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Related Concept Videos

Muscles of the Thorax01:25

Muscles of the Thorax

The thorax muscles are central to the body's respiration and provide essential support and movement for the upper body. They are intricately designed to facilitate the complex breathing process while also contributing to the structural integrity and mobility of the chest and upper limbs.
The diaphragm is at the core of thoracic musculature, the primary muscle involved in breathing. This expansive, dome-shaped muscle marks the division between the thoracic and abdominal cavities. It originates...
Axial and Appendicular Muscles01:18

Axial and Appendicular Muscles

Skeletal muscles, the key players in our body's movement, can be classified into two groups based on their location and function: axial muscles and appendicular muscles. These classifications reflect the primary roles the muscles play in the body's structure and movement.
Axial Muscles
Axial muscles, situated along the body's midline, are intricately connected to the axial skeleton, which includes the skull, spine, ribs, and sternum. These muscles facilitate facial expressions and play a...
Muscles of the Abdomen01:21

Muscles of the Abdomen

The abdominal wall encircles the abdominal cavity, providing flexible protection and shielding the internal organs from harm. It is bordered at the top by the xiphoid process and costal margins, at the back by the vertebral column, and at the bottom by the pelvic bones and inguinal ligament. The abdominal wall is divided into two regions — the anterolateral and posterior regions.
Anterolateral Region
The anterolateral region comprises five paired muscles classified into the lateral and anterior...
Muscles of the Vertebral Column01:27

Muscles of the Vertebral Column

The back muscles that lie deep into the thoracolumbar fascia are called intrinsic or true back muscles. These muscles are divided into four layers: superficial, intermediate, deep, and deepest layers.
Superficial Layer:
The superficial layer consists primarily of the splenius muscles, which include the splenius capitis and splenius cervicis. These muscles are mainly responsible for the head and cervical spine movements, including extension, rotation, and lateral bending. The splenius capitis...
Muscles of the Anterior Neck01:26

Muscles of the Anterior Neck

The anterior neck muscles are the group of muscles covering the front part of the neck. These muscles are classified into three subgroups. The first one is the superficial muscles, the most visible muscles in the front of the neck. It includes the platysma and sternocleidomastoid. The second group is the suprahyoid muscles, located above the hyoid bone. This group comprises the digastric, mylohyoid, geniohyoid, and stylohyoid. Lastly, the infrahyoid muscles are found below the hyoid bone and...
Muscles that Move the Forearm01:16

Muscles that Move the Forearm

The muscles that move the forearms can be divided into four groups: forearm flexors, forearm extensors, forearm pronators, and forearm supinators. The flexors and extensors act on the elbow joint, while the pronators and supinators act on the radioulnar joints.
Forearm Flexors
The biceps brachii, brachialis, and brachioradialis are forearm flexors. The biceps brachii is made up of two heads. Its long head originates at the supraglenoid tubercle of the scapula, whereas that of the short head is...

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Related Experiment Video

Updated: Jun 30, 2026

Muscle Function Obtained with Motion Mode Ultrasound and Surface Electromyography during Core Endurance Exercise
09:21

Muscle Function Obtained with Motion Mode Ultrasound and Surface Electromyography during Core Endurance Exercise

Published on: August 25, 2022

Muscle strength at the trunk*.

G L Smidt, L R Amundsen, W F Dostal

    The Journal of Orthopaedic and Sports Physical Therapy
    |January 1, 1980
    PubMed
    Summary
    This summary is machine-generated.

    Trunk extensor muscles generate greater force than flexors across all contraction types. Eccentric contractions produced more force than concentric ones, and muscle lengthening yielded higher force than shortening in isometric tests.

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    Area of Science:

    • Biomechanics
    • Kinesiology
    • Human Movement Science

    Background:

    • Understanding trunk muscle strength is crucial for injury prevention and rehabilitation.
    • Isometric, concentric, and eccentric contractions represent different modes of muscle activation with varying force outputs.
    • Previous research has explored trunk muscle strength, but specific comparisons across contraction types and muscle groups require further investigation.

    Purpose of the Study:

    • To quantify and compare the strength of trunk flexor and extensor muscles in healthy males.
    • To analyze strength differences during isometric, concentric, and eccentric muscle actions.
    • To investigate the influence of muscle length (shortened vs. lengthened positions) on force production.

    Main Methods:

    • Subjects performed isometric, concentric, and eccentric contractions of trunk flexors and extensors in a standardized sidelying position.
    • A custom-built force table (Iowa Force Table) was utilized to measure muscle strength.
    • Muscle strength was quantified as the moment of force (Newton-meter, Nm), accounting for external force and moment arm.

    Main Results:

    • Greater moments of force (Nm) were recorded in the muscle-lengthened position compared to the muscle-shortened position during isometric contractions.
    • Eccentric contractions consistently yielded higher Nm values than concentric contractions for the same muscle groups.
    • Trunk extensor contractions consistently produced greater Nm than trunk flexor contractions across all tested modes (isometric, eccentric, concentric).

    Conclusions:

    • Muscle length significantly influences isometric force production, with greater force generated in the lengthened state.
    • Eccentric muscle actions are more powerful than concentric actions for trunk muscles.
    • Trunk extensors are inherently stronger than trunk flexors, highlighting their greater contribution to spinal stability.