A rep is a repetition — that is, the number of times you do an exercise before you take a short break. A set is a group of repetitions, like two sets of 15 reps. Strength training is a type of ...
Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. April 10, 2026 Add as ...
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‘Reps in Reserve’ Is Key to Building Muscle
If you're curious about how to build muscle without completely overdoing it, implementing "reps in reserve" (RIR) into your workouts could be a total game-changer. RIR is a training method that helps ...
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