.3, F.sub.4, F.sub.5 are 
calculated per step 302. 
The measuring values K are read in step 303 and stored in step 304. The 
maxima M.sub.i are determined in step 305. 
The maxima are evaluated in steps 306 to 322 to establish the ranges 
O2,O1,S,U1,U2 in which the respective maxima are located. When a maximum 
exceeds the boundary value F.sub.i an alarm goes off as in steps 307 and 
311. In steps 308,312,315,318 and 321, the number of maxima in the 
respective ranges O2,O1,S,U1,U2 are counted. To permit calculation of 
average values for the maxima, the individual maxima in each range 
O2,O1,S,U1,U2 are summed. 
In steps 323 to 325, the intervals, d.sub.i, during which the measured 
values K exceed the boundary value F.sub.5 are determined and the area 
under the load-time curve for these loading intervals is obtained by 
integration. 
A determination as to whether the loading cycle was exceeded is made in 
step 326. The algorithm returns to step 303 if the answer is in the 
affirmative while analysis proceeds if the answer is no. 
In the first part of the analysis at step 327, the total number of maxima 
is calculated. The fraction of the total number of loading cycles in each 
range O2,O1,S,U1,U2 can then be obtained as in step 328. In step 329, the 
average of the maxima is calculated for each range. This completes the 
algorithm.