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