The key difference between concentric and eccentric contractions is that concentric contraction causes muscles to shorten while eccentric contractions cause muscles to elongate.
Muscle contraction is a complex process which changes the length of the muscle fibers. Muscle fibers generate tension. It involves the interaction between contractile proteins actin and myosin in the presence of calcium. There are different types of muscle contractions based on the changes in the length of the muscle during contraction. Isometric and isotonic are the two main types. Isotonic contractions generate a force by changing the length of the muscle while isometric contractions generate a force without changing the length of the muscle. Isotonic contractions are categorized into two types as concentric and eccentric contractions.
CONTENTS
1. Overview and Key Difference
2. What are Concentric Contractions
3. What are Eccentric Contractions
4. Similarities Between Concentric and Eccentric Contractions
5. Side by Side Comparison – Concentric vs Eccentric Contractions in Tabular Form
6. Summary
What are Concentric Contractions?
Concentric contraction is a type of isotonic contraction which causes muscles to shorten while generating a force. Concentric contraction occurs throughout the muscle in the direction of contraction of a muscle. These contractions are required when lifting a load. For instance, when lifting a heavy load, a concentric contraction of the biceps causes the arm to bend at the elbow. During the concentric contraction, cross-bridge cycling occurs in order to produce the force.
Figure 01: Types of Contraction
A sarcomere is the functional unit of a muscle fiber. It contains both thin actin filaments and thick myosin filaments. When the muscle fiber is activated by a nerve impulse and calcium ions, the filaments, actin and myosin, move relative to each other to produce shortening of the sarcomere, muscle fiber and the whole muscle.
What are Eccentric Contractions?
Eccentric contraction is a type of muscle contraction which causes muscles to lengthen. It occurs in response to a greater opposing force which is higher than the force generated by the muscle. Therefore, they occur against or in the opposite direction of contraction of a muscle. Eccentric contractions mostly decelerate the muscle joints. These contractions also can alter the position of the load force.
Figure 02: Sarcomere Shortening and Lengthening
Eccentric contractions can be voluntary or involuntary. During eccentric contractions, cross-bridge cycling occurs to control the extension of the muscle even though the sarcomere, muscle fiber, and muscle are lengthening.
What are the Similarities Between Concentric and Eccentric Contractions?
- In both concentric and eccentric contractions, length of the muscle changes.
- They generate force.
- Strength training involves both eccentric and concentric contractions.
- In both contractions, cross-bridge cycling occurs.
What is the Difference Between Concentric and Eccentric Contractions?
Concentric contraction is a type of muscle contraction that permits the muscle to shorten. In contrast, eccentric contraction is a type of contraction that causes muscle lengthening. So, this is the key difference between concentric and eccentric contractions. During concentric contraction, sarcomere, muscle fiber, and the muscle shorten while during eccentric contraction, they lengthen.
Below infographic tabulates the differences between concentric and eccentric contractions in more detail.
Summary – Concentric vs Eccentric Contractions
Concentric and eccentric contraction are two types of isotonic muscle contractions. The concentric contraction causes shortening of the muscle while eccentric contraction causes lengthening of the muscle. Thus, this is the key difference between concentric and eccentric contractions. Sarcomere, muscle fiber and muscle shorten during concentric contraction. In contrast, sarcomere, muscle fiber and the muscle lengthen in the eccentric contraction.
Reference:
1. “Types Of Muscle Contractions: Isotonic And Isometric | Lifetime Fitness And Wellness”. Courses.Lumenlearning.Com, 2020, Available here.
2. “Muscle Physiology – Types Of Contractions”. Muscle.Ucsd.Edu, 2020, Available here.
Image Courtesy:
1. “1015 Types of Contraction new” By OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Sarcomere” By David Richfield (User:Slashme) Richfield, David (2014). "Medical gallery of David Richfield". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.009. ISSN 2002-4436. – Own work (CC BY-SA 3.0) via Commons Wikimedia
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