Skeletal Muscle Structure and Function Skeletal Muscle Attached

Skeletal Muscle Structure and Function

Skeletal Muscle • Attached to bones – Movement – Breathing – Posture – Heat Production • Striated • Voluntary – Under conscious control

Muscle Actions • Flexion – decrease the angle at a joint • Extension – increase the angle at a joint • Abduction – movement away from the mid line • Adduction – movement toward the midline

Flexion

Extension

Abduction

Adduction

Muscle Cells • ‘Sarcomere’ – muscle cell – Z line to Z line – Sarcoplasmic reticulum • Many nuclei – Allows for more protein synthesis – Important for strength training

Muscle Cells • Made up of myofibrils – Actin (thin) – Myosin (thick) Gives striated appearance

Sarcomere • H zone – Myosin filaments only • A band – Crossover point for actin and myosin • Z line – Actin only

Sliding Filament Model • A muscle contracts due to: 1. Nerve Impulse 2. Release of Ca++ 3. Formation of cross bridges between actin and myosin – myosin changes shape using ATP 4. Sliding of actin over myosin – Reduces distance between the Z lines 5. Muscle is contracted (Power Stroke) – Repeats many times

Sliding Filament Model

Sliding Filament Model

Sliding Filament Model

Contraction will continue… • As long as Ca++ and ATP are present

Regulation of the Formation of Cross Bridges • Troponin – ‘spots’ on the actin filament • Tropomyosin – thin protein that runs the length of the actin filament • Both are regulatory proteins located on actin filament

Tropomyosin • Blocks the cross bridge site on actin while the muscle is relaxed • Ca ++ binds to troponin and causes a shift in the tropomyosin • This exposes the cross bridge site and a strong connection (muscle contraction) can occur.

Troponin / Tropomyosin

Muscle Tone • Muscles are in a constant “weak” contracted state • Cross bridge formation allows for a strong connection and muscle contraction – Can regulate how strong the contraction can be • Tetanus • Rigor Mortis

Muscle Fiber Types • Slow twitch –I • Fast twitch – IIx – IIa

Fiber Types • Influenced by – Genetics – Hormones – Exercise Habits • Differences: – The production of ATP – Speed of contraction

Slow Twitch (I) • Have many mitochondria – Can make a lot of ATP • Good aerobic capacity • High resistance to fatigue • Endurance athletes have a higher % of slow twitch

Sprinters – fast twitch • Big, powerful muscles • Muscles are able to maximize stored energy in short bursts of all out activity

Fast Twitch Fibers (II) • Small number of mitochondria • Less resistant to fatigue • Good anaerobic capabilities • Power Athletes have a higher % of fast twitch • Sedentary individuals have 50/50.

Marathoners – slow twitch • Muscles utilize energy more efficiently and for longer periods of time.

Can you go from one type to another? • Exercise can cause changes in muscle, not fiber type. • Strength training increases the number muscle fibers and power • Endurance training increases in aerobic capacity – Creation of more mitochondria

Muscle Atrophy • Results from a lack of muscle use • Periods of prolonged rest – Bed rest – Immobilization – Space flight • Reduction in protein synthesis • Increased muscle protein breakdown

Training Methods • • Stretching Plyometrics Weight Training Cardio

Stretching • Muscle group is deliberately elongated • Improves muscle's elasticity and muscle tone • Increases muscle control, flexibility and range of motion (ROM).

Stretching • Stretching is a part of any therapeutic program. • Used to reduce injury, increase performance. • Stretching can strengthen muscles. • Stretching can be dangerous when performed incorrectly. – No bouncing

Stretches • Static – stretch and hold • Dynamic – stretching while moving • PNF - proprioceptive neuromuscular facilitation

Agonist / Antagonist • One muscle contracts, the opposite muscle must lengthen

Plyometrics

Plyometrics • produces fast, powerful movements • improves the functions of the nervous system • explosive exercises – a muscle is loaded and then contracted in rapid sequence

Plyometrics – Plyometrics is used to increase the speed or force of muscular contractions – used for a variety of sport-specific activities. – Benefits range from injury prevention, power development and sprint performance

Weight Training • Develops strength and size of muscles. • Resistance – Weights – Bands – Isometrics • Passive Lifting • Negatives

Isometric Contraction • No movement in muscle length

Concentric Action • Shortening of the muscle

Eccentric Action • Lengthening of the muscle • Causes the most muscle soreness – Ex. Stepping down

Cardio Training • Aerobic means "living in air" • refers to the use of oxygen to meet energy demands during exercise via aerobic metabolism • moderate intensity activities performed for extended periods of time

Spot Reduction • fat can be turned into muscle in a specific area of the body. – ex. Abs • NO CAN DO!!!!

Steroids • body produces steroids naturally to support such functions as fighting stress and promoting growth and development. • Promote protein synthesis. • Does not improve performance. . • Anabolic steroids - artificially produced hormones – similar to male-type sex hormones in the body. – testosterone - mature male hormone – Testosterone promotes the masculine traits that boys develop during puberty • deepening of the voice • growth of body hair. • aggressiveness • Mimicks the effect of naturally produced testosterone on the body.

Problems Associated with Steroids • • • • premature balding or hair loss dizziness mood swings, including anger, aggression, and depression delusion paranoia problems sleeping nausea and vomiting trembling high blood pressure that can damage the heart or blood vessels over time aching joints greater chance of injuring muscles and tendons jaundice or yellowing of the skin; liver damage urinary problems shortening of final adult height increased risk of developing heart disease, stroke, and some types of cancer

Risks Associated with Steroids • Risks for Girls • increased facial hair growth • development of masculine traits, such as deepening of the voice, and loss of feminine body characteristics, such as shrinking of the breasts • enlargement of female genitalia • menstrual cycle changes • • Risks for Guys Specific risks for guys include: testicular shrinkage pain when urinating breast development impotence sterility

Human Growth Hormone • Only legal when prescribed by a doctor for a medical condition – Ex. growth hormone deficiency. • However, recent trends show an increase in growth hormone being abused as an athletic supplement.

HGH • Any type of HGH that is not obtained by prescription is not regulated by the government and could be almost anything. • If you buy what may be called "growth hormone, " "growth stimulators, " or "growth factors" online, it's likely they're not really HGH. Many websites claim to be selling growth hormone, but they're really selling amino acids that don't significantly increase growth hormone levels in your body.

HGH “gut”

You Be the EP • A collegiate baseball coach has informed the strength and conditioning department that his pitchers are not to train with weights “because they will lose their flexibility and therefore pitch velocity will decrease. ” What should be the strength and conditioning professional’s response? Is it appropriate for baseball pitchers to train with weights? If so, what modifications should be made to their program? What stretches should pitchers perform to prevent lost joint motion and decreased flexibility?

Answer: • Baseball pitchers should train with weights to prevent injury and improve performance. When designing a program for baseball pitchers in particular, it is essential to address the shoulder internal and external rotators and wrist extensors and flexors to improve balance at the shoulder and elbow joints, respectively. Hypertrophy should not be the goal for these athletes, as increased muscle size may impede joint movement. Rather, focusing on rapid movement should be the goal for resistance training. Stretches targeting the shoulder and elbow joints are essential to preventing lost motion and may include the following: straight arms behind back, seated lean-back, behind-neck stretch, and cross arm in front of chest.