28-year-old Grammy Award winner allegedly doesn’t spend hours in the gym to keep her figure. According to Rihanna’s personal trainer, Jamie Granger, Rihanna stays in shape by following a balanced diet and a regular workout regimen. Other exercises include power lifting and plyometric movements to help Rihanna maintain her toned figure. A plyometric movement is considered a quick and powerful movement that begins with muscle lengthening and is followed by muscle shortening.