Kinesiology: Muscle Activity and Strength

Electromyography (EMG)

Electromyography (EMG)

An equipment use for recording muscle output and activity using surface, needle, or indwelling wire electrodes.

1. Isometric

2. Concentric

3. Eccentric

4. Isotonic

5. Isokinetic

5 types of motions that muscle activation produces.

Isometric

A muscle activation wherein it produces force with not apparent change in joint angle. Also called static, or holding, contractions.

Concentric

It occurs as the muscle shortens and the muscle’s proximal and distal insertion points move closer towards each other. It produces acceleration of body segments.

Eccentric

It occurs as the muscle lengthens and the muscle’s points of insertion move away from each other. It often occurs against gravity as the muscle controls the speed with which gravity moves the joint. It decelerates body segments and provides shock absorption as when landing from a jump or in walking.

Positive work

Concentric motion is sometimes also referred to as ______________. A force exerted by the muscle to produce movement of a joint; in other words, the motion is produced by the muscle.

Negative work

Eccentric motion is sometimes also referred to as ______________. An outside force produces joint motion while the muscle controls the rate at which that motion occurs; an external force, often gravity, is responsible for motion that is done to the muscle.

Isotonic

It refers to the contraction of a muscle detached from the body and lifting a load vertically against gravity. A shortening of the muscle occurred and the load on the muscle was constant throughout the excursion.

Isokinetic

It occurs when the rate of movement is constant using an electromechanical device.

antigravity muscles or postural muscles

Muscles that work against gravity as we sit or stand.

Type I

Type of muscle fibers that can resist fatigue and are able to maintain sustained activity.

Type II

Type of muscle fibers that are used for rapid movement during explosive activities. It can produce force and power rapidly but have low endurance; therefore, they cannot sustain activity for prolonged periods.

Quadriceps

Which one has type I muscle fiber? Quadriceps or Gastrocnemius?

Gastrocnemius

Which one has type II muscle fiber? Quadriceps or Gastrocnemius?

Upper extremity extensors

Which one has type I muscle fiber? Upper extremity extensors or Upper extremity flexors?

Upper extremity flexors

Which one has type II muscle fiber? Upper extremity extensors or Upper extremity flexors?

Gluteals

Which one has type I muscle fiber? Gluteals or Hamstrings?

Hamstrings

Which one has type II muscle fiber? Gluteals or Hamstrings?

Agonist or Prime Movers

It is the principal muscle producing a motion or maintaining a posture. It actively contracts to produce a concentric, eccentric, or isometric contraction.

Antagonist

It is a muscle group that provides the opposite anatomic action of the agonist. Its passive elongation or shortening allows the desired activity to occur.

Synergist

It is a muscle that contracts at the same time as the agonist. It may provide identical or nearly identical activity to that of the agonist. It stabilizes proximal joints for distal joint movement.

biceps-brachialis muscles

A person is in supine position with the arm at the side doing an elbow flexion. Which group of muscles act as the agonist for the first part of elbow flexion up to 90º?

Triceps

A person is in supine position with the arm at the side doing an elbow flexion. Which group of muscles act as the agonist as the elbow passes 90º?

Stress

It is a force or load that is applied to a body, segment, or muscle.

Viscosity

It is the resistance to an external force that causes a permanent deformation.

Extensibility

It is the ability to stretch, elongate or expand.

Elasticity

It is the ability to succumb to an elongating force and then return to normal length when the force is released.

TRUE

TRUE OR FALSE

The more extensibility a tissue has, the less viscosity it has, and vice versa.

Viscoelasticity

It is the ability to resist changing its shape when a force is applied to it, but if the force is sufficient to cause change, the tissue is unable to return to its original shape.

Strain

It is the amount of deformation a structure is able to tolerate before it succumbs to the stress.

Toe Region

In a stress-strain curve, it is the initial region, a resting state, wherein tissue has a crimped or wavy appearance.

Elastic Region

In a stress-strain curve, this region is the point at which the tissue’s elastic properties are stressed.

Plastic Region

In a stress-strain curve, this region has microscopic damage, some of the tissue ruptures because it is unable to withstand this amount of stress. It is at this point that permanent change in the tissue’s length occurs.

Necking Range

In a stress-strain curve, this region has more and more microscopic ruptures occur until the tissue becomes macroscopically damaged. It is at this time that the force or load required to create tissue damage is less than previously because the tissue is weakening.

Failure range

In a stress-strain curve, if the stress increase continues, immediately before the tissue ruptures entirely, a give in the structure is felt and then the tissue rips apart, moving into this range.

Creep

It is the elongation of tissue from the application of a low-level load over time.

Muscle Strength

It is the capacity of a muscle to produce force, and the ability of a muscle to generate active tension.

Parallel

In terms of muscle fiber arrangement, which one provides greater force? Parallel or Series?

Series

In terms of muscle fiber arrangement, which one provides greater speed of motion? Parallel or Series?

Long

In terms of muscle size, which one provides more segment mobility? Long or short?

Short

In terms of muscle size, which one provides more segment stability? Long or short?

FALSE

TRUE OR FALSE

The less muscle fibers a muscle has, the more force that muscle has the potential to exert.

Sarcolemma

Plasma membrane of a skeletal muscle fiber.

Actin and Myosin

2 protein filaments of myofibril.

Fusiform

In this muscle fiber arrangement, the fascicles are parallel and long throughout the muscle. These are designed to produce greater shortening distance but less force.

Pennate

In this muscle fiber arrangement, they produce greater forces to the sacrifice of speed since their total cross section is larger.

Endomysium

A fascial layer that surrounds a single muscle cell or fiber.

Perimysium

A fascial layer that surrounds groups of muscle fibers or fascicles.

Epimysium

A fascial layer that surrounds an entire muscle.

Passive elastic component

It refers to the muscle’s component due to the collective fascial layers.

Resting length

It is a position of the muscle in which there is no tension within the muscle. It is defined as the length at which the maximum number of actin-myosin cross-bridges is available.

Active tension

This is responsible for muscle tension during shortening.

Passive tension

This is responsible for muscle tension during lengthening.

Moment Arm

It is the lever arm that produces rotation around a joint. It is also the length of a perpendicular line from the joint’s axis of motion to the muscle’s force vector or line of pull.

Speed

It is the rate of motion.

Velocity

It is the rate of motion in a particular direction.

Functional excursion

It is the distance to which the muscle is capable of shortening after it has been elongated as far as the joint(s) over which it passes allows.

Passive insufficiency

When muscles become elongated over two or more joints simultaneously, they may reach the state of ___________________.

Active insufficiency

It occurs in multi-joint muscles when the muscle is at its shortest length when its ability to produce physiologic force is minimal.

Optimal sufficiency

It occurs when stabilization by antagonists allows the multi-joint agonist to perform the desired function.

TRUE

TRUE OR FALSE

For the same force output, energy expenditure (oxygen consumption) is less for an eccentric contraction than it is for a concentric contraction.