It seems you're looking for a report or information on a specific Les Mills Body Attack class, particularly a master class with a torrent identifier of 42-58. However, without more context, it's challenging to provide a detailed report or direct information about this specific class.

Les Mills Body Attack is a high-energy, cardio-based workout that focuses on improving cardiovascular fitness, burning calories, and enhancing overall physical fitness. It's part of the Les Mills program, which offers a variety of group fitness classes. Master classes are typically advanced sessions led by experienced instructors, often used for instructor training or for members looking for an extra challenge.