WO2012168676A1

WO2012168676A1 - Force measurement apparatus and associated methods

Info

Publication number: WO2012168676A1
Application number: PCT/GB2012/000473
Authority: WO
Inventors: Graham Arnold; Rami J. ABBOUD
Original assignee: University Of Dundee
Priority date: 2011-06-06
Filing date: 2012-05-28
Publication date: 2012-12-13
Also published as: GB2491584A; GB201109423D0

Abstract

A plantar foot force measurement apparatus for measuring force over a plantar foot region. The force measurement apparatus comprises a sensing platform configured to receive an entire plantar foot region. The apparatus further comprises a plurality of force measurement sensors associated with the platform. At least one force measurement sensor is configured to measure a force substantially parallel to the platform.

Description

FORCE MEASUREMENT APPARATUS AND ASSOCIATED METHODS

FIELD OF THE INVENTION

The present invention relates to a plantar foot force measurement apparatus and associated measurement methods; in particular, but not exclusively, for the measurement of shear stress between a foot and a surface.

BACKGROUND TO THE INVENTION

Medical theory and research have established a link between mechanical stress on the foot and the development of medical problems. Stresses in skin tissue can lead to medical problems such as sclerosis or lesions. For example, stresses in the plantar foot region can contribute to foot ulcers, particularly where another factor such as diabetes leads to an increased susceptibility. In severe cases, the development of a foot ulcer can lead to complications resulting in at least partial amputation.

Pedobarographs have been developed to measure the contact pressure in the plantar foot region. Accordingly, localised variations, such as peak stresses, can be measured in the plantar foot region of sample groups to help identify general areas that may be more prone to ulcers. Likewise, individual patients with higher stresses in the plantar foot region can be identified; and higher measured localised stresses can indicate specific areas of the individual's foot more likely to develop problems, such as ulcers. However, the functionality of the plantar foot region is complex and the mechanics of ulcer development are not yet fully understood.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a plantar foot force measurement apparatus for measuring force over a plantar foot region, the force measurement apparatus comprising:

a sensing platform configured to receive an entire plantar foot region;

a plurality of force measurement sensors associated with the platform;

wherein at least one force measurement sensor is configured to measure a force substantially parallel to the platform.

In use the measurement apparatus may be located in/on a floor, typically permitting a user to step on the platform with at least one foot. The provision of a sensor configured to measure a force substantially parallel to the platform may permit the measurement of shear stress in the foot. The measurement of shear stress in the foot may be beneficial in understanding the mechanics of the foot, such as the development of foot ulcers.

Providing a sensing platform configured to receive an entire plantar foot region may permit the measurement of one or more forces in the entire plantar foot region; such as under controlled conditions. For example, the platform may permit forces in different portions of a foot to be measured substantially simultaneously.

The plurality of sensors may be associated with a sensing area of the platform larger than the entire plantar foot region.

Providing sensors associated with a sensing area larger than the entire plantar foot region may permit the apparatus to be used for dynamic measurements. For example, providing such a sensing area may ensure a margin for error in the placement of a foot, such as when stepping on the platform as part of a normal stride pattern in order to measure typical forces during a single stepping action (e.g. without stride adjustment or targeting).

The provision of a platform configured to receive an entire plantar foot region may permit the measurement of forces acting on the foot in different areas of the plantar region substantially simultaneously. For example, such a platform may permit the measurement of local forces in the foot during a discrete movement of the foot, such as during a stepping action.

At least one sensor may comprise a multidirectional sensor.

At least one sensor may be configured to measure force in a plurality of substantially horizontal directions. The sensor may be configured to measure a lateral component of force in the plantar foot region.

At least one sensor may be configured to measure a magnitude of force.

At least one sensor may be configured to measure a direction of force.

At least one sensor may comprise a capacitance sensor. At least one sensor may comprise a deformation sensor. At least one sensor may comprise an actuator. For example, the sensor may comprise a pillar with an upper portion for interfacing with the plantar foot region. The sensor may comprise a lower portion configured to register a movement of the upper portion. The pillar may be configured to transfer the movement of the upper portion to the lower portion. The upper portion may be configured to move as a result of a force applied by a plantar foot region. The lower portion may be configured to convert movement of the upper portion to a measurement signal. The sensor may comprise a transducer. The sensor may comprise a resistive sensor. The sensor may comprise a strain gauge. The sensor may comprise a piezo element. The sensor may comprise a plurality of strain gauges, each strain gauge configured to measure force in a different direction.

The platform may comprise a stiffness configured to support a weight of a user, such as a dynamic weight of a user, with minimal deformation. The platform may comprise a stiffness appropriate for supporting the entire weight of a user on a portion of the user's foot, such as the weight of a user jumping on a ball of their foot. For example, the platform may comprise a thick panel. The stiffness of the platform may minimise deformation of the platform under loading, thus enabling more accurate measurement of forces in the plantar foot region. The platform may comprise a stiff material, such as a metal, composite or the like. The platform may be reinforced. The platform may comprise one or more structural ribs.

The apparatus may be configured to protrude a sensor upper portion from a top surface of the platform. The apparatus may be configured to protrude the sensor upper portion by a predetermined distance. The predetermined distance may be adjustable.

The platform may be configured to receive at least a portion of the sensors. For example, the platform may comprise a plurality of openings for receiving sensors, such as individual openings corresponding to each sensor. At least a portion of the sensor may extend through the platform from a bottom surface to the top surface of the platform.

The apparatus may comprise a sensor module comprising an array of sensors.

The sensor module may comprise a sensor printed circuit board (PCB). The sensor PC8 may define a structural member for supporting the sensor and for supporting at least a portion of a weight of a user. The sensor PCB may comprise a stiff substrate portion. This may permit the sensor to be rigidly supported; such that the position of the sensor does not deviate, or only minimally deviates, from the platform under load, such as under the weight of a user, The stiff substrate portion may limit the deformation of the sensor PCB under load. Accordingly, the sensors may more accurately measure the applied force. The sensor may be soldered or otherwise electrically coupled to the sensor PCB. The sensor may be mounted to the sensor PCB with adhesive. The sensor module may comprise a control PCB. The apparatus may be configured to avoid loading the control PCB, such as with a mechanical load associated with a portion of the weight of a user. The control PCB may be isolated from a load path for supporting the weight of a user. The control PCB may be mounted adjacent the sensor PCB, such as underneath the sensor PCB. The control PCB may be supported by the sensor PCB. For example, the control PCB may be suspended from the sensor PCB. The platform may be configured to receive the sensor module. The sensor module may abut the platform. The sensor module may be attached directly to the platform. For example, the sensor module may be secured to platform by a fastener. The sensor module may be mounted to the platform, such as with adhesive.

The provision of sensors in a sensor module may permit selective adaptation of a shape and/or of a magnitude of the sensing platform.

The sensor module may be configured to measure force in a discrete portion of the platform.

The sensor may be configured to be calibrated. The sensor may be configured to ensure a negligible force reading in an unloaded state (such as a zero or a background reading). For example, the sensor may comprise a compensation system, such as a balancing bridge.

The apparatus may comprise a calibration tool.

The module may be configured to store sensor information locally. For example, the module may comprise a data carrier to store calibration information, such as a calibration curve (e.g. on a flash memory). The module may comprise a microcontroller. The module may provide a data output. The module may comprise an analogue to digital converter.

The module may be configured to be independently associated with the platform. For example, the module may comprise a connector for independent connection to the platform, such as individual attachment to the platform.

The apparatus may comprise a plurality of modules.

Each module may be substantially identical.

The provision of substantially identical modules may permit economies of scale, such as reduced fabrication costs. Substantially identical modules may permit an interchangeability of modules, such as for repair and/or replacement.

Each module may be configured to measure forces in a particular plantar region. For example a first sensing module may have a greater density of sensors over a given area than a second sensing module. Providing a module with a greater density of sensors may permit a higher resolution of force measurement in a particular target plantar region, such as an anterior and/or a lateral and/or a central region. Providing a module with a lower density of sensors may permit lower complexity and/or fabrication cost and/or data processing capacity. A lower density module may be substantially similar to a higher density module with a selection of sensor/s omitted from the lower density module with respect to the higher density module. The provision of modules configured to be independently associated with the platform may permit local variations, such as deformation of the platform.

The platform may be supported on a base. The base may comprise one or more boss/es for supporting the platform. For example, the boss may comprise one or more base rib/s configured to distribute a load applied to the platform, such as a weight of a user. The boss may support the module. For example, the module may be supported on two sides by first and second base ribs. The platform may be supported by the boss via the module. For example, the sensor PCB may be sandwiched between the boss and the platform. Supporting the platform with the boss via the module may permit the sensor to maintain a relative position to the platform during a measurement.

The base may be configured to receive the module/s. For example, the base may comprise a cavity/ies for the module/s.

The platform may be configured to receive a plantar region in different conditions, such as dry and/or moist conditions (e.g. sweaty). The sensor upper portion may comprise an interface configured to receive a plantar region in different conditions. The sensing platform and the sensor upper portion interface may comprise similar friction characteristics. For example, the interface and the platform may comprise a similar material and/or a similar surface texture, such as roughness. The provision of similar friction characteristics may permit a substantially homogenous interaction between the sensing surface and the plantar region. The sensing platform and the sensor upper portion interface may comprise contrasting friction characteristics. The provision of contrasting friction characteristics may permit a concentration of a force. For example, where a plantar region has a substantially lower friction with a platform than with a sensor, a force applied by the plantar region to the sensor (such as a shear force) may be higher than where the plantar region has the same, or a higher, friction with the platform than with the sensor. The sensing platform and the upper portion interface may have varying relative friction characteristics under different circumstances. For example, the platform and the interface may have similar friction characteristics with a plantar region in non-humid circumstances, and the interface may have a higher friction with the plantar region in humid circumstances relative to the platform with the plantar region. The sensing platform and the upper portion may have similar relative friction characteristics under different circumstances.

The apparatus may comprise a covering, such as for over the platform. For example, the top surface of the platform and/or the upper portions of the sensors may be covered by a flexible material, such as a rubber membrane. A covering over the top surface of the platform and the upper portions of the sensors may ensure that friction between the apparatus and a plantar foot region is substantially uniform. The covering may provide protection of the sensors, such as from debris and/or wear and/or overstressing; and/or may provide for easy cleaning of the apparatus, such as sterilisation between users. The covering may be configured to distribute forces. For example, the covering may be configured to transfer a point load applied above the platform upper surface to one or more adjacent sensors. The covering may be configured to assist the transition of measurement between adjacent sensors, such as to smooth measurements. The covering may be removable. The covering may be non- removable. The covering may be substantially waterproof.

The apparatus may comprise a data memory. For example, the apparatus may be configured to buffer measurement data.

The apparatus may be configured to accommodate atmospheric variations, such as temperature and/or pressure variations. For example, the apparatus may comprise a reference sensor (e.g. on each module). The apparatus may comprise an atmospheric control. For example, the apparatus may comprise a cooling unit. The apparatus may comprise an atmospheric measuring device, such as a thermometer.

The apparatus may comprise a user interface. The apparatus may be configured to connect to a network. For example, the base may be connected to a computer. The apparatus may comprise a visual interface. For example, the apparatus may provide a graphical representation of the measurement data. The apparatus may provide measurement data as vectors showing magnitude and direction. The measurement data may be time dependent.

The apparatus may be configured to be used in conjunction with motion analysis apparatus. For example, the apparatus may be configured to be synchronised with a video recording apparatus.

The apparatus may be configured to measure a net force associated with a foot. For example, the apparatus may be configured to measure a total force exerted by a foot on the platform, such as a total shear force and/or a normal force.

At least one force measurement sensor may be configured to measure a force substantially perpendicular to the platform.

Providing at least one force measurement sensor configured to measure a force substantially perpendicular to the platform may permit the measurement of a normal force, such as a weight of a user. The measurement of forces both substantially parallel and perpendicular to the platform may permit the association of a shear stress with a normal force; and/or of a normal force with a shear stress. The apparatus may be configured to measure plantar foot forces of multiple feet substantially simuitaneously. For example, the apparatus may comprise multiple sensing platforms each configured to receive an entire plantar foot region. The platform may be configured to receive multiple entire plantar foot regions. The provision of an apparatus configured to measure plantar foot forces of multiple feet substantially simultaneously may permit the measurement of plantar foot forces in left and/or right feet during a discrete action, such as walking.

The apparatus may be configured for mobile use. For example, the platform may be incorporated into an item of footwear, such as a sole or an insole of a shoe.

In a second aspect of the invention, there is provided a method of measuring force over a plantar foot region, the method comprising:

receiving a foot on a sensing platform;

measuring a force substantially parallel to the platform.

The method may comprise measuring a shear stress in at least a portion of the plantar foot region.

The method may comprise receiving an entire plantar foot region on the platform.

The method may comprise measuring forces in different portions of the foot substantially simultaneously.

The method may comprise measuring forces in different directions substantially simultaneously.

In a third aspect of the invention there is provided a shear force measurement apparatus for measuring a force between a body part and a surface, the apparatus comprising a sensing surface and a force measurement sensor configured to measure a force substantially parallel to the sensing surface.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. For example, it will readily be appreciated that features recited as optional with respect to one aspect may be additionally applicable with respect to any other aspect, without the need to explicitly and unnecessarily list those various combinations and permutations here. For example, features of the force measurement apparatus of the first aspect may be combined with the force measurement apparatus of third aspect.

It will be appreciated that one or more embodiments/aspects may be useful in measuring forces, such as a plantar foot shear forces. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a plantar foot force measurement apparatus for measuring force over a plantar foot region in accordance with an embodiment of the present invention;

Figure 2 shows a perspective view of a sensing module of the apparatus of Figure 1;

Figure 3 shows a perspective view of a top and bottom housing of the apparatus of Figure 1 ;

Figure 4 shows a detail plan view of a sensor located in a portion of the platform of the apparatus of Figure 1 ;

Figure 5 shows a schematic cross-sectional view of a portion of the apparatus of Figure 1 ;

Figure 6 shows a representation of the apparatus of Figure 1 in exemplary use;

Figure 7 shows a further representation of the apparatus of Figure 1 in exemplary use.

DETAILED DESCRITPION OF THE DRAWINGS

Reference is first made to Figure 1 in which there is shown a plantar foot force measurement apparatus 10 in accordance with an embodiment of the present invention for use in measuring force over a plantar foot region. The apparatus 10 comprises a platform 12 and an array 13 of sensors 14 distributed across an top surface 16 of the platform 12. The platform 12 has a thickness 17 and is mounted on a base 18. A power cable 20 connects the apparatus 10 to a power source; and a data communication cable 22 connects the apparatus 10 to a computer (not shown).

The array 13 covers an area of the top surface 16 of the platform 12 which is substantially greater than a typical footprint. Accordingly, in use the apparatus 10 is configured to receive an entire plantar foot region without, for example, adjustment of stride, enabling an accurate representative measurement of forces over the entire plantar foot region to be made. As will be described in further detail below, the sensors 14 extend from below the platform 12 through respective holes 50.

Figure 2 shows an individual module 30 of the apparatus 10 of Figure 1 , comprising sensors 14 arranged on a sensor PCB 34. The module 30 comprises a square grid of sixteen sensors 14 in total. Each sensor 14 comprises a transducer 27 with a pillar 26 mounted on top of a transducer base 28. Each sensor 14 comprises a contact interface 24 on top of the pillar 26. The pillars 26 transfer movements of the contact interfaces 24 to the transducer bases 28, where the movement is converted to an electrical signal via strain gauges. Each transducer base 28 is mounted to the sensor PCB 34 by soldered legs 32. Each transducer base 28 is adhered to the sensor PCB 34 with an epoxy glue prior to the soldering of the legs 32 in order to ensure a secure mechanical connection between the transducer base 28 and the sensor PCB 34. The sensor PCB 34 has a substrate with a relatively large thickness 31 to improve the stiffness of the sensor PCB 34; to enable better conformity between the sensors 14 and the platform 12 under loading. A control PCB 36 is mounted underneath the sensor PCB 34. The control PCB 36 comprises a microcontroller; an analogue/digital convertor; circuitry to balance the strain gauges and to provide a zero force settings memory (all not shown); and a connector 40 for power and network links. The network link allows the modules 30 to communicate over simple multidrop network, using a single set of interconnections. The control PCB 36 is narrower than the sensor PCB 34, the sensor PCB 34 having side regions 35a and 35b that overhang corresponding side regions 38a and 38b of the control PCB 36. Accordingly, the sensor PCB 34 can be directly supported from underneath, without contact with the control PCB 36.

Figure 3 shows the base 18 and the platform 12 disassembled. The base comprises a series of parallel upright ribs 42 for supporting the modules 30. The ribs 42 are positioned to support the side regions 35a and 35b of the sensor PCB's 34, with the control PCB's 36 suspended freely between the ribs 42. In turn, the sensor PCB's 34 support the platform 12. The ribs 42 are longitudinally arranged, providing passages between the ribs 42 for accommodating the modules 30 and internal cabling. The ribs 42 support the side portions 35a, 35b of longitudinally adjacent modules 30. In the embodiment shown, the ribs 42 are configured to support seven modules 30 arranged longitudinally in each of the four passages. The base 18 further comprises bosses 44 for supporting the platform 12; in particular adjacent a portion 46 of the base 18 for housing platform control electronics (not shown). The control electronics include a memory buffer for temporarily storing data prior to transmission to the computer; and connection interfaces (all not shown) for receiving/transmitting data from/with each of the modules and for supplying power to each of the modules from the power cable 20. The control electronics are located longitudinally adjacent the ribs 42, such that internal wires connecting the modules 30 and the platform control electronics run alongside the ribs 42. The base 18 includes holes 48 with screwthread for securing the platform 12 to the base 18. Figure 4 shows in detail the arrangement of the sensors 14 in the holes 50 in the platform 12. The pillar 26 is located in the centre of each hole 50, with a gap 52 separating the pillar 26 from the platform 12. The gaps 52 surround each interface 24 when in a neutral, non-deflected position and the gaps 52 are large enough to ensure that the pillars 26 can be displaced during a measurement without sides of the holes 52 contacting the pillar 26. Thus the gaps 52 ensure that the platform 12 does not interfere with the operation of the sensors 14.

Figure 5 shows a partial schematic cross-section of the apparatus of Figure 1 illustrating an attachment of the modules 30 to the platform 12. The modules 30 are attached to the platform 12 such that the contact interfaces 24 protrude from the top surface 16 of the platform 12, by about 1mm. The ribs 42 support the platform 12 indirectly via the sensor PCB's 34 such that the central ribs 42 can support the side portions 35a, 35b of two laterally adjacent modules 30. The sensor PCB's 34 of adjacent modules 3Q can abut, thus increasing the concentration of sensors 14; for example, compared to an arrangement (not shown) whereby the sensor PCB's 34 are separated by the ribs 42. The side portions 35a, 35b support platform ribs 54 such that the platform 12 is supported at either side of each module 30. In addition, the platform 12 comprises fixation ribs 56 for securing each module 30 to the platform 12. The fixation ribs 56 are positioned centrally above each module 30 and comprise threaded holes 58. A screw 60 with a washer 61 is inserted through a first hole 62 in each control PCB 36, through a spacer 63 and through a secondhole 64 in each sensor PCB 34; and screwed into the platform hole 58. Accordingly, each module 30 is centrally screwed directly to the platform 12. In between each fixation rib 56 and each support rib 54, the platform 12 comprises recesses 66 in its underside to receive the transducer bases 28, such that the transducer bases 28 are free from direct contact with the platform 12. The control PCB 36 is narrower than the sensor PCB 34 and is free from contact with the ribs 42. Accordingly, the control PCB 36, whose components may be fragile, is supported by the module 30 and is substantially isolated from loading, such as the weight of a user transferred via the ribs 42 to the base 18.

Figures 6 and 7 show exemplary uses of the apparatus 10. Prior to measurement of forces in a plantar foot region, the sensors 14 of each module 30 are calibrated using a calibration tool. Each sensor 14 is subjected to 6 different forces, including forces in different directions and of different magnitudes, thus generating calibration curves. Calibration curves for each sensor 14 are stored on each module 30, enabling adjustment of data whilst measuring prior to transmittal of data from the module 30 via the network link 40. In Figure 6, a user has placed their foot 70 on the platform 12. The array 16 of sensors 14 is substantially larger than the area of the foot 70 such that the user has not had to consider positioning when placing their foot 70 on the platform 12. The foot is stationary and the apparatus 10 measure forces over the entire plantar foot region whilst the user is standing on the platform 12. The module 30 samples data from the sensors 14 at a rate of 50Hz, cycling through the sensors 14 sequentially, although higher frequencies such as 200Hz are possible, if desired. In Figure 7, the user is shown with their foot 70 in partial contact with the platform 12 at the anterior region 72 of the foot 70: typical of an end phase of a stepping action prior to the removal of the foot 70 from the platform 12. The apparatus 10 measures the distribution of forces over the foot 70 throughout the duration of the foot's 70 contact with the platform 12 during such a stepping action. The measurements are relayed to the computer and recorded and displayed, showing the magnitude and direction of local forces in the foot against time.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, in the embodiments shown, the sensors are distributed evenly over the platform. However, the skilled person will appreciate that another distribution pattern may be more appropriate for particular purposes, such as clustering sensors more closely where a higher resolution is desired, such as in target areas of greater interest. Similarly, where the sensor pillars shown here are square in cross-section, and the receiving holes round, the skilled person will appreciate that the sensor pillars and/or holes may have other cross-sections, such as either/both round or oblong. Also where sensors with a relatively small interface area are shown, the interface area may be larger, such as by using caps on the tops of sensor pillars and/or increasing the cross-section of the sensor pillars themselves.

Claims

CLAIMS:

1. A plantar foot force measurement apparatus for measuring force over a plantar foot region, the force measurement apparatus comprising:

a sensing platform configured to receive an entire plantar foot region;

a plurality of force measurement sensors associated with the platform;

2. The apparatus of claim 1 , wherein the plurality of sensors is associated with a sensing area of the platform larger than the entire plantar foot region.

3. The apparatus of claim 1 or 2, wherein the at least one sensor comprises a multidirectional sensor.

4. The apparatus of any preceding claim, wherein the at least one sensor is configured to measure force in a plurality of substantially horizontal directions.

5. The apparatus of any preceding claim, wherein the at least one sensor comprises a transducer.

6. The apparatus of any preceding claim, wherein the at least one sensor comprises a plurality of strain gauges, each strain gauge configured to measure force in a different direction.

7. The apparatus of any preceding claim, wherein the platform comprises a stiffness configured to support a weight of a user with minimal deformation of the platform.

8. The apparatus of any preceding claim, wherein the apparatus is configured to protrude a sensor upper portion from a top surface of the platform.

9. The apparatus of any preceding claim, wherein the platform is configured to receive at least a portion of the sensor.

10. The apparatus of any preceding claim, wherein the apparatus comprises a sensor module comprising an array of sensors.

11. The apparatus of claim 10, wherein the sensor module comprises a sensor printed circuit board (PCB).

12. The apparatus of claim 11, wherein the sensor PCB defines a structural member for supporting the sensor and for supporting at least a portion of a weight of a user.

13. The apparatus of any of claims 10 to 12, wherein the sensor module comprises a control PCB, and the apparatus is configured to avoid loading the control PCB.

14. The apparatus of any of claims 10 to 13, wherein the sensor module abuts the platform.

15. The apparatus of any of claims 10 to 14, wherein the module is be configured to store sensor information locally.

16. The apparatus of any of claims 10 to 15, wherein the module comprises a microcontroller.

17. The apparatus of any preceding claim, wherein the sensor is configured to be calibrated.

18. The apparatus of any preceding claim, wherein the platform is supported on a base, the base comprising one or more boss/es for supporting the platform.

19. The apparatus of claim 18, wherein the platform is supported by the boss via the module.

20. The apparatus of any preceding claim, wherein the sensing platform and a sensor upper portion interface comprise similar friction characteristics.

21. The apparatus of any of claims 12 to 14, wherein the sensing platform and the sensor upper portion interface may comprise contrasting friction characteristics.

22. The apparatus of any of claims 12 to 14, wherein the apparatus comprises a covering over the platform.

23. The apparatus of any preceding claim, wherein the apparatus is configured to accommodate atmospheric variations, such as temperature and/or pressure variations.

24. The apparatus of any preceding claim, wherein the apparatus is configured to be used in conjunction with motion analysis apparatus.

25. The apparatus of any preceding claim, wherein the apparatus is configured to measure a net force associated with a foot.

26. The apparatus of any preceding claim, wherein at least one force measurement sensor is configured to measure a force substantially perpendicular to the platform.

27. The apparatus of any preceding claim, wherein the apparatus is configured to measure a shear force in a plantar foot region.

28. The apparatus of any preceding claim, wherein the apparatus is configured to measure a normal force in a plantar foot region.

29. A method of measuring force over a plantar foot region, the method comprising: positioning a foot on a sensing platform;

measuring a force substantially parallel to the platform.

30. A shear force measurement apparatus for measuring a force between a body part and a surface, the apparatus comprising a sensing surface and a force measurement sensor configured to measure a force substantially parallel to the sensing surface.