By: Nicole Nichols, SparkPeople Blogger
2/26/2010 10:19 AM   :  78 comments   :  22,232 Views

See More: fitness, quick tips, strength training, Fitness Defined,

Usually, the average exerciser doesn't think about physiology or kinesiology when he or she is exercising. Sure, you think about form, doing your exercises correctly, and achieving balance—both in terms of overall fitness (a balance of cardio, strength training and flexibility) and individual workouts (a balance in the body where you exercise all of your major muscle groups). And that's great! But there is also a lot going on in your body during each workout, and sometimes, learning more about exactly what is happening can help you work out more effectively so you can get better results.

Whether or not you've heard of concentric and eccentric muscle contractions, you can benefit from learning the difference—especially because focusing on ONE of them can help you get even better results from your strength training program—without spending more time in the gym.

Fitness Defined: Concentric and Eccentric Muscle Contractions (And Why It Matters)

Concentric (Positive) Contractions: Put simply, this contraction shortens your muscle as it acts against resistive force (like a weight). For example, during a biceps curl, the biceps contract concentrically during the lifting phase of the exercise.

Eccentric (Negative) Contractions: During these contractions, the muscles lengthen while producing force—usually by returning from a shortened (concentric) position to a resting position. Using the same example above, the lowering the weight back down during a biceps curl is an eccentric contraction for the biceps. Think of this as "putting on the breaks." You're basically slowing the descent of the weight back down instead of allowing the weight (and gravity) to just pull your arm back down passively.

So why does this matter?
It's a good idea to include both concentric and eccentric contractions in your strength-training program. Luckily, most traditional exercises include these movements—a lifting phase (using the shortening or concentric phase) and a lowering phase to return to the start position. However, how much time you spend in each phase can affect your results. Here are some facts:

• Your muscles can generate more force during the eccentric phase of an exercise. For example, you may only be able to lift a 10-pound dumbbell for a biceps curl. But likely, you could hold and lower (the eccentric phase) a 15 or 20 pound weight.
• By slowing down the negative (eccentric) phase of your exercise, you can help your muscles build greater strength. This is why, typically, people are advised to lower weights or return them to the start position slowly.
• Negative training is a type of strength training designed for greater strength gains. It involves using heavier weights than you could typically lift concentrically and focusing just on the eccentric phase of the exercise. This does pose a higher risk for injury and should not be practiced by beginners, however.
• You can also use negative training to your advantage—as a way to progress to exercises that are currently too difficult for you. For example, maybe you have a goal to perform real pull-ups but don't have the strength yet to lift yourself all the way up (concentric phase). You could help work up to that movement by focusing on the lowering phase. Stand on a box or step to come up to the "up" position and then work on slowly lowering yourself back down. After each lowering, step back up onto the box and repeat the lowering phase again. You'll be working the same muscles and still benefit from the exercise this way.

So next time you're in a class or following along with a DVD and the instructor tells you to lower the weights more slowly than you lifted them, you'll know that you're helping your muscles develop greater strength by doing so. And if you ever hit a plateau in your strength-training program focusing a little more on the negative part of your training can be just the ticket you need to make it to the next level.

Happy Lifting (and Lowering)!

Have you ever tried negative training? Will you think more about the eccentric phase of your exercises now that you know how much it can help you?