Transtibial (TT) amputations, or below-knee amputations, are among the most frequently performed major limb removals. To replace the missing limb, numerous prosthetic devices were developed. A study of the state-of-the-art in TT prostheses shows that none of the commercially available devices are capable of mimicking an able-bodied ankle-foot complex. Still on a research level, some powered prosthetic devices have the potential to improve amputee walking experience, but still need heavy and bulky actuators to provide the necessary power of propulsion. With the AMP-Foot 2.0, the authors propose a new concept for an energy efficient, powered transtibial prosthesis. Its design enables the use of a low power actuator which stores energy in springs during the complete stance phase that can be released at push-off. Thanks to this, the size and weight of the actuator can be decreased considerably while the ankle still provides the full power necessary for forward propulsion. A prototype of the AMP-Foot 2.0 has been built and experiments with a transfemural amputee were conducted. The captured data is presented and analyzed throughout this paper.