Human performance augmentation through technology has been a recurring theme in science and culture, aiming to increase human capabilities and accessibility. We investigate a related concept: virtual performance augmentation (VPA), using VR to give users the illusion of greater capabilities than they actually have.We propose a method for VPA of running and jumping, based on in place movements, and studied its effects in a VR exergame. We found that in place running and jumping in VR can be used to create a somewhat natural experience and can elicit medium to high physical exertion in an immersive and intrinsically motivating manner. We also found that virtually augmenting running and jumping can increase intrinsic motivation, perceived competence and flow, and may also increase motivation for physical activity in general. We discuss implications of VPA for safety and accessibility, with initial evidence suggesting that VPA may help users with physical impairments enjoy the benefits of exergaming.