Eccentric, Concentric, and Isometric contractions

Welcome back! How was last week? Have you been keeping up with your workouts? How has your nutrition been? Have you seen an improvement in your energy during the day? I’d love to hear from you in the comments.

We’ve covered a lot in this program so far. We discovered how learning just a few basic movements can help you perform the exercises of your workouts with proper attention to form. We discovered different ways of creating smart goals and achieving them using tiny habits. We’ve also touched on some basic nutrition principles to help fuel your performance and add to your recovery.

We’re nearing the end of our 12 weeks together, though, so these last three weeks will be dedicated to helping you learn some principles for designing your own fitness, nutrition, and lifestyle program if you decide not to continue into the Momentum series of our online training programs. If you are continuing into the Momentum program, don’t worry  on, the information in these next three weeks will be further expanded upon.

This week we will be covering the basic principles you’ll need to consider when designing your training program. Today we’ll be starting with the three types of muscle contractions you can train for any exercise, the different results each will have on your goals, and why focusing your attention into training tempo can help accelerate your results.


Concentric contractions occur when any time a muscle shortens in length under load. Think of your bicep contracting and shortening as you bring the dumbbell up during a bicep curl. In order for you to curl a 25 pound dumbbell your biceps must produce more than the force it’s leveraging down your forearm and into your elbow joint.


An eccentric contraction occurs whenever a muscle increases its length under load. Using the same bicep curl example, the eccentric contraction would take place as you slowly lower the dumbbell back to side. The biceps are said to be in an eccentric contraction as long as they are exerting a force slightly greater than would allow for the dumbbell to free fall.


An isometric contraction occurs whenever the muscle is exerting force against a load, but the muscles length does not increase or decrease. Imagine doing a dumbbell bicep curl but pausing when you get halfway through the movement. If you held the dumbbell there and did not move it, your biceps would be performing an isometric contraction. Other examples of isometric contractions are holding a plank position or holding a wall sit. Your muscles are exerting force, but they are neither shortening nor contracting, rather they are keeping the same length.

So why is it important to learn about these different types of muscle contractions? Couldn't you just do a bicep curl and be done with it?

If you want to get the best results from your training, knowing why your body is making the changes its making will help you form the best decisions about how you design your training. Your body gets stronger, faster, leaner, and more agile because of something we call the S.A.I.D. principle. S.A.I.D. stands for Specific Adaptations to Imposed Demands. We’ll go over the S.A.I.D. principle in more detail during the next lesson, but essentially it means your body is going to change differently based on your choices of exercise you make.

By focusing on how long you perform each of the concentric, eccentric, and isometric phases of an exercise, what we call the tempo, you can stimulate different results from your body. Knowing how and when to manipulate the tempo of your exercises will help you continually progress over the long term as you force your body to adapt to each new change.

During your Accelerator program you’ve been focusing on a 3 1 1 repetition tempo, meaning the eccentric phase of each exercise lasts for one second, the isometric hold lasts for one second, and the concentric contraction lasts for 1 second. This repetition tempo is great when starting out on fitness program, as it allows you to focus your attention on the control of every rep and proper breathing technique. The longer time spent in each eccentric phase of a rep is also a strong stimulator of muscle growth, ultimately helping to build a strong foundation for the following training program.

However, your training tempos will need to be changed on a regular basis in order to continually promote adaptation from the body. If you stick to the same tempo for too long you will stop seeing improvements, or what has come to be called plateauing. As you move through your fitness journey, each consecutive training plan should have a focus on transforming one area of your fitness. The three different types of muscle contractions all have their own effects on those adaptations, so selecting the proper tempo will become important.  

For example, if you’re training for muscle endurance you’ll want to include long eccentric contraction and short isometric and concentric contractions. 6 seconds eccentric, 1 second isometric, and 1 or 2 seconds concentric would fit endurance training well. On the opposite side is strength training which requires a maximal amount of explosivity and stretch reflex from the muscles involved. In strength training, the shortest eccentric and concentric contraction possible while maintaining form is encouraged. Isometric contractions are completely done away with as they reduce the stretch reflex, diminishing the amount of force and power able to be generated.

If this all seems overwhelming, don’t worry because we’ll be tying all the concepts we go over this week into an easily understood method for designing a training program. I’d love to hear how your training plan has been going so far? Do you feel more comfortable with the movements? Have you been focusing on your breathing and repetition tempo? What have been  some of your biggest wins? What were some of the biggest challenges? Let me know in the comments!

As always, thank you for joining in on today’s lesson. If you got something out of it or have any questions, please let me know in the comments. If you’re enjoying this fitness program and know of a friend or family member who could also benefit, please feel free to share the sign up link with them. And, as always, the secret to getting ahead is getting started. So go get started!

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