Muscle Action

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Del curso dictado por University of Florida

Science of Training Young Athletes Part 2

30 calificaciones

University of Florida

Science of Training Young Athletes Part 2

30 calificaciones

In this course you will learn how to design the type of training that takes advantage of the plastic nature of the athlete’s body so you mold the right phenotype for a sport. We explore ways the muscular system can be designed to generate higher force and power and the type of training needed to mold the athlete's physical capacity so it meets the energy and biochemical demands of the sport. We also examine the cost of plasticity when it is carried beyond the ability of the body to adjust itself to meet the imposed training stresses. The cost of overextending plasticity comes in the form injuries and chronic fatigue. In essence, a coach can push the athlete’s body too far and it can fail. Upon completion of this course you will be able to assemble a scientifically sound annual training plan.

De la lección

Sport specific strength and power

Training an athlete’s strength and power so it improves their sport performance is a challenging aspect of coaching. Here is the important knowledge you must have: First, you must understand the important terminology such as strength, torque, work and power. Second, you must be able to apply the principle of specificity and transfer of training effects to the athlete’s strength and power development. Third, you must know what peripheral structural adaptations and central adaptations you are trying to accomplish.

Introduction3:59

Terminology10:33

Measurement3:50

Muscle Action6:32

Transfer of Strength and Power4:32

Training Prescription2:29

Conoce a los instructores

Dr. Chris Brooks
Instructor
Coaching Science Coordinator for USA Track and Field

So now we come muscle action terminology.

The terminology used to describe the movement actions of muscles,

is really relevant because as you will see on the next lesson, this understanding

helps you select resistance exercises with a high muscle action specificity.

During the performance of sports skills an active muscle can produce different

types of movements.

Sometimes tension is produced in the muscle but the joints don't move.

This movement is referred to as Static.

The sprint start is an obvious application of highly

tense muscles that produce no movement.

When the active muscle causes either a decrease or

an increase in the joint angles,

the resulting movement produced is referred to as, Dynamic.

The term Concentric identifies movement when the muscle fibers are shortening and

joint angles are decreasing.

And when muscle fibers tense while concurrently lengthening,

the joint angle increases.

When I straighten my arm for example, the biceps muscle is lengthening.

The term used to describe this phenomenon is Eccentric.

The term Isometric describes a situation

when there is a muscle tension, but no joint movement.

In other words, no work is being done.

Now in all three situations, the muscle and its tendons are involved.

The combination of the muscle and

tendon is referred to as the Muscle Tendon Complex.

So you can see,

that there are many complexities when describing muscle actions.

And there are other complexities as well.

So, let's just talk about a few more.

First, the muscle fibers may be shortening while the tendon lengthens.

That is the muscle and tendon, have different actions.

And second, there is variation in the mechanical force production of

a muscle as it moves through its range of motion.

And third, a muscle cannot produce a uniform or isotonic force.

That is, there is no such thing as natural isotonic movement.

Fourth, the word contraction, in describing muscle action,

is quite often applied incorrectly.

Not all muscle actions involve a contraction.

We've already discussed eccentric muscle

action when referring to the lengthening of the muscle fibers.

In the strength training literature, this is referred to as a contraction.

The exact terminology used is eccentric contraction.

Now by definition, contractions means the process of becoming smaller.

Eccentric muscle action is therefore not a true contraction.

There is also the situation when considerable muscle tension

is being produced, but there is no external joint movement.

The term isometric contraction is used to describe this situation.

The muscle itself contracts, however the tendon stretches.

And the muscle tendon unit as a whole therefore,

results in no external joint movement.

Contraction, by definition therefore, only applies to concentric muscle activity.

Eccentric and isometric muscle

tendon actions are not contractions in the true meaning of the word.

And number five,

the term isokinetic is used to describe constant rate of movement.

Now, a muscle does not shorten at a constant velocity while performing

sports skills.

It is possible to use specially designed exercise machines to

control a limb's velocity, and this makes the movement, theoretically, isokinetic.

However, uniform limb velocity does not occur when performing sports movements.

And six, the forces typically produced while performing a sport

skill involve a combination of concentric, eccentric and isometric actions.

When running or jumping for example, the quadriceps muscle of the thigh,

moves through eccentric action first as the foot strikes the ground.

And this is followed by a brief isometric action,

that stops the downward movement of the body.

And then there's a concentric contraction during the propulsion phase.

The culmination of eccentric,

concentric action forms the stretch-shortening cycle.

The stretch-shortening cycle is just an economical way to enhance

the performance of the muscle.

And we're going to return to this notion in the next lesson.

And finally, in some instances gravity is the force causing

the eccentric action of muscle.

Such as when a gymnast is moving into the iron cross.

In this case, maintaining isometric action

becomes important to performing this skill effectively.

Indeed, isometric actions are a significant part of the skill itself.

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