title: Get fitter (much) faster. Your workouts don't have to last long--but they have to be hard.
authors: Alexandra
authors: A
authors: Sifferlin
mesh_terms: D015444:Exercise / Q000502:physiology*; D006801:Humans; D005082:Physical Exertion / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D013997:Time Factors