Biomechanics




Why Can You Lift More On Flat Bench Press Than On Incline?

Although you may come across a lifter, once in a while, who is stronger on incline bench press than flat bench, most of the time the regular flat bench press is stronger. Why is this?

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Forearm Extensor Muscles - Origins, Insertions, and Actions, with Video Presentation

The following is information on the extensor muscles of the forearms. These videos were produced to help students of human anatomy at Modesto Junior College study their anatomical models.

They are done with models showing the muscular structure of the arm.

The following two videos present an overview of the major flexor muscles of the forearm, which are the muscles of the posterior compartment.

Each video is followed by information on the origin, insertion, and actions of each muscle covered in the video.

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Forearm Flexor Muscles - Origins, Insertions, and Actions, with Video Presentation

These videos were produced to help students of human anatomy at Modesto Junior College study their anatomical models.

They are done with models showing the muscular structure of the arm.

The following two videos present an overview of the major flexor muscles of the forearm, which are the muscles of the anterior compartment. These muscles not only are responsible for flexion of the wrist, but are also the extrinsic muscles of the hand, responsible for much its gripping strength.

Each video is followed by information on the origin, insertion, and actions of each muscle covered in the video.







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Tension, Compression, Shear and Torsion

Strength coaches and physical therapy types are always talking about the types of stresses our bodies undergo. But they usually sprinkle around words such as stress, strain, load, tension, shear, compression, torsion, etc. more like they are decorating a cake than trying to teach us something. I sometimes wonder why so many like to impress us with their vocabulary but so few ever want to take the time to clue us in to the fundamental meaning of their jargon. So, here I'll take the time to explain what all the words mentioned in the title mean.

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Acromioclavicular Joint (AC Joint) Overview and Injuries

The abbreviation AC or AC joint stands for the acromioclavicular joint. The acromioclavicular is one of the three articulations of the shoulder girdle. See the shoulder complex for a general overview of the shoulder girdle and its joints.

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Fundamentals of Biomechanics by Duane Knudson: GUS Recommended for Basic Biomechanics

Whether you're a personal trainer, strength coach, or just a strength training enthusiast, you really should have one good textbook on the basics of biomechanics. Although Basic Biomechanics by Susan J. Hall is often recommended for a primer, I think there are better choices today for the beginner to biomechanics concepts. The basic textbook that I recommend is Fundamentals of Biomechanics by Duane V. Knudson. Written in an accessible style and laid out so that key and related concepts are presented together, the book just makes sense, even to someone with only a basic science background. Of course, the better your background, the more in-depth your understanding will be. As with any college level textbook, not every page of the book will be useful to every person, depending on your particular needs and practice, but Fundamentals Of Biomechanics covers the basic and more advanced concepts very well. Knudson weaves simple real-world examples throughout the book to help explain the application of the different concepts discussed. The format and integration of the various concepts, I find to be superior to the Hall book.

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Inertia

Inertia: The property of an object that causes it to resist changes to its state of motion by an application of force. A stationary object will tend to resist being moved, and a moving object will resist change in its speed or direction of movement. Comparing two objects of different masses, the object with the most mass will resist changes in its state of motion the most, and so is said to have the most inertia. So, for example, a train has much more inertia than a car, and a football linebacker has more inertia than a gymnast. Although the heavier object has the most inertia, as above, it is the mass that determines inertia, as measured in kilograms.

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Relative Strength

Relative Strength: Strength relative to body weight. Literally, relative strength is a person's strength per kilogram or pound of body weight.

Since absolute strength is the total strength, as defined by the total force that can be exerted regardless of body weight, relative strength is found by dividing the absolute strength by body weight.

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Condyoid Joint

Condyloid Joint: Also called an ellipsoidal joint, ovoid, or condylar joint, a bi-axial diarthrodial or synovial joint were one oval-shaped articulating surface (a condyle), fits into a corresponding ovoid depression in the other articulating surface. Movement is possible in two planes and includes flexion, extension, abduction, adduction and circumduction, but not rotation. See the diarthrodial article for examples and other types of joints.

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Close-Packed Position (joints)

A close-packed position in a synovial joint is the position in which the joint surfaces become fully congruent and their area of contact is at a maximum. This position has been described as a "screwed in" or "screwed home" position, where the joint is tightly compressed and the ligaments and joint capsule are tense, allowing no more movement. This type of position results in the bones being "locked together" is essence, as if not joint existed between them, allowing them to transmit static forces most efficiently because the joint is extremely stable.

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What is the Frontal Plane?

The frontal plane is one of several anatomical planes which are used as positional references in biomechanics, kinesiology, anatomy, and related fields. They are especially useful for describing movements. The frontal plane, also called the coronal or lateral plane, is an imaginary plane (a flat, two-dimensional surface) that passes through one side of the body to the other and divides the body into front and back halfs (anterior and posterior). It is perpendicular to any sagittal plane. Many different frontal planes can be imagined to pass through the body, but we usually refer to the frontal plane intersecting the midpoint or center of gravity of the body, to divide it into equal front and back halves. This is the cardinal frontal plane. While there can be many frontal planes, there is only one cardinal frontal plane.

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Bench Press: Elbows Out or Tucked?

Flaring your elbows out on bench press versus tucking them to your sides.

I recently got a bench press question from a member. You know it's funny, I used to get more bench press questions than anything and after a while, I started getting more deadlift questions than anything. Which I liked until I almost have grown sick of talking about the deadlift so it's sort of a treat to get a bench press question again. The question was basically this:

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Mass Versus Weight

Mass versus Weight: The terms mass and weight are commonly interchanged, however an objects mass does not change from one environment to the next, whereas weight can. Mass is the amount of matter in an object and it is also described as a measure of an objects inertia. Inertia can be thought of as how hard it is to stop an object, when in motion, or get it to move, when not in motion. The mass of an object never changes, unless you add mass to it or take mass away.

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Force Velocity Relationship

Force-velocity Relationship: A propery of skeletal muscle contraction in which the force capability of a given muscle contraction is dependent on the velocity of shortening of the muscle.

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Sequential and Simultaneous Lifts? What is the Difference Between Them?

Every once in a while you will hear someone calling the squat a simultaneous lift. You'll even hear people calling the deadlift a sequential lift. What does this mean, and is it correct?

Well, these terms come from the description and measurement of the coordination of human movement, a branch of biomechanics called kinematics. Movements, in this context, are looked at in terms of the movement of body segments, and this means also the action of the body's joints. You may have never given it a second thought, but during some movements the joints act "all at once" or simultaneously and in others they act one after the other in a sequence. Most movements, however, are not really so black and white and fall in a continuum between the two. Sometimes, for instance, a movement may look to be simultaneous, but upon close observation be sequential.

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