Wireless wearable applications which allow for remote biomedical data gathering, analysis and visualisation present a significant opportunity to improve patient care [10] . However, the design and manufacture of wearable systems does present a challenge as relates to their flexibility [11] and ensuring their safe operation [12] – [13] . In this work our goal was to examine the behaviour of a traditional Planar Inverted-F Antenna (PIFA) structure across the frequency band of 700MHz - 4GHz. The specific scenario was a wireless wearables application where nylon was used as a flexible substrate and the antenna was placed directly against the underlying tissue. The RF characteristics were considered for the structure under the action of applied forces which produced multiplanar deformations that correspond to the natural modalities of the antenna and underlying tissue. A shift in the characteristics of the antenna structure was noted due to the change in substrate and effects of the underlying tissue, which was not unexpected [13] . However our specific interest was in understanding how the physical changes to the antenna geometry and surrounding tissue resulted in changes to the RF behaviour. It was observed that the electric field energy varied based on the zone of application of the applied force to the antenna surface. Furthermore, there was greater concentration of the electric field energy into the underlying tissue at higher frequencies.