Aerobic training adaptations (#5)

Increased venous return

Contraction of skeletal muscles surrounding veins increases the pressure within the veins --> pushes open the proximal valve --> forces blood towards the heart

Sympathetic nervous system

- Speeds you up - Fight or flight

Karvonen method

- Takes into account resting HR - RHR + (training % x HRR) - RHR + (training % x (max HR - RHR))

Heart rate

- # of beats per minute (bpm) - Max does not change --> [220 - age] - Increases linearly in response to demand of activity --> continues to rise even after SV levels off - HR is directly proportional to VO2 max --> O2 consumption increases linearly --> 70% of max HR = 70% VO2 max

What does NOT adapt to aerobic training?

- Respiratory capacity (ventilation rate, lung capacity) - Muscle hypertrophy --> might get hypertrophy of type I fibers, but not a primary change and doesn't increase performance - Max HR (220-age)

Endocrine adaptations

- Aerobic exercise leads to increases in hormonal circulation and changes at the receptor level - High intensity endurance training increases the secretion rates of many hormones (including epinephrine) - Trained athletes have blunted responses to sub maximal exercise --> this is why progressive overload is important

Stroke volume (SV)

- Amount of blood pumped out per heart beat - This begins to rise when exercise starts and then levels off when O2 consumption is ~50-60% of VO2 max -Max SV is ~25% less for women compared to men

Oxygen uptake (VO2)

- Amount of oxygen consumed by the body's tissues - The oxygen demand of working muscles increases during aerobic exercise - Resting VO2 value is ~3.5mL of O2/kg of body weight/min --> or 1 MET (metabolic equivalent of tasks) - VO2 values in healthy people ~25-80mL/kg/min or 7.1-22.9 METs

Mean arterial pressure (MAP)

- Average BP throughout the cardiac cycle - NOT the average of SBP and DBP - [(SBP - DBP)/3] + DBP

Control of local circulation

- Blood flow is a function of resistance in the blood vessels - As resistance increases, blood flow is reduced - During aerobic exercise, blood flow to active muscles is increased by dilation of local arterioles --> at the same time, blood flow to other organ systems is reduced by constriction of arterioles

Vasoconstriction

- Decreasing vein size to increase pressure - Does this via sympathetic nervous system

Blood flow at rest

- Distributed throughout the body pretty evenly - Brain, heart, muscles (20%), liver, kidneys, skin

2 physiological mechanisms responsible for regulating SV:

- End diastolic volume (EDV) - Action of catecholamines

Diastolic BP

- Filling - Estimates the pressure exerted when no blood is being forcefully ejected - Normal resting BP ranges from 60-89mmHg - During exercise, this stays the same or decreases slightly

Conversion in fiber types

- From type IIx --> IIa - IIa possess a greater oxidative capacity and are more similar to type I's - The result of this conversion is a greater # of muscle fibers that can contribute to aerobic endurance performance

Cardiac output (CO or Q)

- How much blood is ejected per minute - SV x HR - At rest ~5L/min --> during exercise ~20-22L/min --> endurance trained is ~40L/min - *Increases with aerobic training

End diastolic volume (EDV)

- How much blood is in the left ventricle at the end of the filling phase right before the heart contracts - Aerobic training --> increases amount of blood returning to the heart --> increases EDV --> increases *force contraction

Chronic muscle fiber adaptations

- Increase in size and # of mitochondria - Typically only effects type I fibers, but if intensity is sufficient (running repeated 800m intervals), fast twitch fibers also make a significant contribution to the effort - Reduces muscle mass of fibers - Conversion in fiber types

Increased SV and reduced HR

- Increased SV effects resting HR --> more blood is pumped per contraction so that the heart contracts less frequently

Endurance training results in changes in cardiovascular function:

- Increased max. CO - Increased SV - Reduced HR @ rest - Increased capillarization

Chronic muscular adaptations

- Increased myoglobulin content (a protein; supplies oxygen to skeletal and cardiac muscles) - After training, an athlete can exercise at a greater intensity of a now-higher max. aerobic power - This adaptation occurs as a result of glycogen sparing (less glycogen used during exercise) and increased fat utilization within the muscle, which prolongs performance

Ejection fraction

- Measures the fraction of the EDV blood ejected from the heart each time it contracts

Blood flow during exercise

- Muscles at 85% - Distribution to heart doesn't change

Aerobic metabolism

- Plays a vital role in the performance and recovery of an athlete - Produces more ATP energy than anaerobic metabolism

Action of catecholamines

- Produce a more forceful contraction - Greater systolic emptying of the heart

Systolic BP

- Pushing blood out; contracting - Estimates the pressure exerted as blood is forcefully ejected - When combined with HR, can be used to describe the work of the heart - Normal resting BP ranges from 110-139mmHg - During exercise can rise to ~220-260mmHg

Rate pressure product (RPP)

- Rate x pressure = product - HR x SBP = work that the heart has to do (product)

Parasympathetic nervous system

- Slows you down - "para-chute"

a-vO2 difference

- The difference in the oxygen content between arterial and venous blood - In other words, how much oxygen the muscles used up - Improves with increased capillary and mitochondrial density - Arterial --> before blood enters muscles - Venous --> After blood enters muscles

Increased capillarization

- The increase in capillary density decreases the diffusion distance between O2 and metabolic substrates (used to produce energy)

Frank-starling mechanism

- Venous return causes more blood to return to the heart --> LV fills up and expands --> *stretches heart walls --> More forceful contraction of LV

Chronic respiratory adaptations

- Ventilation generally doesn't limit aerobic exercise and is usually unaffected by training - Ventilatory adaptations result from local, neural, or chemical adaptations

Max oxygen uptake (VO2 max)

- When oxygen consumption can no longer increase to meet demands, VO2 max has been achieved

Conduction of the heart: what makes a heart beat?

1. Sinoatrial (SA) node: - Intrinsic pacemaker of the heart - The heartbeat starts here with electrical impulses 2. Atrioventricular (AV) node: - Electrical impulse is delayed slightly here 3. AV bundle: - Sends impulse to purkinje fibers 4. Purkinje fibers: - Conducts impulse to all ventricles

CO big picture

Aerobic training --> increases SV --> increases CO --> increases amount of blood you can pump to your muscles per minute

Venous return

Blood flow back to the heart by the veins

Blood flow

Blood is pumped to aorta --> arteries --> arterioles --> capillaries --> veins --> heart

External influences: altitude

Chronic adaptations: - Increased formation of hemoglobin (5-15%; molecule that delivers O2) - Increase in RBC's (30-50%) - Increased capillarization - Increased oxygen delivery to the muscles

Heart rate reserve (HRR)

Max HR - resting HR

John wants to run at 70% intensity. John is 40. His resting HR is 60. What's his target HR?

Strict percentage: - 70% of max HR --> 0.7 - 0.7 x 180 = 126bpm Karvonen method: - 60 + (0.7 x (180 - 60)) - 60 + 84 = 144bpm

Designing endurance programs for optimizing adaptations

Training programs require proper: - Progression - Variation - Specificity - Overload - Many sports involve interactions between the aerobic and anaerobic systems and thus require appropriate training - One of the most commonly measured adaptations to aerobic training is an increase in VO2 max

VO2 max can be calculated using the fick equation:

VO2 Max = (CO x a-vO difference)/person's weight in kg