In this paper the ability of three antenna structures to detect changes in the properties and thickness of a deep tissue layer is investigated. The envisioned application is radiomyography which aims to detect muscular activity by the means of electromagnetic waves coupled into the human body. The paper concludes that it is possible to detect changes in the thickness and the properties of the muscle solely by evaluating the reflection coefficient of an antenna structure. The ability to detect these changes strongly depends on the antenna type. Based on the exploration of three antennas types detecting changes in the m7uscular tissue behind 128 different combinations of skin and fat tissue, it is concluded that radiomyography should rely on resonating antenna structures rather than on travelling wave antennas.