5.1 Multi-axis force measuring platforms are used to measure the ground reaction forces produced at the interface between a subject's foot or shoe and the supporting ground surface. These platforms are used in various settings ranging from research laboratories to healthcare facilities. The use of force platforms has become particularly important in gait analysis where clinical evaluations have become a billable clinical service.

5.2 Of particular importance is the application of force platforms in the treatment of cerebral palsy (CP) (1, 2).3 An estimated 8000 to 10 000 infants born each year will develop CP (3) while today’s affected population is over 764 000 patients (4). Quantitative gait analysis, using force platforms and motion capture systems, provides a valuable tool in evaluating the pathomechanics of children with CP. This type of mechanical evaluation provides a quantitative basis for treating neuromuscular conditions. In other words, surgical decisions are in part guided by information gained from the use of force platform measurements (5, 6).

5.3 Another application is treatment of spina bifida. According to the Gait and Clinical Movement Analysis Society (GCMAS) (7), an instrumented gait analysis is the standard of expert care for children with gait abnormalities secondary to spina bifida. The main objective of diagnostic gait analysis is to define the pathological consequences of neural tube defects as they relate to gait. The use of instrumented gait analysis allows physicians to determine which surgical or non-surgical interventions would provide the best outcome.

5.4 More recently, force platforms have been used for pre- and post-surgical evaluation of TKA (total knee arthroplasty) and THA (total hip arthroplasty) patients. Such data provides an objective measure of the mechanical outcome of the surgical procedure.

5.5 In addition to the clinical applications there are numerous medical and human performance research activities which rely on accurate measurement of ground reaction forces by using multi-axis force platform measurement instruments.

5.6 As a standards organization, ASTM has historically provided excellent standards for the calibration of force transducers and force-measuring instrumentation. Force platforms, however, are different from force transducers. Force platforms typically provide a large active working surface, whereas force transducers provide more or less a single point of interaction with the load-applying environment. Moreover, force platforms typically provide six-axis measurements and are expected to be used in environments causing multi-axial loading.

1.1 This standard recommends practices for performance verification of multi-axis force platforms commonly used for measuring ground reaction forces during gait, balance, and other activities.

1.1.1 This standard provides a method to quantify the relationship between applied input force and force platform output signals across the manufacturer’s defined spatial working surface and specified force operating range.

1.1.2 This standard provides definitions of the critical parameters necessary to quantify the behavior of multi-axis force measuring platforms and the methods to measure the parameters.

1.1.3 This standard presents methods for the quantification of spatially distributed errors and absolute measuring performance of the force platform at discrete spatial intervals and discrete force levels on the working surface of the platform.

1.1.4 This standard further defines certain important derived parameters, notably COP (center of pressure) and methods to quantify and report the measuring performance of such derived parameters at spatial intervals and force levels across the working range of the force platform.

1.1.5 This standard defines the requirements for a report suitable to characterize the force platform’s performance and provide traceable documentation to be distributed by the manufacturer or calibration facility to the users of such platforms.

1.1.6 Dynamic characteristics and applications where the force platform is incorporated in other equipment, such as instrumented treadmills and stairs, are beyond the scope of this standard.

1.1.7 This standard is written for purposes of multi-axis force platform verification. However, the methods and procedures are applicable to calibration of force platforms by manufacturers.

1.2 The values stated in SI units are to be regarded as the standard. Other metric and inch-pound values are regarded as equivalent when required.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.