Kin 173 exam 2- skeletal muscle adaptation to exercise

problems with strength test

-1 rep max tests are typically performed incorrectly resulting in an increase in injury -you only focus on a small number of muscle groups -increased cost of needing large number of weights

recommendations to improve strength and power

-60-80% of 1 rep max -8-12 reps -2-4 sets, rest for 2-3 minutes between each

chronic hypertrophy

-actually lasts -structural changes -more myofibrils, actin and myosin, sarcoplasm -more connective tissue surrounding entire muscle

Age related changes in skeletal muscle

-aging is associated with a loss of muscle mass known as sarcopenia -between the ages of 30-50 there is a 10% reduction in muscle fiber mass and an increase in intramuscular fat -between the ages of 60-80, muscle strength continues to reduce approximately 15% per decade -after 80 years in age there is a 30% reduction per decade. -typically greater in women as they age (women have less muscle mass)

What happens during sarcopenia?

-decrease in the fiber circumference of type 2 muscle fibers -decrease in the number of type 1 and type 2 muscle fibers -loss of satellite cell function (it takes older people more time to see changes when they start to exercise) *this is associated with an increased susceptibility to disability in elderly, increased risk of falls, and hip fractures.

DOMS

-delayed onset muscle soreness -muscle soreness that increases in intensity for the first 24 hours after activity, peaks from 24-48 hours, and then declines in the next 5-7 days -most commonly occurs after activities that rely heavily on eccentric muscle contractions.

Peripheral fatigue - accumulation of metabolic by products

-during exercise, energy production system produce number of metabolic by products -hydrogen and lactic acid are produced which act to dysregulate the muscle pH balance -the muscles operate best at pH level between 6.9 and 7.1 -when the pH falls lower than 6.9, the cellular processes of energy production and muscle contraction begin to slow -when the pH reaches 6.4, myosin can no longer bind to actin and muscle contraction stops

Changes in size and metabolic properties of the muscle fiber occurs when after detraining:

-during the first month after cessation of resistance training the size of muscle fibers decreases contributing to strength loss -this muscle atrophy results from an offsetting of the balance between protein synthesis and protein degradation -during atrophy there is a down-regulation of protein synthesis pathways, and an activation of protein breakdown pathways

Local Ischemic Model -Doms theory

-exercise causes swelling in the muscle tissue, which increases tissue pressure resulting in restriction in blood supply =ischemia -ischemia causes pain and leads to muscle spasm, which cause additional swelling and pain

time course for mitochondria changes

-exercise training results in the double of the number of mitochondria over the course of 5-8 weeks -after just 1 week of detraining, 50% of the increased mitochondria are lost -after 5 weeks of detraining, all of the increased mitochondria are lost -it takes four weeks of retraining to regain the adaptations in muscle mitochondria lost in the first week of detraining

what causes muscle fatigue

-fatigue results in the cessation of muscular work or the inability to maintain a given intensity of work -it is basically a phenomenon that includes failures at one or more of the sites along the chain of events that leads to muscular contraction

absolute vs. relative

-for comparisons made on the same person, absolute values are preferred -for comparisons made on two different people, relative expression is preferred.

overload

-how you gain improvements -the principle of progressive overload states that for a tissue or organ to improve its function, it must be exposed to a stimulus greater than it is normally accustomed to. -repeated exposure is associated with an adaptation by the tissue that leads to improved functional capacity of efficiency.

why do we get stronger with resistance training?

-increases in strength are due to neural adaptations and structural and biochemical adaptations to resistance training

what are the structural and biochemical adaptations to resistance training that are associated with increased muscle strength

-increases the number of mitochondria (resistance to fatigue; mitochondria are used aerobically) -increased capillary density and myoglobin in skeletal muscles. (myoglobin takes O2 from hemoglobin) -increased cross sectional area for type 2 muscles fibers (shift type 2x muscle fibers to type 2a muscle fibers)

what are the neural adaptations that happen in the nervous system during first 8 weeks of exercise?

-innervating more motor units -increasing the rate of firing motor units (contracting more times) -improving synchronization of motor units for more efficient muscle recruitment -inhibition of the golgi tendon organ to allow greater maximal force -increases in the perimeter length and area of the motor end plate -increased dispersion of ACh receptors (more ACh on motor endplate)

recommendations to improve endurance

-less than or equal to 50% of 1 rep max -15-20 reps -1-2 sets, rest 2-3 minutes between each

central fatigue

-limiting factor -causes: interruptions in motor coordination in the motor cortex -interference in motor control circuits in the basal ganglia -inhibition of voluntary effort ("i don't want to") -pain perception and tolerance -neural malfunctions- membrane potentials are unable to reach sufficient levels to continue to send action potentials ** most people stop doing activity because of central fatigue, not peripheral fatigue

satellite cells

-located on the outer surface of the muscle fiber, contain one nucleus, and function to facilitate growth, maintenance and repair of damaged skeletal muscle tissue.

Mechanical trauma model

-mechanical forces result in structural changes to the muscle fibers -the presences of cellular debris and immune function cells leads to swelling and inflammation

how does hyperplasia work

-muscle fibers split longitudinally and grow into full size muscle fibers (split like string cheese) -

When does acute muscle soreness occur?

-occurs during and immediately after exercise -muscular contractions can cause local ischemia (restrictions to blood supply) which can stimulate pain receptors -changes in muscle pH can irritate pain receptors -lactic acid may play a role in dysregulating muscle pH which releases to short term muscle soreness immediately after exercise (clears within 30 minutes)

2 principles to apply to any exercise program

-overload -specificity

problems with endurance test

-performing 12-30 reps is difficult for most people -endurance does not have the "cool" factor associated with it. -associated with increased muscle soreness

strength

-refers to the ability of a muscle of muscle group to exert maximal force against a resistance. -tests which only allow <3 reps of a task are considered measures of strength. -standard strength assessment is the one-repetition maximum test -1 rep max is the greatest resistance that can be moved through the full range of motion in a controlled manner.

Muscular endurance

-refers to the ability of a muscle of muscle group to repeatedly exert against a resistance -testing requires numerous repetitions (12) of a task

Power

-refers to the ability to exert force quickly or the amount of work done per unit of time -element of time involved power = force x velocity force = distance/time

muscular flexibility

-refers to the ability to move a joint through its complete range of motion -lab tests quantify flexibility in terms of range of motion expressed in degrees using a goniometer.

absolute strength / power

-represent the actual external load -commonly measured in units (lbs, kgs, N) -"how much you can lift"

relative strength/ power

-represents the external load in relation to some aspects of body weight -"how much you can lift in respect to body weight"

does hyperplasia occur in humans?

-research in inconclusive -very difficult to directly measure the number of new fibers in humans -if it does happen, it is most likely restricted to type 2 muscle fibers -only accounts for about 5-10% of increased muscle size

Peripheral fatigue

-spine to muscle -peripheral muscle fatigue during work is considered an inability for the body to supply sufficient energy or other metabolites to the contracting muscles to meet the increased energy demand -this causes contractile dysfunction that is manifested in the eventual reduction or lack of ability of a single muscle or local group of muscles to do work -running out of fuel - depletion of neurotransmitters and energy sources -build up - accumulation of metabolic by-products

neural adaptations

-strength gains during the first 8 weeks of training are neurally mediated (changes in neural system) -muscle strength can increase 25-100% with little to no increase in size

Hypertrophy

-the increase in size of existing muscle fibers -individual muscle fibers get bigger, they don't change in quantity. -does not occur until more than 6-8 weeks of training *main component of muscle enlargement is hypertrophy

Hyperplasia

-the increase in the number of muscle cells -duplicating (they split in two) -muscle enlargement is generally paralleled by increase in muscle strength -increase muscle strength is not always paralleled by gains in muscle size. (b/c first 8 weeks are all neurological)

should we focus on strength or endurance?

-the modern perspective is now more focus on endurance (b/c you do more repetitive motions in sports) -instead of performing a 1 rep max, the focus is on the number of reps able to be performed at a fixed weight.

specificity

-the principle of specificity states that training effects derived from an exercise program are specific to the exercise performed and muscles involved.

DOMS theories

-the two main theories each suggest that the pain results from the bodies inflammatory response -swelling and inflammation are responsible for the painful sensation known as DOMS

Resistance exercise and sarcopenia

-there are benefits of resistance training for the elderly which include: increased muscular strength and endurance, improving functional independence -increased muscle mass providing additional support for bones and enhanced thermoregulation -resistance has been associated with increased healing following falls and injures and also enhanced quality of life.

reversibility

-this concept holds that when a training program is stopped or reduced, the body systems readjust in accordance with the decreased physiological stimuli. -we stop progressively overloading muscles, then reversibility happens

transient hypertrophy

-tissue edema (swelling)

Peripheral fatigue - depletion of neurotransmitters and energy sources

-we need ACh to bind to neuromuscular junction, calcium dependent binding and ATP dependent release -ACh and calcium are resorbed after release, but not perfectly. Some leakage does occur and enzymes deactivate them. Eventually insufficient levels lead to reduced muscular recruitment and contractions. -the body needs energy to survive and eventually energy shoes can be depleted impairing ATP production (rate of depletion depends on type 1 and 2 fibers) -glycogen depletion has been found to be selective to the muscle groups involved in the activity -pattern of glycogen depletion from type 1 and type 2 muscle fibers depends on duration and intensity of activity ** muscle cramps are peripheral fatigue

Who is stronger? men or women

-when compared in absolute terms, men are stronger than women -when force production per unit of muscle is compared, there are no differences in muscle strength between men and women -the sliding filament theory does not work differently for males and females

how hypertrophy works

-when muscle fibers receive any form of trauma, damage or injury (such as from resistance training overload) -satellite cells that multiply, and the daughter cells are drawn to the damage muscle cite -satellite cells fuse to the existing muscle fiber, donating their nuclei, helping to regenerate the muscle fiber -this satellite cell activation and proliferation period can lat up to 48 hours after the trauma or shock from the sustenance training session.

how long does flexibility hold up for following cessation of exercise?

8 weeks

what is maintained better? muscular strength or endurance?

muscular strength -not as many reps