PHYSCI 5 - Lecture (Chapter 2)

4 core compenets of muscle performance

- strength

- power

- endurance

- flexibility

Strength

the maximal force a muscle can produce

Power

the rate of force production (force x velocity), speed of muscle contraction

Endurance

the ability to sustain repeated or prolonged contraction, how long are you doing it for

Flexibility

the full range of motion at a joint

Cardio and nervous benefits

respiratory, cardiovascular, nervous, immune, digestive, and endocrine systems

Respiratory benefits

improved ventilatory efficiency, ATP needed for fuel source

Cardiovascular benefits

improved cardiac output, lower resting heart rate

Nervous system benefits

better motor unit recruitment and coordination

Immune system benefits

Improved immune surveillance, in moderation, physical activity makes immune system active without increasing inflammation

Digestive system benefits

improved gut motility and metabolic regulation, important to minimize with digestive diseases, physical activity can solve some of this

Endocrine system benefits

improved insulin sensitivity and hormone regulation, insulin is increased by exercise

Stress

normal response to unfamiliar things, talked about based on environment

Exercise as stress

a controlled physical stressor applied to the body, more stress is better during exercise

Stress vs. adaptation

greater stress (within tolerable limits) drives greater adaptation; more stress, more adaptation = better; very thin line between good stress and injuring body

General Adaptation Syndrome

how the body responds to any stressor, Hans Selye (1936); consists of 3 stages: alarm, resistance development stage, and exhaustion stage

The Alarm Stage

- the immediate response to the onset of the stressor

- sympathetic activation

- increase in cardiac output, respiratory rate and blood flow

The Resistance Development Stage

- the body adapts with repeated exposure to the stressor

- body stores more nutrients and oxygen in muscles over time

- increase in glycogen storage, vascularization, mitochondrial density

- body essentially says 'I failed', and responds by storing more energy in muscles

The Exhaustion stage

- tiring because of damage and/or boredom from no stress

- physiological basis of overtraining

- sprains, strains and tears, joint injury

Glycogen storage

in muscles, muscles build a larger fuel reserve

Vascularization

more capillaries form around muscle fibers, improves blood flow

Mitochondrial density

more cellular "power plants" per fiber, needs more ATP and ATP-making facilities

Sprains

ligament injury (bone to bone), typically at a joint

Strains and tears

muscle or tendon (muscle to bone) injury, from mild strain to full tear

Joint injury

from cumulative or acute mechanical overload; sprains, strains, and tears can lead to this

Guiding principles of muscle adaptation

three principles that shape every training program (the overload principle, specificity, the individual's principle), helps to maximize benefits of exercise

The Overload Principle

- stress must exceed what the body is already accustomed to, leads to more overall benefits

- exceed the accustomed load, a workload that matches current capacity and wont force further adapation

- progressive overload

- repetition maximum

Progressive Overload

demand must increase over time to keep producing gains

Repetition Maximum (RM)

- max weight liftable for a given exercise

- for a set number of reps

- need to know how much to handle to decide the stress amount

- power = force x velocity

- heavy and slow builds strength

- light and fast builds power

- hypertrophy

Hypertrophy

muscle protein synthesis and amino acid delivery grow fiber size - muscle growth; fiber growth with overload

RM guideline

- ~4-8 reps per set for strength and hypertrophy; minimum ~3 reps

- want stress to be 75-80% of maximum, 50% for beginner

Specificity (the SAID Principle)

- adaptation is specific to the muscles and movements trained

- Specific Adaptation to Imposed Demands

- train what you want to improve (Adaptation is specific to the muscles and movement patterns trained)

- one limb doesn't equal both limbs (training)

- neural crossover, some coordination transfer occurs -- but not true strength gain

The Individual's Principle

- the same stimulus doesn't produce the same result in everyone

- genetics cause muscles to adapt quickly or slowly

- depends on current muscle composition and training history

- why training programs should ideally be individualized and people should be patient

Delayed Onset Muscle Soreness (DOMS)

- 24-48 hours after exercise

- cause is muscle or connective tissue microtrauma -> inflammation -> sensitized pain receptors

- manage by proper rest to reduce future soreness

Adaptation

physiological changes that increase performance capacity

Resistance training adaptation

- strength, power, and fiber growth

- load drives adaptation, heavier loads = more proteins = more muscle

- more cross-bridges, more actin-myosin connections form under load

- greater motor recruitment causes more muscle fibers activated per contraction

Type IIx

fast-twitch, highly glycolytic, fatigues quickly (produces a lot of force)

Type IIa

Fast-twitch, more oxidative, more fatigue-resistant

The shift

IIx -> IIa, with increased type IIa myosin heavy-chain expression

Muscle cells

type IIx and type IIa

Type 1

less fatigable, lowest amount of force

Aerobic training adapation

endurance, circulation, and oxygen delivery

Atrophy

decrease in muscle size, loss with disuse or detraining

Visible outcomes of progressive overload

increase in maximal strength and power output

VO2 Max

- the max rate the body can take up, transport, and utilize O2

- capacity to deliver O2 to needed muscles

Cadiac output

amount of blood ejected from the heart each minute

Heart rate

how many BPMs

Stroke volume

strength of heart beat

Circulation and respiration

how blood and air are moved to meet demand

Key variables affected by aerobic training

VO2 max, cardiac output, heart rate, stroke volume, circulation and respiration

Untrained

increases cardiac output during exercise mainly through heart rate alone

Trained

increased cardiac output through heart rate and a much greater stroke volume

Training bradycardia

trained individuals also show a loer resting HR

Oxygen extraction (a-VO2 difference)

- how much oxygen the muscle actually uses

- arterial vs. venous oxygen content across the muscle

- widens with training

- supported by increased capillary density and mitochondrial content

Lactate threshold

- the intensity where blood lactate begins to rise sharply, for fatigability

- lactate productions by muscle exceeds the rate of clearance

- trainable

Redistribution of blood flow

- at rest, apportioned across organs by resting metabolic need

- during exercise, vasoconstriction (digestive, renal) and vasodilation (muscle)

Cardiac output at rest

- brain: 15%

- digestive organs: 20-25%

- kidneys: 20%

- muscles: 15-20%

Cardiac output during exercise

- brain: 3-4%

- digestive organs: 3-4%

- kidneys: 2-4%

- muscles: 80-85%

Role of respiratory system

matching airflow to rising oxygen demand

Bronchodilation

airways widen, reducing resistance and increasing airflow

Increase in rate and tidal volume

both breathing rate and volume per breath increase

Increase in minute ventilation

total airflow rises to match O2 demand and CO2 output

Cardiac output =

HR x SV