Definition of muscle up in US English:

muscle up

phrasal verb

US
informal
  • Build up one's muscles.

    • ‘They're better than squats for muscling up the quads and targeting different areas, and they're safer, too.’
    • ‘In my neck of the woods these sleek silver specimens, muscled up with the rich feeding of the ocean, are often called ‘greyhounds of the sea‘.’
    • ‘Of particular interest: trout that muscle up rapidly on environmentally friendly, grain-based feeds, made from oats or barley, for instance.’
    • ‘I'd thought beforehand that he looked far from racing fit, very fat and not muscled up at all.’
    • ‘Even easygainers often have trouble muscling up this area.’
    • ‘They're strong, don't get me wrong, but they're not all muscled up.’
    • ‘They all looked spectacular, all muscled up and filled out.’
    • ‘The 31-year-old did play semipro football for a number of years, and he began lifting weights six years ago to muscle up.’
    • ‘These 10 tips for triceps training will help you muscle up the back of your arms in the shortest time possible.’
    • ‘If there's one bodypart that hardgainers have extra difficulty muscling up, it's thighs.’
    • ‘He finally has gotten serious about his weight problem and has trimmed down and muscled up during the offseason.’
    • ‘With his size he does not have to muscle up to hit home runs.’
    • ‘But now the players are muscling up without bulking up.’
    • ‘Instead, the following triceps guide is designed to muscle up the back of your arms as fast as possible.’
    • ‘For the guy looking to muscle up and lean out, protein is a big part of the puzzle.’
    • ‘Deadlifts are foremost a lower-back exercise, but they muscle up your entire backside from your glutes to your neck.’
    • ‘Players may become bigger and stronger, and such muscling up certainly would help ‘a football linebacker or a professional wrestler or a saloon bouncer,’ he said.’