How repetitions affect muscle development

My workout

Published on 28 October 2020
by Jean-Denis Thomson

Have you ever noticed that your trainer changes the number of reps in your workout mainly based on your training goals, not just your fitness level? It’s true—your trainer adjusts your reps to help you reach your goals. 


Here’s a brief description of reps and how they work:


A repetition includes a concentric and an eccentric phase of movement for the muscles involved. Each time you lift and hold a load is counted as one repetition or rep. Breaks can be added between the contraction phases. 


How many repetitions you do of a particular exercise has a major impact on results. The relationship between reps and muscle development is as follows:


  • One to six repetitions—develops muscle strength


  • Seven to eight reps—improves balance between strength development and muscle hypertrophy


  • Nine to twelve reps—promotes muscle hypertrophy


  • Thirteen to twenty repetitions—develops muscular endurance


In this example, each rep must last six seconds—that is, three seconds of contraction and three seconds of release. The nuances between different contraction times will be explained in future columns. 


The number of reps is critical to achieving your goals, so make sure you talk to your certified trainer to discuss your needs.



Have a great workout!


Jean-Denis Thomson, B.Sc. Kinesiologist

Training Department Director

Énergie Cardio

Jean-Denis Thomson
Kinesiologist, Training Department Director