breaking a sweat

Verb

break a sweat (third-person singular simple present breaks a sweat, present participle breaking a sweat, simple past broke a sweat, past participle broken a sweat)

1. To start sweating, especially due to physical exertion.
   • Are you feeling stronger and more energetic, and even—dare I say it—breaking a sweat? No, not a pink-faced, dripping sweat; nevertheless, a little dewy under the arms and around your forehead.2001, Karon Karter, The Complete Idiot's Guide to the Pilates Method, →ISBN, page 119
2. (idiomatic) To put effort into something; to struggle.
   • He always succeeds effortlessly and never breaks a sweat.