PE 254

Measuring Musculoskeletal Fitness (Chapter 7)

Human Body Muscle Diagram

Behavioral Properties of the Behavioral Properties of the Musculotendinous UnitMusculotendinous UnitBehavioral properties of muscle

tissue:◦Extensibility◦Elasticity◦Irritability◦Ability to develop tension

Behavioral properties common to all muscle:◦Cardiac, smooth, skeletal

Extensibility and ElasticityExtensibility and ElasticityExtensibilityElasticityTwo components:

◦Parallel elastic component (PEC)◦Series elastic component (SEC)

Contractile componentVisoelastic (Having flow-resistive

as well as stretchy properties)

Irritability and the Ability to Irritability and the Ability to Develop TensionDevelop TensionIrritability

◦The ability to respond to electrical or mechanical stimulus.

◦Response is the development of tension. Not necessarily a contraction

Structural Organization of Structural Organization of Skeletal MuscleSkeletal MuscleHuman body has approx. 434

muscles◦40-45% of total body weight in adults◦75 muscle pairs responsible for bodily

movements and postureMuscle FibersMotor UnitsFiber TypesFiber Architecture

Muscle FibersMuscle Fibers

Contain:sarcolemmasarcoplasm

nuclei

mitochondriamyofibrils

myofilaments

SarcomereZ linesM lineA band

myosin filamentsI band

actin filamentsH zone

Motor UnitsMotor Units

Fiber TypesFiber TypesFast Twitch (FT)

◦ Type IIa◦ Type IIb

Slow Twitch (ST)◦ Type I

Peak tension reached in FT in 1/7 time of STST and FT compose skeletal muscles

◦ Percentages of each range from muscle to muscle and individual to individual.

Slow Twitch (Type I)The slow muscles are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.

Fast Twitch (Type II)Because fast twitch fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force.

Type IIa FibersThese fast twitch muscle fibers are also known as intermediate fast-twitch fibers. They can use both aerobic and anaerobic metabolism almost equally to create energy. In this way, they are a combination of Type I and Type II muscle fibers.

Type IIb FibersThese fast twitch fibers use anaerobic metabolism to create energy and are the "classic" fast twitch muscle fibers that excel at producing quick, powerful bursts of speed. This muscle fiber has the highest rate of contraction (rapid firing) of all the muscle fiber types, but it also has a much faster rate of fatigue and can't last as long before it needs rest.

Fiber TypesFiber TypesEffects of training:

◦Endurance training can increase ST contraction velocity by 20%

◦Resistance training can convert FT fibers from Type IIb to Type IIa

Elite athlete fiber type distribution does not significantly differ from untrained individuals

Affected by:◦Age and Obesity

Recruitment of Motor Recruitment of Motor UnitsUnitsCNS enables matching of speed

and magnitude of muscle contraction to requirement of movement.

Threshold activation◦ST activated first (low threshold)◦With an increase in speed, force,

and/or duration requirement, higher threshold motor units are activated (FT fibers)

Change in Muscle Length Change in Muscle Length with Tension Developmentwith Tension DevelopmentConcentric

◦Bicep shortening with the bicep curl (flexion)

Isometric◦Body builders develop isometric

contraction in competitionEccentric

◦Acts as a breaking mechanism to control movement

Roles Assumed by Roles Assumed by MusclesMusclesAgonist

◦Primary & SecondaryAntagonistStabilizerAgonists and Antagonists are

typically positioned on opposite sides of a joint.

Muscular Strength, Power, Muscular Strength, Power, and Enduranceand Endurance

Muscular StrengthMuscular PowerMuscular EnduranceMuscular FatigueEffect of Muscle Temperature

Factors Impacting Force ProductionTorque: turning effect of an

eccentric force◦T= Applied Force * Force Arm

Force arm is the perpendicular distance between the applied force and the axis of rotation

Eccentric force: applied in a direction not in line with center of rotation of non-moving axis

Muscular StrengthMuscular StrengthThe ability of a given muscle

group to generate torque at a particular joint.

Two orthogonal components:◦1) Rotary Component◦2) Parallel to bone

Derived from:◦amount of tension the muscles can

generatemoment arms of contributing muscles with respect to joint center.

Muscular PowerMuscular PowerThe product of muscular force and

the velocity of muscular shortening.

The rate of torque production at a joint

Max. power occurs at:◦approx. 1/3 max. velocity, and◦approx. 1/3 max concentric force

Affected by muscular strength and movement speed

Muscular EnduranceMuscular EnduranceThe ability to exert tension over

a period of time.◦Constant: gymnast in iron cross◦Vary: rowing, running, cycling

Length of time dramatically effected by force and speed requirements of activity.

Training involves many repetitions with light resistance.

Muscular FatigueMuscular FatigueOpposite of enduranceCharacteristics:

◦Reduction in force production◦Reduction in shortening velocity◦Prolonged relaxation of motor units

between recruitmentPossible causes?

Modes of Exercise Isotonic: alternating concentric and eccentric

muscle activation that moves a body part through an arc of motion against resistance

Isokinetic: exercise that involves specialized equipment that provides "accomodating resistance" so that the joint moves at a constant angular velocity

Isometric: muscle action that is performed against resistance at any point in a joint's range of motion, for periods of 5-10 seconds, and that produces no joint movement

Plyometric: exercise that requires eccentric activation of muscles against a resistance, followed by a brief amortization period, followed by concentric activation

OverloadOverload induces muscles to adapt, to increase their ability to generate force.

Once muscles have adapted to overload, the overload stimulus must be increased to produce further training effects (progressive overload).

Effect of Muscle Effect of Muscle TemperatureTemperatureIncreased body temperature,

increases speed of nerve and muscle function

Fewer motor units needed to sustain given load

Metabolic processes quickenBenefits of increased muscular

strength, power and enduranceKey point: Be sure to warm-up!

Common Muscle InjuriesCommon Muscle InjuriesStrains

◦Mild, moderate or severeContusions

◦Myositis ossificans (A condition in which calcium, and eventually bone, become deposited in muscle; often the quadriceps)

CrampsDelayed-Onset Muscle Soreness

(DOMS)Compartment Syndrome (A painful

condition caused by increased pressure within a muscle compartment)

Brzycki's equation to determine max load

The Brzycki equation is as follows:

Weight ÷ [1.0278 - ( 0.0278 × Number of repetitions ) ]

Group ActivitiesGroup ActivitiesMuscular training for athletes for 2012

Summer Olympics:

Boxing Soccer GymnasticsVolleyball Rowing Wrestling

Apply: Frequency, Intensity, Time, and Type(s)

Agonist muscles◦ Primary & Secondary

Antagonist muscles Stabilizer muscles

Video Segmentshttp://www.youtube.com/watch?v=

4dAfseVaqUwhttp://www.videojug.com/interview/

muscle-fitness-2

Monday, October 12Monday, October 12thth Please meet at the Fitness Lab

(PE 2A) for muscular endurance/strength activities.