**4. Portable media device: wireless accelerometer platform for quantifying human movement**

Preliminary testing and evaluation of the portable media device pertained to the evaluation of gait. The portable media device was mounted proximal to the ankle joint and secured by an elastic band. Connectivity to the Internet was enabled through local wireless connectivity, for which the trial data samples were conveyed as email attachments to a predetermined address. Because of the opportunities facilitated by Internet connectivity though the email address, the experimental site and post-processing resources are trans-continentally situated on either side of the United States of America [33].

Upon testing and evaluation notable advantages of the portable media device are evident. The portable media device is lighter than the smartphone. Because it only relies on local wireless Internet connectivity, there is only a fixed cost for the device as opposed to a continuous marginal cost to sustain a telecommunication footprint. The portable media device demonstrated the ability to acquire gait data in an accurate and consistent manner [33]. Further testing and evaluation of the portable media device as wireless accelerometer gait analysis system about the lower aspect of the trunk successfully identified temporal features of gait [34].

As possession of two portable media devices is relatively more feasible than ownership of two smartphones, the application of tandem mounted portable media devices to quantify the disparity present in hemiplegic gait can be readily accomplished. Both portable media devices functioning as wearable and wireless accelerometers were mounted proximal to the lateral malleolus near the ankle joint for the hemiplegic affected leg and unaffected leg. Again the experimental and post-processing resources were trans-continentally situated with the trial data wirelessly conveyed to the Internet as an email attachment [35].

The post-processing aspect derived the affected leg and unaffected leg temporal disparity of stance to stance, time averaged acceleration of stance to stance, and the affected leg/unaffected leg ratio for stance to stance time averaged acceleration less the offset. These quantified gait parameters demonstrated considerable accuracy, consistency, and reliability. From an inferential statistical perspective the temporal disparity of stance to stance and time averaged acceleration of stance to stance for the affected leg contrasted to the unaffected leg demonstrated statistical significance. Future evolutions to the concept envision automated derivation of parameters and machine learning classification [35].

As previously disclosed gait and reflex of the lower limb, such as the patellar tendon reflex, are neurologically associated [19, 36]. Therefore the portable media device provides a useful means of quantifying the patellar tendon reflex response. In particular the localized wireless connectivity to the Internet is interrelated with the generally indoor and localized environment inherent for obtaining a series of patellar tendon reflex response samples. LeMoyne and Mastroianni demonstrated in 2011 the ability to accurately and consistently characterize the reflex response through manual supramaximal stimulation using a portable media device as a wireless accelerometer platform [37].

Further application of the portable media device as a wireless accelerometer platform amalgamated the utility of the potential energy impact pendulum. The portable media device was mounted proximal to the lateral malleolus of the ankle joint by an elastic sock. Each trial sample was transmitted to the Internet through localized wireless connectivity. Post-processing consolidated the accelerometer signals in three dimensions to a single signal presenting acceleration magnitude. The maximum acceleration of the reflex response was the parameter of interest. The application for quantifying reflexes demonstrated the capacity to characterize the reflex response in a considerably accurate and consistent manner [38].
