referring to the drawings , in particular , the inventive system preferably includes a remote port 10 provided in a surface 12 of a hydrodynamic element 14 or a remote port 514 provided in a surface 501 of an enclosed space exercise arrangement 500 . the remote port 10 is exposed to the pressure acting perpendicular to the submerged surface 12 . the remote port 514 is exposed to the pressure of the gas within the enclosed space exercise arrangement the remote port 514 is connected to a transducer 20 by plastic tubing 516 . in this way , pressure is relayed via the plastic elbow joint 16 ( such as craftech part no . 0302 - 1 or value plastics # kl230 - 2 ) and plastic tubing 18 to a connection port 22 of the transducer 20 . for attachment to some arrangements , a straight plastic conductor 301 ( such as craftech part no . 0300 - 5 or value plastics # k230 - 2 ) may mount the remote port in the most advantageous manner ( see fig5 ). the transducer 20 ( such as motorola model mpx - 3100 dp ) measures fluid pressure in a line or provides a differential pressure signal representing two sensed pressures . a second remote port 24 is provided on an opposite surface 26 of the hydrodynamic element 14 . the second remote port 24 is connected to a second connection port 28 of the transducer 20 by means of an elbow joint and plastic tubing in the same manner as the first remote port 10 . the remote ports 10 and 24 are mounted on different sides of an arrangement such as a hydrodynamic element , such as element 14 , to allow a differential pressure to be measured at the transducer 20 . depending on the orientation of the transducer , the remote port may not be necessary . in some cases the pressure may be sensed directly at the transducer ports 22 and / or 8 by positioning the transducer ports in or on the hydrodynamic device or enclosed space arrangement . transducer 20 is advantageously enclosed in a plastic box 32 which can be mounted to a surface by support elements or feet 34 . the transducer 20 includes terminals , such as output 30 , ground 36 , and voltage 38 . these terminals are connected via a cable or wires , respectively 40 , 42 , 44 to the calibration circuit board 50 . the calibration circuit 50 board is preferably positioned within a plastic box 48 ( such as polycase 883 - 043 - 1 with polycase cover 883 - 0471 ) or a container of other material which is waterproof or may be waterproofed . referring to fig3 and 4 particular , the output of the transducer 20 is a voltage signal . this voltage signal varies directly with the differential pressure between the positive and negative ports . the calibration circuit 50 allows the base line voltage signal ( representing the pressure differential ) which is omitted from the transducer , to be adjusted so that the base line signal can be centered on a base line of the computer screen or the like . the adjustment may be made by turning the trimmer 104 which is mounted on the calibration circuit board 50 . as shown specifically in fig3 the signal from transducer 20 is first inverted by inverting amplifier 102 ( i . e . gain equal negative 1 ). the output from the inverting amplifier is input into a second amplifier 103 . the output from the trimmer 104 is also input into amp 103 . the output from the trimmer 104 can be adjusted , thereby adding or subtracting voltage to the signal and allowing it to be centered on the desired base line . the output from amp 103 is input into the data acquisition board 60 . the actual wiring of the arrangement is best shown in fig4 . the calibration circuit board 50 is wired to two transducers 201 , 202 . the output and ground ( common ) from each of the two transducers 201 , 202 is wired to the board 50 . the voltage connection to both transducers is connected directly to the plus 5 volt connection on the data acquisition board 60 . the output of the calibration board 50 consists of an output and ground for each of the transducers connected . the calibration board also has a plus 12 volt and minus 12 volt connection to the data acquisition board to power the circuit . an eight channel arrangement may be provided with eight transducers which are to be wired to four calibration boards ( two transducers per board ). all the boards are preferably housed in a single enclosure or expansion box with output of the same data acquisition board . the calibration circuit board 50 is provided with output terminals 52 connected to the output cable 56 which leads out of plastic box 48 . the cable 56 is connected to a data acquisition board 60 . the data acquisition board 60 ( for example , metrabyte model das 8 - pga ) may be mounted and housed in an expansion box 62 , ( for example , axonix , thinpack model 1100 ). the calibration circuit board 50 may also be placed in expansion box 62 . the data acquisition board 60 preferably has eight analog channel inputs 61 . this arrangement allows eight sensors on different pieces of equipment to be sampled simultaneously , or two sensors on four pieces of equipment , etc . this is extremely useful as it is possible to employ an enclosed space exercise assembly with a plurality of chambers thereby allowing a plurality of exercises using one set - up , i . e . enclosed space exercise shoe 400 with four sensor connection lines 426 , 428 , 430 and 432 positioned on one exercise arrangement . also different chambers may be monitored to provide additional information to check if the exercise is being performed properly . additionally , absolute pressure transducers may be used in some configurations . absolute pressure transducers allow measurement of ambient air pressure or the water depth when the transducer ( or transducer remote port ) is mounted on a surface parallel to the direction of movement of the hydrodynamic device . the expansion box 62 is advantageously connected to a lap top computer 70 preferably secured beneath the lap top computer 70 ). the lap top computer 70 may be , for example , toshiba model t1100 +. the expansion box 62 may simply be connected by a cable 74 to the expansion slot 75 of the computer 70 . of course , a standard desk top type personal computer or the like may also be employed . additionally , a lap top computer ( e . g . dell computer corporation model 316 lt ) which can receive a data acquisition card , ( e . g . metrabyte model das - 8 ) internally , and still have sufficient battery power would be most advantageous . such arrangements provide even further advantages with regard to the ease of use and mobile aspects of the entire system . fig2 shows a preferred arrangement employing an aquatic exercise assembly 100 or aquatic dumbbell including hydrodynamic portions 14 with surface 13 and other surfaces not shown . with this arrangement , it is possible to evaluate information with regard to the force acting on one of the perpendicular sets of surfaces . it is also possible to provide additional parts which are redundant ports for an even more accurate measurement or to check for error and to measure twisting motion or differences due to depth . several alternative arrangements are possible without departing from the principles of the invention . for example , individual pressure transducers may be mounted on surfaces of the aquatic exercise device and then directly wired to the calibration circuit board 50 or transmitted via a transmitter to a receiver which is connected to the calibration circuit board 50 . such a transducer and transmitting arrangement is disclosed in my u . s . pat . no . 4 , 654 , 010 , which is hereby incorporated by reference . as seen in fig5 and as discussed above , the transducers such as transducer 201 and 202 are available in a size which is small enough to provide the transducers within an enclosure 32 which may be attached to a hydrodynamic surface such as thin hydrodynamic surface 314 . the enclosure 32 may be connected by plastic screws or connectors 306 and 304 mounting the feet of the enclosure 32 to the surface 314 . as shown in fig5 pressure ports 301 and 302 may be provided in a simple manner with the pressure port 301 being provided in a surface 312 , the surface forming part of the enclosure 32 . the other port 302 may be provided connected to the surface 316 . this arrangement provides an alternative to having the transducers provided a distance from the remote pressure ports . fig6 a and 6b show still another embodiment of the invention in which a relatively thin hydrodynamic surface at 314 is provided with remote ports 301 , 302 which are connected to the transducers 201 , 202 or the like by a plastic elbow joint connector 316 ( such as craftech part no . 0302 - 1 or value plastics no . kl230 - 2 ). these connectors may be connected to plastic tubing or the like 318 . in the arrangement shown in fig6 a and 6b , the pressure ports 301 and 302 are shown off set , for illustration purposes . it should be understood that the ports may be in alignment one behind the other or several other possible arrangements without departing from the concepts of the invention . fig7 depicts a hydrobell hydrodynamic arrangement 320 with pressure ports 330 and 332 arranged on opposite surfaces . the hand of the user may be clasped around the handgrip 334 . the tubing is provided away from the user ( as far away as possible such that it does not interfere with the exercise ). the ports , tubing and sensor may also be installed inside the handgrip as an alternate arrangement . the data which is provided to the computer of the system can be evaluated in many ways . the system of the invention may employ software to display a graph or the like of differential pressure versus time . the sampling rate for therapy and exercise purposes is generally about 50 samples per second . however , the system designed in software allows sampling in rates of about 250 samples per second without changes in hardware or any other problems . the pressure may be converted into units of force so that by integration of the curves produced during exercise , peak force , average force , impulse and number of repetitions may easily be calculated . if the distance of the movement is also measured by some means other than the sensors of the invention ( such as entering distance data into the computer of the system ), work , power , and torque can also be calculated . software may also be provided for allowing the adjustment of the base line pressure to be handled through the computer . it has been observed that such a software base line adjustment works best for fine adjustment , where as the hardwired hardware adjustment by the calibration board is better for more course adjustment . software may also provide for channel switching , gain switching and to stop and start data collection . all of these functions may also be controlled by hardware switching . however , such software switching makes the equipment completely controllable at the keyboard and also eliminates the parts necessary for the switch box and the connecting cables . however , in some cases an external on - off switch may be more consistent with typical situations ( i . e . the coach could use the external on - off switch as a stop watch which could also start and stop data collection ). the above arrangement may also be used for analyzing and observing swimming technique provided the swimmer is stationary . this is accomplished using water treadmills or swimming flumes or where the swimmer is tethered . according to a further variant of the system of the invention , the remote pressure ports may be provided connected to closed containers to thereby sense the pressure in the closed containers . this arrangement can be used especially for impact situations such as running , boxing , handball and the like . referring to fig8 in particular , the arrangement according to a further aspect of the invention includes a plurality of closed containers 410 through 416 which are each connected to a pressure port such as remote pressure ports 418 through 424 . each of these remote pressure ports may be connected by tubing to a port of one or more transducers such as transducers 201 , 202 . the closed containers 410 through 416 preferably are filled with air . according to the arrangement of fig8 the closed containers 410 through 416 are provided in a sole structure of an athletic shoe such as a running shoe or the like . the closed containers are each provided at locations to sense specific information . for example , in the case of running , it may be desirable to provide several closed containers 410 through 416 positioned at important locations such as the ball of the foot ( 410 ), the arch of the foot ( 414 ) or the heel of the foot ( 416 ). more containers and more pressure ports may be provided as desired . according to a preferred arrangement , the pressure ports 418 through 424 are connected to pressure conduit tubes such as 426 through 432 , respectively . tubes may be connected to the transducer at the shoe or the tubes may be run up to a central transducer arrangement such as transducer arrangement 20 which may be strapped to the user or the like . fig9 and 10 show an enclosed space exercise arrangement or a bellows shaped arrangement generally designated as 500 . the bellows 500 includes a top wall 506 and a bottom wall 502 . these top and bottom walls ( 506 and 502 ) hingeably connected at a pivot point 504 to a top wall 506 . opposite the pivot point 504 is a collapsible end wall or bellows wall 501 . the arrangement is enclosed and made airtight by collapsible side walls 510 and 512 . similar to port 302 as shown in fig5 the bellows 500 includes a pressure port 514 . connected to the pressure port 514 is an interface cable 516 which is connected to a pressure transducer port 22 of transducer 20 . the other transducer port may be exposed to atmosphere for a base comparison . the bellows 500 also includes an intake valve 518 which may be adjusted to regulate the resistance of air flowing through it . the bellows 500 also includes an exhaust valve 520 to regulate the resistance of air flowing out of the bellows . referring now to fig1 a , 11b , and 11c the bellows 500 is shown being utilized as an exercise / therapy device wherein the forces exerted f and f &# 39 ; collapse the bellows 500 . the force is determined from the pressure read from the pressure port 514 . the force required to compress the bellows is regulated by exhaust valve 520 . the reverse motion , to open the bellows , is provided by the subject pulling against straps 522 and 524 . the force required to open the bellows is regulated by intake valve 518 . the performance of the subject is recorded and displayed by computer 100 . fig1 a , and 12b show the bellows 500 used against a stationary surface such as a floor or a bed . the bellows 500 behaves similarly to the bellows shown in fig1 a and 11b except the expansion of the bellows 500 is provided by resiliency in the collapsible side walls 510 and 512 and end wall 508 , or by another appropriate biasing means ( not shown ). the intake valve can be completely opened or slightly closed to damp the re - expansion forces . an alternative for the bellows would be a commercially available chamber , such as the air splint ( jobst institute , inc . ; u . s . pat . reg . 26046 ). after the airsplint was inflated around a joint ( see fig1 ), the valve could be connected to transducer 20 via port 22 and tubing 18 . once connected , the valve could be opened and the pressure within the airsplint could be monitored during exercise . although such a system would require minor modification of existing equipment , it would lack the advantage of constant resistance throughout the range of motion as in the bellows system . the fluid within the airsplint would be trapped and pressure would increase with the range of motion at a joint . provision of valves 518 and 512 between the interior and exterior of the airsplint removes this problem . fig1 shows a right leg of a rider on a horse shown in phantom with the pressure system utilized by securing a closed container on either the medial surface of the rider &# 39 ; s knee , or on the side of the horse . fig1 shows a closed container element 528 provided on a boxing glove 530 to measure impact force . a plurality of sensors may be used on the glove 530 surface to measure boxing technique and determine areas of greatest impact and as a feedback system to avoid injuries to the boxer &# 39 ; s hands and arms . other sensing arrangements may be provided using the basic features of the invention without departing from the principles of the invention . while specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention , it will be understood that the invention may be embodied otherwise without departing from such principles .
a method and device for monitoring and measuring underwater physical therapy or exercise employing fluid elements in either enclosed compressible fluid filled chambers or aquatic exercise devices submerged in water . measurements are taken via pressure ports formed on first and second opposite surfaces of the hydrodynamic device to provide a pressure differential signal . this pressure differential signal may be compared to a calibrated zero signal to form a measurement signal . the measurement signal is then converted to a digital signal for evaluation by a digital computer . the exercise performed may be stored and evaluated . the arrangement provides information with regard to the type of exercise performed and the degree of exercise performed .