Is Lifting a Dumbbell Isometric or Isotonic?

Hand holding free weight
Lifting a dumbbell is an isotonic movement. (Image: Comstock Images/Stockbyte/Getty Images)

As you go about your daily routine, your muscles are hard at work orchestrating the movements that are necessary to complete physical tasks. The human body contains three kinds of muscle — striated, cardiac and skeletal. When you lift a dumbbell, striated skeletal muscle contractions initiate the movement.

Muscle Contractions

When muscles are at work, they generate force. Produced by contractions, this force occurs whether the muscles are shortening or lengthening. According to Michigan State University, the capability of muscles to generate force is termed “muscle strength,” while “muscle endurance” is defined by the muscles ability to maintain this force. Muscles perform two major types of contractions — isometric and isotonic.

Concentric

There are two types of isotonic muscle contractions — concentric and eccentric. If you lift a dumbbell and do a biceps curl, for example, your biceps muscle shortens as you lift the dumbbell up through the curl. This shortening action of the biceps is called concentric contraction. Less external force from the dumbbell and a decrease in muscle tension produces the concentric action. Springfield Technical Community College describes this shortening of muscle as an isotonic contraction.

Eccentric

Muscle contractions are also in control when you bring the dumbbell back to the starting position. Lowering the dumbbell produces an isotonic muscle contraction that is different from that used in raising the dumbbell. According to Michigan State University, lowering the dumbbell from the shoulder position to complete the curl causes your biceps muscle to lengthen. This contraction while the muscle lengthens is called an eccentric contraction, and it is initiated when the external force, or in this case the weight of the dumbbell, is greater than that produced by the muscle.

Isometric

Although lifting a dumbbell is an isotonic movement, if you lift a dumbbell and complete only part of a curl, holding your arm still for several seconds, your biceps remains static, meaning it does not change length. This is an isometric exercise. The University of Nebraska Medical Center explains that even though the muscles do not shorten during isometrics, a buildup of tension provides force.

REFERENCES & RESOURCES
Comments
PARTNER & LICENSEE OF THE LIVESTRONG FOUNDATION

Copyright © 2018 Leaf Group Ltd. Use of this web site constitutes acceptance of the LIVESTRONG.COM Terms of Use, Privacy Policy and Copyright Policy. The material appearing on LIVESTRONG.COM is for educational use only. It should not be used as a substitute for professional medical advice, diagnosis or treatment. LIVESTRONG is a registered trademark of the LIVESTRONG Foundation. The LIVESTRONG Foundation and LIVESTRONG.COM do not endorse any of the products or services that are advertised on the web site. Moreover, we do not select every advertiser or advertisement that appears on the web site-many of the advertisements are served by third party advertising companies.