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tone someone or something up
to make someone or something stronger or more fit, muscularly. I suggested an exercise that would tone him up and make him feel better. The exercises toned up his tummy muscles. I need to get busy and tone myself up.
1. To make something firmer or stronger: Walking to work has toned up my legs. I toned my stomach up by doing sit-ups every day.
2. To become firmer or stronger: My body has really toned up since I started this exercise program.